2021 CAP Virtual Congress / Congrès virtuel de l'ACP 2021

6 Jun 2021, 10:00 → 11 Jun 2021, 23:59 America/Toronto

Underline Conference System

Welcome to the website for the 2021 CAP Virtual Congress abstract submission and scheduling.  The Program Committee is looking forward to offering an exciting and full slate of talks and sessions, along with important networking opportunities. NOTE:  All scheduling is programmed to Eastern Time zone.  Use the button in the top right of the page to select which time zone you want to view the schedule in. As a reminder, the CAP office staff continue to work remotely from home in accordance with the current provincial recommended best practices, therefore, should you have any questions, please contact the CAP office by e-mail at programs@cap.ca.  Robert Thomson, CAP President Manu Paranjape, 2021 CAP Congress Program Chair Francine Ford, CAP Executive Director

Welcome to the CAP2021 Indico site which is being used for abstract submission and, later, congress scheduling.
Bienvenue au site web Indico pour ACP2021. Ce site servira à la soumission de résumés et, plus tard, à la préparation de l'horaire.

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The abstract system for the 2021 CAP Virtual Congress has now been re-opened for invited speaker abstracts and the submission of post-deadline poster abstracts and will close 23h59 EDT on March 31st.  Thinking of submitting an abstract and don't have an Indico account?  Click on the Call for Abstracts link in the menu on the left for information on how to create one.

L'appel à résumés pour le Congrès virtuel de l'ACP 2021 est maintent réouvert pour les résumés des conférenciers invités et pour les résumés d'affiches après la date limite. Il sera fermer à 23h59 HAE mercredi le 31 mars. Vous envisagez de soumettre un résumé et vous n'avez pas de compte Indico ?  Cliquez sur le lien Appel de résumés dans le menu de gauche pour savoir comment en créer un.

CONGRESS REGISTRATION is scheduled to open around 2021 May 1.
L'INSCRIPTION AU CONGRÈS est prévue vers le 1 mai 2021.

Sunday 6 June

S-HS High School Teacher Workshop on Quantum Computing / Atelier des enseignant(e)s du secondaire sur l'informatique quantique

Convener: Daria Ahrensmeier (Simon Fraser University)

17:00 Break 60 minutes

S-HERZ Herzberg Memorial Lecture / Conférence commémorative Herzberg

Convener: Robert Thompson (University of Calgary)

1 Quanta of the Third Kind: Anyons

For many years physicists divided the world of quantum particles into two kingdoms – bosons and fermions. Anyons are particles with a sort of memory, that fall outside those kingdoms. In recent decades theorists have produced an enormous literature about the possible occurrence and properties of anyons. It is only in the last few months, however, that clear experimental confirmation has appeared. I will review the theoretical background and describe the breakthrough experiments. Anyons will be central in a new and promising method of information processing: topological quantum computing.

Speaker: Prof. Frank Wilczek (MIT, Shanghai Jiao Tong U, ASU, Stockholm U.)

19:00 Questions and answers

Monday 7 June

Opening remarks - CAP President

Convener: Robert Thompson (University of Calgary)

M-PLEN-1 Alejandro Adem, NSERC President (CAP) / Président du CRSNG (ACP)

Convener: Robert Thompson (University of Calgary)

11:30 15 Minute Break

M1-1 Degenerate Quantum Gases and cold Atoms and Molecules (DAMOPC) / Gaz quantiques dégénérés et atomes et molécules froids (DPAMPC)

Convener: Duncan O'Dell (McMaster University)

2 (I) Ultracold chemistry with triplet molecules

Cooling atomic gases to ultracold temperatures revolutionized the field of atomic physics, connecting with and impacting many other areas in physics. Recent advances in producing ultracold molecules suggest similarly dramatic discoveries are on the horizon. I will review the physics of ultracold molecules, including our work bringing a new class of molecules to ultracold temperatures. Chemistry at these temperatures has a very different character than at room temperature. I will describe two striking effects: Spin-dependent reactivity and molecular Feshbach resonances.

Speaker: Prof. Alan Jamison (University of Waterloo)

3 (I) Quantum Sensing with Matter-Wave Interferometers

Over the past decade, significant progress has been made in the commercialization of quantum sensors based on ultra-cold atoms and matter-wave interferometry. Nowadays, the first absolute quantum gravimeters have reached the market and there is even a cold-atom machine on the International Space Station. Matter-wave interferometers utilize the wave nature of atoms and their interaction with laser light to create interference between different quantum-mechanical states. Compared to an optical interferometer, the roles of matter and light are reversed: light is used as the "optic" to split, reflect, and recombine matter-waves. The resulting interference contains precise information about the atom's motion, such as its acceleration, as well as the electro-magnetic fields that permeate its environment. These atom interferometers can be designed as extremely sensitive instruments and have already led to breakthroughs in time-keeping, gravimetry, and tests of fundamental physics. In this talk, I will give an overview of laser-cooling and matter-wave interferometry and its applications as a versatile tool, for example, to test Einstein's Equivalence Principle, map the Earth's gravitational field, or aid future navigation systems.

Speaker: Prof. Brynle Barrett (University of New Brunswick)

4 (I) Quantum archæology: how much time does an atom spend tunneling through a beam of light, and how much time do photons spend “trapped” in atoms?

One of the most famous tidbits of received wisdom about quantum mechanics is that “you can’t ask” which path a photon took in an interferometer once it reaches the screen, or in general, that only questions about the specific things you finally measure are well-posed at all. Much work over the past decades has aimed to chip away at this blanket renunciation, and investigate “quantum retrodiction.” Particularly in light of modern experiments in which we can trap and control individual quantum systems for an extended time, and quantum information protocols which rely on “postselection,” these become more and more timely issues.

All the same, the principal experiment I wish to tell you about addresses a century-old controversy: that of the tunneling time. Since the 1930s, and more heatedly since the 1980s, the question of how long a particle spends in a classically forbidden region on those occasions when quantum uncertainty permits it to appear on the far side has been a subject of debate. Using Bose-condensed Rubidium atoms cooled down below a billionth of a degree above absolute zero, we have now measured just how long they spend inside an optical beam which acts as a “tunnel barrier” for them. I will describe these ongoing experiments, as well as proposals we are now refining to study exactly how long it would take to “collapse” an atom to be in the barrier.

I will also say a few words about a more recent experiment, which looks back at the common picture that when light slows down in glass, or a cloud of atoms, it is because the photons “get virtually absorbed” before being sent back along their way. It turns out that although it is possible to measure “the average time a photon spends as an atomic excitation,” there seems to be no prior work which directly addresses this, especially in the resonant situation. We carry out an experiment that lets us distinguish between the time spent by transmitted photons and by photons which are eventually absorbed, asking the question “how much time are atoms caused to spend in the excited state by photons which are not absorbed?”

Speaker: Prof. Aephraim Steinberg (University of Toronto)

5 Localization of composite quantum particles in a random potential

We investigate the effect of coupling between translational and internal degrees of freedom of composite quantum particles on their localization in a random potential. We show that entanglement between the two degrees of freedom weakens localization due to the upper bound imposed on the inverse participation ratio by purity of a quantum state. We perform numerical calculations for a two-particle system bound by a harmonic force in a 1D disordered lattice and a rigid rotor in a 2D disordered lattice. We illustrate that the coupling has a dramatic effect on localization properties, even with a small number of internal states participating in quantum dynamics.

arXiv:2011.06279

Speaker: Fumika Suzuki (IST Austria (Institute of Science and Technology Austria))

6 Simulating gravity-assisted loading and motion of laser-cooled atoms in hollow-core optical fibres

Hollow-core optical fibres provide μm-scale confinement of photons and atoms and reduce the power requirements for optical nonlinearities. This platform has opened tantalizing possibilities to study and engineer light-matter interactions in atomic ensembles. However, the purity, efficiency and nature of these interactions are contingent on the number, geometry and movement of atoms within the fiber. It is thus of interest to have a handle on loading atoms into and their motion inside the fiber.

Starting from ~ μK MOT (Magneto-Optical Trap) clouds positioned a few mm above the fiber, optical dipole potentials have been used to guide matter into the hollow fibers. To study the effect of different experimental conditions on the loading process, we use parallel programs to re-create the trajectories of atoms into vertically oriented hollow fibres with core diameters: 7 μm and 30 μm. We make predictions about the effects of the initial MOT temperature and position, of different guiding optical potentials on the loading efficiency, as well as of higher-order waveguide modes excited in the fiber. We compare the results of these simulations with reported experiments. Additionally, atomic motion inside the hollow fiber is visualized in order to predict ensemble features such as atom-cloud length, atom-atom distances and position-velocity distributions. These play a role in determining how transversely-confined light couples with the ensemble. Lastly, as the attempted schemes of gravity-assisted loading from a vertically positioned MOT appear to grant efficiencies in the limited range of 0.01 to 1%, potential alternatives are explored in order to realize a more direct interfacing of atoms into the fiber.

Speaker: Sreesh Venuturumilli (University of Waterloo)

7 (G*) Quantum bifurcations in a Bose-Einstein condensate

We model an atomic Bose-Einstein condensate (BEC) near an instability, looking for universal features. Instabilities are often associated with bifurcations where the classical field theory provided here by the Gross-Pitaevskii equation predicts that two or more solutions appear or disappear. Simple examples of such a situation can be realized in a BEC in a double well potential or in a BEC rotating in a ring trap. We analyze this problem using both Bogoliubov theory and exact diagonalization. The former describes elementary excitations which display complex frequencies near the bifurcation. We make connections to the description of bifurcations using catastrophe theory but modified to include field quantization.

Speaker: Ms Denise Kamp (McMaster University)

8 Propagation of correlations in the Bose Hubbard model

Lieb-Robinson and related bounds set an upper limit on the speed at which information propagates in non-relativistic quantum systems. Experimentally, light-cone-like spreading has been observed for correlations in the Bose-Hubbard model (BHM) after a quantum quench. Using a two-particle irreducible (2PI) strong-coupling approach to out-of-equilibrium dynamics in the BHM we calculate both the group and phase velocities for the spreading of single-particle correlations in one, two, and three dimensions as a function of interaction strength in the Mott insulating phase. Our results are in quantitative agreement with recent measurements of the speed of spreading of single-particle correlations in both the one- and two-dimensional BHM realized with ultracold atoms. We demonstrate that there can be large differences between the phase and group velocities for the spreading of correlations and explore how the anisotropy in the velocity varies across the phase diagram of the BHM. Our results establish the 2PI strong-coupling approach as a powerful tool to study out-of-equilibrium dynamics in the BHM in dimensions greater than one.

Speaker: Malcolm Kennett (Simon Fraser University)

9 (G*) Manipulation of phonon modes in a trapped-ion system by optical tweezers

In recent years, multi-species trapped-ion systems have been investigated for the benefits they provide in quantum information processing experiments, such as sympathetic cooling and combining long coherence time of one species with ease of optical manipulation of the other. However, a large mass-imbalance between the ions result in decoupling of their motion in the collective vibrational (phonon) modes that are used to mediate entanglement between ion-qubits. We theoretically and numerically investigate a scheme that introduces far off-resonant optical tweezers, tightly focused laser beams on individual ions, of controllable strength in a conventional Paul (RF and DC) trap. The tweezers enable site-dependent control over the trapping strength and manipulation of the phonon mode structure (eigenfrequencies or eigenvectors) of the trapped-ion system. The tweezers provide local control over the effective mass of the ion and hence minimize the motional decoupling. We demonstrate an algorithm to program the optical tweezer array to achieve a target set of phonon modes. Our work paves the way for high efficiency sympathetic cooling and fast quantum gates in multi-species trapped-ion systems.

We acknowledge support from TQT (CFREF), the University of Waterloo, NSERC Discovery and NFRF grants, and Govt. of Ontario.

Speaker: Yi Hong Teoh (University of Waterloo)

12:20 Group discussion

M1-2 Classical and Quantum Gravity I (DTP) / Gravité classique et quantique I (DPT)

Convener: Robert Mann (University of Waterloo)

10 (I) On the firewall puzzle

Many of previous approaches for the firewall puzzle rely on a hypothesis that interior partner modes are embedded on the early radiation of a maximally entangled black hole. Quantum information theory, however, casts doubt on this folklore and suggests a different tale; the outgoing Hawking mode will be decoupled from the early radiation once an infalling observer, with finite positive energy, jumps into a black hole.

In this talk, I will provide counterarguments against current mainstream proposals and present an alternative resolution of the firewall puzzle which is consistent with predictions from quantum information theory. My proposal builds on the fact that interior operators can be constructed in a state-independent manner once an infalling observer is explicitly included as a part of the quantum system. Hence, my approach resolves a version of the firewall puzzle for typical black hole microstates as well on an equal footing.

Speaker: Beni Yoshida (Perimeter Institute)

11 (I) Quantum Gravity Phenomenology from the Generalized Uncertainty Principle

One of the cornerstones of Quantum Mechanics (QM), Heisenberg’s Uncertainty Principle (HUP), establishes that it is not possible to simultaneously measure with arbitrary precision both the position and the momentum of a quantum system. This principle, however, does not prevent one from measuring with infinite precision the system’s position. However, theories of Quantum Gravity, aiming to bridge between General Relativity and QM, predict the existence of a minimal observable length - a minimal uncertainty on the position generally of the order of the Planck length. This prediction results therefore in a contradiction with HUP, requiring a modification of the principle. This need gave rise to the Generalized Uncertainty Principle (GUP). In this talk, I will show how the GUP can change known aspects of standard QM, leading to ways to test Quantum Gravity.

Speaker: Pasquale Bosso (University of Lethbridge)

12 Scalar-tensor gravity as an imperfect fluid, with applications

Scalar-tensor gravity can be described as general relativity plus an effective imperfect fluid corresponding to the scalar field degree of freedom of this class of theories. A symmetry of electrovacuum Brans-Dicke gravity translates into a symmetry of the corresponding effective fluid. We present the formalism and an application to an anomaly in the limit of Brans-Dicke theory to Einstein gravity.

[Based on V. Faraoni & J. Côté, Phys. Rev. D 98, 084019 (2018); Phys. Rev. D 99, 064013 (2019)]

Speaker: Valerio Faraoni (Bishop's University)

13 (G*) Test of Quantum Gravity in Statistical Mechanics

We study Quantum Gravity effects on the density of states in statistical mechanics and its implications for the critical temperature of a Bose Einstein Condensate and fraction of bosons in its ground state. We also study the effects of compact extra dimensions on the critical temperature and the fraction. We consider both neutral and charged bosons in the study and show that the effects may just be measurable in current and future experiments.

Speaker: Mitja Fridman (University of Lethbridge)

14 (G*) Analyzing Loop Quantum Cosmology of Bianchi II Space with Numerical Methods

Loop Quantum Gravity (LQG) is one proposed approach to quantize General Relativity. In previous literature LQG effects have been applied to Bianchi II spaces and here we numerically solve the resulting equations of motion using the fixed step 6th order Butcher-1 Runge-Kutta method. We also test, for a wide range of initial conditions, analytic transition rules for the Kasner exponents and show in which cases these transition rules hold.

Speaker: Timothy Blackmore (University of New Brunswick)

15 (G*) Effective loop quantum gravity framework for vacuum spherically symmetric space-times

Guided by the application of loop quantum gravity (LQG) to cosmological space-times and techniques developed therein, I will present an effective framework for vacuum spherically symmetric space-times. Stationary solutions of the effective theory give an LQG corrected metric with a number of interesting properties including curvature scalars that are bounded by the Planck scale and a minimal (non-zero) mass for black hole formation. Finally, the vacuum solution we derive is only valid down to some minimum (non-zero) radial coordinate; this necessitates the inclusion of matter fields for a description of the full space-time and in particular address the question of singularity resolution.

Speaker: Jarod Kelly (University of New Brunswick)

Effective loop quantum gravity framework for vacuum spherically symmetric space-times

16 Dust collapse and bounce in effective loop quantum gravity

Using Loop Quantum Gravity corrections one can study quantum gravity effects for a dust-gravity system, resulting in a Loop Quantum version of Oppenheimer-Snyder collapse. In this talk I will explain how this model is built up and the consequences of adding holonomy corrections to the classical theory. In particular, we see that, in the black hole formation, there is a bounce when the energy density of the dust field reaches the Planck scale and the matter starts expanding. This expansion reaches, eventually, the apparent horizon, at which point the horizon disappears and there is no longer a black hole.

Speaker: Robert Santacruz (University of New Brunswick)

12:10 Questions/Answers and Discussion Period

M1-3 Physics for a larger audience (DPE) / La physique pour un plus vaste auditoire (DEP)

Convener: Daria Ahrensmeier (Simon Fraser University)

11:45 DPE Mingling

17 (I) Assessment of Physics Competency in a First-Year Integrated Science Course

Launched in 2016, our four-year Integrated Science program is intended for students who have a passion for science and who wish to dissolve the barriers between the traditional scientific disciplines. The highlight of the program is a second-semester, first-year “megacourse” that takes a radical approach to first-year science by asking four overarching questions: How did Earth evolve, what is energy, what is life, and how does my smartphone work? Students completing the megacourse receive credit equivalent to second-semester biology, calculus, chemistry, and physics. At the same time, students are introduced to astronomy, earth sciences, computer science, and statistics, scientific disciplines to which first-year students typically receive no exposure. Along with a quick overview of the course, we will explore how students are assessed to ensure that they are sufficiently competent in each of the four main disciplines, particularly in physics.

Speaker: Gurpaul Kochhar (Western University)

M1-4 DPMB 101 - Part 1 (DPMB) / DPMB 101 - Partie 1 (DPMB)

Convener: Cornelia Hoehr (TRIUMF)

18 (I) Introduction to machine learning and its applications in biophysics and computational biology

Speaker: Yi-Hsuan Lin (University of Toronto)

ML_abstract_CAP.txt

M1-5 Spectroscopy I (DNP) / Spectroscopie I (DPN)

Convener: Corina Andreoiu (Simon Fraser University)

19 (I) Study of exotic nuclei along the neutron drip line and beyond

I will show and discuss the recent progress of spectroscopic studies of neutron-rich nuclei near and beyond the neutron drip line, using the large acceptance multi-purpose spectrometer SAMURAI at RIBF at RIKEN [1]. After a brief introduction on characteristic features of structures near and beyond the neutron dripline, we focus on the recent experimental results on the observation of 25-28O [2] beyond the neutron drip line, and the Coulomb and nuclear breakup of halo nuclei such as 6He and 19B [3]. Future perspectives on the spectroscopy of such extremely neutron-rich nuclei are also discussed.

[1] T. Nakamura, H. Sakurai, H. Watanabe, Prog. Part. Nucl. Phys. 97, 53 (2017).

[2] Y. Kondo, et al. Phys. Rev. Lett. 116, 102503 (2016).

[3] K.J. Cook, et al., Phys. Rev. Lett. 124, 212503 (2020).

Speaker: Prof. Takashi Nakamura (Tokyo Institute of Technology)

20 (G*) Investigation of resonance states in 11Li

Understanding the structure of complex many-body nuclei is one of the central challenges in nuclear physics. The conventional shell model is capable of explaining the structure of stable nuclei, but it starts to shatter towards the driplines or rare isotopes. To explain the new trends in the shell model at the driplines, it is essential to study these exotic nuclei. Halo nuclei are prime examples of some of the unusual characteristics of rare isotopes. The development in the radioactive ion beam facilities made it possible to explore different aspects of halo nuclei. 11Li is a two-neutron halo with a 9Li core. In this study, the resonance states of the 11Li have been investigated through the deuteron scattering off an 11Li. The experiment was performed at the IRIS facility at TRIUMF with an 11Li beam accelerated to 7.3A MeV. The scattered deuterons were detected using a silicon and CsI(Tl) detector. The missing-mass technique was used to obtain the excitation spectrum. The observed resonance spectrum from inelastic scattering and the ground state of 11Li from elastic scattering will be presented that will show the excited states seen for 11Li. Their characteristics will be discussed.

Speaker: Mukhwinder Singh (SMU)

21 Preliminary Characterization of Silicon Detectors for the Neutron Beta Decay Experiment (Nab) using the Manitoba II 30 keV Proton Source

Neutron beta decay is a fundamental nuclear process that provides a means to perform precision measurements that test the limits of our present understanding of the weak interaction described by the Standard Model of particle physics and puts constraints on physics beyond the Standard Model. The Nab experiment will measure a, the electron-neutrino angular correlation parameter and b, the Fierz interference term. The Nab experiment implements large area segmented silicon detectors to detect proton momentum and electron energy to determine a to a precision of $\delta a / a \sim 10^{-3}$ and b to a precision of $\delta b = 3 \cdot 10^{-3}$. The Nab silicon detectors are being characterized by protons prior the execution of Nab experiment. This talk will present preliminary measurements on the electronic response of detector pixels.

Speaker: Nicholas Macsai (University of Manitoba)

M1-6 Spectroscopy II (DNP) / Spectroscopie II (DPN)

Convener: Pietro Spagnoletti (Spagnoletti)

22 (I) Recent highlights from the GRIFFINspectrometer

The Gamma-Ray Infrastructure For Fundamental Investigations of Nuclei (GRIFFIN), is a state-of-the-art spectrometer designed for the $\beta$-decay studies of exotic nuclei produced at the TRIUMF-ISAC facility. It provides unique research opportunities in the fields of nuclear structure, nuclear astrophysics, and fundamental interactions.

The spectrometer is composed of an array of 16 Compton suppressed clover-type high-purity germanium (HPGe) detectors as a core, and complemented by a powerful set of ancillary detectors that comprise plastic-scintillators for beta tagging, LN2-cooled Si(Li) detectors for conversion electron measurements and an array of eight LaBr$_3$(Ce) scintillators for lifetime measurements [1].

Innovative results using the GRIFFIN spectrometer have been recently published, including the precision measurements of the Fermi super allowed beta emitter $^{62}$Ga, the astrophysically-motivated investigations of the $^{132}$In, $^{129}$Cd, $^{129}$In nuclei and the nuclear structure of $^{80}$Ge. An overview of the future scientific opportunities together with the recent experiments will be provided.

References
[1] A.B. Garnsworthy et al. NIM A:918:9–29, 2019

Speaker: Dr Victoria Vedia (TRIUMF)

23 (G*) Lifetime Measurement of the First 2+ State in 40Ca Using Direct Population via an Alpha-transfer Reaction

At TRIUMF, Canada’s particle accelerator centre, the TIGRESS Integrated Plunger (TIP) and its configurable detector systems have been used for charged-particle tagging and light-ion identification in Doppler-shift lifetime measurements using gamma-ray spectroscopy with the TIGRESS array of HPGe detectors. An experiment using these devices to measure the lifetime of the first $2^+$ state of $^{40}$Ca has been performed by projecting an $^{36}$Ar beam onto a $^\text{nat}$C target. Analysis of the experimental gamma-ray spectra confirmed the direct population of the first $2^+$ state. Since the centre-of-mass energy in the entrance channel was below the Coulomb barrier, the reaction mechanism is believed to be the transfer of one alpha particle from the $^{12}$C target to the $^{36}$Ar beam nucleus, rather than fusion-evaporation from a compound $^{48}$Cr nucleus. The low centre-of-mass energy resulted in the direct population of the $2^+$ state of $^{40}$Ca, which eliminated feeding cascades, and therefore restricted the decay kinetics predominantly to first order. Currently, Monte-Carlo simulations using the Geant4 framework are being developed to locate the precise beam spot and to verify the reaction mechanism. Simulations with the correct parameters are expected to reproduce the experimental energy spectra and angular distributions of alpha particles while providing a Doppler Shift Attenuation Method measurement of the lifetime of the first $2^+$ state in $^{40}$Ca. In the future, the observed reaction mechanism can be applied to N=Z radioactive beams to provide direct access to low-lying excited states of nuclei with (N+2) and (Z+2), enabling transition rate studies at the N=Z line far from stability. Results of analysis of the experimental data and simulations will be presented and discussed.

Speaker: Tongan (Frank) Wu (Simon Fraser University)

24 (G*) Electromagnetic Transition Rate Studies in $^{28}$Mg

Neutron rich Mg isotopes far from stability belong to the island of inversion, a region where the single particle energy state description of the shell model breaks down and the predicted configuration of nuclear states becomes inverted. Nuclei in this region also exhibit collective behaviour in which multiple particle transitions and interactions play a significant role in the nuclear wavefunctions. This is seen through intruder states of opposite parity in highly excited nuclei approaching the island of inversion, and can be observed through electromagnetic transition strength measurements.

In-beam reaction experiments performed at TRIUMF, Canada's particle accelerator centre, allow for precision measurements of nuclei far from stability. Using TIGRESS in conjunction with the TIGRESS Integrated Plunger for charged particle detection, electromagnetic transition rates can be measured to probe nuclear wavefunctions and perform tests of theoretical models using the well-understood electromagnetic interaction.

The approved experiment will use TIGRESS and the TIGRESS Integrated Plunger to measure the lifetime of the first excited state in $^{28}$Mg, which due to the relatively long lifetime was unable to be precisely measured in a previous Doppler Shift Attenuation Method (DSAM) measurement. To become sensitive to longer lived states, this experiment will use the Recoil Distance Method (RDM) to exploit the Doppler shift of gamma rays emitted in flight, which when compared to data obtained with Monte Carlo simulations performed using the Geant4 framework allow for the determination of a best fit lifetime. Additionally, this experiment will aim to further investigate an anomalously long-lived, highly-excited, negative parity intruder state seen in the DSAM experiment, the lifetime of which is accessible through RDM experiments. Work done in preparation for this experiment as well as future experiments to probe lifetimes in excited states of island of inversion nuclei $^{30-32}$Mg will be discussed.

Speaker: Matthew Martin (Simon Fraser University)

M1-7 ACC Developments in Canada (DAPI) / Développements ACC au Canada (DPAI)

Convener: Kirk Michaelian (NRCan/RNCan)

25 Accelerator Science in Canada

Accelerator Science is both a discipline in its own right within modern physics and provides highly powerful tools for discovery and innovation in many other fields of scientific research. Accelerators do support different disciplines of subatomic physics, material sciences, life sciences and applications in research and industry. Accelerator Science Community does perform R&D to improve operational facilities and prepare technologies for new facilities unveiling new opportunities and unprecedented performance parameters. Having delivered nearly five decades of discovery, TRIUMF has a vibrant reputation globally as Canada’s particle accelerator laboratory and a hub for particle accelerator physics and technology with a wide network of international connections. In collaboration with CLS, the Fedoruk Centre and Canadian Universities, we want to grow the impact of Accelerator Science in Canada on the society and the potential to address key issues of the society of today.

Speaker: Prof. Oliver Kester (TRIUMF)

26 (I) Superconducting Radiofrequency Science and Technology in Canada

Superconducting radiofrequency (SRF) cavities have been used for more than 50 years to increase the energy of charged particles. In Canada there are two accelerator centres which use SRF technology, i.e TRIUMF and the Canadian Light Source (CLS). The CLS was the first light source to use an SRF cavity in a storage ring from the beginning of operations in 2004. TRIUMF began developing SRF technology in 2000 which led in 2006 to the commissioning of the ISAC-II heavy ion superconducting linac for the post-acceleration of radioactive beams. More recently, the ARIEL SRF electron accelerator was installed at TRIUMF as a second driver for radioactive isotope production. In this talk, I will first give an overview of Canada’s SRF infrastructure and the underlying concepts. Then, I will briefly present how performance has globally evolved since the early days. Nowadays, state of the art niobium cavities reach fundamental limitations in terms of accelerating gradient (energy gain per unit length) and power dissipation. Increasing performance requires specialized chemical and surface treatments which must be tailored to specific cavity types and exploring materials beyond bulk niobium. I will highlight recent research highlights from TRIUMF and UVic including results from testing new surface treatments on unique multimode coaxial resonators and material science investigations using beta detected nuclear magnetic resonance (beta-NMR) and muon spin rotation and relaxation (muSR).

Speaker: Tobias Junginger (University of Victoria)

27 (I) CLS2: A Next Generation Light Sournce for Canada

The CLS2 is a concept design of a next generation synchrotron light source to keep Canada at the forefront of scientific research that is uniquely available to researchers with access to such national infrastructure. Canada's research priorities in health and medicine, agriculture and food security, advance materials and industrial research, will all be enabled with national access to a next generation synchrotron. The CLS has provided critical research for Canada and the world, including covid-19 research that can only be performed on a synchrotron, and all OECD countries are in the process of commissioning, investing in or planning a next generation light source such as CLS2. This presentation of a new concept for a next generation synchrotron is a world leading design with the highest brightness in its class. The Conceptual Design Report currently being written is aimed at the government, industry and scientific community who will be the users of the facility and to engage them in the creation of a Technical Design Report and a project proposal to realise a future light source for Canada beyond the CLS which is approaching end-of-life.

Speaker: Dr Mark Boland (CLS University of Saskatchewan (CA))

28 (I) A Prototype Compact Accelerator-based Neutron Source (CANS) for Canada

The Canadian scientific community lost their local source of neutron beams for materials research on March 31st 2018, due to the closure of the National Research Universal reactor at Chalk River National Laboratories. Furthermore, the dwindling global supply of neutrons has made it increasingly difficult for local scientists to access neutron beams. There is a growing demand for the development of new generation facilities in Canada to address the drought which the local neutron user community is experiencing. A compact accelerator based neutron source (CANS) offers an intense, pulsed source of neutrons with a capital cost significantly lower than spallation sources. Research and development for a prototype CANS at the University of Windsor is currently underway. This facility will serve three major beam lines including, a neutron science station, a boron neutron capture therapy station and a PET isotope station. An outline of the proposed parameters of the facility and the design strategy for the target-moderator-reflector assemblies for the neutron science and BNCT stations will be presented.

Speaker: Dr Dalini Maharaj (University of Windsor)

29 Improvement of the Efficiency of the TRIUMF Charge State Booster

The Electron Cyclotron Resonance Ion Source is a versatile and reliable source to charge-breed rare isotopes at the TRIUMF's Isotopes Separation and Acceleration (ISAC) facility. Significant research work has been done by different groups worldwide to improve the efficiency and performance of the ECRIS as a charge state booster. The most recent of these research works is the implementation of the two-frequency heating on the ECRIS. At the ISAC facility of TRIUMF, a 14.5 GHz PHOENIX booster which has been in operation since 2010 was recently upgraded to accommodate the two-frequency heating system using a single waveguide. The efficiency for charge breeding into a single charge state, which depends on the rare isotope that is being charge-bred, has been determined to be between 1 - 6 and will be improved by the activities started at TRIUMF. The CSB, and the corresponding beam transport lines are being investigated in terms of beam properties like beam emittance from the extraction system, and after the beam separation. A systematic investigation of the effect of the two-frequency heating technique on the intensity, emittance, and efficiency of the extracted beam is presently being conducted.

Speaker: Mr Joseph Adegun (TRIUMF)

M1-8 Frustrated Magnetism (DCMMP) / Magnétisme frustré (DPMCM)

Convener: Michel Gingras

30 (I) Magnetoelectric generation of a Majorana-Fermi surface in Kitaev's honeycomb model

Recently, Kitaev materials have attracted great interest due to their potential to realize a quantum spin liquid ground state which hosts gapless Majorana excitations. In this talk, after a review of the physics of Kitaev materials, I will discuss the effects of static magnetic and electric fields on Kitaev's honeycomb model. Using the electric polarization operator appropriate for Kitaev materials, I will derive the effective Hamiltonian for the emergent Majorana fermions to second-order in both the electric and magnetic fields. While individually each perturbation does not qualitatively alter Kitaev spin liquid, the magneto-electric cross-term induces a finite chemical potential at each Dirac node, generating a Majorana-Fermi surface. I will argue this gapless phase is stable and exhibits typical metallic phenomenology, such as linear in temperature heat capacity and finite, but non-quantized, thermal Hall response. Finally, I will discuss the potential for realization of this, and related, physics in Kitaev materials such as RuCl3.

Speaker: Jeffrey Rau (University of Windsor)

11:50 Questions & answers

31 (I) Magnetic order and spin liquid physics in cluster Mott insulators

I will discuss muon spin rotation (muSR), nuclear magnetic resonance (NMR) and thermodynamic measurements on several Mo3O8-based cluster Mott insulators consisting of a 1/6th-filled breathing Kagome lattice. Depending on sometimes subtle structural differences between these various materials, a number of different magnetic phases can be stabilized, including possible quantum spin liquids: a long-range entangled state with emergent fractionalized excitations.

Speaker: Jeffrey Quilliam (Université de Sherbrooke)

11:59 Questions & answers

12:03 Open discussion period

M1-9 Dark matter experiment and Channel of detection I (PPD) / Expérience sur la matière sombre et canal de détection I (PPD)

Convener: Simon Viel (Carleton University)

32 (I) Challenges for Direct Dark Matter Detection Searches

The current and upcoming astroparticle physics program will help understand the nature of the universe with the possible discovery of the nature of dark matter. The efforts towards greater sensitivities to the small signal induced by the very rare event direct dark matter experiments aim to detect turn into a continuous fight against radioactive background. There are various methods to reduce or mitigate background sources. These mainly include the selection of very radio-pure materials to build the experiment and the detectors, detector technologies able to discriminate signal to background events and the choice of deep underground sites to locate the experiments. In this talk I will review the challenges for direct dark matter search experiment along with the current R&D efforts in detector technologies.

Speaker: Dr Silvia Scorza (SNOLAB)

2021June07_CAP_Scorza.pdf

33 Status of the NEWS-G dark matter experiment first run data analysis and installation at SNOLAB

The NEWS-G collaboration aims to detect sub-GeV WIMPs using Spherical Proportional Counters (SPC). During the past 6 years, the collaboration developed a new 140 cm diameter detector. This detector - larger than the previous generation - is made from stringently selected materials for their radio-purity and is enclosed in a spherical shielding made of different layers of polyethylene and low background lead. Finally, the inner surface of the detector was plated with a half millimeter of pure copper to reduce Pb-210 induced backgrounds. A new calibration method using a UV laser was also used in addition to Ar-37, neutron, and gamma sources. The new detector performed a first measurement campaign at the Laboratoire Souterrain de Modane in France in 2019 before being moved and installed at SNOLAB. Here we present a summary of the work done on the data analysis of the first campaign. This presentation will be followed by a status of the current installation and the first data taking of the experiment at SNOLAB.

Speaker: Alexis Brossard (Queen's University)

CAP_2021_Alexis_Brossard_NEWSG.pdf

34 Current Status of DEAP-3600

DEAP-3600 is a direct dark matter search experiment located 2km underground at SNOLAB. The experiment is located at this depth to shield the sensitive detector from cosmic rays. The experiment uses a liquid argon target to search for WIMP dark matter candidates. Liquid argon is chosen as a target material for three reasons: it has a good scintillation light yield, it is transparent to its own scintillation light, and the nature of its scintillation enables the significant reduction of some backgrounds via pulse shape discrimination. Approximately 3300 kg of liquid argon is used within the DEAP-3600 experiment. The liquid argon is contained within a hollow acrylic sphere with an inner radius of approximately 85 cm. The acrylic sphere is surrounded by 255 photomultiplier tubes to detect the scintillation light. A TPB wavelength shifter is applied to the inside face of the acrylic vessel, the wavelength shifter turns the 128 nm light produced by scintillating argon to 420 nm where the PMTs are more sensitive.

This talk will give an update on the current status of the experiment and an overview of some of the recent analyses performed. Several hardware upgrades are scheduled to occur in 2021, these upgrades will be described as well as the future plans for the upgraded detector.

Speaker: Mark Stringer (Queen's University)

DEAP3600Experiment_4thJune.pdf

12:30 15 Minute Break

M2-1 Interaction between matter and light (DAMOPC) / Interaction entre matière et lumière (DPAMPC)

Convener: Duncan O'Dell (McMaster University)

35 (I) Ionization of biologically relevant molecules studied with an independent atom model including geometric overlap

If one wishes to understand and successfully simulate the radiation damage of biological tissue one needs to understand the fundamental ionization processes of molecules in the gas or vapour
phase first. The latter problem has been addressed in a number of studies in recent years, but experimental data have remained scarce and accurate cross-section predictions based on first-principles quantum-mechanical calculations challenging due to the complexity of the molecules of interest. There is thus a role to be played by simplified modelling - provided the models used
can be shown to work for simpler systems for which reliable theoretical and experimental data are available for comparison.

We have recently developed one such model. It is based on the independent atom model (IAM) according to which a cross section, e.g., for electron removal from a molecule can be obtained from atomic cross sections for the same process. Instead of simply adding up the cross sections for all the atoms that make up the molecule we take geometric overlap into account, which arises when the atomic cross sections are pictured as circular disks surrounding the nuclei in the molecule. The overlapping areas are calculated using a pixel counting method (PCM) and, accordingly, we label our model IAM-PCM.

The IAM-PCM has been applied to a number of ion-impact collision problems with target systems
ranging from relatively simple molecules, such as water and methane to complex biomolecules,
such as the RNA and DNA nucleobases [1], and also including atomic and molecular clusters [2].
In this talk, I will explain the model, present a selection of recent results and discuss what can be learned from them.

[1] H. J. Lüdde et al., J Phys. B 52, 195203 (2019); Phys. Rev. A 101, 062709 (2020); Atoms 8, 59 (2020).

[2] H. J. Lüdde et al., Eur. Phys. J. B 91, 99 (2018).

Speaker: Prof. Tom Kirchner (York University)

36 (I) Many-body QED with atoms and photons

An exciting frontier in quantum information science is the creation and manipulation of quantum systems that are built and controlled quanta by quanta. In this context, there is active research worldwide to achieve strong and coherent coupling between light and matter as the building block of complex quantum systems. Despite the range of physical behaviours accessible by these QED systems, the low-energy description is often masked by small fluctuations around the mean fields. In contrast, we describe our theory/experimental program towards novel forms of light-matter quantum systems, where highly correlated Rydberg material is strongly coupled to cavity fields. We call this new domain of strong coupling quantum optics, "many-body quantum electrodynamics." I describe our laboratory efforts towards the exploration of new physics for light-matter interaction, where locally gauged quantum materials are entirely driven by quantum optical fluctuation. Genuinely surprising phenomena may arise from the universal features of non-perturbative physics of many-body QED.

Speaker: Prof. Kyung Choi (University of Waterloo)

37 Light-matter Interaction in Plasmonic Nanohybrids

The study of plasmonics has the potential to reshape the physics of light-matter interactions in metallic nanohybrids and their applications to nanotechnology. Metallic nanohybrids are mode metallic nanoparticles and quantum emitters such as quantum dots. Recently, there is a considerable interest to study the light-matter interaction in the nanoscale size plasmonic nanohybrids. When an external light falls on the QEs, electrons in the QEs get excited from the ground state to the excited states and electron-hole pairs are created in the QEs. Similarly, when the external light (photons) falls on the MNPs it modifies the plasmonic properties of these particles. We know that there are free electrons on the surface of the MNPs. These free electrons oscillate as the charged waves on the surface. The quantized particles of the charged wave are called plasmons. When external light photons fall on the surface of the MNPs, there is an interaction between the photons and plasmons. This interaction produces new types of quantized quasi-particles called the surface plasmon polaritons (SPPs) It interesting to note that exciton energies and SPP energies can be modified by manipulating the size and shape of the QEs. It is also found that exciton and SPP energies can also be modified by applying an external field such as external control lasers, external stress-strain fields, and magnetic fields. Here we study the light-matter interaction in plasmonic nanohybrids made of an ensemble of metallic nanoparticles and quantum emitters. The study of linear and nonlinear plasmonics has the potential to reshape the physics of light-matter interactions and their applications to nanotechnology and nanomedicine. Further, we include the effect of the dipole-dipole interaction (DDI) on the light-matter interaction in plasmonic nanohybrids. We found that the SPP field also induces dipoles in QEs and MNPs and they interact with each other via that the anomalous dipole-dipole interaction. It is shown that the anomalous DDI is many times stronger than the classical DDI. The nonlinear plasmonics such as two-photon spectroscopy and Kerr nonlinearity is also explored. Finally, we have examined that these nanohybrids can be used to fabricate the nanosensors and nano switches for the applications of nanotechnology and nanomedicine.

Speaker: Dr Mahi Singh (Western)

38 (G*) Two-photon decay rates in heliumlike ions: finite nuclear mass effects$^*$

Spontaneous two-photon decay rates for the $1s2s\;^1S_0$ -- $1s^2\;^1S_0$ transition in helium and its isoelectronic sequence up to $Z$ = 10 are calculated, including the effects of finite nuclear mass. We use correlated variational wave functions in Hylleraas coordinates and pseudostate summations for intermediate states. The accuracy of previous work is improved by several orders of magnitude. Length and velocity gauge calculations agree to eight or more figures, demonstrating that the theoretical formulation correctly takes into account the three effects of (1) mass scaling, (2) mass polarization, and (3) radiation due to motion of the nucleus in the center-of-mass frame [1].

Algebraic relationships are derived and tested relating the expansion coefficients in powers of $\mu/M$, where $\mu/M$ is the ratio of the electron reduced mass to the nuclear mass. Astrophysical applications of two-photon transitions to the continuum emission around 400 $\mu$m in planetary nebulae will be briefly discussed.

[1] A. T. Bondy, D. C. Morton, and G.W.F. Drake, Phys.\ Rev.\ A {\bf 102}, 052807 (2020).

$^*$Research supported by NSERC and by SHARCNET.

Speaker: Aaron Bondy

39 Resonant laser ionization spectroscopy to study Rydberg and autoionizing states

Resonant laser ionization spectroscopy uses multiple lasers to step-wise excite atom, therefore is a powerful tool for the study of high energy atomic structures, such as Rydberg states and autoionizing states. At the laser ion source test stand (LIS-stand) in TRIUMF, resonant laser ionization spectroscopy is used to study complex atoms. The spectroscopy results not only provide efficient laser ionization schemes for on-line laser ion source beam delivery of these elements but also the information of Rydberg and autoionizing states. This allows also to refine the energy of the ionization potential of these elements as well as extract information on some electron correlations. An overview of the off-line resonant laser ionization spectroscopy at TRIUMF will be presented.

Speaker: Dr Ruohong Li (TRIUMF)

40 Selective Laser Ablation Ion-Trap Loading of $^{137}\mathrm{Ba}^+$

The $^{137}\mathrm{Ba}^+$ ion is a promising candidate for high-fidelity quantum computing. We generate barium atoms using laser ablation of a $\mathrm{BaCl}_2$ target. The flux of neutral atoms generated by ablation is then ionized near our ion trap-center, giving us trapped ions which we can then use for quantum computing. Laser ablation loading can be used to trap ions more quickly and with less added heat load than other common loading methods. Because of the relatively low abundance of the isotope of interest, a two-step photoionization technique is used, which gives us the ability to selectively load a desired isotope. In this talk, I discuss characterization of the ablation process for our $\mathrm{BaCl}_2$ targets, including typical fluences needed, preparation and lifetimes of ablation spots, and plume temperature estimates. We demonstrate loading of single $^{137}\mathrm{Ba}^+$ ions with high selectivity compared to its 11% natural abundance.

Speaker: Brendan White (University of Waterloo)

13:11 Group discussion

M2-10 Machine learning in HEP & Novel reconstruction techniques I (PPD) / Apprentissage automatique en PHE et nouvelles techniques de reconstruction I (PPD)

Convener: Eric Drechsler (Simon Fraser University (CA))

41 Machine learning techniques for improving water Cherenkov event reconstruction

Hyper-Kamiokande is the next generation water-Cherenkov neutrino experiment, building on the success of its predecessor Super-Kamiokande. To match the increased precision and reduced statistical errors of the new detectors, improvements to event reconstruction and event selection are required to suppress backgrounds and reduce systematic errors. Machine learning has the potential to provide these enhancements to enable the precision measurements that Hyper-Kamiokande is aiming to perform. This talk provides an overview of the areas where machine learning is being explored for water Cherenkov detectors. Results using various network architectures are presented, along with comparisons to traditional methods and discussion of the challenges and future plans for applying machine learning techniques.

Speaker: Nick Prouse (TRIUMF)

CAP_ WatChMaL.pdf

42 (G*) Muon Track Reconstruction for the P-ONE Neutrino Telescope

The neutrino, a fundemental particle, offers the potential to image parts of the universe never before seen and can provide an early warning for cosmic events. With their ability to carry information across the universe unperturbed, neutrinos offer a clear image of the cosmos and can provide insight into its nature with relative ease. Learning from successful neutrino telescopes such as IceCube, the Pacific Ocean Neutrino Explorer (P-ONE) will be built in the Cascadia Basin in the Pacific Ocean, supported by an international collaboration. Located 2660 meters below sea level, P-ONE will consist of 70 strings each equipped with at least 20 sensitive photodetectors and 2 calibrators in an infrastructure provided by Ocean Networks Canada. A key step in the data analysis pipeline is the reconstruction of the path of particles as they pass through the detector. Using simulated data, I will present my work in reconstructing muon tracks in this proposed detector through a likelihood framework.

Speaker: Dilraj Ghuman (Queens University)

dghuman_Muon_Track_Reco_CAP2021.pdf

43 (G*) Machine Learning for Energy Reconstruction at ATLAS

A crucial task of the ATLAS calorimeter is energy measurement of detected particles. In the liquid argon (LAr) calorimeter subdetector of ATLAS, electromagnetically and hadronically interacting particles are detected through LAr ionization. Special electronics convert drifting electrons into a measurable current. The analytical technique presently used to extract energy from the measured current is known as optimal filtering. While this technique is sufficient for past and Run3 pile-up conditions in the LHC, it has been shown to suffer some degradation of performance with the increased luminosity expected at the High Luminosity LHC. This presentation will explore machine learning techniques as a substitute for optimal filtering, examining the strengths, weaknesses, and limitations of both energy reconstruction methods.

Speaker: Lucas Alexander Polson (University of Victoria (CA))

cap_talk.pdf

44 Particle identification at the CERN NA62 experiment using Convolutional Neural Networks

The rare $K^+ \to \pi^+ \nu \bar{\nu}$ decay is an ideal probe for beyond the Standard Model (BSM) physics contributions to the flavor sector. It is heavily suppressed in the SM and its branching ratio is predicted, with remarkable precision for a second order weak process involving hadrons, to be $\left(8.4 \pm 1.0\right) \times 10^{-11}$.

The NA62 experiment at the CERN SPS is designed to study precisely the $K^+ \to \pi^+ \nu \bar{\nu}$ branching ratio. To reach the required signal sensitivity, the overall muon rejection factor must be of the order of $10^{7}$. Therefore, a redundant particle identification (PID) system composed of a Ring Imaging Chernenkov (RICH), a set of three independent calorimeters, and a scintillator-based veto detector is employed.

Machine learning (ML) algorithms were developed to extract PID information directly from the calorimeter hit information, a departure from the previous approach where reconstructed quantities were used. High purity samples of muon, pion and electron single charged track decays were extracted from the NA62 data for the training and validation of the ML methods.

An architecture based on the ResNet-18 network achieved the best $\mu^+$/$\pi^+$ separation with a muon rejection factor of the order of $10^{5}$ while keeping the pion acceptance around 90 %, not including the RICH. The newly developed tool will be incorporated in analysis of the data collected during the 2021 NA62 run.

Speaker: Bob Velghe (TRIUMF (CA))

ml_talk_cap2021.pdf

45 (G*) Parameter estimation of gravitational waves over non-Gaussian transient noise

The Laser Interferometer Gravitational-Wave Observatory (LIGO) is expected to begin its fourth observing run in 2022, with a large projected improvement in detector sensitivity. This sensitivity boost increases the gravitational wave (GW) detection rate, but also increases the likelihood of GW events overlapping with transient, non-Gaussian detector noise, or glitches. This project aims to quantify how GW parameter estimation is affected by simultaneous glitch noise, particularly with regards to salvaging inspiral masses and sky location for electromagnetic follow-up of GW candidates.

Speaker: Yannick Lecoeuche (University of British Columbia)

Parameter estimation of gravitational waves over non-Gaussian transient noise (5).pdf

M2-2 Classical and Quantum Gravity II (DTP) / Gravité classique et quantique II (DPT)

Convener: Sanjeev Seahra

46 Unruh-DeWitt Detector Differentiation of Black Holes and Exotic Compact Objects

We study the response of a static Unruh-DeWitt detector outside an exotic compact object (ECO) with a variety of (partially) reflective boundary conditions in 3+1 dimensions. The horizonless ECO, whose boundary is extremely close to the would-be event horizon, acts as a black hole mimicker. We find that the response rate is notably distinct from the black hole case, even when the ECO boundary is perfectly absorbing. For a (partially) reflective ECO boundary, we find resonance structures in the response rate that depend on the different locations of the ECO boundary and those of the detector. We provide a detailed analysis in connection with the ECO's vacuum mode structure and transfer function.

Speaker: Dr Chen Zhang (University of Toronto and University of Waterloo)

47 Effective Raychaudhuri equation and black hole singularity resolution

We derive Loop Quantum Gravity corrections to the Raychaudhuri equation in the interior of a Schwarzschild black hole and near the classical singularity for several schemes of quantization. We show that the resulting effective equation implies defocusing of geodesics due to the appearance of repulsive terms. This prevents the formation of conjugate points, renders the singularity theorems inapplicable, and leads to the resolution of the singularity for this spacetime.

Speaker: Saeed Rastgoo (York University)

Saeed Rastgoo.mp4

48 Quantum Detection of Inertial Frame Dragging

A relativistic theory of gravity like general relativity produces phenomena differing fundamentally from Newton’s theory. An example, analogous to electromagnetic induction, is gravitomagnetism, or the dragging of inertial frames by mass-energy currents. These effects have recently been confirmed by classical observations. Here we show, for the first time, that they can be observed by a quantum detector. We study the response function of Unruh De-Witt detectors placed in a slowly rotating shell. We show that the response function picks up the presence of rotation even though the spacetime inside the shell is flat and the detector is locally inertial. The detector can distinguish between the static situation when the shell is nonrotating and the stationary case when the shell rotates and the dragging of inertial frames, i.e., gravitomagnetic effects, arise. Moreover, it can do so when the detector is switched on for a finite time interval within which a light signal cannot travel to the shell and back to convey the presence of rotation.

Speaker: Dr David Kubiznak (Perimeter Institute/University of Waterloo)

49 Falcon all-sky searches for continuous waves: results, outliers and artifacts.

Continuous waves from non-axisymmetric neutron stars are orders of magnitude weaker than transient events from black hole and neutron star collisions. Unlike a transient event, a continuous wave source will allow repeated observations. We will present results of all-sky searches for neutron stars and other sources carried out by the Falcon pipeline and discuss interplay between detector artifacts and outliers produced by our searches.

Speaker: Vladimir Dergachev (AEI Hannover)

50 (G*) Prospects for Reconstructing the Gravitational Wave Signal from Core-Collapse Supernovae in the LIGO-Virgo Advanced Detector Era

Our current understanding of the core-collapse supernova explosion mechanism is incomplete, with multiple viable models for how the initial shock wave might be energized enough to lead to a successful explosion. Detection of a gravitational wave (GW) signal emitted in the initial few seconds after core-collapse would provide unique and crucial insight into this process. With the Advanced LIGO and Advanced Virgo gravitational wave detectors expected to soon approach their design sensitivity, we could potentially detect this GW emission from most core-collapse supernovae within our galaxy. But once identified, how well can we recover the signal from these detectors? Here we use the BayesWave algorithm to maximize our ability to accurately recover GW signals from core-collapse supernovae. Using the expected design sensitivity noise curves of the advanced global detector network, we inject and recover supernova waveforms modeled with different explosion mechanisms into simulated noise, tuning the algorithm to extract as much of the signal as possible. We report the preliminary results of this work, including how the reconstruction is affected by the model and what we can hope to learn from the next galactic supernova.

Speaker: Mr Nayyer Raza

51 (G*) Asymptotically Anti-de Sitter Gravitational Solitons

In this talk, I will consider the stability of asymptotically anti-de Sitter gravitational solitons. These are globally stationary, asymptotically (globally) AdS spacetimes with positive energy but without horizons. I will introduce my ongoing project investigating solutions of the linear wave equation in this class of backgrounds. I will provide analytical expressions for the behavior of the scalar field near the soliton bubble and at spatial infinity. The special BPS (supersymmetric) case will then be examined as an example of a solution where stable trapping occurs. This project is joint work with Dr. Hari K. Kunduri and Dr. Robie A. Hennigar.

Speaker: Turkuler Durgut (Memorial University of Newfoundland)

52 (G*) Prospects for measuring off-axis spins of binary black hole sources with A+/AdV+

The mass and spin properties of black hole binaries inferred from their gravitational-wave signatures reveal important clues about how these binaries form. For instance, stellar-mass black holes that evolved together from the same binary star will have spins that are preferentially aligned with their orbital angular momentum. Alternatively, if the black holes formed separately from each other and later became gravitationally bound, then there is no such preference for having aligned spins. Furthermore, it is known that the presence of misaligned spins induces a general relativistic precession of the orbital plane, imprinting unique structure onto the gravitational-wave signal. The fidelity with which gravitational-wave detectors can measure off-axis spins, or equivalently, precession, will therefore have important implications for the use of gravitational waves to study binary black hole formation channels. I will summarize a new study that examines how well the A+/AdV+ detector network will measure off-axis spin components, and report preliminary results comparing spin resolution between the fourth and fifth LIGO-Virgo observing runs using simulated detector noise and multiple sets of simulated signals distributed over the mass-spin parameter space.

Speaker: Alan Knee (University of British Columbia)

53 Hot qubits on the horizon

Perturbation theory for gravitating quantum systems tends to fail at very late times (a type of perturbative breakdown known as secular growth). We argue that gravity is best treated as a medium/environment in such situations, where reliable late-time predictions can be made using tools borrowed from quantum optics. To show how this works, we study the explicit example of a qubit hovering just outside the event horizon of a Schwarzschild black hole (coupled to a real scalar field) and reliably extract the late-time behaviour for the qubit state. At very late times, the so-called Unruh-DeWitt detector is shown to asymptote to a thermal state at the Hawking temperature.

Speaker: Gregory Kaplanek

13:09 Questions/Answers and Discussion Period

M2-3 Physics and Computing I (DPE) / Physique et calcul I (DEP)

Convener: Daria Ahrensmeier (Simon Fraser University)

54 (I) Training Physicists in Software Development: The Case of a Machine Learning Course

Many research efforts in physics rely on design, implementation, and execution of numerical studies. These studies are often the guiding torch of further experimental investigations, but they are rarely carried out with software development principles in mind. As a result, efficiency and verification measures are often not incorporated in the R&D process and this impairs the quality and confidence of technical reports generated based on them. While software development workflow is second nature to those trained in computer science and engineering disciplines, systematic training on it has not been a conventional component of physics programs.

In this talk, I share my experience in designing and teaching a new course on applications of machine learning in physical sciences. I introduce the course and its learning objectives, format, and outline. I then discuss my findings on the mechanisms that can be placed in course projects to better equip young researchers with team-oriented and effective software development practices. I will finally review some of the student feedback from the first offering of this course in 2020 and the resulting improvements I made to the 2021 offering.

Speaker: Pooya Ronagh (University of Waterloo)

13:15 Discussion about teaching coding in physics programs

M2-4 DPMB 101 - Part 2 (DPMB) / DPMB 101 - Partie 2 (DPMB)

Convener: Melanie Campbell (University of Waterloo)

55 Neutrons in Medicine

Neutrons were applied in the study of medicine very quickly. A mere six years after discovery, neutrons were first used for cancer therapy. Interest in neutron radiotherapy waxed and waned over the following decades. The last use of neutron-only therapy, treating cancer of the salivary glands, ceased several years ago.
There is, however, still interest in boron neutron capture therapy (BNCT) for certain brain tumours that have no good current treatment options. Boron neutron capture synovectomy (BNCS) for horribly disabling arthritis has also been explored. The idea behind BNCT is that if tumours can be loaded with boron, then reactions of that boron with neutrons result in heavy charged particles recoiling in the cell. This would be highly effective in killing cells. Ideally, there can be a large difference in the radiation dose delivered to healthy tissue and tumour because only the tumour would contain boron. Healthy tissue would be spared. However, the chemistry to be able to load enough boron into the tumour to make the treatment successful has been a challenge.
Of course, neutron activation has created a variety of radioisotopes that are used for both imaging and treatment of disease. 99mTc is still commonly used in imaging, and for decades was produced in Chalk River, Canada. 125I is used to treat prostate cancers and at any point in time a large percentage of the world’s supply of this agent is produced at McMaster University in Hamilton, Ontario.
Finally, in vivo neutron activation analysis (IVNAA) has been used since the 1960s to study levels of both essential and toxic elements in the body. IVNAA helped physicians understand the challenges of parental neutron therapy for cancer patients and was the first technique to show bone loss in anorexia nervosa patients. IVNAA studies also led to legislative changes in air levels of toxins such as cadmium. Canada is still at the forefront of this area of research: studies measuring people have taken place over the last decade at McMaster. The first in vivo studies of fluorine exposure showed that exposure in Ontario is low, and that the single biggest factor in exposure is tea drinking. Recent studies have been made of aluminum levels in Northern Ontario miners exposed to McIntyre power. Early data shows inhaling powder resulted in uptake of aluminum into the body and the aluminum has persisted in the bones of miners for years or decades.

Speaker: Fiona McNeill (McMaster University)

M2-5 Superheavies and Instrumentation (DNP) / Superlourds et Instrumentation (DPN)

Convener: Gordon Ball (TRIUMF)

56 (I) The Power of Mass-Number Identifications for Heavy Element Experiments

Isotopes of Heavy and Super Heavy nuclei are typically produced in fusion-evaporation reactions. In these types of reactions neighboring isotopes are often produced simultaneously. This makes it incredibly difficult to assign experimentally observed decay properties to specific isotopes. Presently, such assignments are heavily reliant on the use of excitation functions, cross-bombardment reactions, and the assumption that charged-particle emission does not occur. However, without direct-experimental confirmation that a specific isotope or mixture of isotopes had been produced for a given reaction, it is possible that misassignments have been made. At Lawrence Berkeley National Laboratory, the recent addition of FIONA (For the Identification of Nuclide A) to the Berkeley Gas-filled separator now allows for a produced isotope or mixture of isotopes to be directly identified by their mass numbers. Recent measurements were performed on the lightest mendelevium isotopes (A =244-247) to confirm that previously-reported decay properties had been correctly assigned to the appropriate isotope. These studies included the unambiguous identification of the new isotope 244Md. These and other recent results will be discussed. These results highlight the necessity of utilizing mass-number identifications for isotopes produced in fusion-evaporation reactions.

Speaker: Jennifer Pore (Lawrence Berkeley National Laboratory)

57 β-delayed neutron emission studies – How storage rings can provide a complimentary measurement technique

β-delayed neutron emission probabilities of exotic nuclei, along with nuclear masses and β-decay half-lives, are of key importance in the stellar nucleosynthesis of heavy elements via the rapid neutron-capture process (r-process). β-delayed neutron emission influences the final r-process abundance curve through the redistribution of material as neutron-rich nuclei decay towards stability, and by acting as a source of late-time neutrons which can be recaptured during the freeze-out phase. Obtaining a more complete description of this process is vital to developing a deeper understanding observed elemental abundances.
New generations of radioactive beam facilities, with state-of-the-art detector systems, will reach previously inaccessible neutron-rich nuclei for which delayed neutron-emission becomes the dominant decay process. In parallel, cutting edge nuclear models are constantly advancing and the need for accurate nuclear data only grows.
Traditional measurement techniques have relied on the correlated detection of the parent ion and its subsequent decay products, including the neutron. Due to their neutral charge, neutrons are intrinsically difficult to measure. Low detection efficiency imposes a severe loss of statistics in all experiments, thus requiring either higher beam rates, larger detectors or longer beam times. Each of these solutions presents difficulties of their own. However, storage rings can provide a complimentary technique that allows the measurement of key nuclear properties without requiring the detection of the emitted neutron. The ILIMA program at FAIR will use heavy ion detectors, such as the CsISiPHOS detector[1], installed in the ESR and CR to achieve this goal, among others.
Here, we investigate this technique and demonstrate how heavy-ion detection methods can provide complimentary means to study β-delayed neutron emission.
[1] M. A. Najafi et al., NIMA 836, 1-6, (2016)

Speaker: Christopher Griffin (TRIUMF)

58 Resonant Ionization Laser Ion Source at TRIUMF

Resonant laser ionization of atoms provides an efficient and selective means for ion source operation. It uses stepwise resonant excitation of an atom's valence electron into energetically Rydberg states or auto-ionizing levels. A resonant ionization laser ion source RILIS is particularly suited to provide beams of rare isotopes at radioactive isotope facilities like ISAC at TRIUMF.
The operational principle, current developments, application and science with TRIUMF's RILIS will be discussed.

Speaker: Dr Jens Lassen (TRIUMF)

M2-6 Spectroscopy III (DNP) / Spectroscopie III (DPN)

Convener: Kris Starosta

59 (G*) The Spin Flip Pulse in the TUCAN EDM Experiment

The TRIUMF Ultra-Cold Advanced Neutron (TUCAN) collaboration is currently building a next-generation ultra-cold neutron source, with a neutron electric dipole moment (nEDM) measurement as the flagship experiment. The nEDM measurement is based on the Ramsey method of separated oscillating fields to measure the precession frequency of the neutron in combined magnetic and electric fields. The Ramsey method involves the pulsed application of an oscillating magnetic field to produce a π/2 flip of the neutron spins. This talk presents studies of the magnetic field pulse in the nEDM experiment using finite element simulations, with a focus on the suppression and inhomogeneity of the field caused by eddy currents. Further Monte Carlo simulations of the neutron spins are used to optimize the timing of the pulse and simulate the expected behaviour of the neutrons in the full Ramsey measurement.

Speaker: Sean Vanbergen (TRIUMF)

60 (G*) Simulating DAEMON: A new complementary neutron detector for the GRIFFIN decay station

The study of neutron rich nuclei far from the valley of stability has become an increasingly important field of research within nuclear physics. One of the decay mechanisms that opens when the decay Q value becomes sufficiently large is that of beta-delayed neutron emission. This decay mode is important when studying the astrophysical r-process as it can have a direct effect on theoretical solar abundance calculations. In addition, by extracting data on the excited states of the nucleus via the neutron kinetic energies, structural information of nuclei can be obtained through beta-delayed neutron spectroscopy. The utilization of large-scale neutron detector arrays in future experiments is therefore imperative in order to study these beta-delayed neutron emitters.

The deuterated scintillator array, DESCANT, was designed to be coupled with the large-scale gamma-spectrometers GRIFFIN and TIGRESS at the TRIUMF ISAC-I and ISAC-II facilities, respectively. However, DESCANT was originally intended to be a neutron-tagging array for fusion evaporation reactions, and a precise measurement of the neutron energy was not considered a priority over neutron detection efficiency. This limitation could be overcome through the use of thin plastic scintillators, possibly positioned in front of the DESCANT detectors, allowing for a more in-depth analysis of beta delayed neutron emitters at the GRIFFIN decay station. Plastic scintillators are ideal for this enhancement due to their timing properties, customizability, and overall cost effectiveness. The energy of the neutrons can then be determined via the time-of-flight technique, improving the current precision of the neutron energy with the existing setup significantly. To investigate the viability of this augmentation, GEANT4 will be used to simulate and optimize the experimental design, the progress of which will be discussed.

Speaker: Harris Bidaman (University of Guelph)

61 Experimental $\beta$-decay and $\beta$-delayed neutron branching ratios for Se and Br isotopes at N$\approx$60

The understanding of abundances of elements heavier than iron originating from the $r$-process nucleosynthesis in neutron star mergers and core collapse supernovae requires experimental information from the involved neutron-rich nuclei from close to the neutron-dripline to the line of stability. The $\beta$-delayed neutron emission plays important roles in this process shifting the decay chain to lower masses and increasing the neutron density in the environment. The $\beta$-delayed neutron branching ratio and the respective $\beta$-decay half-life are also important for improving theoretical models, and to achieve more realistic models of the decay heat in a fission reactor.

In order to provide new experimental data of half-lives and $\beta$-delayed neutron branching ratios, since 2016 the BRIKEN campaign based at the RIB facility of RIKEN, Japan, has allowed the measurement of hundreds of nuclei with unknown or incomplete decay information. The use of a fragmentation facility such as RIKEN allows to reach the most neutron-rich exotic nuclei that were not accessible before. The Advanced Implantation Detector Array (AIDA) based on silicon DSSDs was used to register implants and $\beta$-decays with high position resolution. Surrounding AIDA, a 4$\pi$ array of $^{3}$He neutron counters embedded in a polyethylene moderator matrix, and two HPGe clovers inserted in this matrix registered the neutrons and $\gamma$-ray emitted after nuclei decays in AIDA.

This contribution will report on the results of decay studies around the doubly-magic $^{78}$Ni region. The focus of our data analysis are deformed neutron-rich Se and Br isotopes around N=60.

Speaker: Roger Caballero-Folch (TRIUMF)

62 (G*) Integrated photon-sensor tests for nEXO

nEXO is a next generation time projection chamber searching for neutrinoless double-beta decay in 5 tonnes of liquid xenon enriched in the isotope Xe-136. Interactions within LXe produce anti-correlated scintillation and ionization signals, which will be used to reconstruct the energy, position, and multiplicity of each event. Silicon photomultipliers (SiPMs) have been identified as the devices to detect the vacuum ultraviolet scintillation light for nEXO. SiPMs are silicon devices ~ 1 cm^2 with single photon sensitivity, and have a quantum efficiency of ~ 15% at 175 nm. A baseline characterization of the many SiPMs that will be distributed among the nEXO collaboration is necessary: the detector will employ tiles of SiPMs, organized into staves, yielding a photo-coverage area of ~ 4.5 m^2. The development of integrated SiPM tiles is advanced within the collaboration, requiring precise testing in conditions similar to their deployment. I will present on the status and plans for SiPM mass testing using an environmental test stand capable of measuring ~ 150 cm^2 of SiPMs at 168K with quick turnaround between tile deployment, facilitating both a high-rate of baseline SiPM characterization, and precision testing of integrated tiles.

Speaker: Mr Lucas Darroch (Graduate Student)

M2-7 Accelerator Applications (DAPI) / Applications d'accélérateurs (DPAI)

Convener: Mark Boland (Canadian Light Source)

63 (I) Secondary Particle Production for Fundamental Science at TRIUMF

For 50 years, TRIUMF has stood at the frontier of scientific understanding as Canada’s particle accelerator centre. Driven by two made-in-Canada cutting edge accelerators - the world’s largest cyclotron, and our new high-power superconducting linear accelerator - we continue to ask the big questions about the origins of the universe and everything in it.

With over five decades of experience in the production of accelerator-based secondary particles for science, TRIUMF also ensures that Canada remains on the leading edge of supplying radioisotopes, neutrons, photons, and muons enabling fundamental science in the fields of nuclear, particle and astrophysics, as well as solid state and medical sciences and applications.

ISAC-TRIUMF is the only ISOL facility worldwide that is routinely producing radioisotope beams (RIB) from secondary particle production targets under irradiation in the high-power regime in excess of 10 kW. TRIUMF’s current flagship project ARIEL, Advanced Rare IsotopE Laboratory, will add two new target stations providing isotopes to the existing experimental stations in ISAC I and ISAC II at keV and MeV energies, respectively. In addition to the operating 500 MeV, 50 kW proton driver from TRIUMF’s cyclotron, ARIEL will make use of a 30 MeV, 100 kW electron beam from a newly installed superconducting linear accelerator. Together with additional 200 m of RIB beamlines within the radioisotope distribution complex, this will put TRIUMF in the unprecedented capability of delivering three RIBs to different experiments, while producing radioisotopes for medical applications simultaneously – enhancing the scientific output of the laboratory significantly.

Speaker: Alexander Gottberg (TRIUMF (CA))

64 (I) Medical isotope production and research with IAMI at TRIUMF

From its inception, the Life Sciences division at TRIUMF has leveraged the laboratory’s extensive particle accelerator expertise and infrastructure to develop novel technologies that help understand life at the molecular level. This includes novel technologies and research in particle beam therapy and biobetaNMR, but also prominently the production of short-lived (half-life <2 hr) positron emitting isotopes like F-18, C-11 and a number of emerging isotopes, including, but not limited to Ga-68, Zr-89, Cu-64 and cyclotron-produced Tc-99m. More recent efforts have focused on the development of various therapeutic isotopes: Alpha-emitting isotopes like Ac-225 for targeted alpha therapy (TAT), or Hg-197 for targeted radionuclide therapy (TRT) with an Auger emitter.

In order to better enable a new generation of scientists and experiments with a wider array of isotopes, TRIUMF is currently construction the Institute for Advanced Medical Isotopes (IAMI). IAMI will be commissioned and ready for operation in early 2023. This facility will house a dedicated TR24 (24 MeV) cyclotron, and several state-of-the-art laboratories for the development of radiopharmaceuticals from all accelerators on site. This presentation will provide an overview of the facility and the research that is planned to take place at IAMI. It will significantly increase British Columbia’s and Canada’s capacity for the sustainable and reliable production and distribution of medical isotopes currently critical for Canadian health research and clinical use, and ultimately allow Canada to maintain leadership in the realm of isotope production and application across the life sciences.

Speaker: Cornelia Hoehr (TRIUMF)

65 Ultrafast Electron Scattering for Materials Research

In this talk I will describe how combining ultrafast lasers and electron microscopes in novel ways makes it possible to directly ‘watch’ the time-evolving structure of condensed matter on the fastest timescales open to atomic motion. By combining such measurements with complementary (and more conventional) spectroscopic probes one can develop structure-property relationships for materials under even very far from equilibrium conditions and explore how light can be used to control the properties of materials.

I will give several examples of the remarkable new kinds of information that can be gleaned from such studies and describe how these opportunities emerge from the unique capabilities of the current generation of ultrafast electron microscopy instruments. For example, in diffraction mode it is possible to identify and separate lattice structural changes from valence charge density redistribution in materials on the ultrafast timescale and to identify novel photoinduced phases that have no equilibrium analogs. It is also possible to directly probe the strength of the coupling between electrons and phonons in materials across the entire Brillouin zone and to probe nonequilibrium phonon dynamics (or relaxation) in exquisite detail.

Speaker: Prof. Bradley Siwick (McGill University)

66 (G*) Characterization of the Isobar Separator for Anions for Accelerator Mass Spectrometry measurements

Accelerator Mass Spectrometry (AMS) provides high sensitivity measurements (typically at or below 1 part in $10^{12}$) for rare, long-lived radioisotopes when isobars (other elements with the same atomic weight as the isotope of interest) can be eliminated. In AMS laboratories, established techniques are used for the removal of the interfering isobars of some light isotopes. However, for smaller, lower-energy AMS systems separating the abundant isobars of many isotopes, such as the sulfur-36 in measurements of chlorine-36, remains a challenge. For some heavy isotopes, such as strontium-90 and cesium-135,137, even high energy accelerators are unable to separate the interfering isobars.

The Isobar Separator for Anions (ISA), which has been integrated into a second injection line of the 3 MeV tandem accelerator system at the A. E. Lalonde AMS Laboratory, will provide a universal way to measure rare radioisotopes without the interference of abundant isobars. The ISA is a radiofrequency quadrupole (RFQ) reaction cell system, including a DC deceleration region, a combined cooling and reaction cell, and a DC acceleration region. The deceleration region accepts a mass analyzed beam from the ion source (with energy 20-35 keV) and reduces the energy to a level that the reaction cell can accept. RFQ segments along the length of the cell create a potential well which limits the divergence of the traversing ions. DC rod offset voltages on these RFQ segments maintain a controlled ion velocity through the cell. The cell is filled with an inert cooling gas that has been experimentally selected to provide the lowest ion energy and the highest transmission, and with nitrogen dioxide, a reaction gas chosen to preferentially react with the interfering isobar. In the case of chlorine-36, the sulfur-36 isobar has been shown to be reduced by over $10^{6}$. Preliminary characterization of the ISA and its incoming and outgoing ion beams will be presented.

Speaker: Erin L. Flannigan (University of Ottawa)

67 (G*) Negative Ion Source Development for Accelerator Mass Spectrometry

Negative Ion Source Development for Accelerator Mass Spectrometry
CJ Tiessen, WE Kieser, and XL Zhao
Accelerator mass spectrometry (AMS) is a highly sensitive technique used for the analysis of long-lived radioisotopes. While carbon-14 dating is the most well known application, AMS can be used to measure other isotopes such as beryllium-10, aluminum-26, iodine-129, and uranium-236 which are useful in geology, archeology, environmental tracer and chronology studies, nuclear waste monitoring, and nuclear forensics. The technique uses a combination of electrostatic analyzers, mass-separation magnets, electrostatic lenses, as well as a tandem accelerator. In the accelerator, an electron stripping gas canal is used to convert incoming negative ions to positive ions while simultaneously disintegrating molecular isobars. Ions from the samples are injected into the accelerator using a cesium sputter negative-ion source. The focus of this work is to model the electrodynamics within the ion source, including the effects of the more intense positive cesium ion beam and the sputtered sample negative-ion beam. Simulations using Integrated Engineering Software’s Lorentz 2E ion optics software will guide the design of a new ion source with the goal of increasing the emitted sample ion current while also improving the emittance of this beam. Following a short overview of the AMS system, details of the ion source, including the mutual space-charge interaction of the two beams, will be presented.

Speaker: Collin Tiessen (Andre E. Lalonde Accelerator Mass Spectrometry Lab)

68 Development of an isotopic biodosimeter to assess radon gas exposure

The radioactive decay of radon in the home is the leading cause of lung cancer in non-smoking Canadians (REF 1,2). Radon produced by the decay of uranium and thorium minerals entering the home may accumulate in concentrations that exceed the national maximum guideline for indoor air of 200 Bq/m³. There is a critical need to develop a practical tool to assess an individual’s exposure to radon and eventually one’s lung cancer risk. An important opportunity is to use keratinizing tissues in the body (hair, nails) as archives of radon exposure. The lead is sequestered from the environment in toenails, including the relatively long-lived (22 yrs) ²¹⁰Pb isotope, which comes from ²²²Rn decay.

In this project, we are using isotope ratio mass spectrometry to quantify the amount of ²¹⁰Pb in a known amount of sample. This method has the advantage of providing a direct and relatively rapid count of the numbers of ²¹⁰Pb atoms. The challenge is that the actual number of ²¹⁰Pb atoms is very low and achieving reliable results requires high sensitivity methods specifically designed for the extraction of lead from the biological matrix. In the first stages of the project, we are using isotope dilution methods coupled with multiple collector inductively coupled plasma mass spectrometry (MC-ICPMS). Initial results demonstrate that femtogram quantities of lead can be measured.

The next stage of the project involves the design and construction of a laser ablation ion source coupled to the Multiple Reflection Time of Flight (MR-TOF MS) at the TITAN instrument at TRIUMF. The laser ion source in combination with the MR-TOF MS offers high sensitivity and the ability to separate isobars of ²¹⁰Pb. The laser beam, after passing through optical telescope system and polarizers for pulse energy modulation, is focused on a small point on the sample surface located in a high-vacuum chamber. Thus, the laser source enables spatial mapping of ²¹⁰Pb isotopic composition and allow one to map the accumulation of the radon daughter products over the growth of tissue. Ultimately, an accurate measurement of the number of accumulated atoms in an individual’s biological tissue may be a personalized biodosimeter for radon.

1. Gogna, Priyanka, et al. "Estimates of the current and future burden of lung cancer attributable to residential radon exposure in Canada." Preventive medicine 122 (2019): 100-108
2. Stanley, F. K., Zarezadeh, S., Dumais, C. D., Dumais, K., MacQueen, R., Clement, F., & Goodarzi, A. A. (2017). Comprehensive survey of household radon gas levels and risk factors in southern Alberta. CMAJ open, 5(1), E255–E264. https://doi.org/10.9778/cmajo.20160142
3. Stanley, Fintan KT, et al. "Radon exposure is rising steadily within the modern North American residential environment and is increasingly uniform across seasons." Scientific reports 9.1 (2019): 1-17.

Speaker: Mr Behnam Ashrafkhani (University of Calgary)

M2-8 Contributed Talks I (DCMMP) / Conférences soumises I (DPMCM)

Convener: Michel Gingras

69 When does entropy promote local organization?

Crowded soft-matter and biological systems organize locally into preferred motifs. Locally-organized motifs in soft systems can, paradoxically, arise from a drive to maximize overall system entropy. Entropy-driven local order has been directly confirmed in model, synthetic colloidal systems, however similar patterns of organization occur in crowded biological systems ranging from the contents of a cell to collections of cells. In biological settings, and in soft matter more broadly, it is unclear whether entropy generically promotes or inhibits local organization. Resolving this is difficult because entropic effects are intrinsically collective, complicating efforts to isolate them. Here, we employ minimal models that artificially restrict system entropy to show that entropy drives systems toward local organization, even when the model system entropy is below reasonable physical bounds. By establishing this bound, our results suggest that entropy generically promotes local organization in crowded soft and biological systems of rigid objects.

Speaker: Prof. Greg van Anders (Queen's University)

12:48 Questions & answers

70 Magneto-Thermal Conductivity Oscillations in Spin-Orbit-Coupled Nodal Superconductors

The symmetries of unconventional superconductors may be classified by the locations of their gap nodes. Recently, the role of spin-orbit coupling (SOC) has become important, as sufficiently strong SOC generates novel mixed-parity superconductivity. In this talk, I show that the nodal structure of unconventional superconductors may be determined by angle-dependent magneto-thermal conductivity measurements, provided the SOC is larger than the quasiparticle scattering rate. This effect is complementary to vortex-induced magneto-thermal oscillations identified previously, and is dominant in strongly anisotropic materials. As an application, I present results for the magneto-thermal conductivity of the "Rashba bilayer" YBa$_2$Cu$_3$O$_{6.5}$, which possesses a so-called "hidden spin-orbit coupling." We find that the SOC endows $\kappa_{xx}/T$ with a characteristic field-angle dependence that should be easily observed experimentally.

Speaker: Bill Atkinson (Trent University)

12:53 Questions & answers

71 Lanczos recursion on a quantum computer for the Green's function and ground state

A state-preserving quantum counting algorithm is used to obtain coefficients of a Lanczos recursion from a single ground state wavefunction on the quantum computer. This is used to compute the continued fraction representation of an interacting Green's function for use in condensed matter, particle physics, and other areas. The wavefunction does not need to be re-prepared at each iteration. The quantum algorithm represents an exponential reduction in memory over known classical methods. An extension of the method to determining the ground state is also discussed.

Speaker: Dr Thomas Baker (University of York)

12:58 Questions & answers

72 Anomalously fast cooling and heating in a colloidal system

Since the temperature of an object that cools decreases as it relaxes to thermal equilibrium, naively a hot object should take longer to cool than a warm one. Yet, some 2300 years ago, Aristotle observed that “to cool hot water quickly, begin by putting it in the sun.” In the 1960s, this counterintuitive phenomenon was rediscovered as the statement that “hot water can freeze faster than cold water” and has become known as the “Mpemba effect.” While many specific mechanisms have been proposed, no general consensus exists as to the underlying cause. Here we demonstrate the Mpemba effect in a controlled setting, the thermal quench of a colloidal system immersed in water, which serves as a heat bath. Our results are reproducible and agree quantitatively with calculations based on a recently proposed theoretical framework. By carefully choosing parameters, we observe cooling that is exponentially faster than that observed using typical parameters, in accord with the recently predicted strong Mpemba effect. We then show that similar phenomena can be observed when heating—these are the first observations of an inverse Mpemba effect. In this case, a cold system placed in a hot bath will reach equilibrium more quickly than a warm one placed in identical conditions. Our experiments give a physical picture of the generic conditions needed to accelerate relaxation to thermal equilibrium and support the idea that the Mpemba effect is not simply a scientific curiosity concerning how water freezes into ice—one of the many anomalous features of water—but rather the prototype for a wide range of anomalous relaxation phenomena that may have significant technological application.

Speaker: John Bechhoefer (Simon Fraser University)

13:03 Questions & answers

73 Constructing two-dimensional molecular networks on metal surfaces: a scanning tunneling microscopy study

Molecular self-assembly is one of the most important bottom-up fabrication strategies to produce two-dimensional networks at solid surfaces. The formation of complex two-dimensional (2-d) surface structures at the molecular scale relies on the self-assembly of functional organic molecules on solid substrates. Driven by an intricate equilibrium between molecule–molecule and molecule–substrate interactions, a number of different non-covalent molecular interactions can be used to generate stable 2-d geometric structures. For example, in the case of halogen-terminated monomers halogen bonding.

In addition to being the building blocks of self-assembled networks, halogen-terminated molecules can be activated on surfaces to form 2-d π-conjugated polymers. Ideally the process follows a two-step procedure whereby the carbon halogen bonds break to form organometallic structures and subsequent covalent C-C coupling. These organic analogues of graphene, the only natural 2-d conjugated polymer, represent a promising new class of high-performance functional nanomaterials.

In this work we study the adsorption of a tribromo-substituted heterotriangulene molecule (TBTANGO) the Au(111) and Ag(111) surfaces using room temperature scanning tunneling microscopy in ultrahigh vacuum. The resultant two-dimensional molecular networks range from: self-assembled networks held together by non-covalent Br⋅⋅⋅Br halogen bonds on Au(111); organometallic networks with C-Ag-C linkage on Ag(111); and a π-conjugated polymer when the TBTANGO monomers are deposited directly onto a hot Au(111) surface.

Speaker: Prof. Mark Gallagher (Lakehead University)

13:08 Questions & answers

74 Sea spray freezing measurements with MRI and portable NMR

Seawater spray and precipitation are two main sources of icing and ice accumulation in cold ocean regions, presenting a major challenge for shipping and operating maritime equipment [1].
There is a limited number of analytical techniques to study seawater spray ice formation. MRI is known for its non-invasive capabilities in measurements of a solid ice [2,3]. In this work, we investigated the potential of MRI as an analytical measurement technique for studies of the seawater spray ice.
The signal detected with MRI/NMR comes from pockets of brine in the forming ice, and the unfrozen water, with the 1H NMR signal from the brine decreasing as the temperature drops and the brine freezes further. 3D MRI showed different freezing patterns and temperature gradients depending on the initial freezing temperature and the surface geometry. T1-T2 maps indicated strong changes in relaxation parameters as the freezing progresses, indicating changing environment for the brine in the growing ice [4]. In a separate freezing series using Na NMR, the amount of sodium in the brine remained almost unchanged until the brine reached the eutectic temperature, and the sodium precipitation accelerated.
These measurements were done on an MRI scanner, with the freezing setup designed to fit a 4 cm i.d. RF probe inside a 2.4 T superconducting magnet. To explore a possibility of using NMR for freezing studies in a more open environment, we also used a portable, unilateral NMR device to characterize sea spray freezing on a cold surface. The device consisted of a flat 3-magnet array [5] with the sensitive volume (approx.2 mm x 15 x 15 mm) at 1 cm away from the magnet surface. 1D-resolved 1H NMR measurements provided information on the brine concentration, T2 and diffusion at a range of temperatures.
The results provide information on the changing environment in brine in freezing sea sprays, with a potential for NMR studies both in the lab and in the field.

[1]A.R. Dehghani-Sanij, S.R. Dehghani, G.F. Naterer, Y.S. Muzychka, Ocean Eng. 143 (2017) 1–23.
[2]M.W. Hunter, R. Dykstra, M.H. Lim, T.G. Haskell, P.T. Callaghan, Appl. Magn. Reson. 36 (2009) 1–8.
[3]J.R. Brown, T.I. Brox, S.J. Vogt, J.D. Seymour, M.L. Skidmore, S.L. Codd, J. Magn. Reson. 225 (2012) 17–24.
[4] G.Wilbur, B.MacMillan, K.M.Bade, I.Mastikhin, J. Magn. Reson. 310 (2020) 106647.
[5] J.C.Garcia-Naranjo, I.Mastikhin, B.J.Colpitts, B.J.Balcom, J. Magn.Reson. 207 (2010) 337-344

Speaker: Dr Igor Mastikhin (University of New Brunswick)

13:13 Questions & answers

75 Untangling time scales in entanglement growth in the disordered Fermi Hubbard model

Many-body localization impedes the spread of information encoded in initial conditions, providing a intriguing counter point to continuing efforts to understand the approach of quantum systems to equilibrium and also opening the possibility of diverse non-equilibrium phases.
While much work in this area has focused on systems with a single degree of freedom per site, motivated by rapid developments in cold atom experiments, we focus on the Fermi Hubbard model, with both spin and charge degrees of freedom. To explore the spread of information between these in the presence of disorder, we compare the time dependence of the entanglement entropy with the time dependence of the charge and spin correlations, and in addition we rewrite the Hamiltonian in terms of charge and spin-specific integrals of motion, allowing us to distinguish time scales associated with charge-charge, spin-spin, and charge-spin correlations.

Speaker: Rachel Wortis (Trent University)

13:18 Questions & answers

M2-9 Dark matter experiment and Channel of detection II (PPD) / Expérience sur la matière sombre et canal de détection II (PPD)

Convener: Simon Viel (Carleton University)

76 Solar KK axion search with NEWS-G

In theories with extra dimensions, the standard QCD axion has excited states with higher mass. The axion of such theories, named the Kaluza-Klein (KK) axion, would have a significantly shorter decay time for higher mass states. This would allow for axion decays on Earth, even in the absence of a strong magnetic field. It would also mean that a fraction of heavier mass axions created in the Sun would remain gravitationally trapped in the Solar System, dominating the local density of axions.

NEWS-G is a dark matter direct detection collaboration that aims to detect low mass WIMPs using a gaseous target detector. The detector is a gas-filled metallic sphere with a high voltage electrode in its centre. While WIMP detection is its main purpose, it is also particularly suitable to KK axion detection. Since the rate of KK axion decays depends only on volume, not on mass, the use of a low density target is an asset: it allows to distinguish such decays from the background by identifying the separate locations of the capture of the two resulting photons.

This talk will cover arguments in favour of the existence of (solar) KK axions, and the work performed on data from NEWS-G detectors to set new constraints on the solar KK axion model.

Speaker: Francisco Andres Vazquez de Sola (Queen's University)

CAP-2021_FVazquez_SearchingSolarKKAxions.pdf

77 (G*) The stability of the DEAP-3600 dark matter detector and projected sensitivities for time-varying signals

DEAP-3600 is a direct detection dark matter experiment with single-phase liquid argon as the target material to search for nuclear recoil signal from the interaction of WIMPs, one of the most widely accepted hypotheses for dark matter. Along with the occurrence of this elastic interaction of WIMP and target nuclei, theories also predict the dark matter signal could vary over the course of a year because of the rotation of the sun and hence the earth around the galactic center. This type of modulation is not expected in most of the known backgrounds and the observation of this type of modulation signal will extend the sensitivity of WIMP search in DEAP-3600. The detector stability of DEAP-3600 is studied which will lead to a measurement of the Ar39 half-life and annular modulation of the dark matter signal. In this talk, the sensitivity studies of the detector will be presented.

Speaker: Gurpreet Kaur (Carleton University)

CAP_7_June_GurpreetKaur.pdf

78 (G*) Dark Sector Portals & New Anomalously Penetrating Particles at the LHC with the MoEDAL-MAPP Experiment

The Large Hadron Collider (LHC) at CERN supports a plethora of experiments aimed at improving our understanding of the universe by attempting to solve the many answered questions in physics, such as: What is the nature of dark matter? Why is electric charge quantized? Why do the free parameters of the Standard Model (SM) have their particular values? To-date, the SM has been stringently tested at the LHC and completely validated by the recent discovery of the Higgs boson by the ATLAS and CMS experiments. However, no smoking-gun signal of new physics beyond the SM (BSM) has been detected at the LHC to-date. The Monopole and Exotics Detector at the LHC (MoEDAL) is specifically dedicated to investigating various BSM scenarios through searches for highly ionizing particles, such as magnetic monopoles and multiply electrically charged particles, as avatars of new physics. Currently, MoEDAL has taken data for $pp$ collisions at center-of-mass energies of $\sqrt{s}=8$ and $\sqrt{s}=13$ TeV, providing the world's best laboratory constraints on magnetic monopoles with magnetic charges ranging from two to five times the Dirac charge. During the ongoing Long Shutdown 2, the MoEDAL collaboration has been preparing the MoEDAL Apparatus for Penetrating Particles (MAPP) detector upgrade. The aim of the MAPP detector is to expand MoEDAL's physics program by including searches for new mini-ionizing particles (mIPs) and long-lived neutral particles (LLPs). The proposed placement of the MAPP detector is $\sim50$ m from the interaction point, in the UGC1 gallery; a generously sized cavern adjacent to the MoEDAL region at interaction point 8. This presentation provides a progress update on the new MoEDAL Apparatus for Penetrating Particles (MAPP) detector currently planned for deployment by run-3 and phased throughout. A brief overview of the two subdetectors, MAPP-mCP and MAPP-LLP is presented. Lastly, benchmark studies involving renormalizable portal interactions that couple a dark sector to the SM are presented for each subdetector to illustrate the performance capabilities of the MAPP detector in the upcoming Run-3.

Speaker: Michael Staelens

CAP2021-PPD Presentation v2.pdf

79 Dark Matter Search with a low-threshold SuperCDMS HVeV detector

For many years the SuperCDMS collaboration has been developing cryogenic
low-threshold silicon and germanium detectors for dark matter searches. The recently developed gram-scale high-voltage eV-resolution (HVeV) detectors are designed to be operated with a high voltage bias (on the order of 100 V) to take advantage of the Neganov-Trofimov-Luke amplification to resolve individual electron-hole pairs. An improved version of the HVeV detector achieved a phonon energy resolution of 2.7 eV without the voltage assisted amplification. Background data with exposures on the order of 1 gram-day were acquired with this detector in an above-ground laboratory, without bias voltage (0 V) as well as at high voltages. We compare the 0 V data with high voltage data, in an attempt to understand the spectrum observed. The 0 V data were also used to set a nuclear recoil dark matter limit.

Speaker: Ziqing Hong (University of Toronto)

0VeV-CapCongress.pdf

13:30 15 Minute Break

M-SCIPOL Science Policy Workshop / Atelier de politique scientifique

Convener: Maikel Rheinstadter (McMaster University)

80 (I) ‘em jlHvaD Hoch The Science (& Art) of Compelling Storytelling

Polish up your Klingon (the title is a bit of a teaser; it is a Klingon translation of “Tell me more”)! Effective communication is key when it comes to talking about your research, presenting your research at conferences, and writing papers; Even more so when trying to sell your ideas and research to funding agencies and politicians and decision makers. Lorna Somers has perfected the art of storytelling, speaking at educational, arts and charitable organizations throughout the world. “Tell me more!” is what we want our listeners to say when we are talking about our research. But they will not get there if they do not understand what we are talking about or why it is relevant and important! During this workshop, Lorna will teach us how to effectively communicate in different contexts and with different audiences.

Speaker: Lorna Somers

M-SOCIAL Networking/Social Activities / Maillage et activités sociales

M-PPD Thesis prize winner talks (PPD) / Conférences des lauréats de meilleures thèses (PPD)

Convener: Matthias Danninger (Simon Fraser University (CA))

81 (I) First application of CsI(Tl) pulse shape discrimination at an $e^+ e^-$ collider to improve particle identification at the Belle II experiment

The Belle II experiment operating at the SuperKEKB electron-positron collider is the first high energy collider experiment to use CsI(Tl) pulse shape discrimination (PSD) as a new method for improving particle identification. This novel technique employs the particle-dependent scintillation response of the CsI(Tl) crystals which comprise the electromagnetic calorimeter to identify electromagnetic vs. hadronic showers. The new dimension of calorimeter information introduced by PSD has allowed for significant improvements in neutral kaon vs. photon discrimination, an area critical for the Belle II flagship measurement of $\sin(2 \phi_1)$ using $B \rightarrow J/\psi K^0_L$. This talk will describe the implementation of PSD at Belle II including the development of the pulse shape characterization algorithms and new simulation methods to compute the CsI(Tl) scintillation response from the ionization dE/dx of the secondary particles produced in the crystals. The performance of PSD for $K^0_L$ vs photon separation will be presented and the significant improvement over traditional shower-shape approaches will be demonstrated. Ongoing studies exploring new directions for PSD at Belle II will also be presented including new methods of pulse shape characterization with machine learning as well as using PSD to enhance cluster finding and low momentum charged particle identification.

Speaker: Savino Longo (University of Victoria)

PPDThesisPrize_SavinoLongo_CAP2021.pdf

82 (I) Measurements of Z boson production in association with two jets using the ATLAS Run-II dataset

The electroweak production of a Z boson in association with two jets is measured using the full Run-II dataset of the ATLAS experiment. This EW-Zjj process is a fundamental process of the Standard Model (SM), it is sensitive to vector boson fusion Z boson production via the WWZ triple gauge vertex. The process is difficult to study, so an advanced methodology is employed to measure the EW-Zjj signal by exploiting topological features. This methodology and the large dataset collected during Run-II have made it possible to measure the cross section of EW-Zjj differentially for the first time. The cross section is measured as a function of four observables: the invariant mass of the two jet system, the rapidity interval spanned by the two jets, the signed azimuthal angle between the two jets, and the transverse momentum of the Z boson. The observed total fiducial cross section of EW-Zjj is 37.14 ± 3.47 (stat.) ± 5.79 (syst.) fb.

The techniques developed for this analysis can be applied to the measurement of other electroweak processes such as vector boson fusion Higgs production. EW-Zjj is also an important background for vector boson scattering processes that are of growing interest for searches of deviations from the SM. The differential cross sections themselves provide two avenues for testing the SM. First, the measurements are sufficiently precise as to distinguish between different state-of-the-art theoretical predictions. Knowledge gained here is applicable to other areas, such as Higgs physics. Second, the differential cross sections are used to test deviations from the SM attributed to higher order corrections in the WWZ vertex by exploiting the sensitivity of a parity-odd observable with an effective field theory approach.

Speaker: Stephen Weber (Carleton University (CA))

14:45 15 Minute Break

M-PLEN-2 Avery Broderick, Univ. of Waterloo / PI (DTP/PPD) (DPT/PPD)

Convener: Mark Walton (University of Lethbridge)

83 Unmasking Black Holes with the Event Horizon Telescope

Black holes are, without question, one of the most bizarre and mysterious phenomena predicted by Einstein’s theory of general relativity. They correspond to infinitely dense, compact regions in space and time, where gravity is so extreme that nothing, not even light, can escape from within. And, their existence raises some of the most challenging questions about the nature of space and time. Over the past few decades, astronomers have identified numerous tantalizing observations that suggested that black holes are real. This past April, the search for confirmation changed dramatically with the publication of the first image ever taken of a black hole, rendering tangible what was previously only the purview of theory and science fiction. I will describe how these observations were made, how the images were generated, how quantitative measurements were obtained, and what they all mean for gravity and black hole astronomy.

Speaker: Avery Broderick

15:30 15 Minute Break

M3-1 Nonlinear and Quantum Optics (DAMOPC) / Optique non linéaire et optique quantique (DPAMPC)

Convener: Duncan O'Dell (McMaster University)

84 (I) Nonlinear Atomic Force Microscopy

We propose a driving scheme in dynamic Atomic Force Microscopy (AFM) to maximize the time the tip spends near the surface during each oscillation cycle. Using a quantum description of the oscillator that employs a generalized Caldeira-Leggett model for dissipative oscillator-surface interaction, we predict large classical squeezing and a small amount of skewness of the probability distribution of the oscillator. Our model also predicts that a dissipative surface force may enhance quantum effects in the motion of a micro-mechanical oscillator that interacts with a surface.

Speaker: Karl-Peter Marzlin (St. Francis Xavier University)

85 (I) Prospects for quantum computing with Ba+ ions

The quest to engineer quantum computers of a useful scope faces many challenges that will require continued investigation of the physics underlying the devices. In this talk, we focus on trapped ion quantum computing. We discuss our efforts to implement quantum information processing with Ba+ ions and provide an overview of possible future benefits this ion could provide for quantum computing efforts, including architectures that are well suited for implementing quantum error correction, and exploration of exotic methods to encode quantum information more efficiently in quDits (multi-level versions of the more familiar two-level quBits). To this end, we present novel measurements related to an all-optical technique for isotope-selective ion production, and discuss why this technique may be critical for building quantum computing devices using the isotope Ba-133+.

Speaker: Prof. Crystal Senko (University of Waterloo)

86 (I) Polarization control of spontaneous emission for rapid quantum state initialization

We propose an efficient, nanoplasmonic method to selectively enhance the spontaneous emission rate of a quantum system by changing the polarization of an incident control field, and exploiting the polarization dependence of the system's spontaneous emission rate. This differs from the usual Purcell enhancement of spontaneous emission rates as it can be selectively turned on and off. Using a three-level system in a quantum dot placed in-between two silver nanoparticles and a linearly-polarized, monochromatic driving field, we present a protocol for rapid quantum state initialization; while maintaining long coherence times for control operations. This process increases the overall amount of time that a quantum system can be effectively utilized for quantum operations, and presents a key advance in quantum computing.

Speaker: Chitra Rangan (University of Windsor)

87 Time-resolved spectroscopy of Xe giant plasmonic resonance by in situ measurement method

Time-resolved spectroscopy of multi-electron dynamics associated with the Xe giant plasmonic resonance is demonstrated by applying an attosecond in situ measurement method. The Xe giant resonance was first noticed through enhanced photoionization around 100 eV using synchrotron X-ray beams. Recently, this was revisited with high harmonic spectroscopy, where enhanced extreme ultraviolet (XUV) emission was measured above the photon energy of 90 eV. Although this is remarkable progress, achieved using a table-top XUV source with excellent coherence, we need phase information to understand electron interactions during the resonant excitation. To measure this, we introduce a weak field to perturb recollision electron trajectories during the XUV generation process. This modulates the emitted XUV beam, allowing us to determine emission times of each XUV frequency. Consequently, we observe a large group delay variation around 84 eV of the XUV spectrum, which coincides with the strong amplitude enhancement at the resonance. This reveals the time-dependent response of the resonance, showing a tail with a decay time of 200 as. Since the emission time is the frequency derivative of the spectral phase, this measurement corresponds to the full characterization of the X-ray pulse influenced by the resonance.
This is an evidence that in situ methods can probe multi-electron correlation. Our demonstration to measure the delay of the plasmonic resonance implies that in situ methods are a viable alternative to photoelectron streaking utilizing recollision electrons as exquisitely sensitive probes to characterize ultrafast electron dynamics. Although the in situ method does not distinguish between the ionization and recombination steps of high harmonic generation, it is still valuable for simple approaches pursuing attosecond science. The application of in situ techniques, as demonstrated here in a many-body system, presents a new direction of strong-field attosecond physics where ultrafast many-body dynamics are measured and controlled by all-optical metrologies.

Speaker: Dr Dong Hyuk Ko (University of Ottawa)

88 (U*) Connection between non-analyticities and universal structures in many-body systems

The study of many-body quantum systems undergoing non-equilibrium dynamics has received a lot of interest in the past few years. One way to characterize such systems is by monitoring non-analytic behavior of physical quantities that might occur as a function of time. This is precisely the aim of the theory of dynamical phase transitions. Another way is by looking at universal structures that generally form in many-body systems, as seen through the wavefunction. In this case, Catastrophe theory is a framework which allows one to mathematically describe universal features of wavefunctions via a set of scaling exponents. We found strong evidence suggesting that in fact both theories are related. By studying the transerve field Ising model with infinite range interactions, which can be simulated in ultra-cold atoms and trapped ions experiments, we were able to relate non-analyticities occurring at critical times to universal structures appearing in the wavefunction. More precisely, we numerically calculated a quantity called the Loschmidt rate function as a function of time, and found kinks occurring periodically in time that coincided with the universal structures of the time-evolved wavefunction, identified via scaling laws.

Speaker: David Linteau (McGill University)

89 Multidimensional Raman Solitons as Drivers of the High Harmonic Generation Process

High harmonic generation (HHG) in gasses has become a method of choice among table-top extreme ultraviolet (XUV) sources. In order to generate higher photon energies from this process, many strategies can be implemented, including red-shifting and compressing the driver pulses. Here, we propose a new approach for inducing a red-shift to driver pulses and compressing them to few-cycle durations in a single stage. This method uses the recently discovered multidimensional solitary states (MDSS) pulses that result from the nonlinear Raman process in gas-filled hollow-core fibers. It has a few key advantages: 1) MDSS are created from relatively long pulses, making this method suitable for any laser source offering sub-picosecond pulses. 2) The MDSS pulses can be compressed by simple propagation through glass. 3) In contrast with commonly-used optical parametric amplifiers, the induced red-shift can be modest, allowing to reach a target XUV photon energy while minimizing the detrimental effects of long driver wavelengths on HHG efficiency.
To produce MDSS pulses, the output pulses of a Titanium-Sapphire system are stretched to 400 fs and coupled to a hollow-core fiber filled with nitrogen. In the fiber, intermodal nonlinear processes occur which lead to the red-shifted MDSS pulses. Then, CaF2 plates inserted into the beam path compress the pulses down to 12 fs and these are sent to an argon-filled cell where HHG occurs. From this simple apparatus, the HHG spectrum is expanded to cover the M$_{2,3}$ edge of cobalt and $10^9$ photons/second are generated at 60 eV. This significant XUV photon flux allows for the implementation of X-ray resonant magnetic scattering measurements on a cobalt/platinum ferromagnet, an example of photon-hungry application. Although such flux has previously been generated in a different gas from the direct output of the same laser system, the conversion efficiency of our approach is one order of magnitude higher as it allows to reach the target photon energy by generating harmonics in argon, a gas that offers a large generation efficiency. Due to its simplicity and versatility, our approach can readily be adapted to different applications and could be particularly interesting for high power Ytterbium laser systems offering sub-picosecond pulses.

Speaker: Katherine Légaré (INRS)

90 (G*) Broadband and high sensitivity THz system with grating-assisted noncollinear phase-matching

Time-domain terahertz (THz) spectroscopy has been widely exploited in studying semiconductors, superconductors, topological insulators, and metal-organic frameworks. A high-sensitivity THz system can resolve weak spectroscopic features and a broadband system allows experimentalists to rely on additional spectral information to investigate novel phenomena in materials. In a standard configuration relying on difference frequency mixing to generate and detect THz radiation, the spectroscopy signal can be improved by increasing the nonlinear interaction length inside a nonlinear crystal. However, the accessible spectral bandwidth is then limited by phase-matching conditions. Here we demonstrate a time-resolved THz system relying on noncollinear THz generation and detection schemes in thick nonlinear crystals to perform high-sensitivity and broadband spectroscopy. This concept relies on a phase grating etched on the front surface of two 2-mm thick gallium phosphide (GaP) crystals (THz generation and detection crystals) to diffract the incident near-infrared pulses. Our scheme exploits the long interaction length in these crystals to improve the signal strength and dynamic range in the system. In addition, the noncollinear geometry yields optimizable phase-matching conditions to access a broad spectral bandwidth. We compare our results with those obtained with a traditional broadband collinear system using a pair of thin GaP crystals without gratings. The noncollinear geometry shows a significant increase of the maximum signal amplitude, by a factor of 20, while also achieving a large spectral bandwidth reaching up to 7 THz. We also achieve a dynamic range above 80 dB between 1.1 and 4.3 THz. Our concept could be extended to other nonlinear crystals besides GaP to improve THz generation and detection in different spectral regions. In conclusion, this work paves the way towards high-sensitivity THz spectroscopy over a broad bandwidth in low power experiments and could enable high-field THz generation above 3 THz.

Speaker: Wei Cui (University of Ottawa)

91 (U*) Calculation of High Harmonic Spectrum from a 1D periodic potential

In this research project, I calculated the high-harmonic spectrum from a 1D periodic potential. I investigated numerical methods for solving the 1D time-dependent Schrodinger equation of a particle in a double-well potential, as well as determining its ground state. I used the Crank Nicolson method [1], which is a finite difference method that can be used for numerically solving second-order partial differential equations. Using this method, I calculated the time evolution of an electronic wave function in a harmonic potential. My code was bench-marked against analytic solutions of the harmonic oscillator wave functions. I extended the use of this code by implementing the imaginary time method [2] to determine the ground state of an electron in a double-well potential. The time-independent Schrodinger equation is solved in the Bloch state basis to calculate the band structure of two different 1D periodic potentials. The calculations of dispersion relation are used to calculate the High Harmonic Spectrum and the final results are compared with [3].

[1] Wachter, C. (2017). Numerical Solution of the Time-Dependent 1D-Schrodinger Equation using Absorbing Boundary Conditions (Bachelor Thesis, University of Graz, Austria). Retrieved from https://physik.uni-graz.at/~pep/Theses/BachelorThesis_Wachter_2017.pdf

[2] Williamson, A. (1996). Quantum Monte Carlo Calculations of Electronic Excitations.
Retrieved from http://www.tcm.phy.cam.ac.uk/~ajw29/thesis/node27.html

[3] Wu, M. (2015). Attosecond Transient Absorption in Gases and High Harmonic Generation in Solids (Doctoral dissertation, Louisana State University, USA). Retrieved from https://digitalcommons.lsu.edu/cgi/viewcontent.cgi?article=4320&context=gradschool_dissertations

Speaker: Shubham Kukreja (University of Windsor)

92 High Harmonic Generation and Strong Field Dynamics in a Wannier Basis

High harmonics generation (HHG) in solids is a decade old field and yet the understood mechanisms leading to HHG is still an incomplete picture. They fail to capture real-space motion like lateral tunneling ionization. We investigate theoretically high harmonic generation in solids using a localized basis of Wannier states. Wannier states are localized wavefunctions overcoming the infinite nature of Bloch states in real space. We develop a semi-classical model for interband generation, which allows the characterization of HHG in terms of classical trajectories. Our semi-classical approach is in quantitative agreement with quantum calculations. The success of the model completes the single-body picture for HHG in semiconductors. It reveals a complete picture of the mechanisms shaping HHG. Both the ionization and recombination events are altered by real-space processes that are intuitively explained by the Wannier-Stark ladder. An electron tunnel ionized by a strong electric field undergoes a diagonal transition on an energy vs position diagram. The angle of that transition depends on two competing terms: the reduced energy gap due to the Stark effect which favours more horizontal transition and the dipole coupling matrix element, which favours vertical transition. We find that for the recombination, the electron prefers to align in real space with its parent hole. The importance of our semi-classical theory extends beyond HHG; it enables modeling of dynamic processes in solids with classical trajectories, such as for coherent control and transport processes, potentially providing better scalability and a more intuitive understanding.

Speaker: Guilmot Ernotte (University of Ottawa)

16:24 Group discussion

M3-2 Physics and Computing II (DPE) / Physique et calcul II (DEP)

Convener: Patricia Mitchler (Canadian Association of Physicists)

93 (I) Building computation skills into our physics program

Computational skills are integral to physics research; they enable the operation of instruments, facilitate the analysis of data, and elucidate physical phenomena through simulation. The same can be said for physics curricula; not only does this reflect the importance in research but incorporating computation into physics courses provides its own pedagogical value. Not surprisingly, many undergraduate programs include dedicated courses that teach introductory computer programming and/or computational methods. We have recently begun integrating computational activities into our second-year physics courses and have adopted a centralized approach: Exercises alternate between multiple courses and are administered independent of the course instructors. Our goal is to provide regular, cohesive exposure of computation, contextualized to their courses, without overburdening one specific course/instructor. We will discuss the structure of these exercises, how they fit into the broader picture of computation in our program, and the overall impact on our students (both perception and proficiency).

Speaker: Michael Massa (University of Guelph)

94 Covid-19 project: What a physics instructor learned by working with engineering coop students to create open probl

Covid-19 project: What a physics instructor learned by working with engineering coop students to create open problems using WeBWorK

BCcampus has funded a number of projects to increase the use of Open Educational Resources (OER) in the British Columbia. There are initiatives to make either Zero (or low cost) Textbook Credentials. One of the major stumbling blocks to having all first-year textbooks in engineering programs be OER was that lack of a book on Mechanics, both statics and dynamics, that was comparable to the commercially available books. These textbooks contain more than 7000 problems as well as about 1000 worked out examples that use high quality 2D and 3D images. In addition they often come bundled with an online homework system.

UBC Mechanical Engineering had begun creating problems of this level of complexity using
WeBWorK. WeBWorK is an open-source on-line homework system for delivering individualized homework problems over the web. It gives students instant feedback as to whether or not their answers are correct. WeBWorK has been used by the mathematics community for decades, but there are not many physics problems in the Open Problem Library (OPL) and very few, less than 100, of the type needed for first and second-year engineering students.

Due to Covid-19 lockdowns this summer, I had spare time on my hands and the Federal Government was providing large subsidies for coop students. A small project at UBC with one engineering professor and two students turned into a larger project with six students. I, a physics instructor at a community college, supervised three of those students as well as working with a professional graphic artist. The project has continued and I am now in my third semester supervising two students. In this January-April 2021 semester, I am teaching the course associated with this project, a first-year physics course in mechanics, both statics and dynamics, geared for engineering students. This is an ongoing project and I invite others to join us in this work.

I will present what I learned about WeBWorK, supervising coop students to create questions, and working with a professor from a large university to create open educational resources.

Speaker: Jennifer Kirkey (Douglas College)

M3-3 MR and PET Imaging - Part 1 (DPMB) / Imagerie RM et TEP - Partie 1 (DPMB)

Convener: Emily Heath

95 Comparison of Cylindrical and Spherical Geometric Models to Infer Cell Sizes in a Celery Sample

Temporal diffusion spectroscopy (TDS) has been used to infer axon sizes using geometric models that assume axons are cylinders. A celery sample was imaged to test if the importance of other geometric models. The vascular bundles and collenchyma tissue (~20 μm cells) in celery can be modeled as containing cylindrical cells. Whereas the parenchyma cells are rounder and are 3-4 times larger in diameter. Thus we imaged celery to test TDS with oscillating gradient spin echo (OGSE) to see if the spherical cell model and cylindrical cell model infer significantly different cell sizes to determine how important the geometrical model is.
A small section of a celery stalk was cut to fit inside a 15 mL sample tube filled with water. The image slice was chosen to be perpendicular to the length of the celery stalk. The sample was imaged using a 7T Bruker AvanceIII NMR system with Paravision 5.0 and BGA6 gradient set with a maximum gradient strength of 430357 Hz/cm, and a 3.5 cm diameter bird cage RF coil. Each 20 ms apodised cosine gradient pulse ranged from n = 1-20, in steps of 1. Two different gradient strengths were used for each frequency and gradient pulses were separated by 24.52 ms. A 1mm thick slice was acquired with the following imaging parameters: 2 averages, 2.56 cm FOV, TR = 1250 ms, TE = 50 ms, matrix 128 x 128, 200 μm in plane resolution, acquisition time 26.67 minutes per scan (scans performed = 40, 17.78 hours).
The inferred diameters of cells in celery (14±6μm to 20±12μm) were not statistically different when using the two different geometric models. This is the first step toward understanding the importance of geometric models for TDS.
The authors wish to acknowledge funding from NSERC and Mitacs.

Speaker: Sheryl Herrera (University of Winnipeg)

96 Medical Image Fusion Based on Modified Parameter- Adaptive Simplified Pulse-Coupled Neural Network

Positron Emission Tomography (PET) images of the brain can reflect the level of brain molecular metabolism with low spatial resolution, while magnetic resonance imaging (MRI) brain images can provide anatomical structure information with high spatial resolution. In order to achieve the complementary of molecular metabolism information and spatial texture structure, it is meaningful to fuse the two types of images. Traditional fusion methods are prone to color distortion of PET image or unclear texture of MR image. A novel medical image fusion algorithm is proposed here. Firstly, the source image is processed with nonsubsampled shearlet transform (NSST) to obtain low-frequency sub-band and a series of high-frequency sub-bands, which can effectively extract the contour and texture details of the image; Secondly, a regional adaptive weighted fusion is adopted for the low- frequency sub-band, which is conducive to the high fidelity of the fused PET image color. while the improved Laplacian gradient sum is used as the input excitation of the parameter- adaptive simplified pulse-coupled neural network (PA-SPCNN) to fuse the high-frequency sub-bands, which improves the clarity of the fused MRI image texture. Finally, inverse NSST is performed on the fused low-frequency and high-frequency sub-bands to obtain the fused image. The experimental results show that the proposed algorithm can retain the basic information of the source image, and show the metabolic status of the functional image without losing the texture features of the structural image. The fusion algorithm achieves good results in both subjective and objective evaluation.

Speaker: Xiumei Yin (Anhui University)

97 Inferring axon diameters in white matter tracts of the live mouse brain

Tissue microstructure, such as axon diameters, can be inferred from MRI diffusion measurements either through relating models of the geometry of the tissue and MR parameters, or through directly relating MR measurements to tissue parameters. Some have implemented geometric models to infer axon diameters using temporal diffusion spectroscopy. In order to target smaller diameter axons, we have replaced the pulsed gradient spin echo pulse sequence used in most temporal diffusion spectroscopy measurements with oscillating gradient spin echo sequence (OGSE). Here we use OGSE temporal diffusion spectroscopy to infer axon diameters is white matter tracts of the live mouse brain.
Axon diameters in the live mouse brain were inferred using oscillating gradient spin echo temporal diffusion spectroscopy. Two sets of five images were collected in less than 11 minutes from which the measurements were made. Diameters ranged from 4 to 12 μm in various white matter regions including the optic tract, corpus callosum, external capsule, dorsal hippocampal commissure and fasciculus retroflexus. Confirmation of axon diameters using electron microscopy remains to be done. The short imaging time suggests this is the first step toward a feasible imaging method for live animals and eventually for clinical applications.
The authors wish to acknowledge Rhonda Kelley for her help with animal care and imaging. The authors acknowledge funding from NSERC and Mitacs.

Speaker: Melissa Anderson (University of Manitoba)

98 (G*) Mapping Magnetic Field Around Metal with Pure Phase Encoding Magnetic Resonance Imaging

Magnetic Resonance Imaging (MRI) detects signal from hydrogen nuclei in biological tissue. MRI requires a homogeneous static magnetic field to generate artifact-free images. The subject is spatially encoded with magnetic field gradients. The signal is acquired in the frequency domain and the image is reconstructed by inverse Fourier transform. Objects with high magnetic susceptibility, such as MRI-safe metallic implants, distort the surrounding magnetic field. This leads to severe artifacts that appear as signal voids in the conventional MRI images, due to rapid intravoxel dephasing, in addition to misregistration of frequencies to position.
Pure phase encoding techniques with short encoding times are largely immune to magnetic field inhomogeneity artifacts. This is because the constant signal evolution times can be sufficiently short that no appreciable dephasing has occurred. High quality artifact-free MRI images were acquired with pure phase encoding techniques, from which the magnetic field distribution around the metal was derived. This approach was compared with conventional MRI methods, which failed to map the magnetic field in high susceptibility regions. Although it is challenging to apply the proposed method in a routine clinical MRI scan, the measured magnetic field distribution could enable the development of novel nonlinear encoding techniques, where the metal induced magnetic field distortion is exploited to provide spatial information.

Speaker: Ms Layale Bazzi (University of Windsor)

99 (G*) Cariporide Effects on Intracellular pH (pHi) Using CEST-MRI in Rat Model of Glioblastoma

Introduction: pHi is a hallmark of altered cellular function in the tumour microenvironment and its response to therapies. One of the main acid-extruding membrane transport proteins in cells is the Na+/H+ exchanger isoform 1 (NHE1). Chemical exchange saturation transfer (CEST) MRI uniquely images pHi. In CEST-MRI, contrast is produced by exciting exchangeable tissue protons at their specific absorption frequency and observing the transfer of magnetization to bulk tissue water. Amine and amide concentration-independent detection (AACID) is a ratiometric approach that uses the distinctive sensitivity of amine and amide protons to CETS contrast. The AACID value inversely relates to tissue pHi. One way to achieve tumour acidification as a therapeutic strategy is by blocking the NHE1 transporter. Cariporide is a potent inhibitor of NHE1. We have shown that cariporide can selectively acidify U87MG glioma in mice. The goal of this study was to determine whether cariporide also selectively acidifies a rat C6 glioma tumour model immediately following injection by mapping tumour pHi.
Methods: A 2μL suspension of 10^6 C6 glioma cells were injected into the right frontal lobe of six 8-week-old male rats. To evaluate the effect of cariporide on tumour pHi, rats received an IP injection of the drug (6mg/kg in 2ml) two weeks after tumour implantation. They received the drug inside a 9.4T scanner to measure the change in pHi following injection.
Results: Five minutes after injection we started collecting CEST-MRI for 3 hours. For data analysis, we compared the first maximum change in AACID value post-injection with the pre-injection value. Approximately 60 minutes after injection, the average AACID value in the tumour significantly increased (p<0.05). The average AACID value in tumour post-injection was 5.4% higher compared to pre-injection corresponding to a 0.26 lower pHi. The average AACID value in contralateral tissue also increased in a similar way.
Conclusion: We did not observe selective tumour acidification following injection as was observed in the previous study. The reason for this discrepancy is currently unknown but may be related to potential differences in tumour vasculature that may limit the ability of cariporide to infiltrate the tumour. Future work includes increasing cariporide dose and modifying our quantification method to increase the temporal stability of the AACID measurement.

Speaker: Maryam Mozaffari (Department of Medical Biophysics, Robarts Research Institute, Western University)

100 (G*) The Use of a Novel Sampling/Reconstruction Method for Non-Proton and Low Field MRI

**Introduction:** MRI’s low sensitivity, caused by the use of nuclei with low-gyromagnetic ratios or low magnetic field strength, can presently be improved with expensive high-field MRI-hardware and/or expensive enriched-isotopes. We propose a new method that does not require any extra signal-averaging or hardware to improve the quality of MRI images. We will use a significant k-space under-sampling acquisition method where only a certain percentage of the k-space points will be acquired per image, corresponding to the acceleration-factor (AF); it follows that one can acquire ten under-sampled images in the same time as one fully-sampled image. Averaging each possible combination of images of the under-sampled set, a density decay curve can then be fitted and reconstructed using the Stretched-Exponential-Model (SEM) combined with Compressed Sensing (CS).¹

**Method:** ¹H MR was performed on a resolution-phantom at the low-field (0.074T) MRI scanner using a home-built RF coil. Nine 2D fully-sampled k-spaces were acquired. Combinations of 2, 3, and 4 averages were carried out for each possible permutation, resulting in 14 k-spaces total (2 combinations for 4 averages, etc.); these were retroactively under-sampled for three AF’s (7, 10, 14). 3 Cartesian sampling schemes (FGRE, x-Centric², & 8-sector FE Sectoral³) were used. The SNR attenuation is assumed to represent a decrease of the resonant isotope density in phantom after diluting it with the non-resonant isotope. The resulting signal decay (density) curve was fitted using the Abascal method.¹

**Results:** The SNR of the 9 k-space averaged image and the original image was 16 and 5, respectively. The SNR of the three sampling schemes is 15 for FGRE, 19 for x-Centric, and 17 for FE Sectoral.

**Conclusion:** The improved SNR of the generated images for all sampling schemes demonstrate that the SEM equation can be adapted for fitting the SNR decay dependence of the MR signal. Since this technique does not require extra hardware, the proposed method could be implemented in current MRI-systems and yield improved images. Due to the CS-based reconstruction, the higher AF leads to more visible artefacting; this could be reduced by a Deep Learning-based correction after the fact.⁴

**References:** **1** Abascal et al. IEEE Trans Med Imaging (2018); **2** Ouriadov et al. MRM (2017); **3** Khrapitchev et al. JMR (2006); **4** Duan et al. MRM (2019)

Speaker: Samuel Perron (University of Western Ontario)

101 Monte Carlo Simulation for Magnetic Resonance Diffusion Measurements

Magnetic resonance imaging (MRI) is widely used as a non-invasive diagnostic technique to visualize the internal structure of biological systems. MRI has limited spatial resolution and the microscopic behaviour within an image voxel cannot be visualized with qualitative images. Quantitative analysis of molecular diffusion provides insights into the microscopic structure beyond the MRI image resolution. It is challenging to analytically derive the MR diffusion signals for complex microscopic environments, particularly with susceptibility effects. In this work, an easy to use open-source Monte Carlo algorithm has been developed to simulate MR diffusion measurements under arbitrary conditions.
The self diffusion of water molecules can be described by Brownian motion. The Monte Carlo method was applied to simulate the Brownian motion in a user-defined microscopic environment. The fast simulation can be performed on any MRI experiments with user-defined magnetic field distribution. The method has been applied to predict nanoparticle configuration. Magnetic nanoparticles, serving as biosensors, distort the local magnetic field leading to changes in the MR diffusion signals. The simulation agreed with the experimental results. The nanoparticle concentration in water can be determined with MR diffusion measurements.
We have developed an efficient, easy to use algorithm for rapid diffusion simulation in different microscopic environments with arbitrary magnetic fields. This simulation will be employed to optimize the nanoparticle biosensor systems for a wide range of targets, including cancer cells and COVID virus.

Speaker: Mr Tristhal Parasram (University of Windsor)

M3-4 Black Holes (DTP) / Trous noirs (DPT)

Convener: Masoud Ghezelbash (University of saskatchewan)

102 Unexpectedly exciting axisymmetric apparent horizons

In numerical relativity, marginally outer trapped surfaces (MOTSs) (often referred to as apparent horizons) are the main tool to locate and characterize black holes. For five decades it has been known that during a binary merger, the initial apparent horizons of the individual holes disappear inside a new joint MOTS that forms around them once they are sufficiently close together. However the ultimate fate of those initial horizons has remained a subject of speculation. In this talk I will introduce new mathematical tools that can be used to locate and understand axisymmetric MOTS. In particular I will show that the MOTS equations can be rewritten as a pair of coupled second order equations that are closely related to geodesic equations and hence dubbed the MOTSodesic equations. Numerically, these are very easily solved and in the linked talks by KTB Chan, R Hennigar and S Muth they will be used to identify and study rich families of previously unknown MOTS in a variety of black hole spacetimes, including both exact solutions and binary merger simulations. I will also show that the MOTS stability operator bears the same relation to MOTSodesics as the Jacobi deviation operator does to geodesics and consider the implications.

Speaker: Ivan Booth (Memorial University)

103 The fate of apparent horizons in a binary black hole merger

The common picture of a binary black hole merger is the “pair of pants” diagram for the event horizon. However, in many circumstances, such as those encountered in numerical simulations, the event horizon may be ill-suited and it is more practical to work with quasi-local definitions of black hole boundaries, such as marginally outer trapped surfaces (MOTS). The analog of the pair of pants diagram for the apparent horizons remains to be fully understood. In this talk, I will discuss the complete picture for the merger of two axisymmetric black holes. I will begin by introducing new classes of MOTS present in Brill-Lindquist initial data. I will then discuss the role played by these and related surfaces in understanding the final fate of the apparent horizons of the initial two participants in the merger.

Speaker: Robie Hennigar

104 (G*) Marginally Outer Trapped (Open) Surfaces in 4+1 Dimensional Spacetimes

In the case of binary black hole mergers, the surface of most obvious interest, the Event Horizon, is often computationally difficult to locate. Instead, it is useful to turn to quasi-local characterizations of black hole boundaries, such as Marginally Outer Trapped Surfaces (MOTS), which are defined for a single time slice of the spacetime, and the outer-most of which is the apparent horizon. In this talk, I will describe ongoing work focused on understanding MOTS in the interior of a five-dimensional black hole; both static and rotating. Similar to the four-dimensional Schwarzschild case previously studied, we find examples of self-intersecting MOTS with an arbitrary number of self-intersections. This provides further support that self-intersecting behavior is rather generic. I will also discuss the second stage of our research, which is for a rotating 5D black hole spacetime. These two cases fit into a larger project involving exploration of the generality of self-intersecting behaviour in MOTS, within spacetimes of increasing diversity.

Speaker: Sarah Muth (Memorial University of Newfoundland)

105 (G*) The many marginally outer trapped surfaces of Schwarzschild spacetime

Despite the constant stream of black hole merger observations, black hole mergers are not yet fully understood. The phenomenon seems simple enough, but the details of how the two apparent horizons end up as one horizon is unclear due to the non-linear nature of the merger process. Recent numerical work has shown that there is a merger of self-intersecting Marginally Outer-Trapped Surfaces (MOTS) during the black hole merger. Following papers have investigated further into MOTS in a simpler and static scenario, that of a Schwarzschild black hole. Such cases require less machinery and are solved with everyday computers. Those numerical calculations show an infinite number of self-intersecting MOTS hidden within the apparent horizon, as well as open surfaces (MOTOS). The importance of Schwarzschild MOTS are not to be undermined due to its relative simplicity as such MOTS describe an extreme-mass-ratio black hole merger, where one of the black holes is far more massive than the other. In this talk, I will discuss the current understanding of black hole mergers as have numerically been shown and my work investigating Schwarzschild MOTS in maximally-extended Kruskal-Szekeres coordinates.

Speaker: Kam To Billy Chan (Memorial University of Newfoundland)

106 Magnetic Modes of Gravitational Collapse

The observation of supermassive black holes (SMBHs) of mass over a billion solar masses within the first billion years after the Big Bang challenges standard models of the growth of massive objects. Direct collapse black holes arising from a short-lived supermassive star phase have been proposed as a means to form the SMBHs in the required time. In this work we show that a weak cosmological magnetic field may be sufficient to allow direct collapse into very massive objects, overcoming the normal barrier of angular momentum. A dynamo action in the accretion phase emphasizes the effect of the magnetic field. I also review generally the four distinct modes of gravitational collapse with magnetic fields: strong field/strong coupling, weak field/strong coupling (emphasized here), strong field/weak coupling, and weak field/weak coupling.

Speaker: Shantanu Basu (University of Western Ontario)

107 (U*) Black Hole Heat Engines and Critical Behaviour

One of the more exciting things to emerge from black hole thermodynamics in the past 10 years is the understanding that black holes can undergo a broad range of chemical-like phase transitions, including liquid-gas phase transitions, triple points, superfluid transitions, polymer-type transitions, and exhibit critical behaviour. It is even possible to consider black holes as the working material for heat engines. The efficiencies for a variety of black holes can be calculated and compared against each other.

In this talk I will discuss the connection between critical behaviour and the efficiency of black hole heat engines. I first consider the heat capacity of static black holes at constant volume such that Cv=0 Using the near critical expansion of the equation of state, the coefficients appearing in this expansion can be found from an engine cycle placed along a critical point on a PV plot.

I will discuss the importance and applications of the simplifications made, along with how this result allows one to go from the near critical expansion of the equation of state directly to a conclusion about the behaviour of a heat engine near the critical point.

Speaker: Sierra Jess (University of Waterloo)

108 (U*) Efficiency of Black Hole Heat Engines and Universality

One of the more exciting things to emerge from black hole thermodynamics is that black holes can form the working material for heat engines. I explore the connection between the critical behaviour of black holes and their efficiency as heat engines over a range of dimensions and for a variety of theories of gravity.

I first show that their efficiency as heat engines near the critical point can be written in general dimensions in terms of the variables characterizing the geometry of the cycle and the critical exponents. Engines near the critical point approach the Carnot efficiency, with the rate of approach determined by the universality class of the black hole. I will specifically consider a broad range of charged black holes, Lovelock black holes, and black holes with isolated critical points. I will then discuss work in progress exploring this formalism for black holes whose specific heat at constant volume is nonzero, applying it to examples such as rotating black holes and STU black holes.

Speaker: Maria DiMarco (University of Waterloo)

109 (G*) Thermodynamics of Exotic Gauss-Bonnet Black Holes

We examine the thermodynamics of a new class of asymptotically AdS black holes with non-constant curvature event horizons in Gauss-Bonnet Lovelock gravity, with the cosmological constant acting as thermodynamic pressure. We find that non-trivial curvature on the horizon can significantly affect their thermodynamic behaviour. We observe novel triple points in 6 dimensions between large and small uncharged black holes and thermal AdS. For charged black holes we find a continuous set of triple points whose range depends on the parameters in the horizon geometry. We also find new generalizations of massless and negative mass solutions previously observed in Einstein gravity.

Speaker: Brayden Hull (University of Waterloo)

110 (G*) Signatures of Primordial Black Holes in theories of Large Extra Dimensions

Additional spatial dimensions compactified to submillimeter scales serves as an elegant solution to the hierarchy problem. As a consequence of the extra-dimensional theory, primordial black holes can be created by high-energy particle interactions in the early universe. While four-dimensional primordial black holes have been extensively studied, they have received little attention in the context of extra-dimensions. We adapt and extend previous analyses of four-dimensional primordial black holes for the purpose of studying the impact extra-dimensions have on cosmology. We find new constraints on both extra-dimensional primordial black holes, and the fundamental extra-dimensional theories by combining an analysis of Big Bang Nucleosynthesis, the Cosmic Microwave Background, the Cosmic X-ray Background, and the galactic centre gamma-rays. With these constraints we explore to what extent these extra-dimensional primordial black holes can comprise the dark matter in our universe.

Speaker: Avi Friedlander (Queen's University)

16:12 Questions/Answers and Discussion Period

M3-5 Nuclei & Astrophysics I (DNP) / Noyaux et astrophysique I (DPN)

Convener: Greg Hackman (TRIUMF)

111 (I) Exotic Nuclear Decay at the Limits of Stability

Studies of atomic nuclei furthest from stability often reveal surprising phenomena such as exotic structures, highly-deformed shapes and rare modes of radioactive decay. Understanding the properties of the most exotic nuclei is crucial for constraining nuclear reaction rates in explosive astrophysical scenarios and explaining the elemental abundances of the stable and radioactive isotopes that they eject into the universe. These studies pose a significant experimental challenge that requires powerful rare-isotope production and accelerator facilities coupled with state-of-the-art detection systems. In this presentation, I will describe some of the more exotic modes of radioactivity that are relevant in neutron-deficient nuclei, what they can tell us about nucleosynthesis and I will present a novel detector called the Regina Cube for Multiple Particles that was designed and built at the University of Regina for experiments at TRIUMF with the GRIFFIN spectrometer.

Speaker: Prof. Gwen Grinyer (University of Regina)

GwenGrinyer_CAP_2021.pdf

112 Using the DRAGON to understand pollution in globular clusters

Globular clusters contain some of the oldest stars in the universe and provide a key method of understanding the formation and evolution of galaxies. Unfortunately, there are a number of mysteries about the history of globular clusters. One of the most important is the existence of multiple populations, and evidence that the current generation of stars within globular clusters has been elementally polluted by the ashes of some unknown previous stellar event or events.

At present, the uncertainties in the stellar nuclear reaction rates are too high for astrophysical models to identify the polluting site or sites. Sensitivity studies have identified a number of important reaction rates, including $^{39}$K($p,\gamma$)$^{40}$Ca, along with the most important resonances which must be measured. Once these reaction rates have been determined, the polluting site can be identified.

In this talk we will present results from direct measurements of important resonance strengths in $^{39}$K($p,\gamma$)$^{40}$Ca performed with the DRAGON recoil separator at TRIUMF in Vancouver, Canada including the first direct measurement of the resonance predicted to dominate the reaction rate in the expected range of astrophysical temperatures.

Speaker: Philip Adsley (Wits/iThemba LABS)

113 Direct measurement of the $^{26m}$Al(${\it p}$,$\gamma$)$^{27}$Si reaction at DRAGON using an isomeric radioactive ion beam

The investigation of radiative capture reactions involving the fusion of hydrogen or helium is crucial for the understanding of stellar nucleosynthesis pathways as said reactions govern nucleosynthesis and energy generation in a large variety of astrophysical burning and explosive scenarios. However, direct measurements of the associated reaction cross sections at astrophysically relevant low energies are extremely challenging due to the vanishingly small cross sections in this energy regime. Additionally, many astrophysically important reactions involve radioactive isotopes, which pose challenges for beam production and background reduction.

One of the key aspirations in experimental nuclear astrophysics is the determination of the stellar origin of the cosmic γ-ray emitting isotope $^{26}$Al, which is still posing an experimental challenge.
The observation of the characteristic 1.809 MeV $\gamma$-ray signature throughout the interstellar medium as well as isotopic excesses of $^{26}$Mg found in meteorites provided evidence for the existence of $^{26}$Al in the early Solar System, however, its exact origin is still being discussed. Understanding the stellar nucleosynthesis of $^{26}$Al is complicated by the presence of a 0$^{+}$ isomer located 228.31 keV above the ground state. Since said level undergoes super-allowed $\beta^{+}$ decay directly into the $^{26}$Mg g.s., the emission of the 1.809 MeV $\gamma$-ray is bypassed, and the isomer does not contribute to the directly observed galactic $^{26}$Al abundance, however, influences the $^{26}$Al:$^{27}$Al ratio in presolar grains. Thus, only by studying the reactions involved in the production and destruction of both, $^{26}$Al and $^{26m}$Al, one can identify how various astrophysical environments contribute to the $^{26}$Al $\gamma$-ray flux.

To date, the available experimental information on the rate of the $^{26m}$Al(${\it p}$,$\gamma$)$^{27}$Si reaction is rather limited and considerable uncertainties still remain. In this contribution, I will present results obtained from a recent analysis of an inverse kinematics study performed with DRAGON (Detector of Recoils And Gammas Of Nuclear Reactions) using isomeric $^{26m}$Al beam to investigate the 448 keV resonance in $^{26m}$Al(${\it p}$,$\gamma$). Additionally, a brief overview of other recent experimental activity at DRAGON will be presented.

Speaker: Annika Lennarz (TRIUMF)

M3-6 Traps I (DNP) / Pièges I (DPN)

Convener: Matthew Williams (TRIUMF)

114 (I) Towards measuring the Fierz interference parameter in 6He β decay from a Penning trap using the CRES technique

Measurements of correlation parameters in nuclear β decay have a long history of helping shape our current understanding of the fundamental symmetries governing our universe: the standard model. A variety of observations indicate this model is incomplete, so scientists continue to search for what may lie beyond the standard model. Nuclear β decay continues to play an important role in this search for new physics, one that is complementary to other searches. To achieve the precision required to be competitive with the LHC, for example, elegant and sensitive techniques are required. The 6He Cyclotron Radiation Emission Spectroscopy (CRES) experiment under development at CENPA, the University of Washington, aims to make the world's most sensitive search for tensor components to the weak interaction by an energy-spectrum shape measurement of this pure Gamow-Teller decay. As demonstrated by Project 8, the energy of β-decay electrons emitted in a magnetic field can be measured to 15 eV. If the 6He ions are confined in a Penning trap to avoid wall effects, the ultimate precision on the Fierz interference parameter is estimated to be ΔbFierz=10–4. This talk will outline the 6He CRES experiment and our plans to observe the cyclotron radiation of electrons emitted from 6He confined in a Penning trap.

Speaker: Prof. Dan Melconian (Texas A&M)

115 (G*) Mass investigations at the intersection of the N=82 shell closure and the proton drip-line

The proton drip-line is not firmly established for heavy masses. Near N=82, the masses of neutron-deficient Yb and Tm isotopes were measured. In Tm (Z=69), the precise location of the drip-line could be determined, and for both isotopic chains the stabilizing effect of the N=82 shell was examined.  These elements now represent the largest atomic numbers at which this shell closure has been directly probed through the 2-neutron separation energy.

These measurements were accomplished using the recently commissioned Multiple Reflection, Time-Of-Flight Mass Spectrometer at the TITAN facility. Its sensitivity and in-device beam purification capabilities permitted the determination of not only the ground-state masses, but also that of a long-lived isomer in $^{151}$Yb. In this presentation an overview of the measurement technique will be given before the scientific results are discussed.

Speaker: Brian Kootte (TRIUMF/University of Manitoba)

M3-7 Jules Carbotte Memorial (DCMMP) / En mémoire de Jules Carbotte (DPMCM)

Convener: Michel Gingras

116 (I) Disordered array superconducting loop-based synaptic networks and neurons for neuromorphic computing

High-temperature superconductor YBa2Cu3O7 (YBCO) can be systematically disordered by irradiating with a He-ion beams to induce a metal-insulator transition (MIT). Therefore, tunnel junctions demonstrating Josephson tunneling properties can be constructed in planar YBCO films using a He-ion microscope. We have used superconducting loops with disordered YBCO junctions to develop devices that together form fully recurrent neural networks.
Arrays of disordered loops with junctions in planar YBCO thin films with can demonstrate both neuron-like and synapse-like properties. A different architectural approach has been taken by replacing individual synaptic connections with a disordered array of superconducting loops with Josephson junctions. The disordered array can be connected to neurons at its incoming and outgoing nodes to form a fully connected and recurrent neural network and this demonstrates properties of a synaptic memory. The advantage of this approach is that the available memory increases exponentially with increasing size of the array while still fully connecting all the neurons in the network. A neuron-like device is designed with disordered YBCO Josephson junctions that demonstrate leaky integrate-and-fire properties with spiking output and dynamically varying threshold. I will discuss the designs and demonstrate them using equivalent circuit simulations and propose a collective synaptic network architecture that can also work with various other materials that are of interest.

Speaker: Robert Dynes (University of California San Diego)

117 (I) Remembering Jules Carbotte

I was a graduate student in Jules Carbotte's group in the early 1990s, during the heyday of high temperature superconductivity. At the time (for me), everything was new and everything was exciting and it felt as if we were about to learn something beautiful about the world. I recognize now how many of those feelings are tied to where I was and who I was working for. Indeed, I have much to thank Jules for: for helping to create a community of people working together on a common problem; for his infinite patience as a supervisor; and for the joy that physics gave him, which he shared freely with his students. In this talk, I will pay tribute to my former supervisor and mentor.

Speaker: Bill Atkinson (Trent University)

118 (I) Eliashberg Theory and Jules Carbotte

This talk will focus on an overview of Eliashberg theory, a formalism that Jules was very well known for. But I will also discuss some potential shortcomings of this framework, as time permits, from the weak coupling to the strong coupling limit, with polaron physics, and applicability to the hydride and superhydride materials.

Speaker: Frank Marsiglio (University of Alberta)

16:15 Discussion, comments, and contributions

M3-8 Applied Physics (DAPI) / Physique appliquée (DPAI)

Convener: Steffon Luoma

119 Robust Design from Systems Physics

A crucial challenge in engineering modern, integrated systems is to produce robust designs. However, quantifying the robustness of a design is less straightforward than quantifying the robustness of products. For products, in particular engineering materials, intuitive, plain language terms of strong versus weak and brittle versus ductile take on precise, quantitative meaning in terms of stress–strain relationships. Here, we show that a “systems physics” framing of integrated system design produces stress–strain relationships in design space. From these stress–strain relationships, we find that both the mathematical and intuitive notions of strong versus weak and brittle versus directly characterize the robustness of designs. We use this to show that the relative robustness of designs against changes in problem objectives has a simple graphical representation. This graphical representation, and its underlying stress–strain foundation, provide new metrics that can be applied to classes of designs to assess robustness from feature- to system-level.

Speaker: Prof. Greg van Anders (Queen's University)

120 Functionalized surfaces of graphene field effect transistors for gas sensing

Graphene is among the most promising materials considered for next-generation gas sensing due to its properties including high mechanical strength and flexibility, high surface-to-volume ratio, large conductivity, and low electrical noise. While gas sensors based on graphene devices have already demonstrated high sensitivity, one of the most important figures of merit, selectivity, remains a challenge. In the last few years, however, surface functionalization emerged as a potential route to achieve selectivity. In this talk, we focus on experiments where we functionalized the surface of CVD graphene field-effect transistors (GFET) through thermal evaporation of metal-free phthalocyanines and copper phthalocyanines. We present and discuss sensitivity and selectivity results obtained when such sensors are exposed to volatile organic compounds such as ethanol, toluene, formaldehyde, and acetone. In general, the functionalized GFET presented enhanced selectivity for oxygen-containing molecules (formaldehyde and acetone).

Speaker: Dr Natalia Alzate-Carvajal

121 Development of graphene-based field-effect transistor (GFET) sensors for a simulant of chemical warfare agents

Chemical warfare agents (CWAs) are potential threats to civil society and defence personnel. In recent years, many efforts has been deployed to develop a scalable, rapid and accurate detection system to identify trace amount of CWAs. Here we report a graphene-based field-effect transistor (GFET) sensor able to detect 800 ppb of dimethyl methyl phosphonate (DMMP), a simulant of the nerve agent sarin. We observe enhanced sensitivity when the GFET sensor is exposed to few mWs of UV light. Back gate measurements performed before and during exposures to the analyte allow us to investigate the sensing mechanism while monitoring the induced changes in carrier concentration and mobility in graphene.

Speaker: Dr Ranjana Rautela

122 Optically enhanced gas sensing performance of graphene field effect transistors

Graphene field effect transistors (GFETs) have an enormous potential for the development of next-generation gas sensors, but more efforts are required to improve their sensitivity and selectivity. In this talk we discuss UV illumination as a promising method to enhance the performance of GFETs for the detection and recognition of analytes such as ethanol, water vapor and dimethyl methylphosphonate (DMMP), a molecule with structural similarities to nerve agents such as sarin. We show that illuminating the devices in operando with a UV LED results in both improved sensitivity and selectivity. By monitoring the sensing response of the GFETs as a function of gate voltage, we directly demonstrate that a shift in the Dirac point due to the optical doping is associated with the increased sensitivity. Moreover, we discuss how the substrate and fabrication residues on the surface of the graphene sensors can play a role in modifying the sensing performance.

Speaker: Dr Jaewoo Park (University of Ottawa)

123 Multilayer Graphene as Adaptive Thermal Camouflage

In this work we explore the use of multi-layer graphene (MLG) films grown by chemical vapor deposition for adaptive thermal camouflage. Using different ionic liquids, we tune the opto-electronic properties of MLG (150 – 200 layers) and investigate changes in optical reflectivity and emissivity in the infrared region (IR). We fabricate devices having a metallic back electrode supporting a porous membrane onto which we deposit the MLG. We use both non-stretchable polyethylene (PE), and stretchable polydimethylsiloxane (PDMS) as porous membranes. Using a thermal imaging system, we demonstrate that even when the device temperature is maintained higher than the environment, the MLG emissivity can be electrically controlled such that the device appears indistinguishable from the environment [1]. Moreover, we evaluate the performance of such devices based on flexible textiles towards developing a new material platform for defense applications.

Speaker: Saher Hamid (University of Ottawa)

Hamid-CAP Recording-07 June 2021.mp4

124 Fourier-transform infrared spectroscopy of alkanethiol self-assembled monolayers formed on digitally photocorroded surfaces of (001) GaAs

The science and technology of alkanethiol self-assembled monolayers (SAMs) on gold and other solid surfaces is a subject of ongoing research driven by the fundamental interest and attractive practical applications. The structural organization of alkanethiol SAMs is dominated by the strong intermolecular interaction, manifested by the enhanced quality of SAMs formed by long chain alkanethiols. Thiol ligands cover a larger number of binding sites on nanostructured rather than atomically flat gold surfaces,$^{1, 2}$ ascribed to the presence of curved surfaces of nanoparticles and vertices of nanostructured surfaces. The observation of this effect on surfaces of compound semiconductors, such as GaAs, is highly challenging due to the problem with maintaining surface stoichiometry and controlling oxide formation on these materials. Thus, there is anecdotal evidence that formation of high-quality SAMs on compound semiconductors requires flat surfaces.
We have investigated formation of mercaptohexadecanoic (MHDA) SAMs on digitally photocorroded (DIP) surfaces of (001) GaAs/Al$_{0.35}$Ga$_{0.65}$As nanoheterostructures (5 pairs of GaAs/AlGaAs, d$_{GaAs}$ = 12 nm, d$_{AlGaAs}$ = 10 nm). The DIP process allows etching with a step resolution of better than 0.1 nm, making possible also in situ deposition of different SAMs on freshly etched surfaces. The FTIR spectroscopy revealed the growing absorbance intensity and decreasing vibration energy of the -CH$_2$ modes of MHDA SAMs formed on surfaces of GaAs with the increasing nano-scale roughness produced in an ammonia solution. The absorbance amplitude of 1.08 x 10$^{-2}$ (E$_{CH2}$ = 2919.6 cm$^{-1}$, FWHM = 20.3 cm$^{-1}$) observed for the SAM developed on the surface of the 5$^{th}$ GaAs layer was 11-fold greater than that on the surface of the 1$^{st}$ GaAs layer (E$_{CH2}$ = 2922.0 cm$^{-1}$, FWHM = 25 cm$^{-1}$), which suggests formation of an excellent quality MHDA SAM. Our results suggest the feasibility of attractive applications of the DIP process for the research of atomic scale interfaces involving III-V semiconductors and manufacturing of advanced sensors and nanodevices.

1. X.-M. Li, J. Huskens and D. N. Reinhoudt, J Mater Chem 14 (20), 2954-2971 (2004).
2. C. Vericat, M. E. Vela, G. Benitez, P. Carro and R. C. Salvarezza, Chem Soc Rev 39 (5), 1805-1834 (2010).

Speaker: Mr René St-Onge (Laboratory for Quantum Semiconductors and Photon-based BioNanotechnology, Laboratoire Nanotechnologies Nanosystèmes (LN2) - CNRS UMI-3463, Interdisciplinary Institute for Technological Innovation (3IT), Department of Electrical and Computer Engineering, Université́ de Sherbrooke)

125 Measuring water depth on an inclined road

The National Research Council Canada (NRC) was contracted by Infrastructure Canada and the City of Toronto to improve the understanding of the performance of various catch basin covers under various conditions. A full scale model roadway was built 10.7 m long and 2.6 m wide in the NRC's Coastal Wave Basin and the water depth in front of the catch basin varied from 0.5 - 15 cm, the road grade was varied from 0.5 - 10.0% and the cross slope was varied from 2.0 - 4.0%. Early in the test protocol it was noted that the capacitance wire wave gauges used to measure the water depth on the roadway provided inconsistent results. In this work we will compare water depth measurements from a manual point gauge, an acoustic sensor and the capacitance wave probes. We will examine in which way each of the sensors is biased and examine the impact of those results.

Speaker: Louis Poirier (National Research Council Canada)

126 (G*) Molybdenum stable isotope measurements of petroleum coke in the Athabasca Oil Sands Region

Molybdenum possesses seven stable isotopes and the relative amounts of these isotopes are found to vary in nature. This is because physical and chemical processes can redistribute the isotopes in a system due to the differences atomic masses. Specific processes can leave an “isotopic fingerprint” that may be recorded in the isotopic composition of the element in a given sample. The interpretation of these data can enable one to elucidate source(s) and processes that may have affected the element. An important example of a potential Mo source is petroleum coke (PC). This is a by-product from the extraction of crude oil from the Oil Sands in northern Alberta and although it is employed as a fuel source, it is not used as quickly as it is produced, allowing it to accumulate on site [1]. There is evidence PC dust spread by wind contributes to an increase in polycyclic aromatic hydrocarbons (PAH) and polycyclic aromatic compounds (PAC) accumulating in lichen samples in forests in the Athabasca Oil Sands Region [2]. This could mean that trace metals are deposited in forests or bodies of water. Natural sources of the surrounding oil sands and bitumen seeps mean that the Athabasca River contains relatively high concentrations of metals compared to glacial counterparts. It is vital to distinguish between the natural and anthropogenic inputs so that appropriate procedures can be put in place to minimize human impacts on the region. Concentration measurements of Mo in aqueous environments provide ambiguous results as they do not necessarily distinguish between natural and industrial sources. Isotope abundance data can provide additional information on the source and history of the material. This project measured the isotopic composition of Mo leached from PC. Isotope determination was done using the double spike method measured with a Neptune multi-collector ICP-MS. The δ97/95 values for three oven dried PC leachate samples were determined to be +0.13 ‰, +0.34 ‰, and +0.81 ‰ with a 2σ uncertainty of 0.06 ‰. These samples had concentrations of 3.16, 9.47, and 0.55 µg/L respectively (uncertainty of 5 %). The isotopic composition of samples from this region gives a better understanding of the sources and sinks of Mo and can be combined with snow, lichens, and water to identify potential environmental concerns caused by PC distributed by wind.
1. J. M. Robertson et al. Aqueous- and solid-phase molybdenum geochemistry of oil sands fluid petroleum coke deposits, Alberta, Canada. Chemosphere 217, (2019).
2. M. S. Landis et al. Source apportionment of an epiphytic lichen biomonitor to elucidate the sources and spatial distribution of polycyclic aromatic hydrocarbons in the Athabasca Oil Sands Region, Alberta, Canada. Science of the Total Environment 654, (2019).

Speaker: Courtney Kruschel

127 (G*) Self-witnessing coherent imaging for artifact removal and noise filtering in laser keyhole welding

High-power lasers are rapidly becoming standard tools in advanced manufacturing, mainly in the form of laser welding, laser cutting, and laser additive manufacturing. Of these applications, laser welding in the electric mobility sector---particularly in the manufacturing of battery packs---presents unique challenges. Weld depth needs to be precisely controlled, not only to ensure joint strength, but also to ensure the weld does not puncture into the lithium ion cell. In addition, these processes often involve highly reflective metals (such as copper), which have material properties that lead to unstable welds; this requires an unprecedented level of control to ensure weld quality and depth. To better monitor and control weld quality, we need fully in-line monitoring during the process. Inline Coherent Imaging (ICI) is a process monitoring technique that has been demonstrated to measure keyhole depth (down to 15 um axial resolution) at high imaging rates (~200 kHz), even in high aspect ratio features. Due to its interferometric nature, coherent imaging has unparalleled sensitivity and dynamic range. However, it suffers from speckle noise, which degrades high-speed measurements by orders of magnitude, and false interfaces that arise from unwanted interferences (“autocorrelation” peaks). These pose a significant challenge to quality assurance and closed-loop control, particularly in highly dynamic laser processing applications, such as copper welding. To mitigate these problems, we have integrated a second, automatically synchronized, imaging channel into a standard ICI system, by exploiting a previously unused part of the imaging window. This “witness” image allows us to identify real signatures based on correlation and filter out the uncorrelated noise. Using this system, we have demonstrated the complete removal of autocorrelation artifacts, and have increased signal to noise by a factor of two, with no loss of imaging rate or spatial resolution compared to standard ICI. When applied to imaging laser keyhole welding, the false interface detection rate is reduced from 10% to 0.15%, yielding improved tracking of the true morphology.

Speaker: Tessa Krause (Queen's University)

M3-9 Exploring the Energy and Precision Frontier I (PPD) / Frontière d'énergie et de précision I (PPD)

Convener: Alison Lister (University of British Columbia (CA))

128 (I) Highlights ATLAS experiment

In this talk, recent highlights and future prospects will be discussed.

Speaker: Tony Kwan (McGill University, (CA))

Kwan_CAP2021_ATLAS.pdf

129 (G*) Characterizing the Higgs Boson at the LHC

As the most recently-discovered particle of the Standard Model, the Higgs boson is fundamental to our understanding of particle physics and is the focus of much attention at CERN’S Large Hadron Collider (LHC). The Higgs boson’s couplings to other particles are predicted by the Standard Model (SM), so performing precise measurements of these couplings can probe for discrepancies and constrain theories beyond the SM. This talk will present recent work by the ATLAS experiment at CERN to characterize the newly-discovered Higgs boson by measuring its coupling to W bosons using data collected at the LHC from 2015-2018. It will highlight the first ATLAS observation of H->WW* decay in the vector boson fusion (VBF) production channel and its role in rigorously testing the SM.

Speaker: Robin Hayes (University of British Columbia (CA))

RobinHayes-CAPCongress-June2021.pdf

130 (G*) The Search for Evidence of Vector Boson Scattering Between a Photon and a W Boson with the ATLAS Detector

In the Standard Model, the interactions between gauge bosons are completely specified and any deviations from this expectation would indicate the presence of new physics phenomena at unprobed energy scales. The study of the self-couplings of electroweak gauge bosons is therefore a powerful approach to searching for new physics phenomena. The large data samples collected by the ATLAS experiment at the LHC make it possible to now explore extremely rare processes involving the interaction between four gauge bosons.
In this talk I will discuss the search for evidence of one of these rare processes, namely, the vector boson scattering between a W boson and a photon, whose production cross-section has never before been measured by the ATLAS collaboration. Making a measurement of this electroweak process is challenging due to the presence of a large and irreducible background from processes involving the strong interaction, which are mismodelled at high di-jet mass where we expect the greatest sensitivity to VBS. I will discuss analysis techniques being used to make a measurement in the presence of this large and mismodelled background.

Speaker: John Patrick Mc Gowan (McGill University, (CA))

CAP_final (2).pdf

16:30 15 Minute Break

M4-1 Optical spectroscopy (DAMOPC) / Spectroscopie optique (DPAMPC)

Convener: Duncan O'Dell (McMaster University)

131 (I) Radiative efficiency and global warming potential of fluorinated greenhouse gases

The phase-out of ozone depleting substances has led to the release in the atmosphere of new generations of fluorinated coolants and propellants. Those molecules contain C-F bonds, which make them strong absorbers in the mid-infrared spectral region. To properly assess the impact of those molecules on climate, their radiative forcing must be calculated from their experimental and/or theoretical absorption cross-sections.
The common way to obtain the data is through the acquisition of laboratory absorption spectra by Fourier transform spectroscopy. This process allows the study of the temperature and pressure dependence as well as the impact of hot bands and combination bands. However, the acquisition is time-consuming and not always straightforward.
A second method consists into calculating the vibrational band positions and intensities of the molecule by quantum mechanical calculations and simulating the cross-section spectra. The calculations can be carried out by ab-initio or density functional theory methods. Although theoretical data can quickly estimate the radiative efficiency of a molecule, the results are dependent on the levels of theory and still require empirical corrections to match their experimental counterparts. However, theoretical calculations has proven to be an efficient tool to analyze the conformational populations and to provide data on a spectral range that cannot be easily accessed experimentally.
Over the past few years, our group has analyzed the radiative properties of multiple molecules and extracted their radiative efficiency and global warming potential. In this talk, we will discuss recent results and findings. In particular, we will show that the best results come from a compilation of both experimental and theoretical results.

Speaker: Prof. Karine Le Bris (St. Francis Xavier University)

132 (I) On the validity of many-mode Floquet theory

Floquet theory is useful for understanding the behaviour of quantum systems subject to periodic fields. Ho et al. [Chem. Phys. Lett. 96, 464 (1983)] have presented an extension of Floquet theory to the case of systems in the presence of multiple periodic fields with different frequencies. However, unlike conventional Floquet theory, which is well-established, many-mode Floquet theory (MMFT) is somewhat controversial, with conflicting statements regarding its validity appearing in the literature. I will present our recent resolution of these discrepancies.

Joint work with Adam Poertner, supported by NSERC.

Speaker: Prof. James Martin (University of Waterloo)

133 In source laser resonance ionization spectroscopy of radioactive isotopes

Laser resonance ionization (mass) spectroscopy in a hot cavity environment is an ultra-sensitive means for laser spectroscopy of short-lived isotopes. Despite the non-Doppler free nature of hot cavity, in source spectroscopy, this method allows to determine atomic energy levels and through Rydberg series convergence the determination of the first ionization potential. An overview of the ongoing in-source spectroscopy program with radioactive isotopes at TRIUMF - Canada's particle accelerator laboratory will be given.

Speaker: Jens Lassen (TRIUMF)

134 Emergence of light-induced states in the few-photon ionization of atomic helium*

In this joint experimental and theoretical work [1], photoelectron emission from excited states of laser-dressed atomic helium is analyzed. We successfully demonstrate a method that is complimentary to transient absorption (e.g. [2]) for the assignment of light-induced states (LIS). The experiment is carried out at DESY in Hamburg and uses the FLASH2 free-electron laser to produce an extreme ultraviolet (XUV) pulse to which the helium atom is subjected along with a temporally overlapping infrared (IR) pulse in the multi-photon ionization regime ($\approx$10$^{12}$ W/cm$^2$). Analysis of the experiment occurs at the reaction microscope (REMI) end station [3] at FLASH2. The XUV pulse is scanned over the energy range 20.4 eV to 24.6 eV, corresponding to excited states of helium. The resonant, electric dipole-allowed $n$P states corresponding to a first step of single XUV photon excitation are shown to lead to ionization, independent of whether or not the lasers temporally overlap. However, dipole-forbidden transitions to $n$S and $n$D states corresponding to multiphoton (XUV $\pm$ $n$IR) excitation are observed during temporal overlap. Studying photo-electron angular distributions (PADs) in the case where the ionization pathway of a LIS is difficult to resolve energetically allows for an unambiguous determination of the dominant LIS. The IR intensity and relative polarization between the lasers are varied to control the ionization pathway. Numerical solutions of the time-dependent Schr\"odinger equation within a single-active electron model with a local potential completely support the experimental findings in this project.
[1] S. Meister $\textit{et al}$., Phys. Rev. A $\bf{102}$ (2020) 062809; Phys. Rev. A $\bf{103}$ (2021) in press.
[2] S. Chen $\textit{et al}$., Phys. Rev. A $\bf{86}$ (2012) 063408.
[3] S. Meister $\textit{et al}$., Applied Sciences $\bf{10}$ (2020) 2953.
*work supported by NSERC, NSF, and XSEDE

Speaker: Aaron Bondy

17:03 Group discussion

M4-2 MR and PET Imaging - Part 2 (DPMB) / Imagerie RM et TEP - Partie 2 (DPMB)

Convener: Emily Heath

135 (G*) Multi-modal PET-MR imaging of the selective activation of serotonergic neurons in living rodent brains with DREADD technology

The main advantage of hybrid PET-MR imaging systems is the ability to correlate anatomical with metabolic information directly. The bulk of commercially available PET-MR systems are quite large and expensive and mostly used on humans rather than for preclinical animal studies. This has led to a gap of knowledge in PET-MR imaging of small animal models used in preclinical research. Our work takes advantage of a new imaging system developed by Cubresa called 'NuPET'. This device is a MR-compatible PET scanner placed around the subject while they are within the toroidal bore of a MR scanner. With this equipment we are attempting to demonstrate the selective activation of serotonergic neurons in living rodent brains. To specify which neurons are to be activated, we use Designed Receptors Exclusively Activated by Designer Drug (DREADD) technology. These DREADDs are designer G-protein-coupled receptors. Neurons at the site of a stereotactic injection are transfected with a viral vector containing the proteins necessary to force expression of DREADDs in genetically modified rats. These may then be activated by administering the designer drug clozapine-N-oxide (CNO). This technique allows for precise spatiotemporal control of receptor signaling in vivo. Over two experiments (N=5, N=2) we have attempted to image the effect of DREADDs-mediated excitation of 5-HT neurons in rats. Voxel-based analysis of the data thus far show no confirmed statistically significant differences between rats given saline and those given CNO. Numerous methodological issues have been discovered within the experimental design, and are being addressed for a new trial of the technique and technology.

The authors wish to acknowledge funding from NSERC partnership grants, Mitacs, Cubresa, and Research Manitoba.

Speaker: Jarrad Perron (University of Manitoba)

136 (G*) Measuring calcium isotopic composition in the body to understand metabolic processes.

Calcium (Ca) is an essential mineral in the body that helps maintain healthy bone density. Dysreguation of Ca can result in serious health issues and a reliable and efficient method of identifying changes in bone mineral balance can help to provide eaarly diagnosis of deteriorating bone health. The objective of this project is to investigate the application of naturally occurring Ca isotope abundance variations to understand biological processes, including biomineralization. This is because the kinetics underlying metabolic processes that involve Ca are mass dependent and will redistribute the abundances of naturally occuring, stable Ca isotopes. Thus, a careful measurement of Ca isotopic composition of the Ca pools in the body (i.e. bone, blood, and urine) can provide unique insight into the disruption of Ca metabolism. The extent of natural variations of stable Ca isotopes in the human metabolism is limited with a relative natural variation of less than 0.5% in the 44Ca/40Ca isotope amount ratio. Therefore, reliable measurement of Ca isotopic composition has remained very challenging, especially considering low Ca levels and significant procedural blank levels. The goal of this project was so develop a reliable and accurate analytical measurement procedures specifically for small amounts (approx. 1 µg) of Ca in biological materials.

In this study the extraction and isolation of calcium from a diverse set of biological matrices was optimized for low procedural blanks and separation from matrix elements and isobaric interferences such as Na, Mg, K, Mg, Ti, Fe, Ba. A 42Ca–48Ca double spike (DS) was applied to correct for potential isotopic fractionation during sample preparation and measurement. Ca isotope abundance analysis was performed using a multicollector thermal ionization mass spectrometer. The measurement procedure enabled processing of total Ca amounts of 1000 ng, with a total procedural blank of <10 ng and enabled measurement of the Ca isotopic compositions of the reference materials NIST SRM 1400 (bone ash), NIST SRM 1486 (bone meal) and IAPSO (seawater).

Speaker: Dorothy Walls (University of Calgary)

137 (G*) Simultaneous Hyperpolarized 129Xe MRI and [15O]water PET Multi-Modal Imaging: A Proof of Concept Study

Introduction: A non-invasive imaging method: inhaled hyperpolarized (HP) 129Xe magnetic resonance imaging (MRI) is currently used to measure lung structure and function.1 Simultaneous ventilation/perfusion (V/P) lung measurements of functional gas exchange within the lungs can be obtained using this MRI approach because of the high solubility of xenon in lung tissue as compared to other imaging gases. This measurement is possible due to the distinct and large range of chemical shifts (~200ppm) of 129Xe when residing within barrier and RBC (e.g., barrier and RBC phase xenon) compared to the gas phase. Therefore, 129Xe is a unique probe for exploring xenon within and beyond the lung, such as lung parenchyma (barrier), RBC, and even other organs such as the brain, heart and kidney.
[15O]water positron emission tomography (PET) is the gold standard imaging method for determining cerebral perfusion.2,3 In this study, simultaneous 129Xe-based MRI and [15O]water PET images were collected and compared.

Methods: A 60mL plastic syringe was used in which 30mL of the hyperpolarized 129Xe gas was dissolved in [15O]-water solution (30mL) After dissolving, all leftover xenon gas was removed from the syringe. A turn-key, spin-exchange polarizer system (Polarean 9820 129Xe polarizer) was used for obtaining Hyperpolarized 129Xe gas. 129Xe dissolved phase images were acquired in a 3T PET/MRI (Siemens Biograph mMR) scanner. [15O]water PET data were acquired simultaneously with 129Xe MRI using the integrated PET system in the 3T PET/MRI.

Results: Two consecutive 2D axial 129Xe MRI images and two (2D and 3D) [15O]water PET images were acquired simultaneously. 129Xe/PET images indicate that the diameter of the phantom from both PET and MRI images are similar. Both 129Xe images demonstrate a sufficient SNR level (80 and 10 respectively) suggesting that 3D 129Xe imaging is possible.

Conclusions: The results of this proof-of-concept study clearly indicate the feasibility of the simultaneous hyperpolarized 129Xe MRI and [15O]water PET measurements. This demonstration enables the next step, namely, in-vivo double tracer brain perfusion imaging which we plan to perform using a small animal model.

References:
1.Kaushik, S. S. et al. MRM (2016); 2. Fan, A., et. al. JCBFM (2016); 3. Ssali. T., et. al. JNM (2018).

Speaker: Ramanpreet Sembhi (The University of Western Ontario)

138 (G*) On the rationale for a standardized pre-clinical segmentation technique in PET pharmacokinetic

Introduction: A great challenge in quantitative dynamic positron emission tomography (PET) imaging is to determine the exact volumes of interest (VOI) with which one wants to work. They have a tremendous impact on the time-activity curves that are used to extract the pharmacokinetic coefficients. Since PET images are functional and not anatomical, using a bijective relationship with a computed tomography (CT) co-image is neither the sole nor the best possibility. In recent years, many publications have come with ingenious methods to work directly with the PET images, ranging from machine learning algorithms to manual toil to define regions. These techniques have different uses, mainly in the hope of enabling easier and more efficient tumor delimitation. In the case of dynamic images, the temporal aspect of the imaging procedure changes the methods that can be implemented. Furthermore, the need to delimitate specific and precise functional sites render the whole operation computationally and physically challenging, especially in the absence of a common and well-established methodology.
Methodology: In this project, a novel approach using a gradient-based segmentation was used on pre-clinical dynamic PET images on rats. Fourteen different animals were used under similar pre-clinical conditions. The developed segmentation technique uses properties of the image itself, relying on already known properties of the radio-drug used in order to segment automatically the kidney of the animal. The work was conducted using the mini-PET scanner at the Montreal Neurological Institute, according to the ethical guideline from the University of Montréal and the Canadian Tri-Council.
Results: From the preliminary data, the proposed method has a relevant rate of success on clinical images in delimitating the volumes of interest. The respective time-activity curves follow the general pattern of the manual delimitations done by experts, yet with non-negligible differences. So far, the proposed technique offers good result on 8 of the 14 rats, as compared to 12 rats when using a manual segmentation. The greatest strength of the algorithm is its ability to reproduce the same results notwithstanding the operator. The technique can also quantify movement in the organ of interest and work in spite of a great amount of Gaussian noise.
Keywords: Nuclear Medicine, pre-clinical dynamic PET imaging, pharmacokinetic

Speaker: Philippe Laporte (Université de Montréal)

139 (G*) Magnetic Resonance Imaging Data Acquisition Acceleration and Feature Detection with Dictionary Learning

Magnetic Resonance Imaging (MRI) is a powerful imaging modality with excellent soft tissue contrast. Contrast agent such as iron oxide nanoparticles can be used to “tag” individual cells, distorting the magnetic field around them and allowing the imaging of single cells. Time-lapse MRI can be used to track the motion of tagged cells, providing insights in the studies of inflammatory diseases and metastasis of cancer. Current methods have a very limited temporal resolution resulting in a detection limit of 1µm/s . In addition, the manual cell counting is time consuming and difficult.
In this work, a dictionary learning based technique has been developed to accelerate the MRI data acquisition and aid in the task of locating cells. Dictionary learning is a machine learning technique, in which features of an image can be ‘learned’ as atoms. Images can be represented using a sparse combination of atoms. The sparsity property can be used as a constraint in non-linear image reconstruction with data sampled below the Nyquist criteria. The undersampling improved the temporal resolution of the in-vivo measurements by approximately an order of magnitude. The dictionary atom coefficients provided information on the cell locations for feature detection.

Speaker: Mr Mark Armstrong (University of Windsor)

140 (G*) Magnetic Resonance Relaxometry with Neural Networks

Magnetic resonance imaging (MRI) is widely used as a non-invasive diagnostic technique to visualize the internal structure of biological systems. Quantitative analysis of magnetic resonance signal lifetimes, i.e., relaxation times, can reveal molecular scale information and has significance in the study of brain, spinal cord, articular cartilage, and cancer discrimination. Determination of MR relaxation spectra (relaxometry) is an inherently ill-posed problem. Conventional methods to extract MR relaxation spectra are computationally intensive, requiring high quality data and generally lacking the spectrum peak width information. A novel computationally efficient signal analysis method, based on neural networks (NN), has been developed to provide accurate real-time quantitative MR relaxation spectrum analysis.
Deep learning with NN is a technique for solving complex nonlinear problems. NN have been optimized to determine 1D and 2D MR relaxation spectra. Simulated signals with Rician noise were employed for training the neural networks. The network performance was evaluated with simulated and experimental data, and compared with the traditional inverse Laplace transform (ILT) method. NN outperformed ILT. The 1D spectrum peak widths, generally considered not reliable with the traditional approach, could be determined accurately by the NN, noise permitting.
The proposed exponential analysis method is not restricted to magnetic resonance. It is readily applicable in other areas with exponential analysis, such as fluorescence decay and radioactive decay. The method could be extended to higher dimensional spectra and adopted to solve other ill-posed problems.

Speaker: Mr Tristhal Parasram (University of Windsor)

141 Prediction of Alzheimer's Disease Based on Multi-Attentional Mechanisms using Brain PET Image

Positron Emission Tomography (PET) Imaging of the brain might become the most effective imaging technique to predict Alzheimer's disease. However, the definition of the brain in PET images is low and the lesion area is not easy to define, so the accuracy of traditional machine learning algorithms in predicting Alzheimer's disease from PET images is low. Deep learning algorithms can effectively improve the accuracy of prediction. Here, a deep learning model based on multi-attention mechanisms is constructed for the prediction of Alzheimer's disease. Firstly, in order to improve the images and reduce the loss of spatial information caused by convolution, a soft-attention mechanism was introduced to embed non-local modules and CBAM modules into the prediction model, which effectively solved the problems of the lack of detail information and the lack of connection between channels in PET images after deep convolution. Secondly, a split-attention mechanism was introduced, and the influence of different parameters of feature images with different sizes on the prediction accuracy was enhanced by using a packet network. Finally, head movement correction, image registration, craniocerebral separation, Gaussian smoothing and other image preprocessing were performed on the acquired PET images to effectively improve the image features of Alzheimer's disease focal areas in brain PET images. The experimental results showed that the prediction accuracy, sensitivity and specificity of the model in the ADNI database for Alzheimer's disease were 90.5%, 86.1% and 93.5% respectively, which could provide more accurate diagnostic results compared with the existing methods.

Speaker: Yonglin Chen (Anhui University)

M4-3 Teaching and EDI I/Enseignement et EDI I (DPE/DGEP)

Convener: Patricia Mitchler (Canadian Association of Physicists)

142 Sky Stories: The Art of Science Outreach

Our universe is a dynamic, fascinating, and beautiful place. Yet, physics is sometimes perceived as being dry and lacking cultural engagement. To mitigate that perception, we are engaging two powerful partners: our physical universe and our local culture.
The talk will describe a scientific and cultural outreach program developed for underrepresented youth in Newfoundland and Labrador, which offers activities featuring female and Indigenous role models, engage Indigenous story-telling, discuss science-related career opportunities, and emphasize a diverse set of skills required in modern science. We’ll also discuss challenges and opportunities brought by the Covid-19 pandemic and lessons learned on reaching remote communities and engaging teenagers online.

Speaker: Prof. Svetlana Barkanova (Grenfell Campus of Memorial University)

Barkanova Science Outreach CAP2021.pdf

143 University of Winnipeg Undergraduate Programs to Encourage Indigenous Students to Undertake Graduate Studies in Science and Engineering

Undergraduate research activities, strong mentorship and peer support have been demonstrated to improve the experiences of students studying science in the last few years and the community has grown on campus. The University of Winnipeg has a large number of Indigenous students per capita, and is uniquely situated to support and encourage Indigenous students in the sciences. This presentation will describe two programs: the Pathway to Graduate Studies (P2GS) program for junior students and our chapter of the Canadian Indigenous Science and Engineering Society (.caISES), which is open to all Indigenous students studying science. These two programs offer a rich environment for research and scholarly success as well as a means to form a sense of community and belonging on campus. The P2GS program provides opportunities for junior Indigenous undergraduate students to upgrade their basic science skills, gain research experience in a university laboratory, and to form a network of peers, graduate students and faculty, which will help increase their success and participation in natural sciences and engineering (NSE) graduate programs. The P2GS program brings students on campus for four weeks each May. They split their time between science classes led by senior Indigenous students and engaging in research projects with a faculty mentor. The program has had a wide ranging impact, with several of the participants crediting this experience with their decision to continue in NSE or to enroll in graduate school.
Our .caISES chapter meets at least monthly and hosts events which bridge culture and science. Students also attended national and regional meetings for .caISES and the American AISES parent organization. The University of Winnipeg was the recipient of the 2020 Stelvio J. Zanin Chapter of the Year in our inaugural year.
The authors wish to acknowledge funding for the P2GS program from NSERC PromoScience and the University of Winnipeg and from the University of Winnipeg, scholarships and fundraising for .caISES.

Speaker: Melanie Martin (University of Winnipeg)

M4-4 Cosmology (DTP) / Cosmologie (DPT)

Convener: Levon Pogosian (Simon Fraser University)

144 Gravitational Waves interacting with matter in cosmology

We discuss interaction of gravitational waves with matter including plasma and its implications for cosmology.

Speaker: Arundhati Dasgupta (University of Lethbridge)

145 Matter-Geometry Entanglement in Quantum Cosmology

We present a study of the evolution of entanglement entropy of matter and geometry in quantum cosmology. We show that entanglement entropy increases rapidly as the Universe expands, and then saturates to a constant non-zero value. The saturation value of the entropy is a linear function of the energy E associated to the quantum state: S=γE. This result suggests a ‘First Law’ of matter-gravity entanglement entropy in quantum gravity.

Speaker: Viqar Husain (University of New Brunswick)

146 Cosmology on the Beach: a formal analogy

We report a formal analogy between cosmology and earth science. The history of a closed universe is analogous to an equilibrium beach profile (i.e., the depth of the water as one recedes from a beach moving seaward). A beach profile reaches equilibrium in summer and in winter and is described by a variational principle that minimizes energy dissipation. The oceanography side of the analogy gains much needed information from the cosmology side.

[Based on V. Faraoni, Phys. Rev. Research 1, 033002.]

Speaker: Valerio Faraoni (Bishop's University)

147 On the quantum origin of a dark universe

It has been shown beyond reasonable doubt that about 95% of the total energy budget of the universe is given by the dark constituents, namely Dark Matter and Dark Energy. What constitutes Dark Matter and Dark Energy remains to be satisfactorily understood however, despite a number of promising candidates. An associated conundrum is that of coincidence, as to why the Dark Matter and Dark Energy densities are of the same order of magnitude at the present epoch. In an attempt to address these, we consider a quantum potential resulting from a quantum corrected Raychaudhuri/Friedmann Equation in presence of a Bose-Einstein condensate (BEC) of light bosons. For a suitable and physically motivated macroscopic ground state wavefunction of the BEC, we show that a unified picture of the cosmic dark sector can indeed emerge, which also resolves the issue of the coincidence. The effective density of the Dark energy component turns out to be a cosmological constant. Furthermore, comparison with observed data give an estimate of the mass of the constituent bosons in the BEC, which is well within the bounds predicted from other considerations.

Speaker: Saurya Das (University of Lethbridge)

148 (G*) Bubble Nucleation Events are Correlated

False vacuum decay in quantum mechanical first order phase transitions is a phenomenon with wide implications in cosmology, and presents interesting theoretical challenges. In the standard approach, it is assumed that false vacuum decay proceeds through the formation of bubbles that nucleate at random positions in spacetime and subsequently expand. In this paper we investigate the presence of correlations between bubble nucleation sites using a recently proposed semi-classical stochastic description of vacuum decay. This procedure samples vacuum fluctuations, which are then evolved using lattice simulations. We compute the two-point function for bubble nucleation sites from an ensemble of simulations, demonstrating that nucleation sites cluster in a way that is qualitatively similar to peaks in random Gaussian fields. We comment on the implications for first order phase transitions during and after an inflationary era.

Speaker: Dalila Pirvu (Perimeter Institute / University of Waterloo)

149 (G*) Cosmological perturbation theory with matter time.

Cosmology presupposes that on scales of $10^{8}$ light years the universe is the same at every point and in every direction. This is observationally supported by the cosmic microwave background (CMB) which has a temperature of 2.7 Kelvin in all directions. However, there exist small perturbations on this symmetric background - for example the CMB has perturbations of 0.001 Kelvin. A study of these fluctuations is cosmological perturbation theory. In this talk, I will review the standard theory of cosmological perturbations, explain our framework which is different from the standard method and then generalize our framework to include a matter clock.

Speaker: Mr Mustafa Saeed (University of New Brunswick)

150 (G*) Gravitational Wave Backgrounds from Low Scale Inflation

While Big Bang cosmology successfully explains much of the history of our universe, there are certain features it does not explain, for example the spatial flatness and uniformity of our universe. One widely studied explanation for these features is cosmological inflation. I will discuss the gravitational wave spectra generated by inflaton field configurations oscillating after inflation for E-Model, T-Model, and additional inflationary models. I will show that these gravitational wave spectra provide access to some inflation models beyond the reach of any planned cosmic microwave background (CMB) experiments, such as LiteBIRD, Simons Observatory, and CMB-S4. Specifically, while these experiments will be able to resolve a tensor-to-scalar ratio ($r$) down to $10^{-3}$, I show that gravitational wave background measurements have the potential to probe certain inflation models for $r$ values down to $10^{-10}$. Importantly, all the gravitational wave spectra from E- and T-model inflation lie in the MHz-GHz frequency range, motivating development of gravitational wave detectors in this range.

Speaker: Simran Nerval (Queen's University)

151 (G*) Sub-GeV Dark Vector Bosons and their Impacts on Cosmology

The purpose of this presentation is to recognize the effects of electromagnetic energy injection into the early Universe from decaying sub-GeV dark vectors. Decay widths and energy spectra for the most prominent channels in the sub-GeV region are calculated for various dark vector models. The models include the kinetic mixing of the dark photon with the Standard Model photon, $U(1)_{A'}$ , a dark vector boson which couples to the baryon minus the lepton current, $U(1)_{B-L}$, and the last three are dark vector bosons which couple one lepton's current minus a different lepton's current, $U(1)_{L_i - L_j}$ where $i , j = e, \mu, \tau$ . Measurements from Big Bang Nucleosynthesis and the Cosmic Microwave Background are used to constrain the lifetime, mass and coupling constant of the dark vectors.

Speaker: John Coffey (University of Victoria)

152 kSZ Tomography with Foregrounds and Systematics

Much of what we know of the early universe comes from observations of the cosmic microwave background (CMB): a 13 billion-year-old field of microwave radiation that permeates the entire universe. Recent technological advances have made real the possibility of combining CMB measurements with other large data sets to extract hitherto inaccessible cosmological information. One such example is the novel technique of kinetic Sunyaev Zel’dovich (kSZ) tomography in which one combines a CMB temperature map with the positions and distances of galaxies across the sky, using statistical correlations between high-fidelity maps to reconstruct the velocity of those galaxies at the largest angular scales and over an appreciable fraction of the volume of the universe. At these scales and distances the motion of large-scale structure owes its statistical properties to the conditions of the early universe; measuring this velocity map would therefore provide an independent probe into the physics of that era.

The primary challenge in extracting a velocity map using kSZ tomography is characterizing the dominant sources of uncertainty introduced by non-idealities such as redshift measurement error, incomplete sky coverage, galactic and extragalactic contaminants, and confusion with other physical effects in the CMB. To this end we have designed a pipeline to perform the reconstruction using next-generation CMB and galaxy survey data that incorporates these contaminants into its design. We account for redshift errors and demonstrate that masking and other cut sky effects do not influence the reconstruction fidelity. We show that galactic processes do not contribute to the reconstruction noise, and estimate the impact of extragalactic sources that mimic the kSZ signal. We demonstrate that reconstruction is possible with data from next generation surveys and forecast how well the pipeline will perform with realistic contaminants. We estimate a strong signal-to-noise of the velocity map on large scales, making it a new data product on the cutting edge of cosmological research, as the field turns its attention to upcoming high-resolution datasets.

Speaker: Richard Bloch (York University)

17:12 Questions/Answers and Discussion Period

M4-5 Nuclei & Astrophysics II (DNP) / Noyaux et astrophysique II (DPN)

Convener: Barry Davids (TRIUMF)

153 (I) Direct and indirect measurements of charged-particle capture reactions

Experimentally-derived rates of selected charged-particle induced capture reactions are key ingredients in our global understanding of stellar nucleosynthesis. In particular, selected resonant proton and alpha capture reactions on medium-mass stable and radioactive targets are important for nucleosynthesis in a variety of scenarios such as classical novae and the $p$ and $rp$-processes, which form nuclei on the proton-rich side of stability. Select charged-particle reactions are also important for neutron capture processes, e.g. the $s$-process, where they can contribute to the neutron flux. In this talk, I will discuss my group's efforts to constrain important charged-particle capture reactions at both stable and rare-isotope beam facilities and using both direct and indirect measurement techniques. A particular emphasis will be placed on recent results related to the $s$-process neutron source ${}^{22}\mathrm{Ne}(\alpha,n){}^{25}\mathrm{Mg}$, as well as ongoing technical developments and anticipated future work at TRIUMF and the Texas A&M Cyclotron Institute.

Speaker: Prof. Gregory Christian (Saint Mary's University)

154 Nuclear polarization by optical pumping at TRIUMF

The nuclear-polarized beam facility at TRIUMF-ISAC provides radioactive ion beams, highly polarized by laser collinear optical pumping, to several experimental stations. It has successfully delivered 8,9,11Li, most Na isotopes, and 31Mg over the last 20 years for studies in material science, biochemistry, nuclear physics, and fundamental symmetries. An overview of the polarizer facility will be presented and its future development and upgrade will be discussed.

Speaker: Ruohong Li (TRIUMF)

155 (G*) A Measurement of Zinc-65 Using Data from the KDK Experiment

Zinc-65 (Zn-65) is a radionuclide of interest in the fields of medicine and gamma-ray spectroscopy, within which its continued use as a tracer and common calibration source necessitates increasingly-precise nuclear decay data. A Zn-65 dataset was obtained as part of the KDK ("potassium decay") experiment, whose apparatus consists of an inner X-ray detector and an efficient outer detector, the Modular Total Absorption Spectrometer (MTAS), to tag gamma rays. This setup allows for the discrimination of the electron capture decays of Zn-65 to the ground (EC) and excited (EC) states of Copper-65 (Cu-65) using an emerging technique for such a measurement, exploiting the high efficiency ($\sim$98%) of MTAS. Techniques used to obtain the ratio $\rho$ of EC to EC decays are applicable to the main KDK analysis which is making the first measurement of $\rho$ for Potassium-40, a common background in rare-event searches such as those for dark matter. The KDK instrumentation paper (under review by NIM) pre-print is available at arXiv:2012.15232. We present our current methodology and analysis procedures developed to obtain a novel measurement of the electron-capture decays of Zinc-65.

Speaker: Lilianna Hariasz (Queen's University)

Hariasz_CAP_2021_A_Measurement_of_Electron_Capture_Decays_Using_Data_from_the_KDK_Experiment.pdf

M4-6 Traps II (DNP) / Pièges II (DPN)

Convener: Zisis Papandreou

156 (I) Novel ion-trap techniques for precision studies of exotic radionuclides and radioactive molecules

Ion traps have long been recognized as superb precision tools for fundamental physics research.
In contemporary nuclear physics, they are widely employed to prepare, control and study short lived radionuclides with high precision and accuracy. Over the last decade, Multi-Reflection Time-of-Flight (MR-ToF) mass separators have significantly gained in importance at radioactive ion beam (RIB) facilities due to their superb mass resolving powers of R=m/∆m>105 achieved in a few milliseconds.
As a novel application of MR-ToF devices, we are currently developing the Multi Ion Reflection Apparatus for Collinear Laser Spectroscopy (MIRACLS). In this approach, a fast ion beam is bouncing back and forth between the two electrostatic mirrors of an MR-ToF device such that the trapped ions are probed by a spectroscopy laser during each revolution. This boosts the experimental sensitivity by a factor of 30-600 compared to conventional, single-pass collinear laser
spectroscopy (CLS). MIRACLS will hence provide access to ’exotic’ radionuclides with very low production yields at RIB facilities.
While our initial work is focused on highly sensitive CLS for nuclear structure research, the novel experimental techniques developed within MIRACLS open unique opportunities for searches for new physics beyond the standard model of particle physics in radioactive molecules. The latter
have recently been identified as unexplored, yet highly sensitive probes for fundamental physics such as hitherto undiscovered permanent electric dipole moments (EDMs).
This talk will describe the MIRACLS concept, recent highlights as well as its potential for novel precision studies with radioactive molecules in the context of searches for new physics.

Speaker: Dr Stephan Malbrunot-Ettenauer (CERN)

157 (G*) Exploring the limits of existence of heavy, neutron-deficient nuclei

Nuclear isotopes are nuclei with a fixed number of protons Z but with a varying number of neutrons N. The question of how many neutrons a certain element can have while maintaining its stability against neutron or proton emission, or in other words where the proton and neutron drip-lines lie, has been troubling not only nuclear physicists but also astrophysicists since it can help answering fundamental questions like “Where do the stable elements of our universe come from?” Unfortunately, the experimental study of very exotic isotopes very close to the drip-lines is often impossible due to their extremely short half-lives and low production yields.
To tackle the current lack of experimental data, we used the mass measurements of three neutron-deficient nuclei performed with TITAN’s MR-TOF mass spectrometer and known reaction energies to extract the masses of 20 nuclei on the border of nuclear stability or past it. With these new mass values, we determined the proton drip-line in the region around Z=78 and we compared our results with various theoretical models.
With the added benefit of the exotic character of these newly determined masses, we leapt into investigating possible Thomas-Ehrman shifts in the region. This unusual effect has been well established in some light and medium nuclei but never conclusively observed in heavier species.
Our calculation procedure as well as our results will be presented.

Speaker: Eleni Marina Lykiardopoulou (Department of Physics and Astronomy, University of British Columbia, TRIUMF)

158 (G*) Charting the $N = 40$ Island of Inversion with neutron-rich iron isotopes at TITAN

Mass measurement facilities are extremely important in furthering our understanding of nuclear structure away from the valley of stability, including aiding in the search for collective behaviors in exotic nuclei. TRIUMF’s Ion Trap for Atomic and Nuclear science (TITAN) is among the world’s premier precision trapping facilities, with the newly added Multiple-Reflection Time-of-Flight Mass Spectrometer (MR-ToF-MS) expanding its reach. The TITAN MR-ToF-MS was used in the measurement of neutron-rich iron isotopes around $N = 40$. These masses are critical in investigating a potential Island of Inversion at $N = 40$, which has been supported previously in literature by increased collectivity seen in this region. In total, the masses of $^{67-70}$Fe were measured, with $^{69}$Fe and $^{70}$Fe constituting first time measurements and $^{67}$Fe and $^{68}$Fe resulting in improvements over current literature uncertainties. The impact of these mass measurements on the presence of a surfacing Island of Inversion will be discussed.

Speaker: William Porter (TRIUMF/UBC)

M4-7 Exploring the Energy and Precision Frontier II (PPD) / Frontière d'énergie et de précision II (PPD)

Convener: Alison Lister (University of British Columbia (CA))

159 (G*) Measurement of Beam Polarization with Tau Polarimetry for a Potential SuperKEKB Upgrade

A polarized electron beam is being considered as an upgrade for the SuperKEKB accelerator. Having a polarized beam at Belle II opens a new precision electroweak physics program, as well as improving sensitivity to dark sector and lepton flavour violating processes. In order to achieve a polarized beam at SuperKEKB a variety of hardware and technical challenges are being studied. The limiting factor on the precision of these future measurements is expected to be the uncertainty in the beam polarization achieved at the interaction point. The average beam polarization can be measured with high precision by making use of the relationship between beam polarization and the kinematics of tau decays.
In order to develop the tau polarimetry measurement technique, in preparation for a polarized electron beam at SuperKEKB, the data collected by BaBar is being analyzed. BaBar has a enough data to make a polarization measurement with a subpercent statistical uncertainty. This allows the dominant systematic uncertainties to be identified and studied, and the limiting factors for the precision of tau polarimetry to be established. As Belle II is similar in design to BaBar it is expected a similar or better level of precision can be achieved with sufficient data and the installation of polarized beams further motivated. This presentation will be the first time the results using the BaBar data are presented publicly.

Speaker: Caleb Miller (University of Victoria)

TauPolarimetryCAP2021.pdf

160 (G*) Precision measurement of the Z-boson transverse momentum with the ATLAS detector

The ATLAS Experiment at CERN is a general-purpose particle physics detector that measures properties of particles created in high-energy proton-proton collisions fueled by CERN’s Large Hadron Collider (LHC). Searching for undiscovered particles is exciting, but there is still much to be learned about the particles that we know to exist in the Standard Model by making precision measurements of these particles. One area where increased precision is needed is the electroweak sector, where potential tension exists between theoretical predictions and the current best measurements on important properties such as the mass of the W-boson. In this talk, I will discuss our precision measurement of the transverse momentum of the Z-boson, a vital stepping stone to improving our W-boson mass measurement. I will explain how this difficult measurement has been made possible thanks to a unique reduced-background ATLAS dataset.

Speaker: Ben Davis-Purcell (Carleton University (CA))

BDP_pTZ_CAP2021.pdf

BDP_pTZ_CAP2021.pptx

161 (G*) Spin Rotator Design for the SuperKEKB High Energy Ring in a Proposed Polarization Upgrade

The SuperKEKB is a high luminosity e+e- collider with a circumference of 3km located in Japan, which collides 7GeV electrons with 4GeV positrons for precision flavour studies, CP violation, and searches for new physics. We are aiming at upgrading the SuperKEKB with a polarized electron beam, which would provide high precision neutral current electroweak and other measurements. To polarize the electron beam at the interaction point(IP) in the longitudinal direction, a spin rotator must be designed and installed in the SuperKEKB High Energy Ring. The right-side rotator rotates the vertical spin to longitudinal at the IP; the left-side rotator rotates the spin back to vertical.  We present the status of work on a spin rotator conceptual design based on replacing existing dipole magnets with rotator magnets on both sides of the IP. Each rotator magnet in this concept is made of a solenoid-dipole combined function magnet with 6 quadrupoles on the top of each section to compensate for the x-y plane coupling caused by the solenoid. This presentation will include the physics motivation, the conceptual design, and results of the BMAD accelerator simulation of this design, including spin-tracking results.

Speaker: Mr Yuhao Peng

CAP2021_Yuhao Peng.pdf

162 (G*) Search for heavy resonances decaying into a pair of Z bosons with the ATLAS detector

Since the discovery of the Higgs boson with a mass of about 125 GeV in 2012 by the ATLAS and CMS Collaborations, an important remaining question is whether this particle is part of an extended scalar sector as postulated by various extensions to the Standard Model. Many of these extensions predict additional Higgs bosons, motivating searches in an extended mass range. Here we report on a search for new heavy neutral Higgs bosons decaying into a pair of Z bosons in the $\ell^+\ell^- \ell^+\ell^-$ and $\ell^+\ell^- \nu\bar\nu$ final states, where $\ell$ stands for either an electron or a muon. The search uses proton-proton collision data at a centre-of-mass energy of 13 TeV collected from 2015 to 2018 by the ATLAS detector during Run 2 of the Large Hadron Collider, corresponding to an integrated luminosity of 139 fb$^{-1}$. Different mass ranges spanning from 200 GeV to 2000 GeV for the hypothetical resonances are considered, depending on the final state and model. In the absence of a significant observed excess, the results are interpreted as upper limits on the production cross section of a spin-0 or spin-2 resonance. The upper limits for the spin-0 resonance are translated to exclusion contours in the context of Type-I and Type-II two-Higgs-doublet models, and the limits for the spin-2 resonance are used to constrain the Randall-Sundrum model with an extra dimension giving rise to spin-2 graviton excitations.

Speaker: Joseph Carter (University of Toronto (CA))

jcarter.20210607.ATLAS_heavy_ZZ_searches.CAP2021.pdf

Tuesday 8 June

TS1-1 James Peebles' talk (DTP Symposium on Cosmology: James Peebles Nobel Celebration) / Conférence de James Peebles (Symposium DPT sur la cosmologie: le prix Nobel de James Peebles) Sponsored by Perimeter Institute

Convener: Robert Brandenberger (McGill University)

163 (I) Challenges and Opportunties for Modern Cosmology

Remarks and comments on issues of interest in Cosmology followed by questions, answers and discussions with a panel on a set of pre-distributed list of interesting challenges in cosmology.

Speaker: Prof. James Peebles (Princeton University)

TS-3 Plasma Physics Symposium (DPP) / Symposium de physique des plasmas (DPP)

Convener: Lenaic Couedel (University of Saskatchewan)

164 (I) Modelling laser plasma interaction for inertial confinement fusion experiments

The inertial confinement fusion scheme relies on the implosion of a Deuterium-Tritium pellet by the means of tens of laser beams. At maximum of compression, extreme thermodynamic conditions must be reached in order to trigger a thermonuclear wave. Laser-plasma interaction, for such large spatial and temporal scales, may only be described numerically with specific hydrodynamic codes. In the latter, only the laser beams refraction, and energy deposition due to inverse bremsstrahlung, are accounted for. Alas, such a description is incomplete as laser-plasma interaction may trigger to a plethora of physical effects leading to the loss of laser energy. Chiefly, the coherent laser light may be scattered in different directions through wave mixing processes such as Raman or Brillouin back and side scattering, cross beam energy transfer and collective scatterings.
Postponing the description of non-lineal kinetic effects, we recently developed a Monte-Carlo algorithm to describe any kind of convective wave mixing process involving two[1] or more electromagnetic waves and one driven electrostatic wave. The laser beams, described by large bundle of rays, can suffer scattering by any kind of wave coupling phenomenon. In the case of Brillouin backscattering, an incoming ray has a given probability to be scattered, as a collision, in the backward direction by the driven acoustic wave. As all these scatterings are stimulated, the probability of ray deflection depends on the scattered light amplitude. This non-linearity is addressed by means of a fixed-point iteration method. At a given hydrodynamic map, the raytracing is performed several times to estimate the light intensities at each cell, until convergence of the stationary solutions. To date, our method includes: 1°) Raman back and side-scattering, 2°) Brillouin back and side-scattering, 3°) the energy exchange between laser beams and scattered lights, 4°) the collective scattering in which an electrostatic wave is shared by a cone of laser beams.

[1] A. Debayle et al., Phys. Plasmas 26, 092705 (2019)

Speaker: Arnaud Debayle

165 (I) X-ray production using relativistically intense laser pulses

At relativistic intensities, electrons can be driven close to the speed of light, facilitating exploration of a new regime of laser-plasma interactions and high-field science. These intense pulses can drive matter into extreme states of temperature and pressure, mimicking those typically found in astrophysical environments, and leading to the observation of new states of high-energy-density matter. Advancements in intense laser matter interactions have also led to a new generation of pulsed particle and radiation sources, each with ultrashort, femtosecond-scale duration inherited from the laser driver. These sources can be used to study ultrafast dynamic phenomena in dense materials, such as material phase transitions and electron-ion equilibration.

In this talk, I will discuss our recent work performing high-resolution X-ray spectroscopy of K-shell emission from high-intensity (I ∼10^{21} W/cm^2) laser experiments using the ALEPH laser at Colorado State University. Through measurements of K-shell fluorescence, electron emission and XUV spectroscopy of the plasma emission, we examine the generation and propagation of energetic electrons in thin foil and layered targets to elucidate the physics of high-intensity laser solid interactions. I will also discuss the generation of broadband hard X-ray sources through laser wakefield acceleration, generated by an intense laser pulse traveling through low-density plasma, and how these sources can be used to diagnose high-energy-density matter and phase transitions in dense materials.

Speaker: Amina Hussein (University of Alberta)

166 (G*) Generation of focused LWFA electron and gamma beams using a triplet quadrupole magnet system

Tajima and Dawson proposed the idea of laser-wakefield accelerators (LWFAs) during the late 1970s. LWFAs produce low transverse emittance, ultrashort electron bunches of few femtoseconds duration with the potential to drive free electron lasers and compact X-ray and gamma-ray sources. Through the implementation of high-gradient quadrupole magnets, it is possible to focus and transport LWFA electron beams with minimal degradation over long distances. In this research work, we examine the focusing of LWFA electron beams using a triplet quadrupole system. We also look at the subsequent generation of collimated gamma beams. We analyse the changes in electron beam divergence, charge and pointing stability with and without the quadrupole system. Copper autoradiography was performed to look into the generation of intense gamma ray beams through the propagation of focused electron beams through a lead converter. Finally, Monte Carlo simulations will be performed to investigate gamma ray generation and peak gamma ray intensity.

Speaker: Mr Vigneshvar Senthilkumaran (University of Alberta)

167 Nonlinear development of absolute SRS in ignition-scale direct-drive coronal plasmas

The nonlinear behavior of absolute stimulated Raman scattering (SRS) near the quarter-critical density is investigated using one-dimensional (1D) Vlasov simulations with parameters relevant to ignition-scale direct-drive coronal plasmas. Numerical Vlasov simulations show that a strong and stable Airy pattern is formed by the Raman light as it is generated near its cutoff density. This pattern self-consistently modulates the density profile below the quarter-critical density. The density modulation superimposed in the linear density profile results in a change in the nature of SRS in lower density region from spatial (convective) amplification to temporal (absolute) growth. In addition, strong Langmuir decay instability (LDI) cascades produce daughter Langmuir waves (LWs) that seed SRS below quarter-critical density. These effects act to broaden the spectrum of reflected light. More interestingly, collapse of the primary LWs is observed near their turning point, producing hot electrons. These observations provide a new explanation of hot electron generation and SRS scattered light spectra for ignition-scale experiments.

Speaker: Dr Qing Wang (University of Alberta)

168 Ray tracing analysis of stimulated Raman scattering in directly-driven inertial confinement fusion plasmas

Experiments performed at the National Ignition Facility (NIF) have provided evidence that stimulated Raman scattering (SRS) occurs at a level that poses a preheat risk for directly-driven inertial confinement fusion implosions [1]. To help investigate the mechanisms responsible for the generation of this SRS, recent experiments on the OMEGA EP laser (in which similar SRS signatures were observed) were analyzed using a new ray-tracing model. The model is able to explain the time-dependent scattered light spectra from these OMEGA EP experiments: It identifies SRS side-scatter and near backscatter from portions of each incident beam, where either the scattered electromagnetic wave, or the electron plasma wave, are generated in the direction parallel to contours of constant density, as the origin of the major spectral features. As similar effects are known to occur at the ignition scale (on the NIF) [2], it is suggested that the OMEGA EP platform could provide a good surrogate in which to develop SRS mitigation strategies.

This material is based upon work supported by the Natural Sciences and Engineering Research Council of Canada [RGPIN-2018-05787, RGPAS-2018-522497]

[1] M. Rosenberg et al., Phys. Rev. Lett. 120, 055001 (2018).
[2] P. Michel et al., Phys. Rev. E99, 033203 (2019).

Speaker: Steven Hironaka (University of Alberta)

12:15 Break

169 Spectrally accurate global-local gyrokinetic simulations of turbulence in tokamak plasmas

The suppression of turbulence in fusion plasmas, crucial to the success of next-generation tokamaks such as ITER, depends on a variety of physical mechanisms including the shearing of turbulent eddies via zonal flow and possibly the generation of intrinsic rotation. The turbulence exhibits interesting features such as avalanche structures and self-organisation, and its absence is associated with the formation of internal transport barriers. In order to successfully capture all of these effects in gyrokinetic simulation, one may need to allow for the inclusion of global effects (such as radial profile variation), as well as other often-neglected effects that are small in $\rho_\ast$. A careful numerical treatment is necessary to ensure that both the global and local physics are calculated accurately at reasonable expense.

To that end, we develop a novel approach to gyrokinetics where multiple flux-tube simulations are coupled together in a way that consistently incorporates global profile variation while allowing the use of Fourier basis functions, thus retaining spectral accuracy. By doing so, the need for Dirichlet boundary conditions typically employed in global gyrokinetic simulation, where fluctuations are nullified at the simulation boundaries, is obviated. This results in a smooth convergence to the local periodic limit as $\rho_\ast \rightarrow 0$. In addition, our scale-separated approach allows the use of transport-averaged sources and sinks, offering a more physically motivated alternative to the standard sources based on Krook-type operators.

Having implemented this approach in the flux-tube code $\texttt{stella}$, we study the role of transport barriers and avalanche formation in the transition region between the quiescent core and the turbulent pedestal, as well as the efficacy of intrinsic momentum generation by radial profile variation. Finally, we show that near-marginal plasmas can exhibit a radially localized Dimits shift, where strong coherent zonal flows give way to flows which are more turbulent and smaller scale.

Speaker: Denis St-Onge (University of Oxford)

170 (G*) Experimental Studies of the Improved Plasma Confinement on the STOR-M Tokamak

Study of high-confinement mode (H- mode) of tokamak operation plays an important role to optimize conditions for fusion reactors. Many experimental techniques, including electrode biasing and resonant magnetic perturbations (RMP), have been developed to improve the plasma confinement, facilitating transition from low to high confinement mode (L-H transition) and to study the transition mechanism. The H-mode is characterized by a rapid increase in plasma density, in conjunction with a sudden drop in H alpha emissions, indicating an improvement in both particle and energy confinements. The Saskatchewan Torus-Modified (STOR-M) tokamak is a small tokamak with a major radius of 46 cm and minor radius of 12 cm. The operational parameters during the biasing experiments are B_t (toroidal magnetic field) ~ 0.7 T, I_p (plasma current) ~ 25 kA, V_l (loop voltage) ~ 3 V, n_e (average density) ~ 1×10^13 cm-3, T_e (average electron density) ~ 100 eV, and τ_E (global energy confinement time) ~ 2 ms. Hydrogen plasma is used for the experiment. On the (STOR-M) tokamak, the electrode biasing experiments have been carried out to induce a sheared electric field and suppress the turbulence induced transport. The electrode is placed at different radial locations and the biasing voltage and polarity can be varied between shots. Biasing experiments with rectangular AC waveforms have also been carried out in the STOR-M tokamak. The RMP experiments carried out in the STOR-M tokamak using the (l = 2, n = 1) helical coils carrying a static current pulse. The resonant interaction between the plasma and RMP suppresses magnetohydrodynamic (MHD) fluctuations and improves plasma confinement. The current work will focus on the studies of the correlations between different electrostatic and/or magnetic fluctuating signals measured with various diagnostic probes.

Speaker: Mrs Heba Bsharat (University of Saskatchewan )

171 (G*) Stimulated Excitation of Thermal Waves in Magnetized Plasmas and Use in Thermal Conductivity Measurement

There exists an unconventional class of waves known as thermal diffusion waves, or simply thermal waves, that are produced using sinusoidally, time-varying heat sources and they can be used to determine the thermal conductivity in the medium. Recent advancements have resulted in the construction of thermal wave resonator cavities (TWRCs) capable of sustaining quasi-standing thermal waves which have been used to measure the thermal properties of solids, liquids, and gases. The success of TWRC diagnostic techniques with different forms of matter motivates the application of similar methods to magnetized plasmas, where heat transport processes are of particular importance to magnetic confinement fusion devices. Results are presented from experiments in a large linear magnetized plasma device using an electron temperature filament that is formed from a cerium hexaboride crystal cathode that injects low energy electrons along a magnetic field into the center of a pre-existing plasma, forming a hot electron filament embedded in a colder plasma that behaves as a thermal resonator. By oscillating the cathode voltage we produce an oscillating heat source in the filament and demonstrate the stimulated excitation of thermal waves and the presence of a thermal resonance in the finite-length temperature filament. We have successfully used this technique to determine the thermal conductivity in the plasma. A theoretical model of the thermal wave dispersion relation and resonator is compared to the Langmuir probe data from the experiment.

Speaker: Scott Karbashewski (University of Alberta)

172 (I) Nonlinear and noise effects in simulations of Buneman instability

The effects of the modification of the electron distribution function in the nonlinear regime of the Buneman instability and statistical noise effects have been investigated, using high-resolution Vlasov and Particle-in-Cell simulations. It is shown that this modification is a result of electron trapping. In nonlinear regimes, electron trapping and associated modification of the electron distribution function result in excitation of waves moving in the opposite direction of the initial drift velocity of electrons (backward waves). In the PIC simulations, however, the modification of the velocity distribution function occurs due to high statistical noise even in the linear stage, so that the observed growth is inconsistent with the linear theory.

Speaker: Arash Tavassoli

13:40 Break

173 (I) Defect Engineering in Plasma-Treated Graphene Films

Engineering of defects located in-grain or at grain boundary is central to the development of functional materials and nanomaterials. While there is a recent surge of interest in the formation, migration, and annihilation of defects during ion and plasma irradiation of bulk (3D) materials, the detailed behavior in low-dimensional materials remains most unexplored and especially difficult to assess experimentally. A new hyperspectral Raman imaging scheme providing high selectivity and diffraction-limited spatial resolution was adapted to examine plasma-induced damage in a polycrystalline graphene film grown by chemical vapor deposition on copper substrates and then transferred on silicon substrates. For experiments realized in nominally pure argon plasmas at low pressure, spatially resolved Raman conducted before and after each plasma treatment shows that the defect generation in graphene films exposed to very low-energy (11 eV) ion bombardment follows a 0D defect curve, while the domain boundaries tend to develop as 1D defects. Surprisingly and contrary to common expectations of plasma-surface interactions, damage generation at grain boundaries is slower than within the grains. Inspired by recent modeling studies, this behavior can be ascribed to a lattice reconstruction mechanism occurring preferentially at domain boundaries and induced by preferential atom migration and adatom-vacancy recombination. Further studies were realized to compare the impact of different plasma environments promoting either positive argon ions, metastable argon species, or VUV-photons on the damage formation dynamics. While most of the defect formation is due to knock-on collisions by 11-eV argon ions, the combination with VUV-photon or metastable atom irradiation is found to have a very different impact. In the former, the photons are mainly thought to clean the films from PMMA residues due to graphene transfer from copper to silicon substrates. On the other hand, the surface de-excitation of metastable species first impedes the defect generation and then promotes it for higher lattice disorder. While this impediment can be linked to an enhanced defect migration and self-healing at nanocrystallite boundaries in graphene, such effect vanishes in more heavily-damaged films. Finally, these experiments were used as building blocks to examine the formation of chemically doped graphene film in such plasmas using argon mixed with either traces of N- or B-bearing gases.

Speaker: Luc Stafford (Universite de Montreal)

174 Boron substitutional doping of graphene by low- pressure diborane-argon plasma

Polycrystalline monolayer graphene films grown by chemical vapor deposition were exposed to a low-pressure inductively-coupled plasma operated in a gaseous mixture of argon and diborane. Optical emission spectroscopy and plasma sampling mass spectrometry reveal high B2H6 fragmentation leading to significant populations of both boron and hydrogen species in the gas phase. X-ray photoelectron spectroscopy indicates the formation of a boron-containing layer at the surface and provides evidence of a substitutional incorporation of boron atoms within the graphene lattice. To probe plasma’s influence on graphene structure, Hyperspectral Raman Imaging (RIMA for Raman Imaging) is used to obtain qualitative as well as quantitative data on a macroscopic scale. Graphene domains doping by graphitic boration is then confirmed by hyperspectral Raman Imaging of graphene domains. These results demonstrate that diborane-containing low-pressure plasmas are an efficient mean for boron substitutional incorporation in graphene with minimal domain hydrogenation and defect generation.

Speaker: Pierre Vinchon (Université de Montréal)

175 (G*) P3I code: A new code for Plasma Immersion Ion Implantation modelling

: Plasma Immersion Ion Implantation (PIII) is a versatile material processing technique [1,2] with many applications in semiconductor doping, micro- and nanofabrication [3], as well as the surface modification of metals for improved resistance against wear and corrosion. In PIII a solid target is immersed in plasma, and negative polarity high-voltage (typically 1-20 kV) are applied the target. During the PIII pulse electrons are expelled, resulting in a positive ion sheath surrounding the target; ions in sheath implanted on solid surface. PIII provides uniform ion implantation with high ion fluences across broad area targets. The targets need not be planar as the plasma is conformal to the immersed target. For precision PIII processing it is important to accurately predict the implanted ion concentrations. The P2I code was developed by Bradley, Steenkamp, and Risch [4,5] to accurately predict PIII sheath dynamic, ion implantation currents and total delivered ion fluence. The P2I code is an efficient implementation of the numerical solution of Lieberman’s dynamic sheath model [2]. However, experiments typically show an increase in plasma density during high voltage PIII pulses due to various effects including secondary electrons ejected from the target. The increase in plasma density significantly effects the ion implantation current as well as the implanted ion concentrations.
To address these deficiencies, a new code (P3I) as an advanced version of the existing P2I code which address these discrepancies in measurement by accounting for plasma density enhancement effects. In addition, due to the growing interest in the use of PIII to study ion bombardment of plasma-facing components for fusion applications, the P3I code will incorporate aspects of the Stangeby and McCracken Scrape-off layer (SOL) model [6]. This talk will discuss the development of this new code for various PIII applications.

References
[1] A. Anders, Handbook of Plasma Immersion Ion Implantation and Deposition, Wiley (2000).
[2] Michael A Lieberman and Alan J Lichtenberg. Principles of plasma discharges and materials processing. John Wiley & Sons, 2005.

[3] Marcel Risch and Michael P. Bradley, “Prospects for band gap engineering
by plasma ion implantation”, Phys. Status Solidi C 6, No. S1, S210–S213 (2009) / DOI 10.1002/pssc.200881279
[4] M.P. Bradley and C.J.T. Steenkamp, “Time-Resolved Ion and Electron Current Measurements in Pulsed Plasma Sheaths”, IEEE Trans. Plasma Sci. 34, 1156-1159 (2006).
[5] M. Risch and M. Bradley, “Predicted depth profiles for nitrogen-ion implantation into gallium arsenide”, phys. stat. sol. (c) 5, 939-942 (2008).

[6] P.C Stangeby, G.M. McCracken, “Plasma Boundary Phenomenon in Tokamak” Nuclear Fusion, vol 30, No.7 (1990).

Speaker: tahreem yousaf (university of saskchewan)

176 (G*) Time Resolved Characterization of a Plasma Immersion Ion Implantation System

Plasma immersion ion implantation (PIII) is a versatile tool in the field of materials processing, surface modification, and semiconductor manufacturing[1]. By immersing the target directly in the plasma, PIII boasts many advantages over its predecessor, conventional ion implantation, including a simpler design, faster throughput and more uniform implantation over irregular objects[4]. When a negative polarity high voltage (NPHV) pulse is applied to the target, ions are implanted through this plasma sheath and into the target[5]. However, plasma immersion also introduces several complicating factors that challenge optimization. Foremost among them is maintaining constant bulk plasma parameters, specifically ion density and temperature, and appropriately correcting for inevitable fluctuations that occur[2][3].
Experiments were performed at the University of Saskatchewan plasma physics laboratory on a PIII system with an Inductively Coupled Plasma (ICP) device. This experiment utilized two identical RF-compensated Langmuir probes at two different vertical positions above the biased target to study the perturbations both near the target and further away. The results indicate that electron density and plasma potential are very sensitive to the NPHV pulse, and the amplitudes of the perturbation increase with increasing pulse magnitude above 2 kV. Perturbation amplitudes relative to steady state values trend consistently for all pressures at the same power. However, perturbations are quelled significantly when power is increased, regardless of the pressure. Additionally, the electron temperature undergoes fluctuations whose relative amplitudes are generally smaller than those of density and plasma potential, but are consistent across pulse amplitude, power and pressure. Furthermore, the sheath recovery time was measured. It was shown that it predominantly depends on NPHV amplitude, rather than power or pressure. Finally, the velocity of a rarefaction wave that propagates away from the pulser is measured based on the time delay of the peak of these perturbations. These results will contribute to optimizing the process of PIII by quantifying corrections needed to current models used to calculate implantation doses that assume constant plasma parameters. In future studies they will serve as a basis for comparison against future laser-induced fluorescence diagnostic data.

References

[1] Bradley, M. P., Desautels, P. R., Hunter, D. and Risch, M. [2009], `Silicon electroluminescent device production via plasma ion implantation', Physica Status Solidi (C) Current Topics in Solid State Physics 6(S1), 6-9.
[2] Lieberman, M. and Lichtenberg, A. [2005], Principles of Plasma Diagnostics and Materials Processing, Wiley-Interscience.
[3] Risch, M. and Bradley, M. [2008], `Predicted depth profiles for nitrogen-ion implantation into gallium arsenide', Physica Status Solidi (C) Current Topics in Solid State Physics 5(4), 939-942. 
[4] Risch, M. and Bradley, M. P. [2009], `Prospects for band gap engineering by plasma ion implantation', Physica Status Solidi (C) Current Topics in Solid State Physics 6(SUPPL. 1).
[5] Steenkamp, C. J. and Bradley, M. P. [2007], `Active charge/discharge IGBT modulator for Marx generator and plasma applications', IEEE Transactions on Plasma Science 35(2 III), 473-478.

Speaker: Joel Moreno (University of Saskatchewan)

15:00 Break

177 (I) Plasma and dusty plasma pattern formation at high magnetic fields

The vast majority of dusty/complex plasma experiments have involved the suspension of charged, micron-sized particles in plasmas. The particles are suspended due to a delicate balance between gravitational and electrostatic forces. The addition of a magnetic field to these systems has a profound influence on both the surrounding plasma and the dusty plasma as the dynamics of first the electrons, then the ions, and finally the charged dust grains become influenced by the magnetic field. Since the mid-2000s, a number of experimental devices have been built around the world to explore the physics of dusty plasmas in strongly magnetized plasmas. One of these devices, the Magnetized Dusty Plasma Experiment (MDPX) device at Auburn University is a flexible, high magnetic field research instrument with a mission to serve as an open access, multi-user facility for the dusty plasma and basic plasma research communities. In particular, under conditions when the magnetic field is sufficiently large, B ≥ 1 T, a variety of emergent phenomena are observed including the formation of self-ordered plasma structure, specifically plasma filamentation along the magnetic field direction, as well as a new type of imposed spatial ordering of the dust particles. Recent three-dimensional fluid simulations suggest that both of these phenomena are strongly connected to differences in ion and electron transport parallel and perpendicular to the magnetic field. This presentation will provide an overview of recent experiments and the associated simulations.

This work is supported with funding from the U.S. Department of Energy and the National Science Foundation (Physics Division and EPSCoR Office).

Speaker: Edward Thomas (Auburn University)

178 Mode-coupling instability of two-dimensional complex plasma crystals in asymmetric capacitively-coupled radio-frequency discharges

The dependence of the mode-coupling instability threshold in two-dimensional complex plasma crystals is studied. It is shown that for a given microparticle suspension at a given discharge power there exist two thresholds in pressure. Above a specific pressure $p_\mathrm{max}$, the monolayer is always in the crystal phase. Below a specific pressure $p_\mathrm{min}$, the crystalline monolayer undergoes the mode-coupling instability and the monolayer is in the fluid phase. In between $p_\mathrm{in}$ and $p_\mathrm{max}$, the crystal will be in the fluid phase when increasing the pressure from below $p_\mathrm{min}$ until it reaches $p_\mathrm{max}$ where it recrystallises, while it remains in the crystal phase when decreasing the pressure from above $p_\mathrm{max}$ until it reaches $p_\mathrm{min}$. A simple auto-consistent sheath model can explain the melting threshold as a function of pressure and rf power due the changes of the sheath electric field and the microparticle charges leading to the crossing of the compressional in-plane phonon mode and the out-of plane phonon mode.

Speaker: Lenaic Couedel (University of Saskatchewan)

179 (G*) Application of kinetic and regression techniques to measurements made with fixed-bias needle Langmuir probes.

Fixed-bias multi-needle Langmuir probes consisting of several cylindrical probes biased to different potentials can be used to measure plasma parameters on satellite without the need of sweeping bias voltages. Compared to a single Langmuir probe for which voltage is varied periodically in time, fixed bias probes enable measurement with a significantly higher sampling rate and, owing to the high orbital speed of satellites, a much higher spatial resolution when used to diagnose space plasma. The inference of plasma parameters from needle probes is typically based on the Orbit Motion Limit theory (OML) which assumes an infinitely long cylindrical probe, and the absence of nearby objects. These assumptions are rarely satisfied in an actual experimental setup. In this study, three-dimensional kinetic simulations are used to compute currents collected by needle probes on the Norsat-1 satellite, and create a synthetic data set, or solution library. This is then used to construct regression models to infer plasma densities and satellite floating potentials from four-tuples of collected currents. Two regression approaches are considered, consisting of radial basis functions (RBF) and deep learning neural networks. Regression results and OML results will be compared and assessed when the assumptions made in the OML theory are not fully satisfied. The use of regression techniques rather than purely analytic expressions is shown to lead to more accurate inference techniques for measuring plasma parameters in space, than those based on analytic approximations.

Speaker: Guangdong Liu (University of Alberta)

180 (G*) Design and Characterization of a Dust Injector for STOR-M

Affiliation: University of Saskatchewan

Fusion and related plasma physics research enables the development of a new, safe and reliable, high-output fusion energy source. There are however multiple problems to address with fusion devices. One such problem is that of contaminating dust, produced by plasma wall interactions within the reactor.
Dust generation from Plasma Facing Components (PFC) is problematic for tokamaks as they approach suitable reactor conditions. Tungsten dust is especially detrimental in the plasma core, due to associated high Z bremsstrahlung power losses. As Tungsten is a primary candidate for PFC materials in large projects such as ITER, this remains a pressing issue. In order to better understand dust dynamics in tokamaks, a dust injection experiment has been developed for the Saskatchewan Torus-Modified (STOR-M). This experiment will utilize calibrated, spherical tungsten micro-particles. A known quantity of these tungsten micro-particles are to be injected into the STOR-M tokamak, with control over the position of the plume of dust particles. This will enable the study of dust dynamics and the effects of dust particles on the tokamak plasma within STOR-M.
In preparation for this experiment, a dust injector has been designed and built, based on the fast gas valve for the University of Saskatchewan Compact Torus Injector (USCTI). Additionally, an experimental test apparatus has been developed and used to characterize the dust injector.
Two dust injection schemes have been envisaged for STOR-M. The first disperses dust particles directly into the tokamak chamber, where a discharge is to commence around these particles. The second utilizes the USCTI to trap the tungsten particles in an accelerated plasmoid, in order to deliver dust particles to the core of the STOR-M plasma within a time scale of approximately 10 µs. Integration of the dust injector into the STOR-M system is currently underway.

References:

• N. Nelson. “Design and Characterization of a Dust Injector for Future Studies of Tungsten Dust in the STOR-M Plasma”. Masters dissertation. University of Saskatchewan. 2020. https://harvest.usask.ca/handle/10388/13194

• J. Roth et al. “Recent analysis of key plasma wall interactions issues for ITER”. In: Journal of Nuclear Materials390-391 (2009), p.1. doi:10.1016/j.jnucmat.2009.01.037.

• R. D. Smirnov et al. “Tungsten dust impact on ITER-like plasma edge”. In: Physics of Plasmas 22.012506 (2015). doi:10.1063/1.4905704.

• Krasheninnikov S. I., Smirnov R. D., and Rudakov D. L. “Dust in magnetic fusion devices”. In: Plasma Physics and Controlled Fusion 53(8) (2011).doi:10.1088/0741-3335/53/8/083001.

Speaker: Nathan Nelson (University of Saskatchewan)

181 Beyond analytic inference techniques with multivariate regression

For nearly a century, Langmuir probes have been used to infer plasma densities and temperatures from current characteristics. In practically all cases, these inferences are based on analytic expressions obtained theoretically. Despite their limitations, analytic expressions continue to be used because of their relative simplicity, and the fact that they can be used to construct fast inference techniques requiring only modest computing resources. With recent advances in computer technology, and the development of sophisticated plasma simulation models, it is now possible to reproduce in silico, the response of sensors to different plasma environments, while accounting for more physical processes, a more detailed geometries, that possible analytically. However, even the fastest computers and the most advanced numerical models are unable to directly provide sufficiently fast inference algorithms for near-real time data processing. One approach that we have been pursuing consists of using 3D kinetic simulations to calculate sensor responses for a range of plasma parameters of interest, constructing solution libraries; that is sets of computed responses, along with corresponding plasma parameters. These sets can then be used to construct and test multivariate regression techniques whereby selected plasma parameters can be inferred. In this talk I will present the general steps involved in the construction of solution libraries, the use of inference models based on regressions, and the assessment of these methods. I will also present an application of the method to actual space plasma measurements.

Speaker: Richard Marchand

182 (G*) Multivariate Regression Approach in the Prediction of Side Wind Velocity Using Spherical Segmented Langmuir Probe Measurements

This work considers the use of spherical segmented Langmuir probes as a means to measure ionospheric plasma flow velocities. This is done by carrying out three-dimensional kinetic self-consistent Particle in Cell (PIC) simulations to compute the response of a probe to space plasma under a range of space environment conditions of relevance to satellites in low Earth orbit (LEO) at low and mid latitudes. Computed currents and corresponding plasma parameters, including densities, temperatures, and flow velocities are then used to construct a solution library which is used to construct regression-based inference techniques. Model inference skills can then be assessed directly from the synthetic data sets obtained from our solution library. The method is then applied to actual segmented Langmuir probes mounted on the Proba-2 satellite.

Speaker: Mr Akinola Olowookere (University of Alberta)

16:50 Break

183 (I) Flow-Through Z-Pinch Research at Fuse

Flow-through Z-pinches were first discovered over 50 years ago, manifesting themselves as a stable, pinch-like structure that persisted for 100 us in the Newton-Marshal gun experiments at LANL in the late 1960’s. Linear stability analysis performed by Uri Shumlak in the 1990’s showed that when dV_z/dr > 0.1 k V_A the kink mode could be stabilized in a Z-pinch plasma. Experimental work over the last couple of decades have shown that Z-pinches can be stabilized when the sheared axial flow exceeds this threshold. Quasi-steady-state Z-pinches existed near the axis of the assembly region for 20-80 us. The instability growth time from these Z-pinches was about 10 ns. Recent results from the sheared-flow Z-pinch experiment at the University of Washington, FuZE, have shown it may be possible to achieve a thermonuclear fusion burn. The FuZE device achieved 10 us long fusion burns along 30 cm of the Z-pinch plasma. Using adiabatic scaling relationships, it may be possible to build a Q=6 fusion reactor using the traditional Marshall gun approach. The formation and sustainment method relies on creating a neutral gas reserve that can be continuously ionized, supplying the stabilizing plasma flow to the Z-pinch throughout the current pulse. Creating the optimized neutral gas fill profile requires tedious experimentation. Fuse Energy Technologies will be studying the scaling towards a reactor by forming and sustaining flow-through Z-pinches using a new technique. The deflagration ionization process will be replaced with an array of plasma injectors. This novel technique will allow better control of the mass flow into the Z pinch. This process may allow for better comparisons with the scaling relationships. Previous work, recent simulation and experimental results from the Fuse devices will be presented.

Speaker: Dr Raymond Golingo (Fuse)

184 (I) Global simulations of ion temperature gradient modes, from characteristic eigen-structures to turbulent transport

Energy loss in magnetic confinement fusion is dominated by plasma turbulence --- turbulent transport can surpass all other mechanisms by several orders of magnitude. Instability, driven by the Ion Temperature Gradient (ITG) mode is a key contributor to such turbulence, and is the topic of this work. Simulating such small-scale, $\mathcal{O}(\mathrm{mm})$, turbulence over an $\mathcal{O}(\mathrm{m})$ tokamak is computationally intensive, particularly with the 6 or 7-D kinetic models used to clearly capture velocity-space effects, e.g. Landau damping. To mitigate computational demands, these models have often focused on thin annular flux-tubes, which reduces the radial domain to $\mathcal{O}(\mathrm{cm})$.

Fluid modeling (4-D), the approach adopted here, also provides a formidable decrease in computational demands. This permits diverse (high numeracy) global (full-domain) investigations of both large-scale interactions with the equilibrium profiles/gradients, and meso-scale mode-mode coupling. The former is especially important in X-point geometry, where the poloidal boundary is shaped to exhibit a discontinuity which can interact nonlocally with regions well inside the tokamak.

This project extensively characterizes global ITG behavior in realistic devices of both circular$^1$ and X-point geometry. In the linear growth phase, several distinct types of eigen-structure are found, described, and quantified. Thorough investigation of the poloidal mode spectra uncovered a significant shift in mode location, with respect to resonant surfaces, which was unexpected and yet-unreported. The possibility for such behavior was subsequently found within a previously published gyrokinetic model.$^{1,2}$ Notably, linear investigations also clearly demonstrate the suppression of instability by localized neoclassical flows, identifying that they can play a significant role in transport barriers.

In the turbulent phase, study focuses on the energy spectra, nonlinear radial heat flux (from transport coefficients to evolution and structures), and the behavior and traits of turbulent eddies. Even with broadly similar parameters, different X-point devices demonstrated a great diversity in their spectra and structures. Clear power law relations, some common to all cases, some characteristic to particular devices, are detailed. Under certain conditions, interaction with the X-point was found to qualitatively affect the mode throughout the domain.

[1] J. Zielinski, M. Becoulet, A. I. Smolyakov, X. Garbet, G. T. A. Huijsmans,
P. Beyer, and S. Benkadda, ``Global itg eigenmodes: From ballooning angle and
radial shift to reynolds stress and nonlinear saturation,'' Physics of
Plasmas, vol. 27, no. 7, p. 072507, 2020.

[2] X. Garbet, Y. Asahi, P. Donnel, C. Ehrlacher, G. Dif-Pradalier, P. Ghendrih,
V. Grandgirard, and Y. Sarazin, ``Impact of poloidal convective cells on
momentum flux in tokamaks,'' New Journal of Physics, vol. 19, no. 1,
p. 015011, 2017.

Speaker: Jeffery Zielinski (University Of Saskatchewan)

185 Turbulence and transport from multiple entangled electron temperature filaments in a magnetized plasma

Steep thermal gradients in a magnetized plasma can induce a variety of spontaneous low frequency excitations such as drift-Alfven waves and vortices. We present results from basic experiments on heat transport in magnetized plasmas with multiple heat sources in close proximity [1]. The experiments were carried out at the upgraded Large Plasma Device (LAPD) operated by the Basic Plasma Science Facility at the University of California, Los Angeles. The setup consists of three biased probe-mounted CeB6 crystal cathodes that inject low energy electrons along a strong magnetic field into a pre-existing cold afterglow plasma forming three electron temperature filaments. A triangular spatial pattern is chosen for the thermal sources and multiple axial and transverse probe measurements allow for determination of the cross-field mode patterns and axial filament length. When the three sources are placed within a few collisionless electron skin depths, a non-azimuthally symmetric wave pattern emerges due to the overlap of drift-Alfven modes forming around each filament. This leads to enhanced cross-field transport from nonlinear convective (E×B) chaotic mixing and rapid density and temperature profile collapse in the inner triangular region of the filaments. Steepened thermal gradients form in the outer triangular region, which spontaneously generates quasi-symmetric, higher azimuthal mode number drift-Alfven fluctuations. A steady-current model with emissive sheath boundary predicts the plasma potential and shear flow contribution from the sources. A statistical study of the fluctuations reveals amplitude distributions that are skewed which is signature of intermittency in the transport dynamics.

[1] R.D. Sydora, S. Karbashewski, B. Van Compernolle, and M.J. Poulos, and J. Loughran, “Drift-Alfven fluctuations and transport in multiple interacting magnetized electron temperature filaments”, Journal of Plasma Physics, vol. 85, issue 6, 2019, pp. 905850612.

Speaker: Richard Sydora (University of Alberta)

TS-8 Magnetic North VII / Nord magnétique VII

Convener: Bruce Gaulin (McMaster University)

10:59 Magnetic North VII - Session 1 - 11h00-12h30 (Chair: Bruce Gaulin, McMaster University)

186 (I) MBT for TBM ( Topological Band Magnetism )

MBT for TBM (Topological Band Magnetism)

A.H. MacDonald, C. Lei, Shu Chen, O. Heinonen, and R.J. McQueeney
Physics Department, University of Texas at Austin 78712 USA

Bulk MnBi2Te4 and MnBi2Se4 are antiferromagnetic topological insulators [1], and also van der Waals compounds with weakly-coupled seven-atom-thick (septuple) layers. I will discuss the electronic, magnetic, and topological properties of thin films formed by flexibly stacked septuple layers from a theoretical point of view, with the goal of anticipating properties that are achievable using van der Waals epitaxy. Much of the theoretical analysis will be made using an attractively simplified model [2] that retains only Dirac cone degrees of freedom on both surfaces of each septuple layer. The model can be validated, and its parameters can be estimated, by comparing with ab initio density-functional theory (DFT) calculations. I will use the model to explain when thin films exhibit a quantized anomalous Hall effect (QAHE) and when they do not, and to relate the magnetic-configuration-dependent properties of thin films to the magnetic Weyl semimetal limit of the ferromagnetic configuration. MBT thin films can have gate-tunable transitions between topologically trivial and QAH states [3], and metamagnetic QAH states [4], including ones with perfectly compensated antiferromagnetic configurations [5]. I will comment on the magneto-electric [6], and magneto-optical [7] properties of these materials and how they relate to the topological magneto-electric effect, and on the potential role in spintronics.

[1] M.M. Otrokov et al., Highly ordered wide bandgap material for quantized anomalous Hall effect effect and magnetoelectric effects, 2D Mater. 4, 025082 (2017).
[2] C. Lei, S. Chen, and A.H. MacDonald, Magnetized topological insulator multilayers, Proc. Nat. Acad. Sci. 117, 27224 (2020).
[3] C. Lei and A.H. MacDonald, Gate-Tunable Quantum Anomalous Hall Effects in MnBi2Te4 Thin Films, arXiv:2101.07181.
[4] C. Lei, O. Heinonen, A.H. MacDonald, and R.J. McQueeney, Metamagnetism of few layer topological antiferromagnets, arXiv:2102.11405.
[5] C. Lei, O. Heinonen, R.J. McQueeney and A.H. MacDonald, Quantum Anomalous Hall Effect in Collinear Antiferromagnetic Thin Films, to be submitted.
[6] C. Lei and A.H. MacDonald, Spin and Orbital Magneto-electric Response in Magnetized Topological Insulator Thin Films, to be submitted.
[7] C. Lei and A.H. MacDonald, Magneto-Optical Kerr and Faraday Effects in MBT Thin Films, to be submitted.

Speaker: Allan MacDonald (UNIVERSITY OF TEXAS AT AUSTIN)

187 (I) Giant c-axis Nonlinear Anomalous Hall Effect

We report the observation of a giant c-axis nonlinear anomalous Hall effect in the non-centrosymmetric Td phase of MoTe2 without intrinsic magnetic order. Here, application of an in-plane current generates a Hall field perpendicular to the layers. By measuring samples across different thicknesses and temperatures, we find that the nonlinear susceptibility obeys a universal scaling with sample conductivity that is indicative of extrinsic scattering mechanisms. Application of higher bias yields an extremely large anomalous Hall ratio and conductivity.

Speaker: Adam Tsen (University of Waterloo)

12:30 Lunch break - 12h30-13h30

13:29 Magnetic North VII - Session 2 - 13h30-14h30 (Chair: Jacob Burgess, University of Manitoba)

188 (I) Tunneling processes through Yu-Shiba-Rusinov states of magnetic atoms on superconductors

Magnetic atoms on superconductors induce an exchange coupling, which leads to states within the superconducting energy gap. These so-called Yu-Shiba-Rusinov (YSR) states can be probed by scanning tunneling spectroscopy at the atomic scale. Here, we investigate single magnetic adatoms on a superconducting Pb surface.
As YSR states are within the superconducting energy gap, their excitation by electrons requires a subsequent inelastic relaxation process. At strong tunnel coupling, thermal relaxation is not sufficiently fast and resonant Andreev processes become the dominant tunneling process [1]. We obtain direct evidence of these two transport regimes by inserting GHz radiation into the STM junction and analyzing the photon-assisted tunneling maps [2,3].
[1] M. Ruby, F. Pientka, Y. Peng, F. von Oppen, B. W. Heinrich, K. J. Franke, Phys. Rev. Lett. 115, 087001 (2015).
[2] O. Peters, N. Bogdanoff, S. Acero Gonzalez, L. Melischek, J. R. Simon, G. Reecht, C. B. Winkelmann, F. von Oppen, K. J. Franke, Nature Physics 16, 1222 (2020).
[3] S. Acero Gonzalez, L. Melischek, O. Peters, K. Flensberg, K. J. Franke, F. von Oppen, Phys. Rev. B 102, 045413 (2020).

Speaker: Katharina Franke (Freie Universität Berlin)

189 Majorana Bound States Induced by Antiferromagnetic Skyrmion Textures

Majorana bound states are zero-energy states predicted to emerge in topological superconductors and intense efforts seeking a definitive proof of their observation are still ongoing. A standard route to realize them involves antagonistic orders: a superconductor in proximity to a ferromagnet. Here, we show that this issue can be resolved using antiferromagnetic rather than ferromagnetic order. We propose to use a chain of antiferromagnetic skyrmions, in an otherwise collinear antiferromagnet, coupled to a bulk conventional superconductor as a novel platform capable of supporting Majorana bound states that are robust against disorder. Crucially, the collinear antiferromagnetic region neither suppresses superconductivity nor induces topological superconductivity, thus allowing for Majorana bound states localized at the ends of the chain. Our model introduces a new class of systems where topological superconductivity can be induced by editing antiferromagnetic textures rather than locally tuning material parameters, opening avenues for the conclusive observation of Majorana bound states.

[1] S. A. Díaz, J. Klinovaja, D. Loss, and S. Hoffman, arXiv:2102.03423.

Speaker: Sebastián Díaz (University of Basel)

190 Level attraction in a driven cavity magnonic system

Level attraction describes a mode coalescence that can take place in driven open systems. It indicates a development of an instability region in the energy spectrum of the system bounded by exceptional points [1]. This regime has been recently reported in a number of experiments in driven dissipative cavity magnonic systems [2].

Here, we present a framework for describing the mode attraction in a variety of cavity magnonic systems where the interaction between cavity photons and magnons is described in terms of a non-linear relaxation process. We show that the memory function for the photon mode in this approach is expressed through a non-equilibrium susceptibility of the magnonic bath. This allows us to consider a situation in which a bath is driven out of the equilibrium that is necessary to describe the attraction regime. The advantage of this approach is that the susceptibility of the bath can be calculated numerically using first-principle methods.

Using this framework, we demonstrate how mode attraction can appear in driven cavity magnonic systems for certain geometries. This includes non-linear and non-local interactions between cavity photons and magnon modes.

[1] N. R. Bernier et al, Phys. Rev. A 98, 023841 (2018).
[2] Y.-P. Wang and C.-M. Hu, J. Appl. Phys. 127, 130901 (2020).

Speaker: Igor Proskurin (University of Manitoba)

14:30 Break - 15 minutes

14:44 Magnetic North VII - Session 3 - 14h45-15h45 (Chair: Pat Clancy, McMaster University)

191 (I) Microscopic Theory of Spin Frustration in Quantum Magnets

Elementary excitations in highly entangled states such as quantum spin liquids may exhibit exotic statistics, different from those obeyed by fundamental bosons and fermions. Excitations called non-Abelian anyons are predicted to exist in a Kitaev spin liquid - the ground state of an exactly solvable model proposed by Kitaev. Material realization of the spin liquid has been the subject of intense research in recent years. The 4d honeycomb Mott insulator α−RuCl3 has emerged as a leading candidate, as it enters a field-induced magnetically disordered state where a half-integer quantized thermal Hall conductivity was reported. I will present a microscopic theory of generic spin models, including Kitaev and other bond-dependent spin-interactions responsible for disordered phases. Essential ingredients to engineer spin liquids, applications to materials, and the intriguing link to exotic multipolar orders in transition metals will be also discussed.

Speaker: Hae-Young Kee (University of Toronto)

192 Anisotropic magnetic interactions in hexagonal AB-stacked kagome lattice structures: Applications to Mn3X (X = Ge, Sn, Ga) compounds

$\mathrm{Mn}_3\mathrm{X}$ compounds in which the magnetic $\mathrm{Mn}$ atoms form AB-stacked kagome lattices have received a tremendous amount of attention since the observation of the anomalous Hall effect in $\mathrm{Mn}_3\mathrm{Ge}$ and $\mathrm{Mn}_3\mathrm{Sn}$. Although the magnetic ground state has been known for some time to be an inverse triangular structure with an induced in-plane magnetic moment, there have been several controversies about the minimal magnetic Hamiltonian. We present a general symmetry-based model for these compounds that includes a previously unreported interplane Dzyaloshinskii-Moriya interaction, as well as anisotropic exchange interactions. The latter are shown to compete with the single-ion anisotropy which strongly affects the ground state configurations and elementary spin-wave excitations. Finally, we present the calculated elastic and inelastic neutron scattering intensities and point to experimental assessment of the types of magnetic anisotropy in these compounds that may be important.

Speaker: Andrey Zelenskiy (Dalhousie University)

193 (G*) Constraints on the Spin Hamiltonian and Entropy of the Dipole-Octupole Spin Liquid Candidate Ce2Zr2O7 from Low Temperature Heat Capacity

The Ce3+ pseudospin-1/2 degrees of freedom in the pyrochlore magnet Ce2Zr2O7 are known to possess dipole-octupole (DO) character, making it a candidate for novel quantum spin liquid (QSL) ground states at low temperatures. We report new heat capacity (CP) measurements on Ce2Zr2O7, which can be extrapolated to zero temperature to account for R·ln(2) entropy using a form appropriate to quantum spin ice. The measured CP rises sharply at low temperatures, initially plateauing near 0.08 K, before falling off towards a high temperature zero beyond 3 K. Phenomenologically, the entropy recovery above T = 0.08 K gives R·ln(2) less (R/2)·ln(3/2), the missing Pauling, spin ice entropy. At higher temperatures, the same data set can be fit to the results of a numerical linked cluster (NLC) calculation that allows estimates for the terms in the XYZ Hamiltonian expected for such DO pyrochlore systems. This constrains possible exotic and ordered ground states, and clearly favours the realization of a U(1)π QSL state. NLC calculations of the magnetic susceptibility and dynamic structure factor agree with these results and provide further constraints on the experimentally-determined values of the exchange parameters.

Speaker: Evan Smith (McMaster University (Department of Physics and Astronomy))

15:45 Break - 15 minutes

15:59 Magnetic North VII - Session 4 - 16h00-1715 (Chair: Hae-Young Kee, University of Toronto)

194 (I) Exploring Kitaev Magnetism with Resonant X-Rays

The physics of heavy 5d transition metal oxides can be remarkably different from that of their lighter 3d counterparts. In particular, the presence of strong spin-orbit coupling (SOC) effects can lead to the formation of exotic ground states such as spin-orbital Mott insulators, topological insulators, Weyl semimetals, and quantum spin liquids. In materials with an edge-sharing octahedral crystal structure, large SOC can also give rise to highly anisotropic, bond-dependent, Kitaev interactions. The first, and thus far the best, experimental realizations of Kitaev magnetism are honeycomb lattice materials: the 5d iridates A$_2$IrO$_3$ and the 4d halide $\alpha$-RuCl$_3$. However, there has recently been a growing interest in the search for Kitaev magnetism in other families of materials, such as the double perovskite iridates (A$_2$BIrO$_6$) and iridium halides (A$_2$IrX$_6$). In this talk I will describe what we can learn about these novel materials using synchrotron x-ray scattering and spectroscopy techniques, including Resonant Inelastic X-ray Scattering (RIXS) and X-ray Absorption Spectroscopy (XAS). By revealing detailed information about the crystal electric field splitting, SOC strength, and magnetic excitation spectrum, these techniques provide an ideal probe of spin-orbit-driven ground states and Kitaev magnetism.

Speaker: Patrick Clancy (McMaster University)

195 (G*) Exchange Interactions in d$^2$ Systems

We study an effective pseudo-spin model from microscopics for d$^2$ materials on various lattice geometries. It was found that the interplay between electron-electron interactions and spin-orbit coupling generates intriguing multipole-multipole interactions. These interactions give rise to various multipolar phases, which were identified using computational techniques such as classical Monte Carlo and exact diagonalization. Potential applications and extensions of this theory will also be presented.

Speaker: Derek Churchill (University of Toronto)

196 Interaction-stabilized topological magnon insulator in ferromagnets

Condensed matter systems admit topological collective excitations above a trivial ground state, an example being Chern insulators formed by Dirac bosons with a gap at finite energies. However, in contrast to electrons, there is no particle-number conservation law for collective excitations. This gives rise to particle number-nonconserving many-body interactions whose influence on single-particle topology is an open issue of fundamental interest in the field of topological quantum materials.

Taking magnons in honeycomb-lattice ferromagnets as an example, we uncover topological magnon insulators that are stabilized by interactions through opening Chern-insulating gaps in the magnon spectrum. This can be traced back to the fact that the particle-number nonconserving interactions break the effective time-reversal symmetry of the harmonic theory. Hence, magnon-magnon interactions are a source of topology that can introduce chiral edge states, whose chirality depends on the magnetization direction. Importantly, interactions do not necessarily cause detrimental damping but can give rise to topological magnons with exceptionally long lifetimes. We identify two mechanisms of interaction-induced topological phase transitions and show that they cause unconventional sign reversals of transverse transport signals, in particular of the thermal Hall conductivity. Our results demonstrate that interactions can play an important role in generating nontrivial topology.

Reference: Alexander Mook, Kirill Plekhanov, Jelena Klinovaja, Daniel Loss, arXiv:2011.06543 (2020)

Speaker: Alexander Mook

197 Magnets have Two Longitudinal Degrees of Freedom

We argue that the usual magnetization $\vec{M}$, which represents a correlated property of 10$^{23}$ variables, but is summarized by a single variable, cannot diffuse; only the non-equilibrium spin accumulation magnetization $\vec{m}$, due to excitations, can diffuse. For transverse deviations from equilibrium this is consistent with work by Silsbee, Janossy, and Monod (1979), and by Zhang, Levy, and Fert (2002).

We examine the corresponding theory of longitudinal deviations for a ferromagnet using $M$ and the longitudinal spin accumulation $m$. If an initial longitudinal magnetic field $H$ has a frozen wave component that is suddenly removed, the system approaches equilibrium via two exponentially decaying coupled modes of $M$ and $m$, one of which includes diffusion. If the system in a slab geometry is subject to a time-oscillating spin current, the system approaches equilibrium via two spatially decaying modes, one associated with spacial decay away from each surface. We also explore the possibility that decay of $M$ directly to the lattice is negligible, so that decay of $M$ must be mediated through decay to $m$ and then to the lattice.

Speaker: Wayne Saslow (Texas A&M University)

TS-2 Quantum Machine Learning (DTP) / Apprentissage automatique quantique (DPT)

Conveners: Achim Kempf (University of Waterloo), Aida Ahmadzadegan (Perimeter Institute)

198 (I) Quantum Barren Plateaus and Generative Pre-Training

In recent years the prospects of quantum machine learning and quantum deep neural network have gained notoriety in the scientific community. By combining ideas from quantum computing with machine learning methodology, quantum neural networks (QNNs) promise new ways to interpret classical and quantum data sets. However, many of the proposed quantum neural network architectures exhibit a concentration of measure leading to barren plateau phenomena. In this talk, I will show that, with high probability, entanglement between the visible and hidden units can lead to exponentially vanishing gradients. To overcome the gradient decay, our work introduces a new step in the process which we call quantum generative pre-training.

Speaker: Maria Kieferova

199 (I) Interpreting artificial neural networks in the context of theoretical physics.

Since many concepts in theoretical physics are well known to scientists in the form of equations, it is possible to identify such concepts in non-conventional applications of neural networks to physics.
In this talk we examine what is learned by convolutional neural networks, autoencoders or siamese networks in various physical domains. We find that these networks intrinsically learn physical concepts like order parameters, energies, or other conserved quantities.

Speaker: Sebastian Wetzel

200 Quantum Earth Mover's Distance: A New Approach to Learning Quantum Data

In this talk, I will introduce a generalization of the earth mover's distance to the set of quantum states. The proposed distance recovers the Hamming distance for the vectors of the canonical basis, and more generally the classical earth mover's distance for quantum states diagonal in the canonical basis. I will discuss some desirable properties of this distance, including a continuity bound for the von Neumann entropy and its insensitivity to local perturbations, and I will show how these properties make the distance suitable for learning quantum data using quantum generative adversarial networks
Based on https://arxiv.org/abs/2009.04469 and https://arxiv.org/abs/2101.03037.

Speaker: Dr Milad Marvian (University of New Mexico)

12:30 Break (Optional: Discussions)

201 (I) Large Scale QML Research in TensorFlow Quantum

In this presentation you'll see how to use TensorFlow Quantum to conduct large scale research in QML. The presentation will be broken down into two major sections: First you will follow along as we implement and scale up (beyond the authors original size) some existing QML works from the literature in TensorFlow Quantum. We will focus on how to write effective TensorFlow Quantum code, visualization tools and surrounding software that the TensorFlow ecosystem has curated that can be leveraged for QML. In the second half of the presentation we will review our recent work titled "Power of data in quantum machine learning" (https://arxiv.org/abs/2011.01938) and why we think developing an understanding of data is an important step to achieving quantum advantage in QML.

Speaker: Michael Broughton

202 (I) Training quantum computers the same way as neural networks

Despite an undeserved reputation for being hard to understand, the mathematics behind quantum computing is based on relatively straightforward linear algebra. This means that the equations governing quantum computing are intrinsically differentiable. This simple observation has remarkable consequences. In particular, many of the tools developed over the past decades for deep learning, such as gradient-based training algorithms, can be applied to quantum computers with little modification. In this talk, I will overview how these ideas can be explored using freely available open-source software and publicly accessible quantum computing platforms, enabling the discovery and optimization of new and interesting quantum computing algorithms.

Speaker: Nathan Killoran

14:30 Break (Optional: Discussions)

203 (I) Quantum enhanced sampling: an essential tool for today’s quantum computing practitioner

In the distant future we expect to be using large-scale, nearly perfect quantum computers that aid in drug discovery, break RSA encryption, and outperform supercomputers in certain machine learning tasks. Today we have access to small quantum computers afflicted by noise and error. Somewhere between these two extremes lies a momentous event for the field known as quantum advantage: solving a computational problem of practical value, using a quantum computer in an essential manner. With what tools must we equip ourselves in order to reach quantum advantage as soon as possible? This talk will introduce quantum enhanced sampling, a tool for speeding up a critical component of many near-term quantum algorithms: estimation of quantities encoded in quantum operations. This helps to bridge the gap between several near-term quantum algorithms and their far-term counterparts. We will motivate the need for this tool through recent examples in quantum machine learning and quantum chemistry. Then we will give a pedagogical introduction to quantum enhanced sampling methods. Finally, we will show results demonstrating the performance of this method and will discuss the implications for near-term quantum computing.

Speaker: Peter Johnson

204 (I) Variational Neural Annealing

Many important challenges in science and technology can be cast as optimization problems. When viewed in a statistical physics framework, these can be tackled by simulated annealing, where a gradual cooling procedure helps search for ground state solutions of a target Hamiltonian. While powerful, simulated annealing is known to have prohibitively slow sampling dynamics when the optimization landscape is rough or glassy. In this talk I will show that by generalizing the target distribution with a parameterized model, an analogous annealing framework based on the variational principle can be used to search for ground state solutions. Autoregressive models such as recurrent neural networks provide ideal parameterizations since they can be exactly sampled without slow dynamics even when the model encodes a rough landscape. We implement this procedure in the classical and quantum settings on several prototypical spin glass Hamiltonians, and find that it significantly outperforms traditional simulated annealing in the asymptotic limit, illustrating the potential power of this yet unexplored route to optimization.

Speaker: Juan Felipe Carrasquilla

15:45 Break (Optional: Discussions)

205 (I) Classical and quantum control and learning

Control systems are vital in engineering, and machine learning is transforming data science; however, their basic constructs are expressed in terms of classical physics, which impedes generalizing to quantum control and quantum machine learning in a consistent way. We incorporate classical and quantum control and learning and their dependencies into a single conceptual framework. Then we discuss inconsistencies between current definitions of quantum control and quantum learning vs their descriptions achieved by generalizing classical versions using our framework. We illustrate our framework in the context of quantum-enhanced interferometric-phase estimation, which incorporates both control and machine learning.

Speaker: Barry Sanders (University of Calgary)

206 (I) Enhancing Machine Learning and Combinatorial Optimization with Quantum Generative Models

Generating high-quality data (e.g. images or video) is one of the most exciting and challenging frontiers in unsupervised machine learning. Utilizing quantum computers in such tasks to potentially enhance conventional machine learning algorithms has emerged as a promising application, but poses big challenges due to the limited number of qubits and the level of gate noise in available devices. In this talk, we provide the first practical and experimental implementation of a quantum-classical generative algorithm capable of generating high-resolution images of handwritten digits with state-of-the-art gate-based quantum computers. In the second part of my talk, we focus on combinatorial optimization; another key candidate in the race for practical quantum advantage. Here we introduce a new family of quantum-enhanced optimizers and demonstrate how quantum generative models can find lower minima than those found by means of stand-alone state-of-the-art classical solvers. We illustrate our findings in the context of the portfolio optimization problem by constructing instances from the S&P 500 stock market index. We show that our quantum-inspired generative models based on tensor networks generalize to unseen candidates with lower cost function values than any of the candidates seen by the classical solvers. This is the first demonstration of the generalization capabilities of quantum generative models that brings real value in the context of an industrial-scale application.

Speaker: Alejandro Perdomo-Ortiz

17:00 Optional: Discussions

TS-5 Private Sector Physics Symposium (Prof.Affairs/DAPI) / Symposium sur la physique dans l'entreprise privée (affaires prof./DPAI)

Convener: Daniel Cluff (University of Exeter)

207 (I) Breaking the Myth of the "Non-Traditional Physicist": The Real Story about Employment for Physics Graduates

Physics degree holders are among the most employable in the world, often doing everything from managing a research lab at a multi-million dollar corporation, to developing solutions to global problems in their own small startups. Science and Technology employers know that with a physics training, a potential hire has acquired a broad problem-solving skill set that translates to almost any environment, as well as an ability to be self-guided and -motivated so that they can teach themselves whatever is needed to be successful at achieving their goals. Therefore it's no surprise that the majority of physics graduates find employment in private--sector, industrial settings. At the same time, about 25% of graduating PhDs will take a permanent faculty position--yet academic careers are usually the only track to which students are exposed while earning their degrees.

In this talk, I will explore less-familiar (but more common!) career paths for physics graduates, and will provide information on resources to boost your career planning and job hunting skills.

Speaker: Crystal Bailey (Americal Physical Society)

208 (I) Artificial Intelligence for Customer Care

IBM Watson is well known for industry-leading natural language processing that defeated defending champions on Jeopardy! and most recently, learned to debate complex topics with humans. Equally as exciting, though perhaps less publicized, IBM works with government, enterprise, and industry to apply machine learning to real world applications such as customer care. This talk offers a view into the ways AI is transforming the customer service landscape: expanding capacity to serve, improving user experience, saving humans time and organizations money.

Speaker: Melissa Valdez (IBM)

209 (I) Perspectives on Applied AI and Machine Learning

As a trained experimental scientist, when it became clear that I needed to transition to industry I was left to find something that fit my skills. Data science offered that opportunity. I have worked in numerous industries including health care, fintech, oil and gas, and agriculture applying statistical knowledge and machine learning (ML) techniques. Knowledge from my physics degree set me up for success through learning how to solve complex problems while experience has taught me how to approach the problem with business and return-on-investment in mind. Now, at AltaML, I see use cases from many different industries in a single day. We apply ML to everything from safety to agriculture to robotics. I’ll provide some examples of how we’ve applied AI/ML to real-world problems to help people make better decisions.

Speaker: Chad Bryant

13:00 1 hour break

210 (I) Cryogenics in Mining, Deep Mine Cooling By Converting The Heat To Electricity.

Chilling an underground mining project becomes more costly as the depth increases. The air temperature increases as it descends due to auto-compression, additional heat from the host rock, equipment and processes is inevitable. A move to battery powered vehicles may allow for less air flow, legislation changes pending, but battery powered vehicles and the charging process liberate heat. The susceptibility of less air to additional heat becomes an issue if management intends to maintain the same level of activity. This paper discusses the cost comparison results of a feasibility study for a planned mine expansion and prototype testing data of a patent pending cryogenic chilling system. Cryogenic liquids store energy, effectively the heat from the mine is converted to electricity.

Furthermore, compressed air can be produced whilst simultaneously chilling (5000 cfm produces 1.2 MW chilling) and motive force, engines for equipment can be fueled by cryogenic liquids, a vehicle would produce cool clean air for exhaust with about 1/3 motive power to 2/3 chilling. The results obtained from a prototype system, approximately the size of a small spot chilling system, demonstrates conclusively that rapid response to heat added to the air flow is a feature; therefore, Chilling on Demand™ is a feature that can overcome the issues of heat management at lower air flows. Since the chilling is delivered by a cryogenic fluid, extending the depth of a mine only requires an additional surface liquefier module and a longer pipe. Since the system can provide chilling on demand it compliments chilling on demand increasing the economic benefit of installed VOD systems.

Speakers: Daniel Cluff (CanMIND Associates), Sujit Sengupta (AdmiraDHES)

Cryogenics for DEEP MINE CHILLING canmind admiradhes.pdf

211 (I) The winding road from a degree in physics to the development of leading-edge optical sensors

This talk aims to give an example of how a degree in physics can lead to an interesting industrial career in optical sensor development. A broad understanding of different physical laws and behaviors (mechanics, thermodynamics, electromagnetics, optics), combined with a practical grounding in electronics, programming and machining, provides an ideal skill set for developing optical instruments where complex interactions between different sub-systems must be understood and anticipated. I will describe how my university physics degrees led to a varied and interesting career developing satellite instruments for ozone monitoring and wildfire measurement, thermal and terahertz imaging cameras, magnetic tools for pipeline inspection and a laser-based instrument for disease diagnosis in exhaled breath. Along the way I will give a brief introduction to the inner workings of these various sensors.

Speaker: Denis Dufour (INO)

212 (I) Using a Physics Education to Communicate Science to Society

This talk focuses on the responsibility of scientists to counter pseudo-scientific ideas in society, and reviews the factors that have led to a rise in popular anti-science sentiment. I will provide insights into how to communicate the ideas of science with the public, and I will give some examples of important environmental issues that are most commonly misconstrued by the general public, from a pro-science EcoModernist perspective.

Speaker: Al Scott (Honeywell)

15:30 30 minute Break

16:00 Panel Discussion : Career Opportunities in Physics - What to do Next? / Opportunités de carrière en physique - Quel chemin prendre?

TBD

TS-6-1 COVID & Biomicrofluidics (DPMB Symposium) / COVID et biomicrofluidique (Symposium DPMB)

Convener: Melanie Campbell (University of Waterloo)

213 (I) Microfluidic devices for handling small organisms

Microfluidic technology has been used in many application areas including diagnostics, drug delivery and drug discovery. In drug discovery, microfluidic devices have been used to perform combinatorial experiments where several drug candidates can be exposed to biological materials such as protein drug targets, cells or small organisms simultaneously at various concentrations in order to determine a suitable drug candidate for further investigations. Small organisms such as C.elegans worms or Drosophila flies are ideal model organisms that are used in the drug discovery process understand biological processes and studying human diseases at the molecular-genetic level. Nevertheless, these organisms are small and are difficult to handle. Microfluidic devices provide the capability to handle these organisms one at a time but in a parallelized manner allowing unprecedented capability to perform combinatorial analysis.

In this talk, I will present some of the unique microfluidic devices that we have developed in my laboratory to study and perform assays on these model organisms. First, I will describe the work that we have done to characterize the phenomenon of electrotaxis of C.elegans worms. I will demonstrate the use of it to immobilize the worm and sort it as well as measure its neuromuscular response. I will also describe devices to immobilize and image the neurons in Drosophila larva. Finally, I will describe microinjection devices that are capable of immobilization of C.elegans and Drosophila and inject precise regions in them to deliver biomolecules. The versatility of these devices provide new capabilities to biophysicists, medical researchers and drug discovery scientists to study these organisms in great detail.

Speaker: Ravi Selvaganapathy (McMaster University)

214 A nanosurface fluidic device for physical fingerprints of extracellular vesicles for liquid biopsy in cancer

Non-invasive liquid biopsies offer hope for point-of-care glimpse into the molecular hallmarks of the disease, including drug resistance and targets. Among different types of liquid biopsy platforms, tumor-derived exosomes (EXs) are unique due to their intercellular tumor communication and serve as carriers of biological information. Exosomes are nanoscale extracellular vesicles (EVs) released from cells into body fluids, carrying cell cargos such as DNA and RNA reflective of their parental cells. They offer a unique opportunity to access biologically important accepts of disease complexity.
In Mahshid Lab, we develop a new nanoplatform for molecular analysis of single EVs. We harnesses a nanopatterned fluidic device that incorporate SERS (surface enhanced Raman spectroscopy) for molecular profiling of cancerous EVs. Using this approach, we were able to distinguish a library of peaks expressed in GBM (Glioblastoma) EVs from two distinct glioblastoma cell lines (U373, U87) and compare them to those of non-cancerous glial EVs (NHA) and artificial homogenous vesicles. In parallel, we develop a nanofluidic device with tunable confinement to trap EVs in a free-energy landscape that modulates vesicle dynamics in a manner dependent on EV size and charge. We show that the surface charge of particles can be measured by analysis of particle diffusion in the landscape. Since extra-cellular vesicles are representative of their parental cells, their surface charge and size can provide information of their parental cells. As proof-of-principle, we perform size and charge profiling of a population of EVs extracted from human glioblastoma astrocytoma (U373) and normal human astrocytoma (NHA) cell lines.

Speaker: Sara Mahshid (McGill University)

215 (G*) Erythro-VLPS: Embedding SARS-COV-2 Spike Proteins in Red Blood Cell Based Proteoliposomes Leads to Pronounced Antibody Response

Novel therapeutic strategies are urgently needed to control the SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) pandemic. This virus belongs to a larger class of corona viruses currently circulating, which pose major threats to global public health. Here, I present the fabrication and characterization of Erythro-VLPs: Erythrocyte-Based Virus Like Particles, i.e., red blood cell based proteoliposomes carrying the SARS-CoV-2 spike protein.
Erythrocytes can present antigens to the immune system when senescent cells are being phagocytized in the spleen. This capacity together with their high biocompatibility make red blood cells (RBCs) effective vehicles for the presentation of viral immunopathogens, such as the SARS-CoV-2 S-protein, to the immune system. .The proteoliposomes were prepared by tuning lipidomics and proteomics of the RBC membranes on a nanoscale. Epi‐fluorescent and confocal microscopy, dynamic light scattering (DLS), and Molecular Dynamics (MD) simulations were used to characterize the liposomes and the insertion of the S-proteins. The protein density on the outer membrane was estimated to be 70 proteins/μm. The Erythro-VLPs have a well-defined size distribution of 222±6 nm and exhibit dose-dependent binding to ACE-2 (angiotensin converting enzyme 2) in biolayer interferometry assays.
We present direct experimental evidence of a pronounced immunological response in mice after 14 days, after two injections, and the production of antibodies was confirmed in ELISA. In addition, these antibodies were found to be specific for the S-protein RBD sub-domain demonstrating that the protein not hidden or conformationally altered by the developed protocol. This immunological response was observed in the absence of any adjuvant which is usually required for protein-based vaccines.
The RBC platform that we present in this work can easily and rapidly be adapted to different viruses in the future by embedding the corresponding antigenic proteins and opens novel possibilities for therapeutics.
[1] Himbert et al., “Erythro-VLPs: Embedding SARS-CoV-2 spike proteins in red blood cell based proteoliposomes leads to pronounced antibody response in mouse models”, submitted.

Speaker: Sebastian Himbert (McMaster University)

216 (G*) Novel drug delivery system for antibiotic therapy using modified erythrocyte liposomes

As a result of the growing world-wide antibiotic resistance crisis, many currently existing antibiotics have been shown to be ineffective due to bacteria developing resistive mechanisms. There are a limited variety of potent antibiotics that are successful at suppressing microbial growth, such as polymyxin B, however, are deemed as a last resort due to their high toxicity. Adverse side effects associated with polymyxin B treatment include nephrotoxicity, neurotoxicity, and hypersensitivity. Previous research has focused on the development of an effective drug delivery system that can inhibit bacterial growth while minimizing negative side effects. In particular, nanoparticles have been of interest as they can be conjugated to a drug of interest, allowing for effective drug transport to the target. Despite their potential, an antibiotic delivery system has yet to be established, due to the nanoparticles lacking specificity and lack of biocompatibility and rejection. Here, we present a novel antimicrobial drug delivery method that uses modified red blood cells (RBC) that are encapsulated around polymyxin B. These RBC-based antibiotics are made specific to certain bacteria through the addition of the corresponding antibodies to their cell membranes. We investigate whether this drug delivery system is effective at inhibiting bacterial growth and selective, which is important to minimize the negative side effects seen with conventional polymyxin B treatment. This RBC based platform is potentially advantageous to synthetic nanoparticle-based approaches because of their biocompatibility and bioavailability, resulting in longer retention time in the human body.

Speaker: Hannah Krivic (McMaster University)

217 (U*) Laser-based mask characterization for prophylaxis of Covid-19

During the Covid-19 pandemic, face masks have become the new norm with their widespread use in public as part of a multi-barrier approach for infection control, including physical distancing, hand hygiene, and altered social behaviour. Masks provide benefits to both the mask wearer and to those in their proximity when they are worn by all individuals in a common area. The gold standard in personal protective equipment (PPE) remains the N95 respirator, made of synthetic materials with electrostatic properties that filter and retain more than 95% of aerosols <1 µm and larger in size. N95 respirators degrade during washing and disinfection, and as such are single use disposable PPE. Similarly, surgical-style masks made of polypropylene and non-woven materials are unsuited to frequent washing/decontamination with heat or detergents. Owing to their disposable nature, most commercially available PPE such as the above are unsustainable for supplying the public due to supply interruptions, high cost over time, and a lack of aesthetic attributes (colour, pattern) to encourage use.

As a result, textile manufacturers and a new cottage industry of homemade mask makers, including volunteers making donated masks for vulnerable populations, can provide fabric face masks to the public. Recently, the U.S. CDC indicated that commercial manufacturers of face masks will require testing although the conditions of such standards have yet to be outlined. Recently, Dr. Tam has made recommendations for mask materials to elevate the quality of masks being worn by the public, however these recommendations are not easily translatable to actual mask construction and such recommendations are based on very limited testing of fabric masks.

This presentation will discuss the development of a test apparatus for assessing mask efficacy by measuring the aerosols transmitted through the masks. We use a laser-based system, using relatively inexpensive diode lasers to illuminate the exhaled particles, a webcam for data acquisition, and Python-based particle tracking software. We make the approximation that the intensity of the scattered light from the droplets is proportional to the size of the droplet, but we will be able to quantify the droplet size by analyzing the data with Mie scattering theory.

Reference:
https://advances.sciencemag.org/content/6/36/eabd3083?te=1&nl=running&emc=edit_ru_20200822

Speaker: Abbey Richer (University of Windsor)

218 (G*) Quantifying Density Hotspots and Potential Superspreading Events During COVID-19

Social distancing measures have been the main non-pharmaceutical intervention (NPI) against the COVID-19 pandemic. Numerous large-scale analyses have studied how these measures have affected human movement, finding sizeable drops in average mobility. Yet comparatively little attention has been paid to higher-order effects such as “superspreading events” which are known to be outsized drivers of pandemics. Networks with heterogeneous (high variance) distributions of contacts can dramatically accelerate spreading processes, even if the average number of contacts is low. This stresses the need to quantify higher-order effects, and the (in)ability of existing NPI to reduce them.

Here we assess this by applying tools of statistical physics to approximately 12 billion anonymized mobile phone traces from 2.33 million devices in the Chicago metropolitan area, from Jan.1 to Jun.30, 2020, covering the first wave of state- and city-level social distancing measures in the pandemic. To identify potential super-spreading events, we grid these data at a fine spatial and temporal resolution, revealing large, transient co-localizations of people which we term hotspot events. We then ask about the spatiotemporal distribution of these events and the mobility statistics of the people participating in them--both before and after the implementation of social distancing measures.
Encouragingly, we find that distancing policies heralded a dramatic rarefaction of people, reflected in an increase in the entropy of their spatial distribution. As a result, we observe a concomitant drop in hotspot event frequency, with the largest reduction occurring in the urban core. This, however, belies a more worrisome trend: though we observe a large average reduction in the amount people travel (as measured by individual radius of gyration), this fails to be true for the subset of users participating in hotspot events. These users display higher-than-average baseline mobility, which persists (and even increases) during the post-lockdown period.

Our findings indicate that though social distancing policies may succeed in reducing average mobility, their effectiveness in reducing the key driver of spreading processes on networks (the second moment of the degree distribution) may be more limited. This in turn suggests the need for additional NPI specifically targeted at “super-spreading events”.

Speaker: K. Mason Rock (Ryerson University)

219 Filter mask development and PPE distribution from the ground up.

For a lot of us, the COVID-19 pandemic has meant dialing back, hunkering down, and holding off until things get back to normal. For some, though, it has meant ramping up and going the extra mile to get things back to normal. This presentation will attempt to tell a story that starts with a small group of students from Lakehead University and the Northern Ontario School of Medicine that aimed to redistribute and manufacture PPE as a STOPGAP solution to fill shortages in northern Ontario. The initiative grew into a network of doctors, students, professors, staff, and industrial partners working towards keeping people safe- now and into the future. What we discovered is not, in our opinion, as important as how we discovered it, and how a group of passionate people put their lives on hold to develop 3D printed face masks, make test equipment from aquarium parts and hot glue, meet doctors from SickKids hospital on the side of the highway to exchange filters, and partner with business people willing to risk everything to bring Ontario the ability to control its own supply of PPE. We are still working to overcome this challenge, and we hope the story of what we did will inspire others to find creative ways to overcome similar obstacles that may face us in the future.

Speaker: Christopher Murray (Lakehead University)

12:35 TS-6-1 Break (55 minutes)

TS-7 Sensors and Metrology Symposium (NRC) / Symposium sur les capteurs et la métrologie (CNRC)

Convener: Peter Mason (National Research Council of Canada)

11:00 Introductory Remarks - Dr. Julie Lefebvre, NRC

220 (I) Quantum Technologies in Sensing, Imaging, and Metrology: From the Laboratory to Near-Term Commercial Applications

This keynote will provide a high-level overview of the current state-of-the-art in quantum technologies and their applications to sensing, imaging and metrology. I will start with a brief historical view about how National Metrology Laboratories like NIST and NRC-Canada have used these technologies for years. I will then transition to some near-term commercial applications before returning to a long-term view of the future applications of these quantum technologies to National Metrology Laboratories, society, and basic science.

Speaker: Dr Carl Williams (Deputy Director, Physical Measurement Laboratory National Institute of Standards and Technology)

11:35 Questions and Discussion

221 (I) Quantum radiometry and metrology for single-photon detectors and emitters

Single-photon detectors are being increasingly implemented in a variety of applications ranging from quantum information science to spectroscopy and remote sensing. These measurement techniques rely on the accurate detection of single photons at specific wavelengths. National metrology institutes worldwide, including the National Research Council Canada, have been developing characterization techniques and reference standards for such single-photon technologies. The implementation of quantum emitters as metrology single-photon source standards will enable the in-situ characterization of next-generation photonic technologies including quantum photonic integrated circuits, where single-photon sources, detectors, and other optical components for quantum communication and computation are fabricated on one on-chip platform. This presentation will discuss ongoing efforts in the development of characterization methodologies for single-photon technologies, including the need for consistency in the measurement of performance metrics for single-photon emitters.

Speaker: Dr Angela Gamouras (National Research Council of Canada)

12:10 Questions and Discussion

12:15 Break

222 (I) Toward tabletop, quantum-limited mechanical sensing and new optomechanical control

Mechanical systems represent a fundamental building block in many areas of science and technology, from atomic-scale force sensing to quantum information transduction to kilometer-scale detection of infinitesimal spacetime distortions. All such applications benefit from improved readout sensitivity, and many seek new types of mechanical actuation. In this talk I will discuss our efforts to realize a tabletop, room-temperature optomechanical system capable of sensing the broadband (100Hz - 1MHz) quantum noise in the radiation force from incident laser light; this would represent a milestone toward optomechanically tuned squeezed light sources and mechanical sensitivities beyond the standard quantum limit. Time permitting, I will also discuss our progress toward creating a qualitatively different kind of optomechanical system in which light, even an average of a single photon in the apparatus, strongly tunes the spatial extent and effective mass of a mechanical mode.

Speaker: Jack Sankey (McGill University)

12:50 Questions and Discussion

223 (I) Applying Atom-Defined Building Tools to Make Quantum Sensing Devices

After 3 decades of preparation, tools and procedures for reproducible fabrication of atom-perfect silicon structures have matured to a point where it has now become possible to build proto-devices while also planning viable atom-scale manufacturing. In the beginning, device complexity and production rates will be low while manufacturing costs are high, challenges that must be offset by the high value of select initial products. Inherent attributes including ultra high speed, ultra small size/weight/power, variance-free manufacture and routine access to some quantum effects are waiting to be harnessed.
A glimpse of our current capabilities will be shown by examples including structures we can make, unique electronic properties of those, chemical and electromagnetic sensing capabilities and fabrication automation through machine learning.
Near term device objectives such as a quantum metrological current standard, an unusually high temperature capable quantum metrology-based standard thermometer, and a uniquely portable, due to low power consumption, quantum random number generator will be mentioned.
Collaborative work with Professor Konrad Walus, EE, UBC, that shows the unprecedented low power consumption of binary and analog atom-defined silicon circuitry will be briefly sketched.

Speaker: Robert Wolkow (University of Alberta)

13:20 Questions and Discussion

224 (I) Microwave entanglement generation and its application in quantum sensing

Entanglement is the essential resource that defines this new paradigm of quantum-enabled devices. Here I confirm the long-standing prediction that a parametrically driven mechanical oscillator can entangle electromagnetic fields. We observe stationary emission of path-entangled microwave radiation from a micro-machined silicon nanostring oscillator, squeezing the joint field operators of two thermal modes by 3.40(37)~dB below the vacuum level. This entanglement can be used to implement Quantum Illumination (a sensing technique) that employs entangled photons to boost the detection of low-reflectivity objects in environments with bright thermal noise. The promised advantage over classically correlated radiation is particularly evident at low signal photon flux, a feature that makes the protocol potentially useful for non-invasive biomedical scanning or low-power short-range radar detection. In this work, we experimentally simulate quantum illumination at microwave frequencies. We generate entangled fields using a Josephson parametric converter at millikelvin temperatures to illuminate a room-temperature object at a distance of 1 meter in a proof of principle radar setup.

Speaker: Prof. Shabir Barzanjeh (University of Calgary)

13:50 Questions and Discussion

14:00 Lunch session 14h00-15h00 - Government Interest in Quantum Sensing (Introduction)

225 (I) (Lunch session talk) Department of National Defence Quantum S&T Strategy

The DND/CAF is faced with a rapidly evolving defence, safety, and security environment with the emergence of disruptive technologies such as quantum. It is expected that some disruptive technologies, quantum in particular, will have an impact in less than 5 years. Quantum-enabled technologies will have applicability across a wide array of defence applications, such as in sensing (including position, navigation, and timing), communications, computing, and advanced materials. Canada has benefited from early, world-renown strength in quantum technologies. As such, the DND/CAF Quantum Science and Technology Strategy (Strategy) leverages strong national and international partnerships and calls for coherence across departmental investments to accelerate the development of defence-relevant quantum technologies. Enabling Canadian sensitive technologies to develop beyond the laboratory is in the best interest of DND/CAF in order to be prepared for disruptions in the future operating environment. The Strategy also calls for increased quantum internal research capacity and human capital across the department to allow DND/CAF to be in a position to assess, advise, and benefit from allied efforts and face the challenges of the 21st century and beyond.

Speaker: Aimee Gunther (University of Waterloo)

226 (I) (Lunch session talk) NRC’s Quantum Sensors Challenge Program

The National Research Council is launching The Internet of Things: Quantum Sensors Challenge Program in 2021. This program has seven years of funding and aims to develop a disruptive generation of quantum sensors that are orders of magnitude better than sensors that exist today. The program is structured to encourage collaborative research projects between the NRC and researchers in academia, industry, and other government departments. This talk will discuss program details and review the collaborative model.

Speaker: Peter Mason (National Research Concil of Canada)

227 (I) Quantum Magnetometry with the Diamond NV-Centre

The diamond Nitrogen-Vacancy centre (NV-centre) is a defect which occurs in natural diamonds, and can also be introduced artificially. Due to screening effects, the NV-centre defect exhibits remarkably long spin coherence times. This means the diamond NV centre can be used for precision magnetometry, using Optically Detected Magnetic Resonance (ODMR) of the Zeeman splitting. This talk will review the history and basic physics of the diamond NV-centre, and describe work toward a new compact diamond NV-centre magnetometer, with potential applications in geophysical sensing.

Speaker: Michael Bradley (University of Saskatchewan)

15:20 Questions and Discussion

228 (G*) Achromatic multi-mode time bin interferometer for quantum networks

We present a novel quantum multi-mode time bin interferometer that is suitable for a wide range of optical signals and capable of being used for free space quantum channels. Our design uses only reflective optics with curved mirrors providing the one-to-one imaging system necessary for a multi-mode interferometer. The curved mirrors are ideal since, unlike lenses, their focal length depends only on the geometry of the mirror allowing them to be used with a wide range of optical signals and avoid chromatic effects. Furthermore, each curved mirror is placed in a cavity like configuration with a flat mirror, thus created a relatively smaller physical footprint. The small physical footprint allows the interferometer to be placed in a monolithic chassis that is built using additive manufacturing. Additive manufacturing enables nonconventional techniques that allowed for flexure optomechanical components to be built into the monolithic chassis enabling alignment of the interferometer with the reduced physical footprint. The monolithic chassis allows for increased robustness and gives a predictable thermal expansion. In addition, the use of low thermal expansion material, such as Invar, further increases the thermal tolerance of the interferometer, increasing the practicality of the device. Overall, this study advances the practicality of the multi-mode time bin interferometers for free space quantum applications. Thus, further enabling the deployment of quantum technologies to bring about new applications and fundamental research.

Speaker: Ramy Tannous (University of Waterloo, Institute for Quantum Computing)

229 (G*) Towards the atomic scale readout of single acceptor states in p-doped Si

Single acceptor dopants in Si along with dangling bonds are enabling technologies for atomic scale charge and spin-based devices.1 Additionally, recent advances in hydrogen lithography have enabled the patterning of quantum dot based circuit elements with atomic precision.[2] We engineered a single acceptor coupled to a dangling bond wire on highly doped p-type H-Si(100) and characterized its electronic properties with scanning tunneling spectroscopy. The coupled entity has an electronic structure that behaves as a conductive wire from which the charge state of the dopant can be accessed and has a complex dependence on the dangling bond wire length. In addition, dI/dV mapping reveals features reminiscent of charging rings that are centered over the dopant and overlap with the wire.[3] This overlap varies with electric field and its tunability may augment the functionality of dangling bond based quantum devices.

References:
1 A. Laucht et al., "Roadmap on quantum nanotechnologies", Nanotechnology, vol. 32, no. 16, p. 162003, 2021. Available: 10.1088/1361-6528/abb333
[2] T. Huff et al., "Binary atomic silicon logic", Nature Electronics, vol. 1, no. 12, pp. 636-643, 2018. Available: 10.1038/s41928-018-0180-3
[3] N. Turek, S. Godey, D. Deresmes and T. Mélin, "Ring charging of a single silicon dangling bond imaged by noncontact atomic force microscopy", Physical Review B, vol. 102, no. 23, 2020. Available: 10.1103/physrevb.102.235433

Speaker: Max Yuan (University of Alberta)

230 (G*) Hybrid Integration of III-V Nanowires Embedded with Quantum Dots on Photonic Integrated Circuits

Quantum dots embedded in photonic nanowires are highly efficient single photon generators. Integrating such sources on-chip offers enhanced stability and miniaturization; both of which are important in many applications involving quantum information processing. We demonstrate the efficient coupling of quantum light generated in a III-V photonic nanowire to a silicon-based photonic integrated circuit. This hybrid quantum photonic integrated circuit is assembled through a “pick & place” approach using a nanomanipulator in a scanning electron microscope where the nanowires are transferred individually from the growth substrate and carefully placed onto the photonic integrated circuit. The emission properties of on-chip nanowire QDs were measured using an all-fibre pump and collection technique. We demonstrate detected count rates of a million counts per second with single photon purities higher than 95 percent thus showing that using nanowires with embedded QDs coupled to on-chip photonic structures is a viable route for the fabrication of stable single photon sources.

Speaker: Edith Yeung (University of Ottawa)

231 (G*) Optomechanical interface between telecom photons and spin quantum memory

Optically active defects in solids---colour centres---are one of the most promising platforms for implementing quantum technologies. Their spin degrees of freedom serve as quantum memories that in some cases can operate at room temperature. Their control can be achieved with microwave spin control and resonant optical excitation but is hindered by the broadening of optical transitions from thermal phonons and spectral diffusion. Furthermore, spin-qubit optical transitions are often outside the telecommunications wavelength band required for long-distance fiber optic transmission. Harnessing the coupling between mechanical degrees of freedom and spins has emerged as an alternative route for controlling spin-qubits. However, connecting spin-mechanical interfaces to optical links to realize a spin-photon interface has remained a challenge. Here we demonstrate such an interface using a diamond optomechanical cavity that does not depend on optical transitions and can be applied to a wide range of spin qubits.
Our device consists of a diamond microdisk resonator studied in [Optica 3, 963-970 (2016)]. The microdisk is fabricated from optical grade diamond that contains ensembles of NV centres. We use an optical mode at 1564 nm with the quality factor Qo = 150k. The mechanical mode which we use to couple to the NV spin state is a radial breathing mode with a frequency of around 2.1 GHz with the quality factor Qm = 4k. The device operates in the sideband resolved regime enabling optomechanical self-induced oscillations for sufficiently high optical input power of a blue detuned laser. These oscillations can produce the stress of a few MPa, large enough to drive the electronic spins of NV centers. We use a standard diamond NV confocal microscope to initialize and readout the NV state. The MW pulses transfer the population between |-1⟩<->|0⟩ and |+1⟩<->|0⟩ state. We wait for 0.7 us with the mechanical drive that drives the |-1⟩<->|+1⟩ transition.
In our measurements, we observe a coinciding dip in the |+1⟩ population and a peak |-1⟩ population, that verifies that the spins are being optomechanically driven. On calibrating this signal with the MW Rabi contrast and the background signal, we estimate a driving rate of 2pix170kHz and ~45% transfer of spin population between |±1⟩ states. Feasible improvements in device geometry will increase the optomechanically-induced driving rate by a few orders of magnitude allowing for coherent control of NV spins using an optomechanical resonator.

Speaker: Prasoon Kumar Shandilya (University of Calgary)

232 (G*) Suppression of Phonon-Mediated Decoherence using Frequency-Swept Laser Pulses in Optically-Driven Semiconductor Quantum Emitters

Among solid state quantum emitter systems, semiconductor quantum dots are particularly attractive due to their high radiative quantum efficiencies [1], their strong optical coupling enabling fast [2] and arbitrary [3] qubit rotations, and their tunable emission in the range of standard telecommunication wavelengths. For applications such as quantum light sources and quantum nodes, it is essential to maximize the fidelity of the optical control process governing quantum state initialization and control. While the dephasing time tied to radiative relaxation is many orders of magnitude longer than control times achievable with subpicosecond laser pulses, resonant coupling of the electron-hole pair to phonons in the solid-state environment can still contribute to decoherence during the optical control process [2]. This decoherence channel is often referred to as excitation-induced dephasing since the impact on fidelity is dictated in part by the characteristics of the driving laser field. Here we report the demonstration of suppression of phonon-mediated decoherence through the application of frequency-swept laser pulses via adiabatic rapid passage in the strong-driving regime [4]. We also investigate the dependence of the threshold for decoherence suppression on the size and shape of the quantum dot. Our findings indicate that the use of telecom-compatible quantum dots leads to decoherence suppression at pulse areas comparable to a single Rabi oscillation period.

[1] Atature et al. Nat. Rev. Mater. 3, 38 (2018).

[2] Mathew et al. Phys. Rev. B 90, 035316 (2014).

[3] Mathew et al. Phys. Rev. B 84, 205322 (2011); Gamouras et al. J. Appl. Phys. 112, 014313 (2012); Gamouras et al. Nano Letters 13, 4666 (2013); Mathew et al. Phys. Rev. B 92, 155306 (2015).

[4] Ramachandran et al. Opt. Lett. 45, 6498 (2020).

Speaker: Mr Grant Wilbur (Dalhousie University)

233 (G*) A portable diamond-based quantum demonstrator based on a quantum control and readout platform - Démonstrateur quantique portable à base de diamant, basé sur une plateforme de contrôle et de lecture quantique

In addition to being extremely sensitive sensors, nitrogen vacancies (NV) centers in diamond are an ideal showcase of quantum technologies as they work in ambient conditions. Experiments with NV centers usually involve a bulky optical system, together with a wide assortment of signal generators and samplers, which is challenging to synchronize together. Here, we perform quantum control experiments on NV centers which are much more accessible to a broader community. We achieve this by (i) miniaturizing hardware components into a magnetometer the size of Rubik’s cube and (ii) leveraging a commercial platform for control and readout. We interfaced all the quantum magnetometers signal generation and readout components with a modular control platform, thus allowing it to fully operate the sensor. We will present room-temperature results including optically detected magnetic resonance, Rabi and Ramsey oscillations of an ensemble of NV centers. In addition to democratizing complex experiments in quantum physics, our work paves the way for efficient prototyping of quantum sensors with commercial control solutions.

Les centres azote-lacune (NV) dans le diamant sont une vitrine idéale des technologies quantiques car ils fonctionnent dans des conditions ambiantes. Les expériences avec les centres NV impliquent généralement un système optique volumineux, ainsi qu'un large assortiment de générateurs de signaux et d'échantillonneurs, qu'il est difficile de synchroniser ensemble. Ici, nous réalisons des expériences de contrôle quantique sur des centres NV qui sont beaucoup plus accessibles à une plus large communauté. Nous y parvenons (i) en miniaturisant l’électronique dans un magnétomètre de la taille d'un cube Rubik et (ii) en exploitant une plateforme commerciale pour le contrôle et la lecture. Nous avons interfacé tous les composants de génération de signaux et de lecture du magnétomètre quantique avec une plateforme de contrôle modulaire, lui permettant ainsi d’opérer le capteur quantique. Nous présenterons les résultats obtenus à température ambiante, notamment la résonance magnétique détectée optiquement et les oscillations de Rabi et de Ramsey d'un ensemble de centres NV. En plus de démocratiser les expériences complexes en physique quantique, notre travail ouvre la voie à un prototypage efficace des senseurs quantiques avec des solutions de contrôle commerciales.

Speaker: Azfar Badaroudine (Université de Sherbrooke)

16:15 Break

234 (I) Building Magnetic Intelligence: harnessing quantum magnetometry with the diamond NV-centre for end-user applications

SBQuantum are building a Magnetic Intelligence Platform to extract additional information from magnetic fields. The platform uses nitrogen-vacancy diamond sensors to unlock the tensor information from the magnetic field before interpreting this data through a suite of proprietary algorithms for the detection and classification of magnetic anomalies. This presentation will dive through the history of SB Quantum which lead to Magnetic intelligence and discuss potential applications of the platform solution as well as upcoming challenges to its deployment.

Speaker: Rachel Taylor (SB Quantum)

16:50 Questions and Discussion

235 (U*) Photons in the Brain: Imaging Biophotons with Quantum Detectors

Ultra-weak light, known as biophotons, are emitted spontaneously by living organisms, but the origin, wavelength and the underlying mechanisms have not yet been clearly identified; although energy metabolic processes seem to be involved. Moreover, neurons can emit photons and there is strong experimental and theoretical evidence that myelinated axons can serve as photonic waveguides. Thus, it has been conjectured that biophotons are involved in neural communication. The main challenge of imaging biophotons is their low intensity, which requires detectors displaying high sensitivity and very low noise level.

To accommodate for the detection of ultra-weak biophoton signals, we use superconducting nanowire single-photon detectors (SNSPDs) where spectral filtering of blackbody radiation – achieved by spooling the input fibres – yields extreme low dark counts (on the order of 0.5 counts per minute). For our study, we have chosen tadpole and frog Xenopus brains as our models, since these conserve most of the essential cellular and molecular mechanisms from mammalian brains and are easy to manipulate.

In my talk, I will present our setup and results from our recent measurements of biophoton emission. I will also introduce a range of planned measurements e.g. spectral and temporal characterization, application of neural activity stimulators/inhibitors, and discuss some improvements to the experimental apparatus such as implementing fiber-coupling to an array of SNSPDs, EMCCD cameras, and using different biological samples. These measurements are all aimed at our long term goals of understanding how biophotons are generated in neurological cells and determining if biophotons play a role in communication in the nervous system (beyond the current paradigm of electro-chemical signalling processes). This could open the door to the fascinating fundamental question of whether quantum phenomena, such as entanglement, play a role in higher level functions of the brain, e.g., consciousness.

Speaker: Rana Zibakhsh (University of Calgary)

236 (G*) Gated quantum dots in van der Waals materials

Quantum confinement and manipulation of charge carriers are critical for achieving devices practical for various quantum technologies such as quantum sensing. Atomically thin transition metal dichalcogenides (TMDCs) have attractive properties such as spin-valley locking, large spin-orbit coupling and high confinement energies which provide a promising platform for novel quantum technologies. In this talk, we present the design and fabrication of electrostatically gated quantum structures based on fully encapsulated monolayer tungsten diselenide (WSe2) aimed at probing and measuring the properties of the confined single and few-hole states in these structures. Furthermore, we successfully demonstrate that local control gates successfully pinch-off the current across the device with gate voltages consistent with their lithographic widths. Finally, we discuss the origins of the observed mesoscopic transport features related to the quantum dots through the WSe2 channel.

Speaker: Justin Boddison-Chouinard (University of Ottawa)

237 (G*) Super-resolution Ghost-Imaging

In microscopy, the imaging of light-sensitive materials has been a persistent problem, as the sample being studied may be altered or damaged by the illumination itself. Naturally, to overcome over-illuminating the sample, one can reduce the intensity of the classical light source; however, reducing the source intensity comes with a trade-off which affects noise and image quality. In recent years, it has been shown that using quantum illumination as a source for imaging schemes significantly reduces photon illumination of the sample while maintaining image quality. In fact, in our previous work [1] we combine two quantum imaging and detection schemes in a technique coined “Interaction-free-ghost-imaging” and achieve results with low photon number and high contrast images.
A further limitation of all direct imaging schemes, whether they be quantum or classical, is the so-called diffraction limit. When measuring intensity directly, the maximal resolution is dictated by the size of optical apertures in the imaging system. Recent results [2] [3] have shown that performing phase-sensitive measurements, as opposed to intensity measurements, could increase resolution by several orders of magnitude.
We propose an experiment implementing the super-resolution technique in a quantum ghost-imaging scheme. We aim to show that the added benefits of low photon counts along with increased resolution show promise for imaging small light-sensitive objects such as biological cells, and further challenges the notion of how many photons are needed to form a visible image.

[1] Zhang,Y., Sit, A., Bouchard, F., Larocque, H., Grenapin, F., Cohen, E., Elitzur, A., Harden, J. Boyd,R., Karimi, E, “Interaction-free-ghost-imaging of structured objects”, Optics Express 27, 2212-2224 (2019).
[2] Tsang, M., Nair, R., Lu X, “Quantum Theory of Superresolution for two Incoherent Optical Point Sources”, Physical Review X 6, 031033 (2016).
[3] Tham, W., Ferretti, H., Steinberg, A, “Beating Rayeigh’s curse by Imaging Using Phase”, Physical Review Letters 118, 070801 (2017).

Speaker: Florence Grenapin (University of Ottawa)

238 (G*) Multiplexed Single-Photon Source Based on Multiple Quantum Dots Embedded within a Single Nanowire

Non-classical light sources are an important tool for many quantum information processing applications such as quantum key distribution and linear optical quantum computing. Sources based on semiconductor quantum dots offer close to ideal performance in terms of efficiency and single photon purity. However, emission rates are limited by the radiative lifetime of the excitonic complexes. This limitation can be overcome by multiplexing independent quantum dot emitters. Here we propose an approach to deterministically integrate multiple single photon emitters within a single photonic structure based on bottom-up grown nanowires. We use selective-area vapour-liquid-solid epitaxy to incorporate five energy tuned quantum dots in a single nanowire photonic waveguide, all of which are all optimally coupled to the same optical mode. Each dot acts as an independent source of high purity single photons and the total emission rate is found to scale linearly with the number of embedded emitters. This result is an important step towards producing wavelength multiplexed single photon sources where the emission rate is limited by the number of incorporated emitters.

Speaker: Mr Patrick Laferrière (University of Ottawa)

17:30 Wrap Up

11:00 TS1-1 Break

TS4-1 Neutrino-related questions in nuclear and astro-particle physics (PPD Neutrino Physics and Beyond Symposium) / Questions liées aux neutrinos en physique nucléaire et d'astro-particules (Symposium PPD sur la physique des neutrinos et au delà)

Convener: David McKeen (TRIUMF)

239 (I) Ab initio nuclear theory for neutrino physics

As science probes ever more extreme facets of the universe, the role of nuclear theory in confronting fundamental questions in nature continues to deepen. Long considered a phenomenological field, breakthroughs in our understanding of nuclear and electroweak forces in nuclei are rapidly transforming modern nuclear theory into a true first-principles, or ab initio, discipline.
In particular this allows us to attack some of the most exciting questions in physics beyond the standard model such as the nature of dark matter and the nature of neutrino masses through a hypothetical process called neutrinoless double beta decay. We first address the gA quenching puzzle which has challenged the field for over 50 years, then discuss rapid advances which now allow for converged calculations of neutrinoless double beta decay nuclear matrix elements for all major players in ongoing searches 76Ge, 130Te, and 136Xe.

Speaker: Jason Holt

Holt_CAP Online.pdf

240 (I) Search for Majorana Neutrinos in the LEGEND Experiment

The discovery of the lepton-number-violating neutrinoless double-beta decay process will prove that neutrinos are Majorana fermions. The Large Enriched Germanium Experiment for Neutrinoless double-beta Decay (LEGEND) project will search for this decay in $^{76}$Ge. In its first phase — LEGEND-200 — 200~kg of $^{76}$Ge-enriched high-purity germanium detectors will be deployed in a liquid-argon cryostat. It is under construction at the Laboratori Nazionali del Gran Sasso (LNGS) in Italy. The first phase has a background goal of $< 0.6$ counts/(FWHM t y), which yields a $3\sigma$ half-life discovery sensitivity beyond $10^{27}$ years. The second phase — LEGEND-1000 — will comprise 1000 kg of enriched germanium detectors. It will be sited deep underground with SNOLAB as the preferred host. LEGEND-1000 will have a discovery sensitivity beyond $10^{28}$ years. In this talk, I will give an overview of the LEGEND project.

Speaker: Alan Poon (Berkeley Lab)

CAP-talk-LEGEND-2021.06.pdf

TS1-2 New Observational Windows (DTP Symposium on Cosmology: James Peebles Nobel Celebration) / Nouvelles fenêtres d'observation (Symposium DPT sur la cosmologie: le prix Nobel de James Peebles)

Convener: Robert Brandenberger (McGill University)

241 (I) 21cm Cosmology

I will review the present and near-term future prospects for new
cosmology results with 21cm probes. This is a
technology-driven observational field and I will describe experimental
challenges and enabling technology in parallel with the science.

Speaker: Matt Dobbs

242 (I) Multi-line intensity mapping of the high redshift Universe

Line Intensity Mapping has emerged as a powerful tool to probe the large-scale structure across a wide range of redshift, with the potential to shed light on dark energy at low redshift and the cosmic dawn and reionization process at high redshift. Multiple spectral lines, including the redshifted 21cm, CO, [CII], H-alpha, and Lyman-alpha emissions, are promising tracers in the intensity mapping regime, with several experiments on-going or in the planning. I will discuss results from current pilot programs, and prospects for the upcoming TIME experiment and the SPHEREx mission. I will illustrate how the use of cross-correlation between multiple line intensity maps will enable unique and insightful measurements, revealing for example the tomography of reionization and cosmological probes in the high redshift Universe.

Speaker: Tzu-Ching Chang

243 (I) CMB Observations: Recent Progress

Coming soon!

Speaker: Jo Dunkley

11:45 TS4-1 Break

TS4-2 Probing the nature of Neutrino (PPD Neutrino Physics and Beyond Symposium) / La nature du neutrino (Symposium PPD sur la physique du neutrino et au delà)

Convener: David McKeen (TRIUMF)

244 (I) Status of the SNO+ experiment

Neutrinos present a portal into understanding some of the most significant puzzles of modern physics, even as the nature of the neutrino is still mysterious. SNO+ is well positioned to examine some of those puzzles. Located 2 km underground in the Vale Creighton mine in Sudbury at the international facility SNOLAB, SNO+ is the largest liquid scintillator neutrino detector currently in operation. The depth of the experiment makes further measurements of Solar neutrinos possible while the geography makes reactor neutrino measurements possible. The crowning measurement of the experiment is the search for neutrino-less double beta decay which will probe the mass and nature of the neutrino itself. Throughout the filling period, data have been collected that are being used to evaluate the performance of the detector and to make some initial measurements of solar and reactor neutrino physics. Some of those first results will be presented as well as updated results from the previously completed water phase. This presentation will also introduce the physics program of the experiment and give an update of the status of the experiment.

Speaker: Dr Ryan Bayes (Laurentian University)

SNO+Status_CAP2021.pdf

245 (I) Current Status of the nEXO Experiment

nEXO is a proposed next generation neutrinoless double beta decay experiment. The detector is a single-phase time projection chamber filled with 5 tonnes of liquid xenon enriched in {136}^Xe, designed for a half-life sensitivity of ~$10^{28}$ yr. Events in the detector will result in both ionization and scintillation signals, read out by separate electronic systems. Scaling up from the successful 200 kg EXO-200 to the 5 tonne nEXO detector will significantly increase the source mass as well as improve background discrimination through a monolithic detector design. The detector design and research progress on different components will be presented.

Speaker: Dr Erica Caden (SNOLAB)

nEXO_CAP2021_Caden.pdf

12:45 TS1-2 Break

12:45 TS4-2 Break

TS4-3 Accelerator-based Neutrino experiment (PPD Neutrino Physics and Beyond Symposium) / Expériences sur neutrinos par accélérateur (Symposium PPD sur la physique des neutrinos et au delà)

Convener: Deborah Harris

246 (I) The Deep Underground Neutrino Experiment DUNE: review and recent progress

The Deep Underground Neutrino Experiment (DUNE) is a next-generation long-baseline neutrino oscillation experiment. DUNE’s main goal is to provide unprecedented sensitivity in the search for neutrino CP violation, to determine the neutrino mass hierarchy, and to make precision measurements of neutrino mixing parameters. DUNE will be sensitive to low-energy neutrinos coming from supernova bursts, bringing insight for both particle physicists and cosmologists. DUNE’s ambitious physics program also includes searches for proton decay and non-standard neutrino interactions. The experiment will utilize a new broadband high-intensity neutrino beam and a suite of Near Detectors at Fermilab, along with Far Detectors situated 1300 km from Fermilab at the Sanford Underground Research Facility. This presentation reviews DUNE’s extensive physics program and experimental design, as well as recent progress. The ongoing and future activities of the recent Canadian effort will be presented, with an emphasis on how researchers and students can contribute.

Speaker: Claire David (York University (CA))

20210608_DavidC_DUNE_CAP.pdf

247 (I) The T2K, Super-Kamiokande, and Hyper-Kamiokande Experiments

T2K and Super-Kamiokande (Super-K) in Japan represent the current generation of successful campaigns to understand the properties of neutrino mixing, using detectors whose physics reach also extends to studies of astrophysical neutrinos and searches for new physics through processes such as nucleon decay or dark matter annihilation. T2K utilizes Super-K as the far detector in a long-baseline neutrino experiment to study oscillations with accelerator-produced muon neutrino or antineutrino beams. This resulted in the discovery of the $\nu_\mu$ to $\nu_e$ oscillation channel and following hints of CP violation in neutrino oscillations.

Hyper-Kamiokande (Hyper-K) is a next-generation experiment informed by the success of T2K and Super-K. It utilizes a water Cherenkov far detector, whose site construction is underway, 8 times larger than Super-K, and will benefit from an upgraded 2.5 times higher intensity beam than T2K. An Intermediate (distance) Water Cherenkov Detector (IWCD) will help mitigate systematic uncertainties to a level commensurate with this unprecedented statistical precision, affording significant discovery potential of leptonic CP violation. In this talk, I will describe the status of the T2K, Super-K, and Hyper-K projects, and highlight planned Canadian contributions to the water Cherenkov detectors, including new photosensors, new methods of calibration and deep learning event reconstruction, and a prototype water Cherenkov test beam experiment (WCTE) at CERN.

Speaker: Patrick de Perio (TRIUMF)

CAP_T2KHyperK_dePerio.pdf

Google Slides

TS1-3 Dark Matter (DTP Symposium on Cosmology: James Peebles Nobel Celebration) / Matière sombre (Symposium DPT sur la cosmologie: le prix Nobel de James Peebles)

Convener: Robert Brandenberger (McGill University)

248 (I) Making Universal Axions

In this talk, I will describe my efforts to understand the nature of the mysterious dark matter. I provide an overview of the general problem and then describe my current approach to it, which is to characterize the behavior of a proposed dark matter particle, the axion. I will give some insight into how I am using a range of tools -- model building, computation, and high energy astrophysics -- to get at the basic question of ``what is the statistical mechanics of axion dark matter"?

I will discuss work that shows that the self-interaction should not be ignored and that the sign of the interaction makes a significant difference in the evolution of the system, both for QCD axions and fuzzy dark matter.

Speaker: Chanda Prescod-Weinstein (University of New Hampshire)

249 (I) The cosmology of sub-MeV dark matter freeze-in

Dark matter could be a "thermal-ish" relic of freeze-in, where the dark matter is produced by extremely feeble interactions with Standard Model particles dominantly at low temperatures. In this talk, I will discuss how sub-MeV dark matter can be made through freeze-in, accounting for a dominant channel where the dark matter gets produced by the decay of plasmons (photons that have an in-medium mass in the primordial plasma of our Universe). I will also explain how the resulting non-thermal dark matter velocity distribution can impact cosmological observables.

Speaker: Katelin Schutz (UC Berkeley)

250 (I) New Directions for Dark Matter

The identity of dark matter remains a mystery, despite decades of theorizing and detection efforts. This includes the mechanism for its primordial production, its interactions of with itself and with visible matter, and the very nature of dark matter, which could range from a Bose-Einstein Condensate, to Black Holes, to a traditional particle. In this talk I will discuss new directions for dark matter theory and how to experimentally test these ideas. I will focus on two examples, one wherein short-range self-interactions of dark matter lead to the formation of neutron star like cores in dark matter halos, and another wherein dark matter has spin quantum number larger than any particle in the Standard Model, being comprised of particle excitations of a so-called higher spin field.

Speaker: Dr Evan McDonough (University of Chicago)

251 (I) Asymmetric Dark Matter in Main Sequence Stars

A worldwide search is underway for elastic scattering between massive dark matter and nuclei in underground laboratories. Asymmetric dark matter particles with masses above a few GeV could easily be captured in stars via the same process. It has long been known that this can lead to observational consequences, as the weakly-interacting particles act as an efficient heat conductor. This can affect neutrino fluxes, astero/helioseismology, and even change the main sequence lifetime of stars. Modelling this process is not straightforward, and typically makes use of approximations at the limit of their validity. I will present recent results based on the first full set of Monte-Carlo simulations of this process since the 1980s, and compare the standard analytic predictions with these more accurate numerical results in order to tease out what we know and don't know about dark matter heat conduction in stars.

Speaker: Aaron Vincent (Queen's University)

CAP_DM_Stars.pdf

TS-6-2 CAP-COMP Medical Physics (DPMB Symposium) / Physique médicale ACP-OCPM (Symposium DPMB)

Convener: Cornelia Hoehr (TRIUMF)

252 (I) A Generalizable and Efficient Deep Learning Algorithm for Automatic Prostate Segmentation in 3D Ultrasound

Introduction: Three-dimensional transrectal ultrasound (3D TRUS) imaging is utilized in prostate cancer diagnosis and treatment, necessitating manual prostate segmentation which is time-consuming and difficult. The purpose of this work was to develop a generalizable and efficient deep learning approach for automatic prostate segmentation in 3D TRUS, trained using a diverse dataset of clinical images. Large and diverse datasets are rare in medical imaging, so this work also examines the performance of our method when trained with less diverse and smaller datasets.

Methods: Our training dataset consisted of 206 3D TRUS images acquired in biopsy & brachytherapy procedures using two acquisition methods (end-fire (EF) and side-fire (SF)), resliced at random planes resulting in 6,773 2D images used to train a 2D network. Our proposed 3D segmentation algorithm involved deep-learning prediction on 2D slices sampled radially around the approximate centre of the prostate, followed by reconstruction into a 3D surface. A modified U-Net and U-Net++ architecture were implemented for deep learning prediction, as the latter has been shown to perform well with small datasets. Our training dataset was split to train separate EF and SF networks. These split datasets were then reduced in size to 1000, 500, 250, and 100 2D images. Manual contours provided the ground truth for training and testing, with the testing set consisting of 20 EF and 20 SF 3D TRUS images unseen during training.

Results: For the full training set, the U-Net and U-Net++ performed with an equivalent median[Q1,Q3] Dice similarity coefficient (DSC) of 94.8[93.2,95.5]% and 94.7[92.6,95.4]%, respectively, higher than a 3D V-Net and state-of-the-art algorithms in the literature. When trained only on EF or SF images, the U-Net++ demonstrated equivalent performance to the network trained with the full dataset. When trained on EF and SF datasets of 1000, 500, 250, and 100 images, the U-Net++ performed with DSC of 93.7%, 93.9%, 93.2%, 90.1% [EF] and 90.3%, 90.3%, 89.2%, 81.0% [SF], respectively.

Conclusions: Our proposed algorithm provided fast (<1s) and accurate 3D segmentations across clinically diverse 3D TRUS images, demonstrating generalizability, while strong performance with smaller datasets demonstrated the efficiency of our approach, providing the potential for widespread use, even when data is scarce.

Speaker: Nathan Orlando (Western University)

253 Optical fibers as dosimeter detector for proton/neutron fields – a biological dosimeter

Dosimetry is an important part of radiation therapy, ensuring the prescribed treatment is delivered to the patient and avoiding accidental overexposure of adjacent healthy tissue. This includes characterizing proton beams for proton therapy. However, patients in proton therapy facilities are typically also exposed to secondary neutron fields, that are generated in all materials intercepted by the proton beam delivery. As the biological dose from neutrons is larger than from protons, depending on the proton beam delivery, these neutron fields can account for several percent of the overall dose to the patient outside the treated organ. While dosimeters measure the physical deposited dose, they typically do not give information on what type of particle the dose is coming from. Consequently, the biological effect is not well determined if a significant mixed field is present, and the dosimeter cannot completely confirm that the treatment plan is correctly implemented.

As ionizing radiation causes light emission in optical fibres combined with scintillators (Radiation Induced Luminescence – RIL), fibre detectors can be used as dosimeters for radiation therapy, with real-time response. Dosimeters constructed from fibres are extremely compact providing superior spatial resolution, even with the potential of in-vivo dosimetry. Here, we present a combination of several scintillator/fibre detectors that have different sensitivity to proton and neutrons. We tested fibre detectors made with Gd2O2S:Eu, Y2O3Eu, Gd2O2S:Tb, Y2O2S:Eu, YVO4, IG260 and a pure PMMA fibre with 0-400 MeV neutrons and 223 MeV, 63 MeV, 36 MeV and 9 MeV protons. Such a fibre detector combination has the potential to not just measure the physical dose but also to estimate the biological dose.

Speaker: Ms Jana Niedermeier (TRIUMF)

254 (G*) Three-dimensional tumor spheroids as a tool to optimize the nano-bio interface

Radiotherapy and chemotherapy are the gold standard for treating patients with cancer in the clinic but, despite modern advances, are limited by normal tissue toxicity. The use of nanomaterials, such as gold nanoparticles (GNPs), to improve radiosensitivity and act as drug delivery systems can mitigate toxicity while increasing deposited tumor dose. To expedite a quicker clinical translation, three-dimensional (3D) tumor spheroid models that can better approximate the tumor environment compared to a two-dimensional (2D) monolayer model have been used. We tested the uptake of 15 nm GNPs and 50 nm GNPs on a monolayer and on spheroids of two cancer cell lines, CAL-27 and HeLa, to evaluate the differences between a 2D and 3D model in similar conditions. The anticancer drug docetaxel (DTX) which can act as a radiosensitizer, was also utilized, informing future potential of GNP-mediated combined therapeutics. The radiosensitization effects on monolayer vs spheroids with the different sized GNPs was also elucidated. In the 2D monolayer model, the addition of DTX induced a small, non-significant increase of uptake of GNPs of approximately 20% while in the 3D spheroid model, DTX increased uptake by between 50% and 200%, with CAL-27 having a much larger increase relative to HeLa. Further, the depth of penetration of 15 nm GNPs over 50 nm GNPs increased for both cancer spheroids. Measurement of the responses to radiation with GNPs yielded a large radiosensitization effect, with more of the cells on the periphery of the spheroid being affected. These results highlight the necessity to optimize GNP treatment conditions in a more realistic tumor-life environment. A 3D spheroid model can capture important details, such as different packing densities from different cancer cell lines and the introduction of an extracellular matrix, which are absent from a simple 2D monolayer model.

Speaker: Kyle Bromma (University of Victoria)

255 Combining gold nanoparticles with other radiosensitizers for unlocking the full potential of cancer radiotherapy

Effective local therapy is needed to avoid local progression of the tumor, which may further decrease the development of systemic metastases and increase the possibility for resection. Radiation therapy (RT) is frequently used to locally treat the tumor. One of the major issues in RT for treating cancer is the close proximity of adjacent organs at risk, resulting in treatments doses being limited by significant tissue toxicities, preventing dose escalation necessary to guarantee local control. One of the currently adapted approaches to overcome this challenge is to add radiosensitizers to current RT protocol to unlock the full potential of RT. In this talk, I will focus on gold nanoparticles (GNPs), docetaxel, and cisplatin as radiosensitizers. About half of cancer patients (50%) receive radiotherapy, and all of these patients would benefit from this type of novel approaches.

Speaker: Devika Chithrani (University of Victoria)

256 (I) Use of Light Absorbing Polymers for Quantitative Measure of Ionizing Radiation Dose: Challenges and Opportunities

Diacetylene molecules can self-assemble into crystals, with three-dimensional packing and separation between molecules dictated by the chemical groups on either side of the carbon-carbon triple bonds. When exposed to ionizing radiation, like photon, electron and proton beams used in radiotherapy applications, some diacetylene crystals undergo a radical solid-state polymerization reaction, resulting in a long polymer chain with alternating triple- and double- carbon bonds. The π-electrons along the conjugated chain undergo transitions between energy states, absorbing light in the UV-VIS in the process. This radiochromic material becomes deeply coloured, where the absorbance, or optical density, in the visible range of the spectrum is a function of the absorbed ionizing radiation dose. Thus, radiochromic materials have been used for several decades as two-dimensional films for quantitative measure of dose and have been more recently investigated for real-time in vivo dosimetry using optical fibres. Packing of diacetylene monomers within the crystal affects not only probability of polymer chain initiation, but also the rate at which polymerization takes place. Understanding the mechanism for this self-assembly and the effect of different side groups on behaviours relevant to dosimetric applications is of great interest. This talk will first discuss the implications of side group selection on usability of radiochromic material in real-time dosimetry, as illustrated in commercially available films to date. Secondly, we will explore challenges with current commercially available radiochromic materials and finally will consider how they can be improved to meet the required criteria for real-time use in patient dosimetry.

Speaker: Dr Alexandra Rink (Princess Margaret Cancer Center, University of Toronto, University Health Network)

257 Evaluating Machine Learning Models in Predicting the Dose Distribution Index in Radiation Treatment Planning QA

Objective: Dose distribution index (DDI) is a dose-volume parameter used in the treatment planning evaluation. DDI provides the dosimetric estimates on the target coverage, sparings of all organs-at-risk and remaining healthy tissue in the treated organ in a single parameter. In this study, the DDI value was predicted by machine learning model using different algorithms.

Methods: The DDI were calculated using its original formula by definition. On the other hand, machine training was carried out to determine the DDI using the same data of 50 prostate volumetric modulated arc therapy (VMAT) plans from the Grand River Regional Cancer Centre, Kitchener, Ontario. Machine learning algorithms such as linear regression, tree regression, support vector machine (SVM) and Gaussian process regression (GPR) were used to predict the DDI value for each prostate VMAT treatment plan. For comparing the performance of the machine learning algorithms, root mean square error (RMSE), prediction time of the machine learning and training time were determined and compared.

Results: Comparing the RMSE values among all algorithms, only the DDI predicted by the medium and coarse tree regression algorithms showed a relatively large RMSE values in the range of 0.021 – 0.034. For other algorithms such as SVM and GRP, they all performed very well in predicting the DDI with smaller RMSE values ranging from 0.0038 to 0.0193. By considering other factors such as prediction speed and training time, the square exponential GPR algorithm had the smallest RMSE value of 0.0038, a relatively high prediction speed of 4,100 observation per second and a short machine training time of 0.18 second.

Conclusion: It is concluded that the family of GPR algorithms performed best in the dose distribution index prediction. It is expected that the accuracy of DDI prediction will increase with more plan data trained using such algorithm.

Speaker: Dr James Chow (University of Toronto)

258 An AI-assisted Chatbot for Education in Radiotherapy

Objective: We built a RT Bot, a chatbot with characterization for the patient, general public and radiation staff to provide educational information regarding radiotherapy using the artificial intelligence. The Bot was personalized by machine learning to detect the user’s temperament and intent in order to provide the best guidance to the user with a human-like response.

Methods: The Bot was developed using the IBM Watson Assistant functionalities on the IBM cloud. Dataset of information was prepared for different user groups such as descriptions of all processes in radiotherapy, promotion of cancer screening especially high fatality and popular cancer sites, and basic cancer preventive measures such as how to maintain healthy life with suitable diet and exercise. To ensure correct information can be understood and digested by the users with their background (patient, general public and radiation staff), the Bot character was personalized through the IBM Watson Assistant functionalities such as natural language understanding, entities and slots.

Results: The Bot can be operated in a front-end window on any Internet-of-things such as smartphone, tablet, laptop and desktop. In the beginning, the Bot will communicate with the user intentionally with an introduction. The user can then type in any text to answer concerning their enquiry. The Bot usually begins by answering simple questions regarding radiotherapy and providing related information. If the Bot cannot understand the user’s wording, it will provide a guidance to help the user.

Conclusion: A chatbot was built for interdisciplinary educational purpose for the patient, general public and radiation staff using artificial intelligence and machine learning. The Bot may be used by a cancer centres or some private sectors such as high school, community centres, volunteer group and charities, which promote cancer preventive measures and screening for a healthy life or educate user what is cancer and radiotherapy.

Speaker: Dr James Chow (University of Toronto)

259 (G*) Characterization of modified radiochromic materials for measuring ionizing radiation

Purpose: A quantitative measure of delivered ionizing radiation is recommended for quality assurance and quality control purposes for patients undergoing radiotherapy treatments. Current dosimeters are not well suited for direct measurements due to atomic composition and size limitations. We are developing a fiber optic probe dosimeter based on radiochromic material for in vivo dosimetry. Through measuring the change in optical absorption of the radiochromic sensor, we can quantify the absorbed dose of ionization radiation delivered in real-time. The radiation-sensitive material is composed of lithium-10,12-pentacosa diynoate (LiPCDA), which upon exposure, polymerizes and results in an increased optical density. We observed that monomers of LiPCDA can have two distinct crystalline morphologies, with aspect ratios 10:1 producing hair-like structures and 2:1 resulting in platelets, with polymerized absorbance peaks typically centred at 635 nm and 674 nm, respectively. We aim to characterize and compare the dose-response of the two crystal morphologies achieved through desiccation and Li+ concentration.

Method: The hair-like LiPCDA in commercial film was desiccated, producing crystals with an absorbance peak at 674 nm. Both materials were exposed to 50-3000 cGy using a clinical linear accelerator with a 6MV X-ray beam; samples of varying Li+ concentration were exposed to 200-400 cGy. Absorbance spectra for all samples were collected and were imaged with a scanning electron microscope to compare their crystal morphology.

Results: Differences in crystal morphology were not observed when hair-like LiPCDA was desiccated. However, varying the molar ratio of Li+ to PCDA to produce crystals with either 635 nm or 677 nm absorbance peak, differentiable crystal morphologies were observed. The platelet form is ~3x less sensitive to dose but with a more extensive dynamic range relative to hair-like.

Conclusion: Crystals can be preferentially grown and exhibit differing dose-response. The macrostructure effect on radiation sensitivity in the context of radiotherapy will be explored.

Speaker: Rohith Kaiyum (York university)

15:00 TS-6-2 Break (15 minutes)

13:45 TS4-3 Break

TS4-4 Solar, cosmic, extragalactic neutrinos I (PPD Neutrino Physics and Beyond Symposium) / Neutrinos solaires, cosmiques et extragalactiques I (Symposium PPD sur la physique des neutrinos et au delà)

Convener: Deborah Harris

260 (I) Multi-messenger astrophysics with gravitational waves

In less than five years, the field of gravitational wave astronomy has grown from a groundbreaking first discovery to revealing new populations of stellar remnants through distant cosmic collisions. I'll summarize recent results from LIGO-Virgo and their wide-reaching implications, give an overview of the instrumentation of the current Advanced LIGO detectors, and discuss prospects for the future of multi-messenger astrophysics with gravitational wave detectors on Earth and in space.

Speaker: Dr Jess McIver (The University of British Columbia)

261 (I) Studying neutrino properties with neutrino telescopes

Very large neutrino telescopes are multipurpose instruments that can observe tens of thousands of neutrinos interact at energies well beyond those of man-made accelerators. This has made them unique experiments for studying neutrino properties and probing what might be beyond the Standard Model. Exotic neutrino oscillations, new interactions and new force mediators are among these topics. In this talk I will present the newest neutrino oscillations results from IceCube, the future of this experiment and an exciting new opportunity for deploying a neutrino telescope in Canada: the Pacific Ocean Neutrino Experiment, P-ONE.

Speaker: Juan Pablo Yanez Garza

15:10 TS1-3 Break

TS-6-3 Biosensory Physics (DPMB Symposium) / Physique des biocapteurs (Symposium DPMB)

Convener: Ozzy Mermut (York University)

262 Optical Bio-Sensing at the Brain-Machine Interface

New developments toward creating a working 2-way communication between brains and machines offer exciting possibilities, yet are often limited simply by the basic bio-compatibility of the materials employed in their construction. Traditional electrical engineering semiconductors and metals are often quite poor choices for use in a real living wet biological environment, and much recent effort has been devoted to instead develop soft, squishy bio-polymer interface materials, that communicate via photons and not electrons. Inspired by the molecular mechanisms in our eyes that enable vision, photo-reversible azo visible dyes are incorporated into bio-polymers such as silk fibronin, to provide a stable dynamic transduction layer between live neural cells and optical fibres. Sensing neural activity locally and selectively is achieved spectro-scopically via subtle optical changes to the thin dye nano-layers at the fibre ends. Signalling back to a brain can be achieved by simple mechano-transduction via photo-mechanical layers, photo-chemical release of neurotransmitters from artificial vesicles embedded, or via light-reversible changes to surface energy and chemistry. Characterization of the structure and dynamics of these soft active nano-neuro-layers in situ is a key challenge, and results will be detailed from surface energy analysis, and ‘underwater’ Visible Ellipsometry, and Neutron Reflectometry techniques we have developed at McGill, and at Chalk River Laboratories.

Speaker: Christopher Barrett (McGill U.)

263 (I) Synchrony in the auditory periphery

Bilateral symmetry in animals commonly leads to a duality in peripheral sensory apparatus. For example, two eyes, as commonly found in most vertebrates, provide a mechanism to encode information such that subsequent neural processing can create stereoscopic perception. Further, two ears lateralized to the sides of the head are important for sound source localization, a key ecological consideration. Recent evidence expands upon this duality and points to a novel biophysical principle, that of synchrony, doubly at play in the auditory periphery. By synchrony, we mean dynamics associated with weakly-coupled self-sustained (i.e., active) oscillators. This talk will discuss two facets by which this arises in the Anolis lizard. First, within a given inner ear, evidence suggest that the sensory cells acting as mechano-electro transducers metabolically use energy to behave as limit cycle oscillators. Further, these "hair cells" can couple together to form groups (or "clusters") that synchronize, effectively allowing them to greatly increase their sensitivity to low-level sounds. Second, by virtue of direct coupling between the tympana (i.e., "eardrums") via an interaural canal, the two ears can synchrnonize, possibly thereby allowing improvements in localization to low-level sounds. Thus in essence, each eardrum is effectively and meaningfully driven from both sides, not just via sound fields external to the head. Taken together, these considerations illustrate a remarkable example by which collective active behavior can mesoscopically emerge to improve the ability of peripheral sensory systems to encode incident information.

Speaker: Christopher Bergevin (York University)

264 (I) (Learning) visual representations

When you look at a picture, neurons are excited within your eyes and your brain. Those neurons' activation patterns reflect your perception of the stimulus, and can be measured in neurophysiology experiments. Importantly, these neuronal responses are profoundly shaped by visual experience. In this presentation, I will discuss the nature of the brain's visual representations, and the mechanisms through which those representations are learned and refined by visual experience.

Speaker: Joel Zylberberg (York University)

265 Reaction-diffusion modeling of neurotransmitter processing at a high frequency synapse

In the weakly electric fish Eigenmannia (glass knifefish), high frequency (200-600Hz) electric organ discharge (EOD) is driven by high frequency cholinergic synaptic input onto the electrocytes at their electroplaques. Assuming periodic release of ACh into the cylindrical synaptic gap, we solve numerically a one dimensional reaction-diffusion model at 200Hz and 500Hz. The model included the diffusion of ACh and its interactions with AChesterase (AChE) in the gap and with AChRs at the post synaptic membrane. At 500Hz a higher AChE/ACh ratio is needed to remove ACh from the cleft between consecutive ACh releases. Only a small fraction of the ACh molecules reaches the AChRs, and there are residual amounts of ACh molecules from the preceding release. Previous computational studies showed that the persistently present ACh should not impede high frequency electrocyte firing, provided the cholinergic current is subthreshold for triggering firing. Our results suggest that the cholinergic current from the carry-over (persistent) activation of AChRs exceeding the firing threshold sets the upper limit for EOD frequency in Eigenmannia individuals, which is observed around 600Hz.

Speaker: Bela Joos (University of Ottawa)

15:30 TS4-4 Break

TS1-4 Early Universe (DTP Symposium on Cosmology: James Peebles Nobel Celebration) / L'univers jeune (Symposium DPT sur la cosmologie: le prix Nobel de James Peebles)

266 (I) Some challenges for theoretical cosmology

I will review some important challenges for theoretical cosmology, focusing on the trans-Planckian problem for inflation and the anisotropy problem for matter bounce and ekpyrosis, and I will discuss some recent work exploring particular aspects of these problems.

Speaker: Edward Wilson-Ewing (University of New Brunswick)

267 (I) Spectrum of Cuscuton Bounce

I will argue why we need to remain objective about the physics of the early universe and explore different scenarios. In particular, I will present a cosmological bounce model based on Cuscuton gravity that does not have any ghosts or curvature instabilities. I will then discuss if Cuscuton bounce can provide an alternative to inflation for generating near scale-invariant scalar perturbations. While a single field Cuscuton bounce generically produces a strongly blue power spectrum (for a variety of initial/boundary conditions), scale-invariant entropy modes can be generated in a spectator field kinetically coupled to the primary field. Furthermore, this solution has no singularity, nor requires an ad hoc matching condition. Tensor modes (or gravitational waves) in Cuscuton bounce are also stable but similar to most bounce models, the produced spectrum is strongly blue and unobservable.

Speaker: Ghazal Geshnizjani (University of Waterloo)

268 (I) Discriminating between theories of the very early universe

Different theories of the very early universe that can explain our observations of the cosmic microwave background are presented. The current paradigm - inflationary cosmology - has received much attention, but it is not the only theoretically viable explanation; indeed, several alternative scenarios exist. It thus bares the question: how can we discriminate between the various theories, both from a theoretical and an observational point of view? A few pathways to answering this question are discussed in this talk.

Speaker: Jerome Quintin (Max Planck Institute for Gravitational Physics)

TS4-5 Solar, cosmic, extragalactic neutrinos II (PPD Neutrino Physics and Beyond Symposium) / Neutrinos solaires, cosmiques et extragalactiques II (Symposium PPD sur la physique des neutrinos et au delà)

Convener: Marie-Cécile Piro (University of Alberta)

269 (I) The future of high-energy neutrino flavour and the search for new physics

Despite their weak interactions, neutrinos can carry stupendous amounts of information about the cosmos, thanks to their small masses and large abundance. The highest-energy neutrinos can tell us about the largest particle accelerators in the Universe, and can probe energy scales larger than those available at the LHC. I review the ability of future neutrino telescopes including IceCube-Gen2, and Pacific Ocean Neutrino Experiment (P-ONE) to determine the precise flavour composition and source of astrophysical neutrinos above 100 TeV, in light of improved measurements of neutrino properties by JUNO, DUNE and HyperKamiokande. Finally, I will discuss the ability of future neutrino telescopes to search for new physics such as neutrino decay, dark matter and microscopic black holes.

Speaker: Aaron Vincent (Queen's University)

CAP_NeutrinoFlavor.pdf

270 (I) Multi-messenger astronomy and neutrinos

Recent unprecedented developments in astronomical observations have established the era of multi-messenger astronomy. Weakly interacting neutrinos play a fundamental role in the evolution of supernovae, neutron star mergers, and accretion disks around black holes. The byproducts of neutrino reactions with ejected matter as well as their direct detection provide extra insight about the physics of their interiors. The analysis of such signals together with other multi-messengers will shed light in our understanding of related phenomena such as the synthesis of heavy elements and the mechanism of stellar explosions. In this talk, I shall discuss the connection between neutrinos and compact objects in the Galaxy, as well as at cosmological scales.

Speaker: Dr Liliana Caballero Suarez (University of Guelph)

CAP-Caballero2021.pdf

16:30 TS4-5 Break

TS4-6 Neutrinos and more (PPD Neutrino Physics and Beyond Symposium) / Neutrinos et davantage (Symposium PPD sur la physique des neutrinos et au delà)

Convener: Marie-Cécile Piro (University of Alberta)

271 (I) Studying Reactor CEvNS with the Scintillating Bubble Chamber (SBC) Experiment

The Scintillating Bubble Chamber (SBC) experiment is a novel multipurpose technique optimized for low-energy nuclear recoils detection. Two semi-identical detectors are under development by the collaboration, aimed at studying dark matter interactions (SBC-SNOLAB) and reactor CEvNS interactions (SBC-CEvNS). This talk will review the detector strategies and the feasibility studies of the weak mixing angle, neutrino magnetic moment, and a light Z′ gauge boson mediator for different SBC-CEvNS configurations. Finally, we will highlight how world-leading sensitivities are achieved with a one-year exposure for a 10 kg chamber at 3 m from a 1 MW$_{th}$ research reactor or a 100 kg chamber at 30 m from a 2000 MW$_{th}$ power reactor.

Speaker: Pietro Giampa (SNOLAB)

SBC CAP2021 PG.pdf

272 (I) Coherent Elastic Neutrino-Nucleus Scattering and the NEWS-G collaboration

NEWS-G (New Experiments With Spheres-Gas) is a rare event search experiment using Spherical Proportional Counters (SPCs). Primarily designed for the direct detection of dark matter, this technology also has appealing features for Coherent Elastic Neutrino-Nucleus Scattering (CE$\nu$NS) studies. CE$\nu$NS is a process predicted by the standard model and can be used as a tool to probe new physics and other applications, such as monitoring neutrino flux from nuclear reactors or sterile neutrino search.
The NEWS-G collaboration is studying the feasibility of detecting CE$\nu$NS at a nuclear reactor using an SPC. I will discuss the efforts made by the NEWS-G collaboration to assess the feasibility of such an experiment.

Speaker: Marie Vidal

CAP_talk2021.pdf

273 (I) Heavy Neutrino searches at ATLAS

An overview of the latest results and Run 3 prospects for Heavy Neutrino searches at ATLAS will be discussed.

Speaker: Matthias Danninger (Simon Fraser University (CA))

CAP_neutrinoATLAS.pdf

Wednesday 9 June

W-PLEN-1 EDI Survey Presentation by Kevin Hewitt and Anastasia Smolina (CAP/EDI) / Présentation du sondage EDI par Kevin Hewitt et Anastasia Smolina (ACP/EDI)

Convener: Robert Thompson (University of Calgary)

274 EDI Survey Presentation

Presentation of the results of the EDI Survey.

Speakers: Kevin Hewitt (Dalhousie University), Ms Anastasia Smolina (University of Toronto)

W-PLEN-2 Brian Wilson, U.Toronto (DPMB/DAMOPC) (DPMB/DPAMPC)

Convener: Ozzy Mermut (York University)

275 Cancer and Light: How optical sciences and engineering impact cancer research and patient care

The multiple interactions of light with biomolecules, cells and tissues enable established and emerging techniques and technologies used in cancer research and patient care. These approaches range from simple, point-of-care devices to complex, multifunctional platforms combined with complementary non-optical methods, including nanotechnologies, robotics, bioinformatics and machine learning. This seminar will use specific examples from current research to illustrate the biophysical and biological principles underlying the emerging fields of “onco-photonics” or “photo-oncology”.

Speaker: Prof. Brian Wilson (University of Toronto)

11:30 15 Minute Break

W1-1 Photonics and Nano-Optics (DAMOPC) / Photonique et nano-optique (DPAMPC)

Convener: Jens Lassen (TRIUMF)

276 (I) Scanning near-field optical microscopy: from physics to spectroscopic applications

In our presentation, we will offer an overview of aperture-type scanning near field optical microscopy (SNOM) – a family of nano-optical imaging techniques derived from scanning probe microscopy which are capable of subwavelength resolution, and the development of three dimensional (3D) SNOM methods undertaken by our group to locally image the distribution of the electromagnetic radiation in the proximity of nanoparticles and nano-objects. We will discuss a few applications in which we took advantage of 3D-SNOM to design specific optical nanosystems for light harvesting. Specific case studies that will be presented include the design of plasmonic thin-film solar cells enhanced by random arrays of copper nanoparticles, and the use of 3D-SNOM for characterizing evanescent waveguides self-assembled from of copper nanoparticles assembled on thin films of graphene. In the final part of our talk, we will we present near-field scanning thermoreflectance imaging (NeSTRI), a new pump-probe technique invented in our group, in which an aperture-type SNOM is used to contactlessly determine the thermal conductivity of inhomogeneous thin films at the nanoscale. These examples well represent the versatility of SNOM imaging and its potential for designing an even wider family of nano-optical devices.

Speaker: Prof. Giovanni Fanchini (Western university)

277 (I) Nanophotonic platforms for quantum optics with atomic ensembles

I will present my group’s recent efforts to combine atomic ensembles with nanophotonic structures. I will describe our experiment in which photons emitted by a quantum dot embedded in a semiconductor nanowire are sent into an ensemble of laser-cooled caesium atoms confined inside a hollow-core photonic-crystal fibre to realize photon storage and single-photon wavelength conversion. Additionally, I will report on our progress in developing new types of mesoscopic optical cavities based on dichroic mirrors realized with chiral photonic crystal slabs and metasurfaces. This research was undertaken in part due to funding from the Canada First Research Excellence Fund.”

Speaker: Prof. Michal Bajcsy (University of Waterloo)

278 (G*) Nanoscale polymer blister formation using single femtosecond pulses

Blister formation occurs when a laser pulse is focussed through a transparent substrate onto a coated polymer thin film. A pocket of expanding vapor is formed beneath the film, which pushes the film upward locally. This process has been used for Laser-Induced Forward Transfer (LIFT) of materials. Most studies of blister formation and blister-based LIFT use linear absorption of nanosecond or picosecond lasers to obtain large target areas (~100s of µm$^2$). We are the first to achieve nanoscale blisters, through nonlinear absorption of femtosecond pulses.

We spin-coated polyimide films achieving a thickness of 1.3 µm. We used a Ti:Sapphire laser producing pulses of 45-fs duration at a central wavelength of 800 nm. We mounted samples onto a 3D motion stage, and focused single pulses of various energies through the glass substrate onto the polymer-glass interface. Since polyimide is transparent to 800 nm light, we used tightly-focused (NA ≥ 0.4) femtosecond pulses to induce nonlinear absorption. We characterized samples after blister fabrication using atomic force microscopy (AFM). At intensities above 10$^{13}$ W/cm$^2$, interactions of the pulse with both the film and substrate must be considered. We model these interactions and find that the resulting blister volume is proportional to the energy deposited in the film.

The use of 0.95 NA focusing led to a minimum structure diameter of 700 nm, smaller than the wavelength of the laser pulse. In the future, we propose the use of thinner films and shorter wavelengths to reach further into the nanoscale. This technique can be used for direct micro- and nano-fabrication, and potentially to LIFT sensitive materials on the nanoscale. It is a possible alternative to lithography, laser milling, and laser-based additive machining that also leaves the surface composition unchanged, since the laser energy is deposited beneath the film.

Speaker: Alan Godfrey (University of Ottawa)

279 Study of photoluminescence in plasmonic nanoparticles

Currently, plasmonic nanofibers doped with semiconductor quantum dots, organic dye quantum emitters (QEs), and metallic nanoparticles (MNPs) have attracted much attention due to their wide range of applications including waveguides, light-sources, and optical sensors. These nanofibers doped with QEs and MNPs have been fabricated using a variety of metals and emitters. For example, Hu et al. [1] have studied the fabrication of a plasmonic random fiber from gold MNPs and pyrromethene dye molecules (QEs) embedded in the liquid core optical fiber. They found that a narrower and sharper photoluminescence (PL) spectrum can be more easily obtained when there is greater overlap between the plasmonic resonance of the gold-MNP and the dye molecules. Here we have developed a theory of photoluminescence for plasmonic nanofibers [2]. When probe light propagates inside the nanofiber, it induces surface plasmon polariton (SPPs) and electric dipoles in metallic nanoparticles. These dipoles interact with each other via the dipole-dipole interaction (DDI) [3]. The energy of photonic bound states in the presence of the SPP and DDI fields is then calculated. We have demonstrated that the number of bound states can be controlled by changing the strength of the SPP and DDI couplings. The expression of photoluminescence has been calculated using the density matrix method in the presence of the DDI coupling. We found that the intensity of the PL spectrum depends on the quality called quantum efficiency, which depends on the radiative and non-radiative decay rates. We have found that the quantum efficiency is enhanced when the exciton energy is in resonance with the bound photon energy. Further, we predicted that the PL intensity is also enhanced due to the DDI coupling. The enhancement of the PL spectrum can be used to fabricate plasmonic nanosensors.

[1] Hu, Z et al., Gold nanoparticle-based plasmonic random fiber laser. J. Opt. 2015, 17, 35001.
[2] Singh, M. R.; Brassem, G.; Yastrebov, S. G. Optical quantum yield in plasmonic
Nanowaveguide. Annalen der Physik in press, 2021.
[3] Singh, M. R. The effect of the dipole–dipole interaction in electromagnetically induced transparency in polaritonic band gap materials. Journal of Modern Optics 2007, 54, 1739.

Speaker: Grant Brassem (University of Western Ontario)

280 Nonlinear optical properties of graphene: liquid-phase exfoliation vs chemical vapour deposition

Liquid-phase exfoliation (LPE) is a low-cost and scalable technique for producing a wide range of van der Waals nanomaterials that can be incorporated into existing laboratory sample and industrial material production. Liquid-phase exfoliated nanomaterials have the potential to produce devices quickly and at low-cost, with colloidal dispersions easily adaptable to existing production methods. Other methods of nanomaterial production, such as chemical vapour deposition (CVD) and mechanical exfoliation can be costly, time-consuming and require complicated equipment to produce comparatively small area devices. Such methods are excellent for laboratory-scale samples to examine physical properties and produce proof of concept devices. However, LPE can and will bridge the gap towards real-world applications that require faster, easier and more cost-effective production methods. In this work, we investigate the saturable absorption and Kerr nonlinearity of graphene fabricated by LPE and CVD.

Thin films of LPE graphene were produced on BK7 glass substrates, and compared to CVD graphene transferred onto an identical substrate. Through careful consideration of the concentration of graphene dispersion and deposition methods, very thin films of graphene can be prepared. Atomic force microscopy (AFM) measurements showed effective bi-layer graphene thickness for the LPE samples. Z-scan measurements performed with 180 fs pulses at a wavelength of 1030 nm reveal that both LPE and CVD graphene display strong saturable absorption characteristics, with a nonlinear absorption coefficient (β) approaching -10⁴ cm/GW and a Kerr nonlinearity (n2) of -1 cm²/GW. Such strong saturable absorption is ideal for devices such as mode-lockers for ultrafast pulsed lasers. The magnitude of the nonlinear absorption coefficient of the LPE graphene increases with pulse duration, τ, up to 10⁵ cm/GW at around τ = 10 ps. These results pave the way for the use of LPE graphene in nonlinear optical applications such as frequency generation and mode locking.

Speaker: Aidan Baker-Murray (University of Ottawa)

12:07 Group discussion

W1-10 Exploring the Energy and Precision Frontier III (PPD) / Frontière d'énergie et de précision III (PPD)

Convener: Heather Russell (CERN)

281 (I) Towards the Particle Collider Luminosity Frontier: The latest from the Belle II Experiment

The Belle II experiment at the SuperKEKB collider in Tsukuba, Japan began physics data taking in 2019. With a target integrated luminosity of 50 ab-1, Belle II aims to record a data sample that is roughly 40-100 times larger than its predecessors thus enabling some uniquely high-precision studies of b-quark, c-quark, and tau-lepton physics. The experiment provides an interesting environment to search for a wide variety of dark sector particles, possible dark matter candidates, and other low-mass particles predicted by theories of physics beyond the Standard Model. In this talk, I will summarize recent Belle II physics result based on the initial data taking, and discuss future prospects for the experiment.

Speaker: Ewan Chin Hill (University of Victoria (CA))

EwanHill_2021_06_June_09_CAPCongress__PPDenergyPrecisionFrontier_BelleII_v03.pdf

282 (G*) The Search for Charged Lepton Flavour Violation at Belle II

Belle II is a B factory experiment for the SuperKEKb electron-positron collider located at the KEK laboratory in Tsukuba, Japan, operating near the Upsilon(4S) resonance, at an energy of 10.58 GeV. In this talk I will discuss our analysis searching for the ultra-rare charged lepton flavour violating (CLFV) decay $B^+ \to K^+ \tau$ e. This decay is far below experimental sensitivity if we assume the decay rate predicted by the Standard Model. However, many extensions of the Standard Model, specifically those attempting to incorporate the recent “B physics anomalies”, predict much larger branching fractions which are potentially within the reach of experiments. Discovery of this mode would be explicit evidence of physics beyond the Standard Model, while a null result would allow us to place strict constraints on these models. A previous search was done at BaBar in 2012, setting a 90% CL upper limit branching fraction of a few x $10^{-5}$. The much larger integrated luminosity dataset at Belle II can be exploited to improve the analysis sensitivity by at least an order of magnitude. A brief overview of the Belle II experiment and the theoretical aspects of CLFV will be discussed, along with the current status and future potential of our analysis.

Speaker: Trevor Shillington (McGill University)

CAP_2021_Shillington.pdf

283 (G*) Inclusive analysis of $B \to X_u \ell \nu_{\ell}$ and $|V_{ub}|$ determination at Belle II

The Belle II experiment is a next-generation $B$-factory experiment located at the SuperKEKB $e^+e^-$ collider, with the focus on examining the decays of $B\bar{B}$ meson pairs. The Belle II experiment started data taking in March 2019. It has since reached a world-record instantaneous luminosity of $2.4\times10^{34}{\rm cm^{-2}s^{-1}}$, and has accumulated a total of $90.0\,{\rm fb^{-1}}$ to date. One of the main goals of the experiment is the precision measurement of the Cabbibo-Kobayashi-Maskawa (CKM) quark-mixing matrix elements. The $V_{ub}$ element of the CKM matrix describes the coupling strength between $u$ and $b$ quarks. The semileptonic $B$ meson decays of the type $B \to X_u \ell \nu$ play a critical role in the determination of $|V_{ub}|$. An inclusive untagged search for the $B \to X_u \ell \nu$ process at Belle II will be presented. Only the final state charged lepton is selected, while the final state meson and the companion $B$ meson in the event are not reconstructed. The final state neutrino cannot be detected and manifests as missing energy in the event. This decay is suppressed compared to the decay with a charm quark in the final state, $B \to X_c \ell \nu$, which is the main background for this mode. Because the up quark is lighter than the charm quark, the leptons in the $B \to X_u \ell \nu$ decay can reach higher energies. This is exploited in the analysis by extracting the $B \to X_u \ell \nu$ yield in the momentum endpoint region of the charged lepton, where the $B \to X_c \ell \nu$ contributions are negligible. Reconstruction and background suppression methods will be presented, leading to a discussion of the current results and of the prospects for this measurement with the Belle II experiment.

Speaker: Andrea Fodor (McGill University)

2021-06-09_CAP_afodor.pdf

W1-11 Thin Films (DSS) / Couches minces (DSS)

Convener: Steve Patitsas (University of Lethbridge)

284 (G*) Experimental analysis of surface Debye temperature for epitaxial thin films

Defect engineering plays an essential role in materials science and is of paramount importance in thin-film device fabrication. Novel experimental methods are needed to identify and quantify defects during film growth. The Debye temperature (DT) of a solid is a representation of the stiffness and so is sensitive to defect concentrations. The DT tends to decrease in the vicinity of the surface such that the endpoint value found for the top atomic layer is known as the surface DT. In this collaborative project, we have used a suite of surface characterization techniques to characterize and quantify defects on the surface and in the near-surface region in epi-films compared to single crystals. We applied Rutherford Backscattering Spectroscopy (RBS, random and channeling modes), Positron Annihilation Spectroscopy (PAS), and Low Energy Electron Diffraction (LEED) to study defect density and distribution and calculate surface DT for different epitaxially grown thin films (Si films on sapphire, and Ge on Si (001)). We used Rutherford Backscattering Spectroscopy (RBS) in a channeling alignment to measure defect distribution as a function of depth, which can be correlated with PAS measurements, giving information about defect densities. These results were compared with surface DT calculated from LEED patterns which showed that the larger the concentration of defects in the epitaxial layer, the lower is the surface DT. For example, the surface DT’s of bulk Si (001), 1μm Si on sapphire, and 0.6μm Si on sapphire were 609K, 574K, and 535K, respectively. However, experimental uncertainties of LEED DT are large and show dependence on the diffraction peak index, electron energy, and inner potential in calculations. Overall, we found good agreement between estimates of surface DT from LEED, defect densities estimate from RBS, and PAS results.

Speaker: Matheus Adam (Western University)

285 Rivulets and ripples: experiments on how dynamic wetting affects icicle growth

The morphology of ice formed under flowing liquid water is a challenging
free-boundary problem. A common case in nature is the formation of icicles,
which grow as liquid water flows down the surface, freezing as it descends.
Theories of icicle growth have always assumed a thin liquid coat over the
entire icicle's surface. These theories predict the growth in length and mean
diameter well, but have so far failed to explain how ripples form. The ripples
that commonly wrap around icicles have been observed to be solely dependent on
the presence of impurities in the source water in concentrations as low as 20ppm NaCl.

We present experimental observations of the flow and wetting behaviour of water
on actively growing icicles using a fluorescent dye. Sodium fluorescein acts as
both an indicator of liquid and instability triggering impurity. The water does
not coat the entire icicle. Rather it descends in rivulets leaving trails of
water or adding to liquid reservoirs already on the surface. The patches of
water left on the surface are larger for higher concentrations and are
distributed to match the ripples that form.

The wetting behaviour is affected by the ice's texture, surface chemistry, and
topography. We examined these effects by growing icicles on of cylinders of ice
to isolate these effects. While ripples began to form on roughened and
salt-doped ice, they only wrapped around the icicle to form a rib at a hard
edge or near the tip. In those locations the water spreads over the entire
circumference, which may encourage the ripple pattern to wrap around the
icicle. This incomplete coverage appears to affect the morphology of the
growing icicle and may be an important component of the mechanism of ripple
formation.

The presence of impurities appears to trigger a feed-back between the water
distribution and the ice properties: the impurities
cause variations in texture, chemistry and shape, which in turn attracts more
water to those locations, providing more material to freeze.

Speaker: John Ladan (University of Toronto)

W1-12 Magnetic North VII - Session 5 / Nord magnétique VII - session 5

Convener: Christianne Beekman (Florida State University)

286 (I) A Theoretical Outlook on the Properties of Spin Ice and Other Magnetic Pyrochlore Thin Films

Frustrated magnetic materials and strongly correlated electron systems are a forefront of research in modern condensed matter physics and materials science. Despite almost three decades of investigations, the theoretical understanding of these fascinating systems remains incomplete. The most prominent theoretical frameworks used to tackle these systems take the form of an emergent gauge theory akin to the gauge theory that describes conventional electromagnetism.

Spin ice is an unusual substance in which the magnetic moments of individual atoms behave very similarly to the protons in conventional water ice — hence the name spin ice — failing to align even at very low temperatures and displaying the same residual entropy that Linus Pauling calculated for water ice and which is measured experimentally. Spin ices, which belong to the broad class of compounds called magnetic pyrochlores, actually have something in common with electromagnetic fields; both can be described by a gauge theory. Many aspects of conventional electromagnetism are sensitive to constraints from enclosure boundaries, such as total internal reflection used in communication with optical fibers. It is then reasonable to wonder if spin ices have similar sensitivities to boundary effects and confinement. Motivated by the recent experimental realizations of spin ice and other magnetic pyrochlore thin films, I will discuss in this talk some of the exotic physical phenomena that arise when considering spin ice thin films such as, for example, a novel magnetic charge crystallization on the film surface while the bulk remains thermally disordered [1]. From a broader context, magnetic pyrochlore thin films offer a natural platform to study the confinement of emergent gauge fields describing strongly correlated systems and the evolution of nontrivial magnetic correlations as one moves from three to two-dimensional spin textures [2]. Finally, I will discuss the consequences of open surfaces on the mechanism of order by disorder in thin films of the XY pyrochlore antiferromagnet. We find that a complex competition between multiple orders take place, as a function of temperature and film thickness. A gradient of ordering spreads over long length scale inside the film while the nature of the phase transitions is blurred between two- and three-dimensional critical phenomena [3]. Beyond the physics of films, this work may also pertain to near-surface effects in single crystals of rare-earth pyrochlore oxides.

[1] L. D. C. Jaubert, T. Lin, T. S. Opel, P. C. W. Holdsworth and M. J. P. Gingras; Phys. Rev. Lett. 118, 207206 (2017).

[2] Étienne Lantagne-Hurtubise, Jeffrey G. Rau and Michel J. P. Gingras; Phys. Rev. X 8, 021053 (2018).

[3] L. D. C. Jaubert, J.G. Rau, P. C. W. Holdsworth and M. J. P. Gingras; unpublished.

Speaker: Prof. Michel Gingras (University of Waterloo)

287 Collinear and Noncollinear Antiferromagnetic Insulators for Spintronics Applications

Ability to control spin is important for probing many spin related phenomena in the field of spintronics. Spin-orbit torque is an important example in which spin flows across magnetic interface and helps to control magnetization dynamics. As spin can be carried by electrons, spin-triplet pairs, Bogoliubov quasiparticles, magnons, spin superfluids, spinons, etc., studies of spin currents can have implications across many disciplines. In this talk, I first review the most common ways to generate spin flows and then concentrate on how spin can be controlled in insulating materials. In the first part of the talk, I will discuss a linear response theory based on the Luttinger approach of the gravitational scalar potential and apply this theory to magnon transport in antiferromagnetic insulators, ranging from collinear antiferromagnets [1,2,3] to breathing pyrochlore noncollinear antiferromagnets [4,5]. The theory also applies to noncollinear antiferromagnets, such as kagome, where we predict both the spin Nernst response [4] and generation of nonequilibrium spin polarization [5] by temperature gradients, the latter effect constitutes the magnonic analogue of the Edelstein effect of electrons. In the second part of this talk, I will discuss the spin superfluid transport in exchange interaction dominated three-sublattice antiferromagnets. The system in the long-wavelength regime is described by an SO(3) invariant field theory (nonlinear sigma model). Additional corrections from Dzyaloshinskii-Moriya interactions or anisotropies can break the symmetry; however, the system still approximately holds a U(1)-rotation symmetry. Thus, the power-law spatial decay signature of spin superfluidity is identified in a nonlocal-measurement setup where the spin injection is described by the generalized spin-mixing conductance [6,7]. We suggest iron jarosites as promising material candidates for realizing our proposal. Both magnons and spin superfluidity flows are examples of spin flows with low dissipation and as a result our studies pave the way for the creation of novel electronic devices for classical and even quantum information processing where the signals can propagate with almost no dissipation. If time permits, I will also discuss realizations of skyrmion lattices in noncollinear antiferromagnets.
[1] V. Zyuzin, A.A. Kovalev, Phys. Rev. Lett. 117, 217203 (2016).
[2] Y. Shiomi, R. Takashima, E. Saitoh, Phys. Rev. B 96, 134425 (2017)
[3] B. Li, A.A. Kovalev. Phys. Rev. Lett. 125, 257201 (2020)
[4] B. Li, S. Sandhoefner, A.A. Kovalev, arXiv:1907.10567 (2019)
[5] B. Li, A. Mook, A. Raeliarijaona, A.A. Kovalev, arXiv:1910.00143 (2019)
[6] G. G. Baez Flores, A.A. Kovalev, M. van Schilfgaarde, K. D. Belashchenko, Phys. Rev. B 101, 224405 (2020)
[7] B. Li, A.A. Kovalev, arXiv:2011.09102

Speaker: Alexey Kovalev (University of Nebraska-Lincoln)

W1-2 Fields and Strings I (DTP) / Champs et cordes I (DPT)

Convener: Mark Van Raamsdonk (UBC)

288 (I) de Sitter space in string landscape

In this talk I will discuss how one may view four-dimensional de Sitter space as a coherent Glauber-Sudarshan state in string theory. I will also discuss why a de Sitter space cannot exist as a vacuum state in string theory.

Speaker: Prof. Keshav Dasgupta

289 (I) Nonrelativistic Strings and Exotic Geometries

I will discuss different notions of nonrelativistic strings and their target space geometries. The first example comes from a self-contained corner of string theory dubbed nonrelativistic string theory, which is closely related to string theory in the discrete light-cone quantization. The appropriate spacetime geometry for nonrelativistic string theory is a stringy generalization of Newton-Cartan geometry. The second example involves sigma models at a Lifshitz point, which describe strings moving in bimetric spacetime. In the limit when the two metrics coincide, the relativistic sigma model that underlies string theory can be recovered. This study of Lifshitz-type sigma models also provides useful insights for constructing a quantum theory of membranes.

Speaker: Dr Ziqi Yan (Nordita)

290 (I) Generalized ’t Hooft Anomalies and Gauge Dynamics

I will review the recently discovered ’t Hooft anomalies involving higher-form symmetries and discuss some of their implications for the dynamics of vector-like gauge theories.

Speaker: Prof. Erich Poppitz (University of Toronto)

291 Constraining effective theories using causality

Effective field theories (EFT) are widely used to parameterize long-distance effects of unknown short-distance dynamics or possible new heavy particles. It is known that EFT parameters are not entirely arbitrary, and in particular must obey positivity constraints if causality and unitarity are satisfied at all scales. We systematically explore those constraints from the perspective of 2 to 2 scattering processes, and show that all EFT parameters in units of the mass threshold M are bounded below and above: causality requires a sharp form of dimensional analysis scaling.

Speaker: Simon Caron-Huot

292 Holographic Complexity and Black Hole Thermodynamic Volume

I describe the first investigation of the holographic complexity conjectures for rotating black holes. Exploiting a simplification that occurs for equal-spinning odd dimensional black holes, I demonstrate a relationship between the complexity of formation and the thermodynamic volume associated with the black hole. This result suggests that it is thermodynamic volume and not entropy that governs the complexity of formation in both the Complexity Equals Volume and Complexity Equals Action proposals. This proposal reduces to known results involving the entropy in settings where the thermodynamic volume and entropy are not independent, but has much broader scope. Assuming the validity of a conjectured inequality for thermodynamic volume, this result suggests the complexity of formation is bounded from below by the entropy for large black holes.

Speaker: Robert Mann (University of Waterloo)

12:06 Questions/Answers and Discussion Period

W1-3 Quantum I (DPE) / Quantique I (DEP)

Convener: Chitra Rangan (University of Windsor)

293 (I) Looking back at a decade of teaching undergraduate Quantum Computing

Quantum computing is a rapidly growing field both in academia and industry. This is driving the need to expand traditional course offerings and degree programs to train the next generation of researchers and quantum scientists. Most programs have focused on graduate courses and research opportunities for students with a physics background. Laurier’s combination of physics and computer science within a single undergraduate department, provided a unique opportunity to introduce an undergraduate 3rd year course in quantum computing. The course was designed to be open to all science majors who have the required mathematical background. This talk will describe the goals and framework used to build the course, the outcomes so far and the lessons learned along the way.

Speaker: Shohini Ghose

294 Reasoning about uncertainty and measurement in classical and quantum mechanics

Prior research has found limitations in how students reason about uncertainty and measurement in introductory courses, with many students thinking point-like (a single measurement could be the true value) rather than set-like (a set of measurements estimate the parameter). Motivated by the question, "How does that intro-level reasoning influence student thinking about quantum mechanical measurement," we conducted interviews and surveys to probe student reasoning about uncertainty and measurement across classical and quantum mechanical contexts. The work also aims to characterize the possible paradigms of student thinking about uncertainty and measurement across physics contexts, adding nuance to the point- and set-paradigms.

Speaker: Natasha Holmes (Cornell University)

W1-4 Medical applications of Imaging - Part I (DPMB/DAPI) / Applications médicales de l'imagerie - Partie 1 (DPMB/DPAI)

Convener: Dan Xiao (University of Windsor)

295 (I) Photon-Counting X-ray Detectors: A New Generation of Medical X-ray Imaging

Medical x-ray imaging has revolutionized modern medicine. A necessary and critical component of a medical x-ray imaging system is the x-ray detector. Over the past 50 years, x-ray detectors have evolved from film-screen systems, to computed radiographic cassettes, culminating in flat-panel digital x-ray detectors that directly capture image data during patient examination, bypassing the need for an intermediate data readout between data acquisition and image viewing. This approach has increased the efficiency of medical imaging procedures, with the added benefit of improved image quality. Flat-panel detectors also enable cone-beam computed tomography, which is used in dentistry, interventional radiology, and radiation therapy treatment planning and verification. Flat-panel x-ray detectors used in clinical practice are energy-integrators, which means that the image signal is proportional to the intensity of the x-ray beam. Recent technological innovations, largely developed to satisfy the needs of CERN’s particle collision experiments, have resulted in photon-counting x-ray imaging detectors. These detectors enable identifying individual photon interactions at rates adequate for a large range of medical applications. This technology may reduce the radiation dose of x-ray imaging procedures, and may enable new energy-based x-ray imaging methods that estimate the shape of medical x-ray spectra to provide new types of image contrast not possible with energy-integrating detectors. This talk will discuss the basic physics of photon-counting x-ray imaging and the key factors that need to be overcome to realize the full potential of this exciting new technology.

Speaker: Jesse Tanguay (Ryerson University)

296 Advanced Magnetic Resonance Neuroimaging at 0.5-Tesla?... This is not your parent’s MRI!

For almost five decades, Magnetic Resonance Imaging (MRI) has been on a monotonic technological progression towards higher and higher magnetic field strength. This is largely due to the fact that, as any physicist will tell you, nuclear magnetization and therefore MR signal strength scales with the applied field strength. Why then go backwards to a low magnetic field to explore advanced neuroimaging when “everyone knows” we should be using high magnetic fields in MRI?

While strong magnetic field confers many benefits – e.g. bigger chemical shifts, stronger fMRI contrast, etc – it is not a panacea. In contrast, MRI at lower magnetic field exhibits decreased spatial distortion due to lower susceptibility induced field inhomogeneity, decreased RF heating of tissue, improved RF pulse B1 homogeneity, etc. We have recently explored the use of a novel MRI device (Synaptive Medical Inc, Toronto ON) that utilizes a cryogen-free head-only 0.5-T magnet with 16-channel fully digital receive chain and a 100 mT/m gradient set with a usable slew rate of 400 T/m/s. The introduction of modern spectrometer design to a 0.5-T magnet has permitted us to explore a range of advanced neuroimaging applications. This allows us to take advantage of all the benefits of low field while mitigating the drawbacks of decreased signal strength through improved T/R chain and gradient coil design.

Through this research we will explore a spectrum of advanced neuroimaging applications of this technology including:
• “Distortion Free” Diffusion Weighted Imaging, leveraging the high strength/slew gradient design;
• “Band Free” balanced SSFP imaging of internal auditory canal, leveraging the improved field homogeneity and low RF specific absorption rate inherent to low magnet field;
• Accelerated MR screening exams for use in stroke imaging, leveraging the high performance receive chain for generating excellent SNR images.

Speaker: Steven Beyea

297 Design of 1.0T conduction cooled superconducitng magnet for intraoperative magnetic resonance imaging

MRI provides exquisitely detailed images of brain and spinal cord anatomy and pathology. MR images are multi-planar, radiation free and have a greater sensitivity and specificity than either CT or ultrasonography. Although an engineering challenge, the placement of MRI systems in the operating room will revolutionize neurosurgical care. Surgical navigation was repeatedly updated by iMR images able to detect brain shift resulting from CSF leakage. iMRI has also identified a significant number of patients who harboured unsuspected, residual tumour at the end of surgery, thus sparing them the discomfort and expense of reoperation. Newer MRI techniques such as DTI and fMRI were bought into the operating room allowing for locating vital tracts and areas during the surgical process with the concomitant brain shift.
A 1.0T conduction cooled superconducting magnet has been designed for intraoperative MRI. The warm bore of the magnet is 700mm in diameter and 1200mm in length, the magnet with a high homogeneity of a magnetic field in a DSV of300mm. Total weight of the magnet is 1.8 ton,two 4K cryocoolers are applied for cooling the magnet,the magnet is installed in a mover, and still at field during movement.In this paper,electro-magnetic design,quench simulation,eddy current simulation and test results of the magnet are presented.

Speaker: Wenlong Bian (Alltech Medical System)

W1-5 Plasma for biomedical application (DPP) / Plasma pour applications biomédicales (DPP)

Convener: Lenaic Couedel (University of Saskatchewan)

298 (I) Plasma jet as a source of carbon monoxide (CO) for biomedical applications

Carbon monoxide (CO) has a bad reputation due to potential lethal consequences when inhaled at high concentrations in humans. However, at low doses CO exerts a broad spectrum of biological activities that results in a variety of beneficial actions including among others anti-inflammatory, vasodilatory, anti-apoptotic and anti-proliferative effects [1].
Plasma can generate CO from the dissociation of CO2; in this context, non-equilibrium plasma at atmospheric pressure is an attractive in situ CO source since it is able to create CO at low doses from CO2 [2]. Moreover, plasma can be used for biomedical applications and intense research is now being conducted on its potential therapeutic use for the treatment of pathologies such as cancer and skin wounds. Plasmas are very versatile as they possess the capacity to generate large amounts of reactive species combined with electric field, photons and charged particles. However, the combination of plasma and CO for biomedical applications remains to be fully explored.

This presentation will focus on the challenge to develop a plasma reactor to generate controlled quantities of CO that can be used for therapeutic purposes. The reactor is based on plasma jet configuration where the discharge is produced in a coaxial dielectric barrier discharge (DBD) reactor equipped with a quartz capillary tube [3]. Helium with small addition of CO2 goes through the device. To assess and quantify the production of CO from plasma, we developed a system whereby mouse blood hemoglobin, a strong scavenger of CO, interact with the plasma reaction. Once CO binds to hemoglobin, it forms carboxyhemoglobin (COHb), which can be easily and precisely quantified by a spectrophotometer. We will present the first results showing that indirect and direct plasma treatments have different effects on the production of CO and its binding to hemoglobin.

[1] R. Motterlini and L. E. Otterbein, Nat. Rev. Drug Discov., vol. 9, no. 9, pp. 728–743, Sep. 2010.
[2] E. Carbone and C. Douat, Plasma Med., vol. 8, no. 1, pp. 93–120, 2018.
[3] T. Darny, J.-M. Pouvesle, V. Puech, C. Douat, S. Dozias, and E. Robert, Plasma Sources Sci. Technol., vol. 26, no. 4, p. 045008, Mar. 2017.

Speaker: Claire Douat (GREMI - CNRS - University of Orleans)

299 (I) Non-thermal plasma for cancer treatment, influence of the discharge mode on the cytotoxicity of a radio-frequency plasma jet

Non-thermal plasma (NTP) is being increasingly considered for its many medical applications. Even though NTP comprises physical factors such as the electric field and charged particles, NTP is mostly recognized to induce biological responses through its production and delivery of reactive species such as reactive oxygen and nitrogen species (RONS). Precise tuning of RONS is an important issue for plasma medicine as different RONS compositions and concentrations can lead to different clinical outcomes. For example, in some situations NTP was found capable of inducing cell proliferation, thus promoting wound healing, while in other situations NTP was found to induce proliferation arrest, thus yielding anticancer effect [1]. This highlights the fact that NTP should not be considered as a simple drug with its dose defined as a single parameter. NTP can be better viewed as a vector to administer reactive molecules, hence making accessible molecules that cannot be administered via more stable solid or liquid states.
Different NTP devices thus possess different physical properties that produce various RONS leading to distinctive biological responses. For example, varying the driving frequency or the plasma-forming gas can lead to different plasma properties and change drastically the outcome of the treatment. In this work, we use the convertible plasma jet in order to produce three different NTPs using the same plasma-forming gas and the same driving frequency [2]. Investigating the cytotoxic effect of NTP with an in vitro model of triple-negative breast cancer cells in suspension, we observed that cytotoxicity not only depends on the discharge mode, but that the cellular response to the addition of nitrogen or oxygen to the plasma-forming gas is modulated according to the discharge mode. This highlights the fact that fine-tuning of plasma parameters could become an essential step in future NTP treatments in the clinic.

The author acknowledges FRQNT, NSERC, MEDTEQ, Mitacs, TransMedTech, NexPlasmaGen Inc. for research funding.

References
[1] L. Boeckmann, M. Schäfer, T. Bernhardt, M.-L. Semmler, O. Jung et al. Applied Sciences, 10, 6898 (2020)
[2] J.-S. Boisvert, J. Lafontaine, A. Glory, S. Coulombe and P. Wong, IEEE Transactions on Radiation and Plasma Medical Sciences, 4, 644-654 (2020)

Speaker: Dr Jean-Sébastien Boisvert (McGill University and CRCHUM)

W1-6 Cosmology in the Past Century I (DHP) / Cosmologie au siècle précédent I (DHP)

Convener: Louis Marchildon (Universite du Quebec a Trois-Rivieres)

300 (I) Multiples in Scientific Discovery

When an interesting idea appears in natural science there is a good chance that someone else has already thought of it, independently, or will think of it if news does not travel fast enough. Sociologists recognize this as a phenomenon that has something to teach us about the nature of research in science. I will offer examples to be found in the discovery of the idea of the hot big bang cosmology.

Speaker: Prof. James Peebles (Princeton University)

12:15 Discussion Period

W1-7 Nuclei & Astrophysics III (DNP) / Noyaux et astrophysique III (DPN)

Convener: Gregory Christian (Saint Mary's University)

301 (I) Fusion in massive stars: Pushing the 12C+12C cross-section to the limits with the STELLA experiment at IPN Orsay

The 12C+12C fusion reaction is one of the key reactions governing the evolution of massive stars as well as being critical to the physics underpinning various explosive astrophysical scenarios. Our understanding of the 12C+12C reaction rate in the Gamow window – the energy range relevant to the different astrophysical scenarios – is presently confused. This is due to the large number of resonances around the Coulomb barrier and persisting down to the lowest energies measured. In usual circumstances, where the fusion cross-section is smooth it can be readily extrapolated from the energy range measured in the laboratory down to the Gamow window but this is not possible for 12C+12C. Moreover, the existing data on this reaction obtained either through detection of evaporated charged particles or detection of gamma rays do not agree. In addition, there is considerable disagreement in the theoretical extrapolation of the data down to the Gamow window. Classically, the origin of the resonances has been attributed to molecular states based on a 12C+12C configuration, while others have attributed it to low level density in the compound system.
The STELLA experiment has been commissioned at IPN Orsay. A intense 12C beam from the Andromede accelerator is incident on thin self-supporting 12C foils. A target rotation system can allow for cooling supporting beam currents in excess of 1 eμA. Evaporated charged particles are detected with a dedicated silicon array while gamma rays are detected in coincidence with an array of 30 LaBr3 detectors. Results from initial studies with STELLA will be presented which appear to support sub-barrier fusion in this system underlying the fusion resonances.

Speaker: Dr David Jenkins (York University, UK)

302 New measurements of the 17O(alpha,gamma)21Ne reaction

s-process nucleosynthesis can be influenced by so-called 'light element neutron poisons', which absorb free neutrons before they can capture onto iron-peak seed nuclei. The 16O(n,gamma) reaction is one such neutron poison reaction. However, free neutrons can then be released back into the star via 17O(alpha,n)20Ne. The ratio of the neutron and gamma outgoing channels in 17O + alpha reactions is therefore important in determining the effectiveness of 16O as a light element neutron poison, since the 17O(alpha,gamma)21Ne channel would 'lock-up' neutrons in light elements. In this talk, two studies performed at TRIUMF targeting resonances in the 17O(alpha,gamma)21Ne reaction will be presented: a direct measurement with DRAGON and a transfer measurement with EMMA+TIGRESS. The latter experiment is aimed at determining the properties of low-energy resonances, which would be otherwise inaccessible using direct methods.

Speaker: Matthew Williams (TRIUMF)

303 Measurement of the $^7$Be($\alpha,\gamma$)$^{11}$C reaction with DRAGON for neutrino-driven wind nucleosynthesis

Nucleosynthesis in the neutrino-driven wind of core-collapse supernovae has gained in popularity in recent years and it is thought to produce light neutron-deficient nuclei with $A\leq110$ via the $\nu p$-process. However, this scenario exhibits uncertainties related to the explosion dynamics and the underlying nuclear physics input. The $^7$Be($\alpha,\gamma$)$^{11}$C reaction has been shown to affect the production of $90 \leq A \leq 100$ nuclei, by changing the wind composition prior to the νp-processing onset. Nevertheless, there is a lack of experimental information about its rate in the relevant temperature range (T= 1.5-3 GK). To improve the $^7$Be($\alpha,\gamma$)$^{11}$C reaction rate for the $\nu p$-process, the first direct measurement of resonances with unknown strength was recently performed at TRIUMF using an intense radioactive $^7$Be (t$_{1/2}$= 53.24 d) beam and the DRAGON recoil separator. The experimental challenges, preliminary results and nucleosynthesis calculations to study the effect of the new rate will be discussed.

Speaker: Athanasios Psaltis (McMaster University)

W1-8 Exotic Matter I (DNP) / Matière exotique I (DPN)

Convener: Jonathan Zarling (University of Regina)

304 (I) The impact of nuclear structure on constraints of neutron star structure

Accreting neutron stars host a variety of astronomical observables which can be compared to model calculations to obtain dense matter constraints. However, key observables such as X-ray bursts and crust cooling are directly influenced by the structure of atomic nuclei involved in these processes. I will demonstrate the sensitivity of astrophysical models of accreting neutron star phenomena to changes in the input nuclear physics, highlight the subsequent influence on model-observation comparisons, and discuss related experimental work to reduce or remove the most influential uncertainties.

Speaker: Zach Meisel (Ohio University)

305 (G*) The Effect of Nucleonic Interaction on Neutrinos from Neutron Star Black Hole Mergers

During neutron star black hole collision events, 20 percent of the binding energy is released in the form of neutrinos. These mergers form a black hole with a disk of matter accreting into it. The neutrino signal observed on earth will depend on where the neutrinos become free from the system; this is called the neutrino surface. The neutrino surface can be determined based on hydrodynamic simulations of the accretion disk. Energies of released neutrinos are then obtained at the neutrino surfaces and used to calculate the neutrino flux, which will determines the observed signal on earth. The neutrino surface is determined by calculating neutrino cross sections for grid points. Given the relatively high density of accretion disks, the effect of nucleonic interaction on the cross section is examined. This effect can be encapsulated in structure factors which we calculate using energy density functionals in the random phase approximation, and using the viral approximation.

Speaker: Rajan Anderson (University of Guelph)

306 (G*) The decay of the $b_{1}$(1235) meson through the $\omega \pi$ channel at GlueX

A long-standing goal of hadron physics has been to understand how the quark and gluon degrees of freedom that are present in the fundamental QCD Lagrangian manifest themselves in the spectrum of hadrons.
The GlueX experiment at Jefferson lab contributes to the global spectroscopy program using 8-9~GeV linearly polarized photons. This experiment focuses on the exploration of the light-quark domain, potentially accessing hybrid mesons with exotic $J^{PC}$ quantum numbers in photoproduction reactions.

The decay of several exotic mesons (e.g. $\pi_1(1600)$, etc.) to $b_1 \pi$ can be accessed through the decay $b_1 \rightarrow \omega \pi$. In this talk we discuss the decay of the axial-vector meson $b_{1}$ through both charged ($\gamma p \rightarrow \Delta^{+ +} \omega \pi^{-}$) and neutral ($\gamma p \rightarrow p \omega \pi^{0} $) production mechanisms. Understanding the decay of the $b_{1}$ is important, particularly in the context of Partial Wave Analysis and for extraction of the D/S wave ratio, which is of interest to validate predicted couplings to this axial-vector resonance from Lattice QCD calculations.

Speaker: Mr karthik suresh (University of Regina)

W1-9 Superconductors and other Quantum Materials (DCMMP) / Supraconducteurs et autres matériaux quantiques (DPMCM)

Convener: Michel Gingras

307 (I) T-linear resistivity from an isotropic Planckian scattering rate

Perfectly T-linear resistivity is observed in a variety of strongly correlated metals close to a quantum critical point [1] and has been attributed to a scattering rate 1/τ of charge carriers that reaches the Planckian limit [2,3], with ℏ/𝜏 = α 𝑘𝐵𝑇 where α is of order unity. While this relationship is often inferred from simple estimates, a T-linear scattering rate has yet to be measured.
To directly access the Planckian scattering rate, we measured the angle-dependent magnetoresistance (ADMR) of Nd-LSCO at p = 0.24: a cuprate that demonstrates T-linear resistivity over a wide temperature range at the pseudogap critical point p* [4]. The ADMR reveals a well-defined Fermi surface that precisely agrees with ARPES [5]. In addition, we extract a T-linear scattering rate that has the Planckian value, namely α = 1.2 ± 0.4. Remarkably, this inelastic scattering rate is isotropic.
Our findings suggest that T-linear resistivity in strange metals emerges from a generic isotropic, momentum-independent inelastic scattering rate that reaches the Planckian limit.
[1] J. Zaanen, SciPost Phys. 6, 061 (2019).
[2] J. A. N. Bruin et al., Science 339, 804 (2013)
[3] A. Legros et al., Nat. Phys. 15, 142 (2019)
[4] R. Daou et al., Nat. Phys. 5, 31 (2009).
[5] C. Matt et al., Phys. Rev. B 92, 134524 (2015)

Speaker: Gael Grissonnanche (Cornell University)

11:50 Questions & answers

308 (I) Pushing the Size of the Quantum Cluster Numerical Simulations

A method to calculate the one-body Green's function for ground states of correlated electron materials is formulated by extending the variational Monte Carlo (VMC) method [1]. We apply the method to larger-sized Hubbard model on the square lattice correctly reproduces the Mott insulating behaviour at half-filling and gap structures of d-wave superconducting state on the 12 by 12 cluster of the Hubbard model.

[1] Charlebois M, and Imada M., Phys. Rev. X, 10:4(041023) (2020)

Speaker: Maxime Charlebois (Université du Québec à Trois-Rivières)

11:59 Questions & answers

309 (I) Vanishing nematic order beyond the pseudogap phase in overdoped cuprate superconductors

During the last decade, translational and rotational symmetry-breaking phases — density wave order and electronic nematicity — have been established as generic and distinct features of many correlated electron systems, including pnictide and cuprate superconductors. However, in cuprates, the relationship between these electronic symmetry-breaking phases and the enigmatic pseudogap phase remains unclear. I this talk, I will discuss our efforts to employ resonant x-ray scattering in a cuprate high-temperature superconductor (Nd-LSCO) to probe the relationship between electronic nematicity, charge order, and the pseudogap phase. We find evidence for a considerable decrease in electronic nematicity beyond the pseudogap phase, either by raising the temperature through the pseudogap onset temperature T or increasing doping through the pseudogap quantum critical point, p. These results establish a clear link between electronic nematicity, the pseudogap, and its associated quantum criticality in overdoped cuprates. Our findings anticipate that electronic nematicity may play a larger role in understanding the cuprate phase diagram than previously recognized.

Speaker: David Hawthorn (University of Waterloo)

12:08 Questions & answers

310 (I) Quantum materials at the atomic scale

Understanding and controlling the properties of 2D materials to our advantage can be contemplated with the development of experimental tools to probe and manipulate electrons and their interactions at the atomic scale. In this talk, I will present scanning tunnelling microscopy and spectroscopy experiments aimed at: elucidating the nature of atomic-scale defects in 2D materials [1], visualizing moiré patterns between crystals with different symmetries [2] and imaging surface and edge states in a magnetic topological system. Moreover, I will discuss how we leverage our expertise in probing and engineering electronic states at surfaces of 2D materials to further the development of graphene-based gas sensors [3] and gated quantum dot circuits based on 2D semiconductors [4].

REFERENCES

[1] Plumadore et al., PRB, (2020)
[2] Plumadore et al., Journal of Applied Physics, (2020)
[3] Rautela et al., ACS Applied Materials & Interfaces (2020)
[4] Boddison-Chouinard, Appl. Phys. Lett., (2019)

Speaker: Adina Luican-Mayer (University of Ottawa)

12:17 Questions & answers

311 (I) Large Kondo Effect in molecule-linked Au Nanoparticles Assemblies

Interactions between localized, unpaired spins and delocalized electrons play a key role in a range of phenomena, including the Kondo effect, RKKY interactions and high Tc superconductivity. A number of recent studies have explored such interaction using hybrid systems combining 1) molecules with metal ions which contribute unpaired, localized spins and 2) deposited Au films which contribute delocalized electrons. Such studies have successfully observed a small Kondo effect.

Unexpectedly, a different set of studies have reported that using long (therefore, insulating) alkanethiol (CH3(CH2)nSH) molecules as “surface coatings” for Au nanoparticles can generate magnetism in the nanoparticles. Neither bulk gold nor alkanethiols are magnetic by themselves, and it is believed that the thiols (-SH) generate holes in 5d orbitals of gold.

Using short (therefore, conducting) butanedithiol (HS(CH2)4SH) molecules as crosslinkers for Au nanoparticles, we have observed for the first time a Kondo effect in this molecule linker- Au nanoparticle system. The Kondo effect here is much larger relative to other temperature dependent phenomena – more than 10-fold larger than previously reported in studies using deposited Au films. These results afford testing Kondo models in a much stronger regime, and we find that published theory continues to hold. Importantly, we show that by changing the nanoarchitecture of the films, we can raise the Kondo temperature 10-fold, to >250K. These results point to molecule linker-nanoparticle assemblies as a versatile and potentially powerful means to generate materials exhibiting strong electron-electron interactions.

Speaker: Al-Amin Dhirani (Department of Chemistry, University of Toronto)

12:26 Questions & answers

12:30 15 Minute Break

W2-1 Optical Technology and Communication (DAMOPC) / Technologie optique et communication (DPAMPC)

Convener: Jens Lassen (TRIUMF)

312 Eliminating dual-polarization laser emission and spatial hole burning by using parity-time-symmetric eigenstates

Spectral purity in laser emission is key for several applications such as remote sensing, non-linear optics and laser spectroscopy. However, producing single mode emission at high power in free-space, standing-wave resonators is challenging. Nanostructured laser mirrors can be used to achieve that in compact microchip monolithic laser resonators without using any additional intra-cavity element [1,2]. For instance, using a pair of mirrors displaying a π phase shift between orthogonal polarization states at reflection produces the twisted mode operation, which allows one to eliminate the contrast of the standing wave inside the cavity and makes it possible to eliminate multi-longitudinal mode operation originating from axial spatial hole burning. However, dual-polarization emission remains an issue if there is no mechanism to suppress competing polarization states, and this may give rise to unstable emission, in addition to producing dual frequency emission. In this presentation, we propose a resonator made of anisotropic mirrors displaying both birefringence and diattenuation as a mean to eliminate both spatial hole burning and dual polarization emission. The relative angle of the two mirrors’ principal axes is adjusted such that the laser operates just at the transition between broken and unbroken parity-time symmetric polarization states. At this transition point, the two eigen-polarization states are found to merge to a single state, called an exceptional point, while the counter-propagating waves are orthogonal, and no spatial hole burning takes place [3]. Hence, microchip PT-symmetric states are an attractive option to achieve single mode operation from a miniature microchip laser without the need to introduce any additional intracavity element.

[1] J.-F. Bisson, K. N. Amouzou, Controlling spatial hole burning in lasers using anisotropic laser mirrors J. Opt. Soc. Amer. B 36(12), 3322-
3332, (2019).
[2] J.-F. Bisson, K. N. Amouzou, Elimination of spatial hole burning in solid-state lasers using nanostructured thin films Appl. Opt. 59(5), A83-
A91, (2020).
[3] J.-F. Bisson, Y. C. Nonguierma, Single-mode lasers using parity-time-symmetric polarization eigenstates, Phys. Rev. A, 102, 043522, (2020).

Speaker: Jean-Francois Bisson

313 (G*) Temperature Sensitive Electroluminescence Observed in a Reverse Biased, Frozen Polymer P-I-N Junction

The solid polymer light-emitting electrochemical cell (PLEC) possesses a polymer homojunction that is reminiscent of a conventional p-n junction but also exhibits distinct features that are profoundly intriguing. The PLEC junction is formed under bias when the propagating p- and n-doping fronts in the semiconducting polymer make contact. The PLEC junction can be immobilized by cooling after the initial junction formation. Once the junction is fixed by cooling, the “frozen-junction” PLEC exhibits a unipolar electroluminescence (EL) and photovoltaic response. Further, the resulting frozen junction can be relaxed, or partially de-doped into a p-i-n junction by controlled manipulation of ion motion. The as-frozen p-n junction can be relaxed with repeated thermal cycles. More precisely, the de-doping was carried out in a single heating/cooling cycle during which a constant reverse bias (RB) current was applied to monitor the extent of de-doping and the magnitude of RB EL. It is on a frozen polymer p-i-n junction that the most puzzling electroluminescent phenomenon was observed. A model is developed that explains the reverse bias EL as caused by the tunnel injection of electrons and holes from bandgap states into a de-doped “intrinsic” region between the p- and n-doped regions. Moreover, the RB EL exhibits hypersensitivity to temperature when the de-doped cell was cooled. There is currently no explanation to this drastic EL enhancement by cooling. Several possible causes have been ruled out through a series of control experiments.

Speaker: Dongze (Willy) Wang (Queen's University)

314 (G*) Adding a linear contribution to depolarization in simulations of supercontinuum generation

Supercontinuum generation in optical fiber is the result of an interplay between multiple nonlinear processes. Simulations to reproduce experimental observations are well documented: a differential equation known as the generalized nonlinear Schrödinger equation (GNLSE) is solved to determine the effect of propagation on the spectral and temporal profiles of the slowly-varying amplitude of a laser pulse. For the scalar case, the GNLSE has been shown to yield good results. In a more accurate case, it becomes necessary to take into account the polarization evolution of light as it travels through the fiber, for instance for a fiber with two orthogonal principal axes. This is typically added into the GNLSE to form coupled equations including the birefringence of the fiber and additional nonlinear terms coupling the slowly-varying amplitudes of two polarization components. Upon studying the experimental spectra obtained from a germania-doped photonic crystal fiber, we observe that the polarization state varies significantly across the spectrum, leaving the spectral edges with a greater degree of polarization than the areas near the input pump wavelength. We also observe that the spectral region around the pump maintains a low degree of polarization. These trends lead us to believe that a portion of the energy transfer from input polarization state to an orthogonal output state is proportional to the propagation length, consistent with a linear depolarization contribution that cannot be reproduced using only nonlinear equations. We therefore demonstrate the effect of an additional depolarization term to account for the redistribution of energy between polarization modes. Furthermore, the interaction between linear and nonlinear depolarization mechanisms leads to a more realistic estimate of the polarization maintaining capability of an optical fiber over a broadband spectrum.

Speaker: Rachel Ostic (University of Ottawa)

315 (G*) Ultrafast modulation of the properties of a metasurface for terahertz radiation

Next generation wireless communication technologies will rely on techniques able to rapidly change the properties of an optical filter in the far-infrared region. Here we demonstrate ultrafast modulation of a metasurface’s transmission spectrum containing a resonance around the optical frequency of 1 terahertz (THz). The metasurface consists of an array of sub-wavelength gold crosses deposited on a silicon substrate. A femtosecond optical pulse in the visible region is used to inject free carriers in the semiconductor to modify the metasurface properties, while the transmission spectrum is monitored with a broadband time-resolved THz spectroscopy system. As we increase the density of optically injected carriers, we gradually damp the filter resonance, broaden its linewidth and blueshift its frequency. At a carrier density of $2\times10^{17}$ $cm^{-3}$, we completely bleach the resonance, and the full transmission spectrum becomes flat with an overall transmission coefficient approaching T = 0.25. We also investigate the effect of injected carriers in a dynamical context: when the excitation pulse modifies the properties of the metasurface less than 1 ps after the arrival of the THz probe pulse. Interestingly, this scheme prevents spectral components from remaining trapped inside the metasurface and yields a transmission spectrum free of any resonances. In the case of a notch filter, we show that this innovative technique increases the transmission at the resonance by more than 2 orders of magnitude while the off-resonance part of the spectrum decreases by less than 30%. Our experimental results are in good agreement with numerical simulations based on a finite-difference time-domain (FDTD) method, allowing us to reproduce the transmission spectrum and visualize the electric field distribution within the metasurface. Our tunable frequency selection technique has a great potential for applications in adaptive communication devices, THz pulse shaping, and the sub-cycle modulation of nanomaterials with ultrafast carrier dynamics.

Speaker: Ahmed Jaber (University of Ottawa)

316 (G*) An individual optical addressing scheme for trapped Ba+ ions in an open-access quantum information processor

Trapped ions are a leading platform for noisy intermediate-scale quantum (NISQ) computing with high gate fidelities, long coherence times, and natural long range ion-ion interactions. QuantumION is a project which aims to scale trapped ion quantum computing to 16 Ba+ qubits while providing an open-access resource to the whole research community. High fidelity control over each ion is crucial to scalability and direct access to the hardware level is needed to make a useful community resource. This talk presents the synthesis of these two concepts exemplified by the individual addressing scheme at the heart of QuantumION. A femtosecond laser direct write (FLDW) waveguide is used to split a single laser source into 16 path-length matched and fibre coupled beams. Intensity, phase, and frequency can be controlled independently with commercial fibre AOMs. The fibre tip of each beam is imaged onto a chain of ions aided by a micro-machined array of lenses to provide individual control over 16 ions with projected $10^{-4}$ overall crosstalk. This scheme could also allow operation at multiple wavelengths opening the door to individual state readout of the ion chain with the same beam path.

*We acknowledge support from TQT (CFREF) and the University of Waterloo.

Speaker: Mr Nikolay Videnov (University of Waterloo)

13:06 Group discussion

W2-10 Exploring the Energy and Precision Frontier IV (PPD) / Frontière d'énergie et de précision IV (PPD)

Convener: Heather Russell (CERN)

317 Searches for ultra long-lived particles with MATHUSLA

The observation of neutral long-lived particles (LLPs) at the LHC would reveal novel physics beyond the Standard Model. LLP signatures are well motivated and can appear in many theoretical constructs that address the Hierarchy Problem, Dark Matter, Neutrino Masses and the Baryon Asymmetry of the Universe. With the current experimental program at colliders, no search strategy will be able to observe the decay of neutral LLPs with masses above $\sim$GeV and lifetimes at the limit set by Big Bang Nucleosynthesis (BBN), c$\tau$ $\sim$10$^7$-10$^8$ m. To fill this gap, we propose the MATHUSLA detector (MAssive Timing Hodoscope for Ultra-Stable neutraL pArticles), which would be constructed on the surface above CMS in time for the High-Luminosity LHC operations. The large area of MATHUSLA, ~100m x 100m x 30 m, would also allow it to make important contributions also to cosmic ray physics. The detector would be composed of several layers of solid plastic scintillator, with wavelength-shifting fibers connected to silicon photomultipliers, monitoring an empty air-filled decay volume. In this talk, we will report on the analysis of data collected by a test stand installed on the surface above the ATLAS detector, our ongoing background studies, our R&D efforts, and plans for the MATHUSLA construction.

Speaker: Miriam Diamond (SLAC National Laboratory)

MATHUSLA CAP 2021.pdf

318 Search for the rare $K^+ \to \pi^+ \nu \overline{\nu}$ decay at the NA62 experiment at CERN

The rare $K^+ \to \pi^+ \nu \overline{\nu}$ decay is an ideal probe for exploring physics beyond the Standard Model (BSM) at very high energy scales. This loop-dominated weak decay is heavily suppressed in the SM with a predicted branching ratio (BR) of $\left(8.4 \pm 1.0\right) \times 10^{-11}$.

The NA62 experiment at the CERN SPS is designed to study precisely the $K^+ \to \pi^+ \nu \overline{\nu}$ BR using a new decay-in-flight technique. Kaons present in a 75 GeV mixed hadron beam are tagged and their momentum measured before they enter a 60 metres-long evacuated decay volume. The properties of the decay particles are then recorded by a redundant set of detectors, allowing for the reconstruction of the event kinematics and rejection of copious backgrounds. Photon and muon detectors cover the full signal geometrical acceptance.

During the 2016–2018 period, 20 $K^+ \to \pi^+ \nu \overline{\nu}$ candidates were observed compared with 7 expected background events. This is the first evidence of this process with a statistical significance of more than three sigma. The corresponding BR is $\left(11.0^{+4.0}_{-3.5~\mathrm{stat.}} \pm 0.3_\mathrm{syst.}\right) \times 10^{-11}$. This is compatible with the SM prediction within one standard deviation and allows sensitive limits to be placed on a range of hypothetical BSM physics. Plans for the 2021 run will also be presented.

Speaker: Bob Velghe (TRIUMF (CA))

bvelghe_pnn_talk_cap2021_v0.pdf

319 The Canadian Contribution to the ATLAS New Small Wheels

As a part of the Phase-1 upgrade to the ATLAS muon spectrometer, Canada has taken a leading role in the construction, testing, and commissioning of small-strip Thin Gap Chambers or sTGCs, one of two detector technologies to be used in the ATLAS New Small Wheel. This presentation will detail the process in which sTGCs are built to their integration into the ATLAS detector. A focus will be given to Canadian contributions to this international project and its current status.

Speaker: Tony Kwan (McGill University, (CA))

Kwan_CAP2021_sTGC.pdf

W2-11 Test Facility I (PPD) / Installation pour tests I (PPD)

Convener: Silvia Scorza (SNOLAB)

320 (G*) Argon-1: An R&D detector for next generation LAr experiments

Increasing sensitivity in rare event search experiments requires the development and characterization of novel background rejection techniques and technologies. To aid in the development of these techniques for future liquid Argon (LAr) detectors, an R&D detector “Argon-1” has been commissioned at Carleton University. Argon-1 is a single phase 35 kg LAr test detector, employing 65+ channels of silicon photo-multipliers (SiPMs) for light readout. The detector will be used to test novel analogue and digital SiPM technologies, as well as background rejection techniques for next generation LAr detectors such as ARGO; a planned direct dark matter search experiment with a 300 tonne LAr target mass that aims to reach the so-called “neutrino floor”. The first major study will be a test of a novel surface background rejection technique using a layered scintillating surface. The technique works by placing a thin scintillating layer with a sufficiently long decay time constant on the surface of the detector. Events that originate from this pathologically difficult area can be identified readily through pulse-shape discrimination, and a similar technique is being utilized for the DEAP-3600 detector upgrades to target topological alpha backgrounds. In this talk we will discuss the commissioning and instrumentation of Argon-1, in-situ SiPM characterizations in LAr conditions, detector calibration, and present the status of the surface background rejection study.

Speaker: David Gallacher (Carleton University)

Argon1_CAP_2021.pdf

321 (G*) CUTE: an underground test facility for cryogenic detectors

The Cryogenic Underground TEst facility (CUTE), located approximately 2 kilometers underground at SNOLAB, has been operational since 2019. It provides a well-shielded, low-background environment, ideal for testing cryogenic detectors for rare event searches. The primary focus of CUTE is to test detectors in preparation for their use in the Super Cryogenic Dark Matter Search (SuperCDMS) experiment. Due to the facility's low background, early dark matter searches with SuperCDMS detectors or other small scale rare event searches may also be performed. So far, the CUTE facility has tested a variety of devices, including a prototype SuperCDMS high-voltage germanium detector and a 10 gram silicon detector optimized for low-energy nuclear recoils. This presentation will describe the main features and the performance of the CUTE facility and discuss some of the measurements performed to date, including the experimental validation of the vibration isolating system.

Speaker: Richard Germond

CUTE_facility.pdf

322 (G*) A Multi-Photomultiplier Photosensor Module for IWCD/Hyper-K

Hyper-K will be a next-generation long-baseline neutrino experiment in Japan with the main goal of measuring the neutrino flavour mixing parameters and discovering CP violation in the neutrino sector. Its detector complex will benefit from the construction of the Intermediate Water Cherenkov Detector (IWCD). The IWCD will measure the un-oscillated neutrino flux at different off-axis angles, providing a considerable decrease in the systematic uncertainties associated with the extrapolation of cross-sections to the far Hyper-K detector. To accomplish this with optimal efficiency, a high granularity photo-detector system, called multi-PMT (mPMT), is proposed. Each mPMT module will consist of nineteen 3” photo-multiplier tubes (PMT) and a scintillator plate housed under a transparent dome in a cylindrical body. The smaller and fast PMTs will provide a better granularity and time resolution than the standard 20" PMTs used in the Super-Kamiokande detector, allowing better particle identification and trajectory reconstruction. The scintillator plates will work as a veto system for undesired processes. In this talk, I will address the technical challenges and developments towards the construction of the mPMT system.

Speaker: Luan Koerich (University of Regina)

mPMT, Luan Koerich, CAP 2021.pdf

323 Cryogenic detector monitoring and calibration with internally mounted LEDs

As dark matter searches aim to achieve lower energy thresholds, it is important to understand the behaviour of the detectors in these new regimes. Light-emitting diodes (LEDs) offer a simple and flexible source of photons with energy ranges from 0.3 eV (mid-infrared) to 5 eV (near ultraviolet). Prototype cryogenic silicon detectors developed by the SuperCDMS collaboration have been able to achieve energy resolutions below 3 eV. By taking advantage of the Neganov-Trofimov-Luke (NTL) effect, the effective resolution can be reduced to well below the bandgap of silicon at mK temperatures of 1.2 eV. At our R&D facility at TRIUMF, we have been testing two of these “HVeV” detectors using a range of LEDs at mK temperatures. We have demonstrated the LEDs suitability for detector calibration and have applied them to investigate the detector response to photons ranging from sub-gap infrared to near ultraviolet.

Speaker: Dr Adam Mayer (TRIUMF)

CAP2021 - AMayer v3.pdf

W2-12 Magnetic North VII - Session 6 / Nord magnétique VII - session 6

Convener: Adam Aczel (ORNL)

324 (I) Spin-Ice Thin Films: The Effect of Strain and Disorder

Geometrically frustrated systems have an inherent incompatibility between the lattice geometry and the magnetic interactions, resulting in macroscopically degenerate ground-state manifolds. The single-ion anisotropy in these systems gives rise to unusual noncollinear spin textures [1,2], such as a spin ice state that hosts emergent quasiparticle excitations equivalent to magnetic monopoles. There is an enticing potential of using these monopoles for the development of new quantum information applications. To realize this, thin films are required. The thin films in my group are grown using pulsed laser deposition and characterized using capacitive torque magnetometry and neutron measurements. I will show that epitaxial strain and the amount of disorder in the films play important roles in determining their magnetic properties. Furthermore, capacitive torque magnetometry can be used to characterize the transitions between noncollinear spin textures in highly anisotropic systems, such as spin ices. Studying these magnetic-field-induced phase transitions allows extraction of the energy scales associated with the magnetic interactions in the material. I will benchmark the technique using measurements on bulk single crystals, and I will show that thin films of the same spin ice grown on yttria-stabilized zirconia substrates [1] show modified spin ice physics depending on the growth conditions used.

I acknowledge the support of the National Research Foundation, under Grant No. NSF DMR-1847887 (CAREER). Use of National High Magnetic Field Laboratory user facilities was supported by NSF Cooperative Agreement No. DMR-1644779, and the state of Florida.

[1] K. Barry, B. Zhang, N. Anand, Y. Xin, A. Vailionis, J. Neu, C. Heikes, C. Cochran, H. Zhou, Y. Qiu, W. Ratcliff, T. Siegrist, & and C. Beekman, Phys. Rev. Materials, 3, 084412 (2019)
[2] C. Thompson, D. Reig-i-Plessis, L. Kish, A. A. Aczel, B. Zhang, E. Karapetrova, G. J. MacDougall, and C. Beekman, Phys. Rev. Materials 2, 104411 (2018)

Speaker: Christianne Beekman (Florida State University)

325 Strain control of flying spins

With the increasing complexity of quantum devices, the ability to connect non-neighbouring qubits is critical. Flying spin qubits present one solution to connect quantum gates at remote points in a single device. While the coherent transport of spins using moving potential dots defined by a surface acoustic wave (SAW) has been previously shown, we demonstrate the ability to gate the polarization of the flying spins. The polarization of the electron spins is controlled via spin precession around the internal magnetic field experienced by the spin, which is associated with the spin-orbit interaction and travels with the spin. The spin-orbit interaction has multiple components, but it is the strain term resulting from the SAW is shown to dominate the interaction. The strong dependence of the spin precession with strain, itself dependent on the SAW power, is well described by theoretical models. For spins transported in a GaAs nanostructure, we realize the ability to control the spin state of an electron by varying the strength of the SAW. In fact, with the amplitude of the carrier wave acting as a gate, the electron spin orientation can be flipped during transport within the spin coherence time.

Speaker: James Stotz (Queen's University)

W2-2 Quantum II (DPE) / Quantique II (DEP)

Convener: Daria Ahrensmeier (Simon Fraser University)

326 (I) Teaching quantum computing for second year students in science and engineering

I will describe my experience and the students' feedback in the course "Introduction to Quantum Computing" for second year students at University of Victoria. The class was composed by physics, astronomy, mathematics, computer science, electrical, mechanical, and software engineering majors. The course's only pre-requisite was first-year linear algebra, and most of the students had never had previous exposure to quantum theory. Quantum computing provided an accessible setting for motivating the essential concepts of quantum theory, without the need for advanced mathematical skills such as differential equations. It also opened up many opportunities for experiential learning: The students learned quantum algorithms by writing code and submiting jobs to cloud-based quantum computers offered by IBM Quantum Experience and D-Wave Leap. My conclusion was that the course provided an effective alternative to the usual "historic approach" to teaching quantum theory for second year students, with the added benefit of experiential learning with cutting-edge technology.

Speaker: Prof. Rogério de Sousa (University of Victoria)

SLIDES_TeachingQCfor2ndYearStudents.pdf

327 Open Universe: The Adventure of Teaching and Learning Physics Online

Physics is the most fundamental of sciences, so learning it can be a challenge, especially online. However, a fully-online asynchronous delivery mode can offer some advantages, especially for quickly-developing fields such as subatomic physics and astrophysics, whose active research communities often offer extensive educational resources online. Asynchronous online delivery also allows for more diversity and accessibility engaging a wider group of students, and for more time on hands-on activities such as research projects and virtual labs. The talk will outline the structure of three online courses, Astronomy, Astrophysics and Subatomic Physics, at Memorial University, and share tips and strategies on course design and delivery accumulated over a decade of online teaching.

Speaker: Prof. Svetlana Barkanova (Grenfell Campus of Memorial University)

Barkanova Physics Online CAP2021.pdf

W2-3 Medical applications of imaging - Part 2 (DPMB/DAPI) / Applications médicales de l'imagerie - Partie 2 (DPMB/DPAI)

Convener: Melanie Martin (University of Winnipeg)

328 (I) Noble gas MRI: A Decade of Progress Towards Clinical Translation

Inhaled hyperpolarized gas lung MRI was proven to be useful for the observation and treatment planning of several pulmonary diseases including chronic obstructive pulmonary disease, asthma, COVID-19 and lung cancer. The combined economic burden of COPD and asthma in Canada, Ontario being $5.7 billion (2011). While these statistics are alarming, they don’t fully reflect the impact on economic growth and the opportunity costs that stem from such a large number of chronically ill Canadian adults and children. Moreover, both asthma and COPD are progressive and punctuated by sudden, acute worsening of symptoms or “exacerbations” that require immediate medical care – a source of enormous stress on our healthcare system. Lung cancer caused the premature deaths of 21,100 Canadians in 2017 (with an additional 28,600 being diagnosed), accounting for 26% of all cancer related deaths in Canada. People who are diagnosed with lung cancer are most likely to survive if the tumour can be surgically removed. However, nearly 1 in 4 Canadians who have their lung tumour surgically removed have lung complications following surgery called “postoperative pulmonary complications.” Presently, there is very little effort to predict these complications. So, it is not surprising that there has been a growing interest in developing new lung imaging techniques such as hyperpolarized 129Xe MRI to better understand various disruptive pulmonary, cardiac & neurodegenerative chronic diseases. In Canada, four research sites (London, Hamilton, Toronto, and Thunder Bay) have started a 129Xe MRI program, and two other sites (Vancouver, Montreal,) are in the preparation stage. Collectively, these Canadian sites urgently need novel 129Xe MR imaging methods as well as an advanced hardware package including a static-cell xenon polarizer, RF coil asymmetric unshielded rigid transmitter and multi-channel phased array receiver. Thinking about 129Xe’s place in MRI research globally, it is known that presently, 129Xe lung MRI is translating towards a clinical tool, and it has recently been approved and used as a clinical tool in the UK and USA. This opens door for better diagnoses, treatment planning and treatment assessment of patients with chronic lung, COVID-19, cardio and neuro diseases.

Speaker: Prof. Alexei Ouriadov (The University of Western Ontario)

329 Sino Canada Health Institute Intra-Operative MRI

Accurately targeting specific regions of interest in the brain is pivotal for the success of neurosurgical procedures. For example, the outcome of brain tumor resection is improved dramatically when surgeons are better able to define surgical borders. Interventional MRI (iMRI) helps reduce the risk of damaging critical areas of the brain and makes it possible to confirm a successful resection or determine the need for further resection prior to closing a patients head and finalizing the surgery.
The Sino Canada Health Institute (SCHI) is developing a small, lightweight movable system for performing intra-operative magnetic resonance imaging. The scanner will be based on a rampable magnet that can be energized and moved into place over the patient for surgical procedures. When not in use, the magnet will be discharged and stored locally in a small room. Moving the scanner will be facilitated by a track mounted crawler system allowing it to be transported and positioned as needed. The use of optical guidance will ensure precise, consistent placement of the scanner to within 1mm. This will be crucial when taking post-surgery images as consistent alignment with the pre-surgery images is important. A modular approach is being explored such that this technology can be integrated into existing hospitals around the world. Highly optimized rf coil arrays will be employed to help ensure imaging quality, and in addition, novel image reconstruction techniques will be used during post-processing. This will provide the opportunity to achieve high resolution images at relatively low field strengths (of order 1T).
In this talk I will provide details about the design and development of the SCHI iMRI system. This will include technical specifications relating to the magnet mover, rf coil development, as well as provide the latest results from tests of the prototype system.
The authors wish to acknowledge funding from NSERC partnership grants, and Mitacs.

Speaker: Michael Lang (University of Winnipeg)

330 Direct current coil designs for a portable magnetic resonance scanner

Magnetic resonance imaging (MRI) is a powerful non-invasive imaging technique with high resolution and excellent soft tissue contrast. However, access to MRI is limited by the high instrument cost and high maintenance cost. Current scanners cannot be easily relocated because of their size and weight. A low cost, portable scanner will enable point-of-care diagnosis as well as other industrial applications such as agriculture disease screening.
In MRI experiments, a highly homogenous static magnetic field is required to ensure image quality, which is usually achieved by the direct current (DC) shimming coils. Magnetic field gradients are generated by DC gradient coils for spatial encoding. The portable magnetic resonance scanner requires novel DC coils due to the unconventional single-sided configuration. The magnetic field distribution, heat dissipation and volume constraint must be considered in the design. Recent development on shimming and gradient coils for a portable magnetic resonance scanner and future applications will be presented.

Speaker: Ms Jordyn Matthews (University of Windsor)

331 Optimizing Radiofrequency Coils for Single-Sided Portable Magnetic Resonance

Magnetic resonance imaging (MRI) is an imaging modality that offers superior soft tissue contrast without ionizing radiation. MRI requires a static magnetic field and a radiofrequency (RF) magnetic field. The static magnetic field is usually provided by a superconducting magnet, where the high cost limits its accessibility. A portable magnetic resonance device based on a permanent magnet is extremely cost-effective and could provide point-of-care diagnosis for near surface organs. However, the permanent magnet has a low magnetic field strength and severe field inhomogeneity, which bring new challenges for quantitative measurements. The RF magnetic field is generated by the RF coil, which should be designed for the individual MR system. In this work, RF coils are investigated in search for the optimal performance configuration.
A single-sided magnet, based on the design of a three-magnet array [1], provides a static magnetic field with a homogenous volume of approximately 1 cm3 centered 1cm from the surface. The static magnetic field (0.1T) is parallel to the magnet surface. Multiple RF coil configurations were investigated, including a surface loop coil, a D-loop coil, and a meander line coil. The RF magnetic fields were simulated. The coils were constructed and tuned to 4.4MHz. Magnetic resonance experiments were performed on a water phantom. The signal bandwidths and signal-to-noise ratios were evaluated.
The preliminary results indicate further optimization is required for this highly complex system. It will be beneficial to design an RF coil producing a radiofrequency magnetic field that matches the static magnetic field distribution. The open MR system provides an affordable complement to the traditional high field MRI.
Reference: [1] Marble, JMR 186, 100-104 (2007).

Speaker: Ms Doris Rusu (University of Windsor)

W2-4 Application of Atmospheric Pressure Plasmas I (DPP) / Applications des plasmas à pression atmosphérique I (DPP)

Convener: Ahmad Hamdan (Université de Montréal)

332 (I) Controlling Non-thermal Plasmas in Contact with Liquids

The success of non-thermal plasmas in a broad range of applications in materials, medicine, and for the environment lies in their high reactivity at non-equilibrium conditions [1]. Cold atmospheric pressure plasma sources operated with air or noble gases allow plasma treatment at ambient conditions. Plasmas can thus induce novel chemistry into sensitive environments such as nano-scaled structures and biological organisms. In many of these environments, liquid interfaces play a major role, mediating the plasma interaction effect [2].
Applications in biomedicine, nanotechnology and material processing, and environmental science range from wound healing, to assisting cancer therapy, to surfactant free nano-particle synthesis, to water purification. Especially, the clinical results of therapeutic application of plasmas have increased worldwide research in plasma medicine [3]: It has been found that plasma can produce those reactive oxygen and nitrogen species which are known to play a vital role in cell communication. These essential plasma-generated species form a reaction system with complex pathways.
For targeted plasma-application, a precise control of plasma chemical pathways is necessary: Tailoring the plasma chemistry is possible when reaction pathways especially of transient highly reactive species are known. These transient species, which exist only for fractions of a second, initiate all subsequent reaction chains. The talk will address how to identify dominant pathways within the complexity of the respective plasma caused chemical reaction kinetics taking into account the entire plasma-liquid system [4]. Sub-nanosecond dynamic processes can be unravelled with ultrafast non-linear laser spectroscopy, studying turbulent phenomena and stochastic interaction processes at the interfaces. Based on these insights, non-equilibrium physico-chemical processes can be developed that are otherwise only achievable either with by-products of severe ecological impact or at high temperatures not applicable for modification of sensitive systems such as living organisms.

References:
[1] X. Lu, et al., Reactive species in non-equilibrium atmospheric-pressure plasmas: Generation, transport, and biological effects, Physics Reports, 1, 630 (2016)
[2] P.J. Bruggeman, et al., Plasma–liquid interactions: a review and roadmap, Plasma Sources Science and Technology, 053002, 25 (2016)
[3] T. von Woedtke, et al., Plasmas for medicine, Physics Reports, 291, 530 (2013)
[4] S. Reuter, et al., The kINPen—a review on physics and chemistry of the atmospheric pressure plasma jet and its applications, Journal of Physics D: Applied Physics, 233001(51), 51 (2018)

Speaker: Stephan Reuter (Polytechnique Montreal)

333 (G*) Statistical investigation on the number and electrical charge of streamers propagating at air-water interface under various discharge conditions.

Non-thermal plasmas produced by nanosecond discharges is a novel field of plasma physics that have huge interest for medical physics or in liquid treatments due to their high reactivity. Although this field is under investigation since more than one decade, our understanding of the fundamental mechanisms is still at an embryonic level. Moreover, when such a plasma is coupled with a solid or liquid surface, novel processes are identified.

In this paper, we study the dynamics of pulsed nanosecond discharges produced by a positively polarized voltage in air in contact with water. The investigated parameters are the gap distance between the anode and the water surface and the volume of water. The former was adjusted from 10 to 1000 μm, while the latter was adjusted at 20, 60, and 160 ml. These different volumes produce a water film that has a thickness of ~6, 17, and 45 mm, respectively. The discharge dynamics, under different magnitude of voltage (from 8 to 20 kV) was monitored using ICCD camera, and the acquired images were integrated during 2ns.

We observed that the streamer ignites in air at the anode tip and propagates towards the water surface. Initially, it has a disk-like shape that evolves (after a few nanoseconds) to a ring. Another few nanosecond later, the ring breaks into dots that propagate on the water surface. Automated statistical analysis performed on a large number of bullets as well as on their electrical characteristics has revealed that each plasma dot has a constant charge (~ 3-5 nC), regardless the discharge condition.

As for the influence of the gap distance, we observed that its augmentation leads to a reduction of the plasma dots number. This finding can be interpreted by the decrease of the electric field at water surface as well as by the available energy (or charge) in the streamer when this latter reaches the water surface. As for the influence of water volume, we find that the number of dots and the charge pert dot are not significantly affected. However, the propagation velocity is highly affected. More quantitative results will be provided during the conference.

Speaker: Antoine Herrmann (Université de Montréal)

13:25 Open discussion period

W2-5 Fields and Strings II (DTP) / Champs et cordes II (DPT)

Convener: Rainer Dick (University of Saskatchewan)

334 (I) Conformal Field Theory in Embedding Space

We develop the embedding space formalism and determine the full operator product expansion relevant to conformal field theories in arbitrary spacetime dimensions. With the operator product expansion, we then show how to compute generic conformal blocks for correlation functions with any number of quasi-primary operators in arbitrary irreducible representations of the Lorentz group. Concentrating on four quasi-primary operators, we demonstrate how the embedding space formalism can be used to explicitly write down all four-point conformal bootstrap equations. The resulting equations are expressed in terms of generalized four-point scalar conformal blocks, which are somewhat reminiscent of the seed conformal blocks.

Speaker: Jean-Francois Fortin (Laval University)

335 (I) Holographic Complexity in Gravitational Collapse

Through the AdS/CFT correspondence, properties of a quantum field theory are equivalent to geometric quantities in the bulk of anti-de Sitter spacetime. The complexity of the QFT state at some time is conjectured to be either the volume of a slice through AdS or the action on a patch of AdS. We evaluate both types of complexity during the gravitational collapse of a scalar field in AdS, which can have oscillatory behavior prior to forming a black hole horizon, and we determine whether the complexity is quasiperiodic or has a ratcheting behavior as the scalar wave undergoes focusing during collapse.

Speaker: Andrew Frey (University of Winnipeg)

336 Quantum field theory with minimum length

Theories of Quantum Gravity predict a minimum measurable length and a corresponding modification of the Heisenberg Uncertainty Principle to the so-called Generalized Uncertainty Principle (GUP). However, this modification is non-relativistic, making it unclear whether the minimum length is Lorentz invariant. We formulate a Relativistic Generalized Uncertainty Principle, resulting in a Lorentz invariant minimum measurable length and the resolution of the composition law problem. This proved to be an important step in the formulation of Quantum Field Theory with minimum length. We derived the Lagrangians consistent with the existence of minimal length and describing the behaviour of scalar, spinor, and $U(1)$ gauge fields. We calculated the Feynman rules (propagators and vertices) associated with these Lagrangians. Furthermore, we calculated the Quantum Gravity corrected scattering cross-sections for a lepton-lepton scattering. Finally, we compared our results with current experiments, which allowed us to improve the bounds on scale at which quantum gravity phenomena will become relevant.

Speaker: Vasil Todorinov (University of Lethbreidge)

337 (G*) Numerical Loop-Integration Methods for Thermal Field Theory

The basic structure of quantum field theory that is used to describe the Standard Model of fundamental interactions of nature is usually formulated for zero temperature. However, the effects of temperature are extremely important for understanding a number of physical processes such as the electro-weak phase transition and quark-gluon plasma. Thermal field theory is the extension of quantum field theory to a non-zero temperature environment and is achieved by modifying the propagators in loop integrations represented by Feynman diagrams. The Python program pySecDec numerically calculates dimensionally-regularized loop integrals in quantum field theory using the sector decomposition approach. It is shown how pySecDec can be applied to thermal field theory numerical calculations using modifications within the Matsubara formalism. Using the formulated algorithm, a 2-point correlation function (such as those occurring in QCD correlation functions) at finite temperature can be numerically calculated for a variety of spacetime dimensions.

Speaker: Siyuan Li (University of Saskatchewan)

338 Bandlimited UDW detector dynamics on 2+1 flat and spherical spacetimes

The potential breakdown of the notion of a metric at high energy scales could imply the existence of a fundamental minimal length scale below which distances cannot be resolved. One approach to realizing this minimum length scale is construct a quantum field theory with a bandlimit on the field. We report on an investigation of the effects of imposing a field bandlimit on a curved and compact spacetime. To achieve this operationally, we couple two Gaussian-smeared UDW detectors to a scalar field on a S^2 x R spherical spacetime through Dirac-delta switching. Delta switching allows for a non-perturbative analysis that includes higher order effects due to the bandlimit. The bandlimit is implemented through a cut-off of the allowable angular momentum modes of the field. We find that the detectors are less sensitive to the bandlimit on the spherical spacetime, and observe features similar to flat spacetime. These include the response of the detectors depending on their geometry and that smaller detectors couple in a stronger manner to the field.
We also explore two squeezed detector setups in both flat and spherical spacetimes, and find notable difference between the two cases. Due to the compact nature of spherical space, the lack of dissipation of any perturbation to the field results in locally excited signals of the field traveling from pole to pole in the spacetime. Quite strikingly, squeezing increases the response of the detectors in flat space but decreases the response on the spherical spacetime. Moreover, we find that squeezing on a sphere introduces extra anisotropies that could be exploited to amplify or weaken the response of the second detector.

Speaker: Ahmed Shalabi (University of Waterloo)

13:04 Questions/Answers and Discussion Period

W2-6 Experimental Nuclear Physics I (DNP) / Physique nucléaire expérimentale I (DPN)

Convener: Wolfgang Schreyer (TRIUMF)

339 (G*) Nuclear 2$\gamma$ decay of $^{98}$Mo and $^{98}$Zr at the TITAN-EBIT

Nuclear 2$\gamma$ decay is a second-order electromagnetic interaction wherein two photons are simultaneously emitted during a nuclear de-excitation. This transition is uniquely sensitive to the electromagnetic polarizability of the nucleus and has been studied in non-competitive cases for $0_2^+ \longrightarrow 0_1^+$ transitions between the first excited and ground states of even-even nuclei. So far, observations of the non-competitive case have been limited to the closed-shell nuclei $^{16}$O, $^{40}$Ca, and $^{90}$Zr. An important constraint to nuclear structure theories can be provided through experimental observations of 2$\gamma$ transitions in nuclei that exist away from shell closures. However, such cases have eluded further experimental observation, among other reasons, because of a strongly competing internal conversion (IC) branch. We propose to use the TITAN Electron Beam Ion Trap (EBIT) at TRIUMF to selectively block the IC branch by stripping the atom of all electrons which will allow the observation of 2$\gamma$ transitions in $^{98}$Mo and $^{98}$Zr. The experimental concept, status of development, and simulated results will be reported.

Speaker: Zachary Hockenbery (TRIUMF/McGill University)

340 Measurements of polarization power of TUCANs UCN SCM polarizer and prototype spin analyzer

The TUCAN collaboration is developing a new source of Ultracold neutrons (UCN) that will be used in a neutron Electric Dipole Moment (nEDM) experiment, with a goal sensitivity of 10^(-27) e*cm which is 10 times more precise than the best measurement to date. UCNs are neutrons with energies below 300 neV, that are travelling with speeds less than 30 km/h. In order to carry out a world-leading nEDM experiment, high densities of UCN need to be produced as well as precise measurements of the UCN polarization. Initially, we polarize UCN with a super conducting magnet (SCM). These UCN are then loaded into a pair of measurement cells with high E and B fields. In one cell the E and B fields are parallel and in one cell the fields are antiparallel. In the cell the UCN are subjected to a pi/2 pulse, rotating their spin 90-degree to the fields. The rotated spins then free precess, after which they are then rotated back by a second pi/2 pulse. The measured change in the final polarization state is related to a change in precession frequency. The difference of precession frequencies between cells related to a nEDM is then due to the differing directions of E-field direction. So final polarization state is the handle by which we measure an nEDM. In this talk I will discuss measurements of the SCM polarization power and the prototype spin analyzer components analyzing power, as well as simulations of these tests and relevant systematics.

Speaker: Sean Hansen-Romu (University of Manitoba)

341 (G*) The characterization of a spatially resolved multi-element laser ablation ion source

We report on the development of a multi-element ion source for calibration of a multi-reflection time of flight mass spectrometer. A laser ablation ion source (LAS) has been developed that can deliver specific, diverse species of ions from multi-element targets. It has been demonstrated that different target materials may be selectively ablated with a spatial resolution lower than 100𝜇m. Ion bunches produced by laser-ablation of the target surface will be used to characterize the ion extraction and identification capabilities of the Ba-tagging system. The latter is being developed as a future upgrade to the nEXO experiment, which is a proposed neutrinoless double beta decay experiment that will deploy 5-tonnes of liquid xenon enriched in the isotope Xe-136 in a time-projection chamber. The projected sensitivity of nEXO is 10^28 years. Ba-tagging may allow for the unambiguous identification of a candidate 0νββ event as a true ββ decay and increase the sensitivity of nEXO.

We will present the LAS as well as systematic studies on spatial resolution that have been performed.

Speaker: Kevin Murray (McGill University)

342 Search for the high-spin members of the $\alpha$:2n:$\alpha$ band in $^{10}$Be

There is strong evidence that some states in $^{10}$Be exhibit a molecular-like $\alpha$:2n:$\alpha$ configuration. Based on theoretical studies, it appears that the $6.179$ MeV 0$^{+}$ state in $^{10}$Be has a pronounced $\alpha$:2n:$\alpha$ configuration with an $\alpha$-$\alpha$ inter-distance of $3.55$ fm [Itagaki and Okabe, (2000)]. This is 1.8 times more than the corresponding value for the $^{10}$Be ground state. The 2$^{+}$ at 7.542 MeV in $^{10}$Be is believed to be the next member of this rotational band. The state at 10.2 MeV was identified as a 4$^{+}$ member in recent experiments. The algebraic model predicts that the terminating member of this band is the 6$^{+}$ state that should be found around 13 MeV. We performed an experiment to search for the 6$^{+}$ state in $^{10}$Be at around 13 MeV excitation energy in the excitation function for $^{6}$He+$\alpha$ scattering. Stringent limits on the properties of such a state have been established using Monte Carlo methods. The results of this study will be presented.

Speaker: Dr Sriteja Upadhyayula (TRIUMF)

W2-7 Instrumentation II (DNP) / Instrumentation II (DPN)

Convener: Jeffery Martin (The University of Winnipeg)

343 Barium extraction from Xe Gas and identification for nEXO

The proposed nEXO experiment is searching for neutrinoless double beta decay (0νββ) in 136-Xe in a tonne-scale liquid xenon time-projection chamber (TPC). If observed, 0νββ will reveal the Majorana nature of neutrinos and violation of lepton number conservation. Searches for such extremely rare events require excellent background suppression and rejection methods to achieve high sensitivities. The identification or “tagging” of the xenon-136 ββ decay daughter barium-136 offers a very powerful discrimination technique and is being investigated as a potential upgrade for nEXO. By leveraging the 3D reconstruction of the TPC, a sample of xenon surrounding a candidate 0νββ event can be extracted to tag the Ba daughter, if present. To this end, an apparatus is being developed to take a gaseous sample of xenon and extract a barium ion to high vacuum using a RF ion funnel. The ion is then trapped in a linear Paul trap (LPT) and identified via laser spectroscopy in the LPT. The mass is then confirmed in a multi-reflection time of flight (MRTOF) spectrometer. The status of the Ba-ion cooling, trapping and identification will be discussed.

Speaker: Dr Christopher Chambers (McGill University)

CAP2021_mk2.pdf

CAP2021_mk2.pptx

344 Magnetic Field Requirements for the TUCAN nEDM Experiment

The TUCAN collaboration is preparing to make a precision measurement of the neutron's permanent electric dipole moment, $d_n$, with a sensitivity of $\sigma(d_n)\leq10^{-27}e\cdot cm$. To reach the goal sensitivity it is required to have highly uniform and well understood magnetic fields in the measurement cells. With ambient magnetic fields on order of hundreds of $\mu \rm T$, passive magnetic shielding combined with compensation and shim coils are required to achieve the needed field uniformity
($\sigma(Bz) < 40\,\rm pT$) and stability over several measurement cycles.

A magnetically shielded room (MSR) will reduce external fields by a factor of $100,000$, and provide magnetic fields with gradients of $0.1-1\,\rm nT/m$ in its interior. Inside the MSR a cosine theta coil will be used to provide a $1\mu\,\rm T$ holding field in which the neutron's spins will precess during the measurement process. Additional trim and shim coils will be used to reduce non-uniformities in the magnetic field, with dedicated coils to be used for systematics studies.

In this presentation I will summarize our collaboration's strategy to obtain sufficient information about the shape and strength of the magnetic field such that it can be modified and characterized to fulfill the measurement requirements. This covers items such as ambient field compensation coils around the MSR, highly accurate offline magnetic field mapping inside the MSR, and high precision magnetometry and co-magnetometry during the actual measurement of $d_n$.

Speaker: Mark McCrea (University of Winnipeg)

345 Time-dependent thermal modeling for the TUCAN source

I will discuss two time-dependent models of systems relevant to the cryogenic function of TRIUMF Ultra-Cold Advanced Neutron (TUCAN) source. The first is a natural circulation system (thermosyphon) which cools the LD$_2$ moderator. The moderator experiences a heat load of 60~W for the design proton beam current of 40~$\mu$A, and is cooled to 20~K using a distant cryocooler at higher elevation. The thermosyphon features no moving parts and single-phase (liquid) operation. A key discovery made through these studies is that the thermosyphon will continue to flow despite the finite duty cycle with the proton beam pulsing at minute-long timescales. The second example relates to time-dependent models of heat transport in superfluid helium (He-II). At full beam power, $\sim$10~W of heat must be transported by thermal conduction via a 2.5~m long, horizontal channel of He-II to a Cu heat exchanger, while keeping the UCN production bottle at $\sim 1$~K. Normally, we think of He-II as having infinite thermal conductivity. But at lower temperatures or high heat loads, heat transport via the normal component is impeded by vortex tangles in the superfluid component. This Gorter-Mellink thermal conduction regime is expected to limit the cooling of the UCN production volume, and it has led us to drastically change the layout of our (horizontal) UCN source upgrade compared to the previous (vertical) source. I will discuss the time-dependence of temperatures, modelled for both sources, and compared with data in the case of the vertical source.

Speaker: Shawn Stargardter (University of Manitoba)

346 Francium 7S - 8S Stark spectroscopy as a precursor to atomic parity violation tests.

Low-energy precision tests of electro-weak physics keep playing an essential role in the search for new physics beyond the Standard Model. Atomic parity violation (APV) experiments measure the strength of highly forbidden atomic transitions induced by the parity violating (PV) exchange of Z bosons between electrons and quarks in heavy atoms. APV is also sensitive to additional interactions such as leptoquarks, and is complementary to other approaches such as PV electron scattering. Our group is working towards a measurement in francium (Z=87), the heaviest alkali, at TRIUMF where we capture Fr atoms in a magneto-optical trap (MOT) online to ISAC. The APV signal in Fr is $\approx 18\times$ larger than in Cs. Working on the atomic 7S-8S transition, the PV observable will be the interference between a parity-conserving amplitude, the $``$Stark induced$"$ E1 amplitude created by applying a dc electric field, E, to mix S and P states, and the vastly weaker PV-induced amplitude. In preparation, we now explore the Stark amplitude, in particular the ratio of its scalar, $ \alpha$, ($E \;|| \; \epsilon$) and vector, $\beta$, $(E \perp \epsilon)$ components, where $\epsilon$ is the laser polarization. APV tests will require an accurate value for $\beta$, and the measurement of $ {\alpha}/{\beta}$ will provide an important benchmark for theory providing $\beta$. I will discuss our plans for a precision determination of this ratio, including the challenges of producing spin-polarized Fr in a MOT environment and the sub-ms switching of magnetic fields.

Supported by NSERC, NRC, TRIUMF, U Manitoba, U Maryland.

Speaker: Anima Sharma (TRIUMF)

W2-9 Contributed Talks II (DCMMP) / Conférences soumises II (DPMCM)

Convener: Michel Gingras

347 Valley-controlled transport in graphene/WSe2 heterostructures under an off-resonant polarized light

We investigate the electronic dispersion and transport properties of graphene/WSe$_{2}$ heterostructures in the presence of a proximity-induced spin-orbit coupling $\lambda_{v}$, sublattice potential $\Delta$, and an off-resonant circularly polarized light of frequency $\Omega$ and effective energy term $\Delta_{\Omega}$. Using a low-energy effective Hamiltonian we find that the interplay between different perturbation terms leads to inverted spin-orbit coupled bands. At high $\Omega$ we study the band structure and dc transport using the Floquet theory and linear response formalism, respectively. We find that the inverted band structure transfers into the direct band one when the off-resonant light is present. The valley Hall conductivity behaves as an even function of the Fermi energy in the presence and absence of this light. At
$\Delta_{\Omega}$ = $\lambda_{v}$ - $\Delta$ a transition occurs from the valley Hall phase to the anomalous Hall phase. In addition, the valley Hall conductivity switches sign when the polarization of the off-resonant light changes. The valley polarization vanishes for $\Delta_{\Omega}$ = 0 but it is finite for $\Delta_{\Omega}$ $\neq$ 0 and reflects the lifting of the valley degeneracy of the energy levels, for $\Delta_{\Omega}$ = 0, when the off-resonant light is present. The corresponding spin polarization, present for $\Delta_{\Omega}$ = 0, increases for $\Delta_{\Omega}$ $\neq$ 0. Further, pure $K$ or $K^{\prime}$ valley polarization is generated with respect to the sign change in $\Delta_{\Omega}$.

Speaker: Muhammad Zubair (Concordia University)

12:48 Questions & answers

348 Coherence transfer in two-pulse double quantum (DQ) and five-pulse double- quantum modulation (DQM) sequences in EPR: Orientation selectivity and distance measurement

Double-quantum (DQ) coherence transfers in two-pulse DQ and five-pulse DQM (double quantum modulation) EPR pulse sequences, utilized for orientation selectivity and distance measurements in biological systems using nitroxide biradicals, are investigated. Analytical expressions, along with numerical algorithms, for EPR signals are given in full details. It is shown, in general, that a finite pulse, as opposed to an infinite pulse, in conjunction with dipolar interaction between the two nitroxide radicals, is needed to produce non-zero coherence transfers in 02 and 2-1 transitions. Furthermore, the simulations show that the coherence transfer, T02, as effected by a finite pulse, is found to increases as the amplitude of the irradiation field (B1) decreases, being maximum for those coupled nitroxides, whose dipolar axis, i.e., the line joining their dipoles, relative to the external magnetic field, are oriented symmetrically about the angle \theta_0 ~ {54.47}^\circle, at which \left(3cos^2\theta-1\right)=0, for 0^\circle\le\theta\le{90}^\circle, at \pm{10}^\circle from \theta_0 , being symmetric about \theta={90}^\circle in the range 0^\circle\le\theta\le{180}^\circle. It is noted that there is no such value possible for d\le 10 MHz. This is a new result, as far as orientational sensitivity of the forbidden DQ signal is concerned, found here with the help of long quantitative simulations for the first time. In addition, it is shown that only measurements involving one time variable are needed to obtain the Pake doublets in polycrystalline (powder) samples to determine the dipolar constant, proportional to the inverse cube of the distance between the nitroxide radicals. The analytical expressions, derived here for the various signals for fixed orientations of the two nitroxide dipoles with respect to the dipolar axis, oriented at angle \theta with respect to the external magnetic field, show that, in general, the Fourier transforms of the two-pulse DQ sequence exhibit peaks at \pm\frac{3}{2}d\times\left(3cos^2\theta-1\right), whereas the five-pulse DQM sequence exhibits peaks at \pm d\times\left(3cos^2\theta-1\right); where d=\frac{2}{3}D, with D being the dipolar-coupling constant. Furthermore, it is found that the signals from two-pulse DQ and five-pulse DQM sequences are sensitive to the orientations of the two nitroxide dipoles, described by the Euler angles (\alpha_1,\beta_1,\gamma_1);(\alpha_2,\beta_2,\gamma_2). This provides structural sensitivity to the two-pulse DQ and five-pulse DQM signals, useful for understanding details of the configuration of biomolecules. As for the numerically calculated polycrystalline (powder) averages, accumulated over 20 sets of Monte-Carlo orientations of the two nitroxide dipole moments, it is found that the Pake doublets occur at \pm\frac{3}{2}d for the two-pulse DQ sequence and at \pm d for the five-pulse DQM sequence. The magnitudes of coherence transfers in the transitions 02 and 2-1 are found to be about the same; they depend on the amplitude of the irradiation field, as well as on the duration of the pulse. They increase significantly with increasing strength of the dipolar interaction, d, as calculated here for d=10\ and\ 30 MHz, corresponding to the value of r\ =\ 17 and 11 Å. The effect of relaxation in polycrystalline samples is considered by the use of a stretched exponential. The numerical algorithm for the five-pulse DQM sequence presented here is exploited to calculate the intensity of the five-pulse DQM signal to fit the published experimental data; a good agreement is found within the experimental error.

Speaker: Hamidreza Salahi (Concordia University)

12:53 Questions & answers

349 Electronic transport properties of tailored two dimensional materials for chemical sensors

Nanoscale sensors are widely used in industrial, environmental, and healthcare applications. The performance of chemical sensors depends on the host materials properties; low dimensional materials, e.g. graphene or carbon nanotubes, can be used as host materials to detect chemicals in the environment. These materials provide wide surface area per unit of volume capable of hosting concentrations of impurities, and they exhibit conductivity that is sensitive to chemical perturbations. In this work, we obtain the electronic transport properties of low dimensional materials to improve sensitivity and selectivity features of nanoscale chemical sensors. Volatile organic compounds, in the vicinity of the host, can cause alterations in their electronic properties. These alterations, such as variances in the energy-dependent conductance, can be investigated and categorized for each chemical component. We aim at solving the inverse-problem in which the hitherto unknown chemical impurities and their concentrations are determined by analyzing the conductance variance they impart onto the host. Our goal is to quantify the conductance fingerprint that some organic compounds induce on the host and to propose ways of improving the device sensitivity based on these findings.

Speaker: Ms Maryam Abarashi (University of Calgary)

12:58 Questions & answers

350 Modeling Amorphous Silicon Using Neural Networks

In this work, we present a method based on deep learning (DL) to predict the structure of amorphous silicon (a-Si). The accuracy of our approach is validated through training networks to estimate the potential energy. Two architectures, multilayer perceptron (MLP) and convolutional neural network (CNN), have been examined for this purpose.
The models have been trained on a dataset generated by molecular dynamics (MD) simulations. The dataset consists of 216-atom a-Si configurations.
The performances of the two architectures over the test set are compared while they have the same total number of parameters and layers.
The results of training these two neural networks yield a
root mean square error of the order of 0.1 meV/atom. This error was reported in the range of 2-6 meV/atom in previous works [1-3], which confirms the accuracy of our models. Calculation of the average error shows that CNN performs better than MLP.
After validation of our approach, we trained a generative model, variational autoencoder (VAE), to generate a-Si configurations. The generated structures and their structural properties are comparable to the real ones.
In general, the performances of our models are quite satisfactory, and this suggests that they could be used to approximate the potential energy and generate a-Si structures, and thus be a viable model for investigating disordered systems.

References:
1. Li, R., Lee, E. and Luo, T., 2020, A unified deep neural network potential capable of predicting the thermal conductivity of silicon in different phases, Materials Today Physics 12, 100181.
2. Comin, M. and Lewis, L.J., 2019, Deep-learning approach to the structure of amorphous silicon, Physical Review B 100, 094107.
3. Behler, J. and Parrinello, M., 2007, Generalized neural-network representation of high-dimensional potential-energy surfaces, Physical Review Letters 98, 146401.

Speaker: Dr mojde fadaie (University of Montreal)

13:03 Questions & answers

351 Reducing Majorana Hybridization via Periodic Driving

It is an ongoing challenge to engineer setups in which Majorana zero modes at the ends of one-dimensional topological superconductor are well isolated which is the essence of topological protection. Recent developments have indicated that periodic deriving of a system can dynamically induce symmetries that its static counterpart does not possess [1]. We further develop the original protocol [2] where this idea [1] is applied to a system of quantum dot (QD) coupled to a Kitaev chain hosting an imperfect (overlapping) Majorana zero modes. We numerically simulate a protocol in which an electron periodically hops back and forth from the QD and the wire. We demonstrate that the current protocol reduces a non-zero hybridization energy that manifests from imperfect Majoranas by orders of magnitude. Furthermore, we examine the efficiency of the suppression and how robust it is to imperfections.

[1] K. Agarwal and I. Martin, Phys. Rev. Lett. 125, 080602 (2020).

[2] I. Martin and K. Agarwal, PRX Quantum 1, 020324 (2020).

Speaker: Brett Min (McGill University)

13:08 Questions & answers

352 Identifying and Isolating Flat Bands in 2D Systems

Flat band systems are becoming popular due to special properties. For instance, the strong correlation of electrons leads to realization of unconventional superconductivity [1]. Typically, such bands are only approximately flat and are engineered by fine tuning Vanderwaal’s structures. Here we consider Kagome and Lieb lattices with perfectly flat bands. However, at some points in the Brillouin zone the bands superimpose leading to degeneracies. It has been shown that the degeneracy can be lifted when time-reversal symmetry (TRS) is broken [2]. In this presentation, we explore further means to lift the degeneracy while preserving the flat band. We show that the flatness is robust under certain changes to the lattice and that breaking TRS is not sufficient to isolate the flat band. Instead, we show that modulating the flux based on Chern-Simons field as outlined in [3] successfully gaps out the band.
[1] Cao, Y. et al. (2018). Unconventional superconductivity in magic-angle graphene superlattices. Nature, 556(7699), 43-50
[2] Green, D., Santos, L., & Chamon, C. (2010). Isolated flat bands and spin-1 conical bands in two-dimensional lattices. Physical Review B, 82(7).
[3] Maiti, S., & Sedrakyan, T. (2019). Fermionization of bosons in a flat band. Physical Review B, 99(17).

Speaker: Jun Hyung Bae (Concordia University)

13:13 Questions & answers

353 Symmetry Breaking Effects of Instantons in Parton Gauge Theories

Transitions between fractionalized and conventional quantum phases of matter in 2+1 dimensions are conceptually best understood within the framework of parton gauge theories, whereby the confinement of fractionalized excitations and spontaneous breaking of global symmetries in conventional phases is argued to result from the proliferation of gauge monopoles/instantons. To complement recent studies of the quantum numbers and scaling dimensions of monopole operators in parton gauge theories of frustrated quantum antiferromagnets, we provide an explicit semiclassical derivation of instanton contributions to the low-energy effective parton gauge theory for hardcore bosons on the honeycomb lattice using methods originally developed by 't Hooft in the solution of the U(1) problem in quantum chromodynamics. While the symmetry-breaking effect of instantons is typically associated with massless fermions and the Atiyah-Singer index theorem on compact manifolds, we show that the spontaneous breaking of the U(1) boson number conservation symmetry in the superfluid phase results here from Euclidean zero modes of massive Dirac fermions bound to instantons in noncompact spacetime.

Speaker: Shankar Ganesh (University of Alberta)

13:18 Questions & answers

354 Interplay Between Electrostatic and Hydrophobic Interactions in Aqueous Dispersions of OSA-Modified Phytoglycogen Nanoparticles

Phytoglycogen is a natural polysaccharide produced in sweet corn in the form of compact, 42 nm diameter glucose-based nanoparticles. Its highly branched, dendritic structure leads to interesting and useful properties that make the particles ideal as unique additives in personal care, nutrition and biomedical formulations. The properties of phytoglycogen can be altered through chemical modification. We consider the covalent attachment of charged, hydrophobic octenyl succinic anhydride (OSA) chains to the weakly charged, hydrophilic surface of phytoglycogen. When dispersed in water, the OSA-modified particles develop solid-like rheological behaviour with increasing concentration and exhibit a well-defined yield stress at a concentration much smaller than that for native phytoglycogen dispersions. The yield stress vanishes as either salt is added to the system or the pH of the dispersions is reduced below the pKa of the acidic group of OSA, with the material transitioning from a shear-sensitive gel to a flowing liquid to ultimately precipitating out of solution at the highest salt concentrations or lowest pH values. This result highlights the unique interplay between the electrostatic and hydrophobic interactions of the particles and suggests new applications for OSA-modified phytoglycogen.

Speaker: Ms Carley Miki (University of Guelph)

13:23 Questions & answers

13:30 15 Minute Break

W-POS-A #1-4 Poster session (DPE) / Session d'affiches (DEP)

Convener: Daria Ahrensmeier (Simon Fraser University)

355 (G*) POS-A1 -- Mapping the Landscape of Physics Education Research in Canada

This presentation is based on a subset of data from a doctoral project on Physics Education Research (PER) in Canada. Current data describing the landscape of PER in Canada will be shared, offering a characterization of Canadian PER and the people who conduct it. The aim of the presentation is to increase the physics and PER community’s knowledge and understanding of this field beyond the minimal description it has previously received (e.g., young and growing).
People who engage in PER were considered the best representation of the field, and therefore all Canadian PER engagers were sought out for study participation. Methods of identifying PER people included 1) requesting names of Canadian physics education researchers from editors at the Canadian Journal of Physics and committee leaders of the Division of Physics Education and the Division for Gender Equity in Physics at the Canadian Association of Physicists, and 2) conducting an online search for Canadians engaging in PER. Specifically, content analysis, whereby text is systematically examined for variables of interest, was conducted for online faculty profiles at all 96 Canadian universities’ physics and education departments. Across Canada, 150 people were identified as having possible engagement with issues related to the teaching and learning of physics.
To confirm researchers’ PER engagement and learn the areas of research on which they focus, a survey was distributed to all 150 people. Respondents were asked questions about demographics and their PER engagement. The survey response rate was 36.6% (n=55) and results confirmed PER engagement for 42 people in Canada. Detailed results including geographic, demographic, and PER engagement data will be shared in the presentation to describe PER in Canada and the people who conduct it.

Speaker: Lindsay Mainhood

356 POS-A2 -- Home-Based Labs to Develop Broadly Applicable Scientific Skills and Attitudes

First-semester physics labs typically aim to confirm and mirror relationships explored in the lectures. Often using computer-interfaced equipment to measure physical variables, students investigate relationships with time or other variables. We took our move to online delivery in the pandemic as an opportunity to re-think physics labs. We report here a suite of remotely delivered labs developed to introduce scientific attitudes and skills. Emphasized attitudes were collaboration, creativity, perseverance, decision making, communication, and innovation. Skills such as moving from question to hypothesis, spreadsheet basics, linearization, and introductory statistics leveraged simple experiments (time to roll down a ramp, period of a pendulum) into hands-on introductions to scientific tools and ways of thinking. We abandoned the lab manual model, instead requiring students to create plans and communicate their work. Experiment plans included details on the objective/hypothesis, equipment used, experimental setup, detailed procedure of data acquisition, and specifics of data analysis. Sharing created plans occurred before data acquisition. Choosing not to rely on each student having a particular device, we explored kinematics using basic household items, and analysis utilized university-provided Microsoft Excel. Focusing on physics-specific nomenclature (such as uncertainty) gave way to adopting standardized statistical ideas like t-prime comparisons. We believe these labs emphasize attitudes and skills that are more valued across the scientific disciplines than those typically developed in traditional introductory physics labs.

Speakers: Mark Paetkau (Thompson Rivers University), Arnold Sikkema (Trinity Western University)

357 (U*) POS-A3 -- Investigating the Gender Gap in Introductory Physics Courses

The observed gender gap in physics testing is a problem which plagues physics education. Many studies in universities across North America show that female students consistently perform worse than male students on written examinations and concept inventories, though the size of this performance gap varies from study to study. In some cases, this gender gap in performance has been linked to more negative perceptions and lower confidence in physics among female students. The goal of our study was to determine if there is a gender gap in perceived confidence and interest in physics at the introductory level. 
An online survey was distributed to the three streams of introductory physics students at McMaster University which had students answer a range of questions about their undergraduate degree, background, comfort, confidence, and other metrics. We asked students to rate their interest and preparedness in physics before and after taking their introductory course. Upon analysis of these results, a clear gender gap was observed in key areas such as perceived confidence within the course, and the student's level of interest in physics. Female students consistently reported lower perceptions of preparedness and interest in the course relative to their male counterparts. However, when analyzing the change in interest and confidence, the gender gap greatly varied dependant on the introductory stream. An online survey will also be distributed to upper year physics students to probe whether the confidence and interest gap extends throughout undergraduate degrees, or whether the gap narrows as students get accustomed to the university environment. Lower confidence in first year could negatively impact the performance of female physics students at McMaster and could contribute to a lack of gender diversity in upper year physics programs.  
The affirmation of the student gender gap in confidence within introductory physics courses at a large Canadian institution is a troubling but crucial step in creating a welcoming and inclusive physics education environment for all students.

Speaker: Daniel Dobrowolski (McMaster)

358 (U*) POS-A4 -- Students’ Preferences and Participation in Introductory Physics Courses in an Online Environment

Introductory physics courses are required at McMaster for students in a pure physics stream, engineering stream, or life sciences stream. The background preparation of these students, as well as their attitudes towards the course, can vary greatly. There lies huge importance in identifying topics and aspects of introductory physics courses that students enjoy and find challenging as a key method to improving their overall understanding and experience. Additionally, with the recent switch to fully online teaching methods, the way in which students approach their lecture content and participate in classroom activities has also changed. Examining the online lecture attendance in comparison to in-person lectures is a useful way to see what aspects of an online model are beneficial to carry forward once on-campus classes return. 

In this study, a survey was distributed to students in three streams of introductory physics courses, with an open-ended question to identify what they enjoy and find most challenging in physics. Students were able to answer with specific topics covered in the course or general aspects of physics (problem-solving, math, etc.). Interestingly, students enjoyed real-life applications of physics the most, while finding the math and problem-solving aspects of the course most challenging. Kinematics was the most liked topic, while the most challenging topic varied depending on the choice of stream. A similar survey will be distributed to students after they complete a second introductory physics course, allowing this question to be assessed again, as well as their comfort with mathematics, and the topics they deem most relevant to their field of study.  By examining these additional questions, we hope to clarify why students from different science disciplines prefer specific topics, and whether students continue to struggle with the same topics as they progress into upper-year physics courses.

These results can be used as a tool in identifying areas of introductory physics courses that should be improved to help with students' overall understanding and experience.

Speaker: Nitara Fernando (McMaster University)

W-POS-B #5-8 Poster session (DPP) / Session d'affiches (DPP): Poster session

Convener: Lenaic Couedel (University of Saskatchewan)

359 (G*) POS-B5 -- production of Ag nanoparticles by spark discharge in heptane in contact with solution

Plasma-liquid systems are significantly investigated due to their high potential in the production of various nanomaterials. In addition to relatively high efficiency and simplified infrastructure, they are ecologic and do not have any risk during handling as they are confined in solution. In this paper, we develop a novel plasma-liquid technique to produce nanoparticles. Indeed, spark discharges are sustained in heptane (a dielectric liquid) and are in contact with a conductive solution. The solution was silver nitrate and distilled water. Due to the interaction between the spark, which has a high density of species, high pressure, and high temperature, and silver ions, these latter are reduced, then they aggregate as nanoparticles.
Liquid samples from both liquids (heptane and solution) were collected and characterized using different techniques. The results show that material collected from the heptane side is nanocomposite, silver nanoparticles (< 10 nm) in carbon matrix; relatively larger (10-45 nm) of Ag embedded in carbon shell were also found in the sample. The sample collected from the solution presents Ag particles with 10-150 nm of diameter. Discharges run at shorter pulse width (100 ns) results in the same material in both liquids, but the size distribution of nanoparticles was relatively smaller.

Speaker: Kyana Mohammadi

360 POS-B6 -- Impurity transport modelling in a magnetron discharge

Recently, it was observed that under high pressure (p > 10Pa), nanoparticles could be created using sputtering magnetron discharges. Although this device has been widely studied at low gas pressure (p < 0.1Pa) for its industrial application such as thin film coating, there is no plasma model at the fairly high pressure range. The study of physical mechanism driving the transport of these nanoparticles can, for example, give insights on tokamak impurity and dust agglomeration problem.

Experimental studies are in progress at PIIM laboratory in Marseille where magnetically confined plasmas are generated using argon sputtering magnetron discharge with a tungsten cathode (p = 30Pa) [1, 2].

In that context, we propose to develop a reliable numerical model in order to investigate the transport of sputtered tungsten atoms in the discharge as done experimentally at PIIM laboratory. Usually, cold plasma discharges are simulated using PIC-MC or kinetic models [3-5], but we would like to present here the 2D axisymmetric fluid model. We refer to the work of C.Costin [6] which is a low pressure (< 4Pa) 2D magnetron fluid model on a similar geometry setup, extending it to high pressure case including the sputtered tungsten particles in the device. Some results (plasma potential, density profiles of different species…) from the first numerical simulations allowing to validate the model and the code are displayed.

References
[1] Couëdel, L., Arnas, C., Acsente, T., and Chami., A., AIP Conf. Proc., Proceedings of the 8th ICPDP, Prague, (2017).
[2] Arnas, C. et al., Phys. Plasmas 26, 053706 (2019).
[3] T. M. Minea et al., Surface and Coating Technology 116, pp. 558-563 (1999)
[4] I. A. Porokhova et al., Physical Review E 63.5, 056408 (2001)
[5] G. J. M. Hagelaar et al., Journal of Applied Physics 93.1, pp. 67-75 (2003)
[6] Costin, C. et al., Plasma Sources Science and Technology 14.1, 168 (2005)

Speaker: Jong Hern MUN (Aix-Marseille Université, CNRS, PIIM UNR 7345, Marseille, France)

361 POS-B7 -- Optical Emission Interferometry for Monitoring of Plasma Processes

We present our simple and cost-efficient setup for real-time monitoring of substrate thickness in plasma etching/deposition processes. Thin film interference occurs as light from the plasma passes through the substrate material, by observing the cycles of peaks and troughs in the intensity, the rate of etching/deposition was obtained.

Speaker: Mr Yu Ying Chang (Plasmionique)

362 (G*) POS-B8 -- Measurements of a DC Gas Discharge

The DC gas discharge is a non-thermal laboratory plasma that is initiated by an applied electric field. It serves as a useful apparatus for studying fundamental phenomena in plasma physics and has found several applications in materials science and engineering. In contrast to thermally ionized plasma, the distribution function of a gas discharge deviates from Maxwellian at low pressures. It is affected by a high-energy tail due to accelerated electrons and is truncated by inelastic collisions. To have a good understanding of particle kinetics within the plasma, measurements of the distribution function are important. Fortunately, this is made possible with the Langmuir probe diagnostic. In addition to measurement of the distribution function, Langmuir probes can also directly measure several important plasma properties including the electron temperature and plasma density. Furthermore, spatially separated probes can measure gradients in potential that can be used to infer an electric field. To investigate properties of gas discharges and to evaluate the design and implementation of a Langmuir probe diagnostic, an array of several probes was designed and inserted into an intermediate pressure DC gas discharge. Before the Langmuir probe experiments, measurements of the discharge were performed including obtaining IV characteristics and determining breakdown voltages for several gases. Images of the discharges were recorded using a USB camera and emission spectra were obtained using a visible light spectrometer. Langmuir probe measurements were then taken of the electric field in the cathode region and IV characteristics were obtained to determine plasma properties: both by a graphical method and by the calculation of the electron energy distribution function (EEDF) from the second derivative.

Speaker: Edward DeWit (Queen's University)

CAP_2021_Poster.pdf

W-POS-C #9-16 Poster session (DAPI) / Session d'affiches (DPAI)

Convener: Steffon Luoma

363 (G*) POS-C9 -- Energy Compression System Radio Frequency Design at the Canadian Light Source

The Canadian Light Source (CLS) is considering a linear accelerator (LINAC) upgrade. As a result, the radio frequency (RF) structure in the downstream Energy Compression System (ECS) needs to be redesigned. In this paper, we describe the design process followed to determine the geometry of the RF structure cells and coupler. Wakefield simulation results are also presented. The wakefields and input RF fields are applied to beam dynamics simulations.

Speaker: Evan Ericson (Canadian Light Source)

364 (G*) POS-C10 -- Vertical phase space measurement at Canadian Light Source

A key feature of third-generation light sources is their small vertical opening angle, which is difficult to measure experimentally. To reconstruct the vertical phase space, one can scan the beam’s position using X-ray synchrotron radiation (XSR) and a pinhole camera. The XSR diagnostic beamline, operational in the wavelength region of $\lambda$= 0.05 - 0.15 nm, in Canadian Light Source (CLS) is qualified to measure the beam position with X-ray radiation. Using the corrector magnets in CLS lattice made of 12 identical double-bend achromats (DBA) cells, vertical iterations of 100 $\mu$m can be executed parallel to the beam's original orbit. The outcomes of this experiment are: 1) the vertical beam positions that are monitored by BPMs on both sides of the X-ray’s source point, 2) the X-ray image of the beam that is projected through the pinhole and converted to visible light to be captured on the CCD camera. The bumps were simulated using Matlab Middle Layer (MML) for Accelerator control systems to get an insight of the source point's position in the XSR's bending magnet. The simulation shows the position of the source point depends on which corrector sets are chosen. To make a truly parallel bump in the DBA sector and to be able to calculate the source point's actual position, critical in reconstructing the vertical phase space, a particular set of correctors should be chosen.

Speaker: Yasaman Yousefi Sigari (University of Saskatchewan)

365 (G*) POS-C11 -- Design and Simulation of Transparent Injection Upgrade for the CLS Storage Ring

The Canadian Light Source (CLS) synchrotron uses four fast kicker magnets to inject electrons into the storage ring from a 2.9 GeV booster ring. The injection occurs over several turns of the stored beam, which is also perturbed by the injection kickers. The resultant oscillations of the stored beam can negatively affect the quality of beamline experiments, so it is desirable to implement an injection scheme which does not disturb the stored beam. Injection schemes of this type allow for transparent injection and are very desirable for the planned top-up operations of the CLS storage ring. Many alternative injection techniques have been presented in recent years and we have examined several of these techniques as they apply to the CLS storage ring. Pulsed multipole magnets and a non-linear kicker are the most viable alternatives for integration with the current ring. Non-linear kicker designs are also being considered for the proposed CLS 2.0 and studying this injection method in the limitations of the current machine provides additional insight to guide the work on the new machine. Simulation with the accelerator code ELEGANT shows the viability of the non-linear kicker design as developed at BESSY, MAX IV and SOLEIL (other synchrotron facilities) for transparent injection at the CLS.

Speaker: Patrick Hunchak (University of Saskatchewan)

366 (G*) POS-C12 -- Studies of seawater spray icing phenomena with unilateral NMR

Sea spray icing is created by wind/wave-induced spray in harsh arctic and antarctic environments. It is reported that sea spray icing causes hazardous conditions and operational problems for vessels and offshore structures. Nuclear Magnetic Resonance (NMR) is a powerful tool that can provide information about local environment, diffusion, and structure of a sample containing NMR-sensitive nuclei. NMR studies of sea ice are well-known for investigating seawater brine properties and structure. However, typical NMR instruments are big, expensive, and they cannot be moved outside a scientific laboratory. Also, seaspray icing hasn’t been studied with NMR until very recently (Wilbur et al, JMR, 2020). This study was focused on how to measure freezing of a sea-water spray with a portable, unilateral NMR instrument consisting of a handheld 3-magnet array.
For our instrument, the 1H NMR signal was generated approx. 1 cm away from the magnet surface, in the presence of a constant 250 G/cm magnetic field gradient. The pulse sequence used in this study was a combination of the Hahn and CPMG sequences (the CPMG echoes could be either added to increase the SNR, or used for obtaining T2 information). An optimum quality factor for a desired slice thickness was chosen to increase the sensitive volume. Additionally, we explored 1D-imaging with a unilateral NMR by performing Fourier Transform of the echoes acquired in the presence of the constant gradient.
The following parameters of NMR signal from freezing seawater accumulating on a cold surface inside the sensitive volume were measured and analyzed: signal intensity (proportional to the brine concentration), T2 relaxation, and diffusion for a range of temperatures (from-6oCto-14oC) and for two different surface orientations (horizontal and vertical). Results showed differences in signal intensity caused by ice growth rates at different temperatures. The diffusion was highly dependent on temperatures and surface orientations. This study shows that portable NMR devices can be useful for studies of seawater freezing, and freezing in general.

Speaker: Shahla Ahmadi

367 (G*) POS-C13 -- Analyzing Growth/Damp curves in the Canadian Light Source storage ring

The Transverse Feedback system at the Canadian Light Source can identify, categorize, and mitigate against periodic instabilities that arise in the storage ring beam. By quickly opening and closing the feedback loop, previously mitigated instabilities will be allowed to grow briefly before being damped by the system. The resulting growth in the beam oscillation amplitude curve can be analyzed to determine growth/damp rates and modes of the coupled bunch oscillations. Grow/damp curves will be collected and analyzed for various storage ring beam properties, including beam profile density, beam energy, machine chromaticity, injection instability, insertion device gap width, or bunch fill patterns. These results will be used to characterize the known instability growth rates, and search for unknown instability modes that may cause stability problems in the future. The instability analysis in the CLS will also impact the design of future insertion devices that might be added for new beamlines and the design of the CLS2 ring which is being planned.

Speaker: Stephen Martens (University of Saskatchewan)

368 (U*) POS-C14 -- Hyper-Kamiokande Photosensor Test Facility Recommissioning and System Upgrades.

The Hyper-Kamiokande (Hyper-K) experiment is the next generation of the Super-Kamiokande (Super-K) and T2K experiments investigating a breadth of physics topics including neutrino oscillation. The Hyper-K far-distance detector will contain ~40,000 20” photomultiplier tubes (PMTs), while the Intermediate-distance Water Cherenkov detector (IWCD) will contain ~500 multi-PMTs (each containing 19 3” PMTs). To minimize systematic errors in their measurements, a precise understanding of the PMTs’ intrinsic parameters, such as their detection efficiency and timing as a function of the incident photon position and angle, as well as their response to variations in magnetic field, is required.
These parameters can be measured at TRIUMF’s photosensor test facility (PTF). This facility characterizes PMTs by emitting a laser beam from robotic arms that enable fine control of the beam’s 3D position and orientation. The light wavelength and polarization can also be varied to mimic Cherenkov light. Additionally, the facility uses 6 Helmholtz coils to create and control the magnetic field.
Currently, the PTF is being recommissioned in a new location, farther from the magnetic interference of the on-site cyclotron. This poster will outline the software, hardware, and mechanical upgrades being implemented to improve the facilities robustness and the stability and accuracy of the measurements. These upgrades include mechanical modifications to simplify the process of inserting and removing the PMTs as well as the implementation of motor encoders, environmental sensors, and software to prevent collisions of the robotic arms during reflectivity measurements. Moreover, this poster will cover the modelling and measurement of the environmental magnetic field in the facility to reduce the time required to complete the magnetic field compensation process.

Speaker: Skylar Wingfelder (TRIUMF)

369 (G*) POS-C15 -- X-ray Doubleslit Interferometer Progress at CLS

The Canadian Light Source (CLS) is a 3rd generation synchrotron in Saskatoon that is used to produce extremely bright synchrotron light that can be used for research. The light at the CLS is produced by an electron storage ring which has an emmitance of 20 nm. A 4th generation synchrotron (CLS2) is planned which will reduce the emmitance to less than 1 nm and thus reduce the transverse beam size significantly, making it very challenging to measure. A doubleslit interferometer can be used to measure small transverse beamsizes. An x-ray doubleslit interferometer will be designed and manufactured for the current CLS with the goal of using this setup at CLS2. Various constraints require the doubleslit to have dimensions on the micrometer scale, making the manufacturing very difficult.

Speaker: Nicholas Simonson (University of Saskatchewan)

370 POS-C16 -- Femtosecond Streaking in Ambient Air

We demonstrate a novel method to measure the temporal electric field evolution of ultrashort laser pulses. Our technique is based on the detection of transient currents in air plasma. These directional currents result from subcycle ionization of air with a short pump pulse and the steering of the released electrons with the pulse to be sampled. We assess the validity of our approach by comparing it with different state-of-the-art laser-pulse characterisation techniques. Notably, our
method works in ambient air and facilitates a direct measurement of the field waveform, which can be viewed in real time on an oscilloscope in a similar way as a radio frequency signal.

Speaker: Kyle Johnston

W-POS-D #17-27,110 Poster session (DPMB) / Session d'affiches (DPMB)

Convener: Emily Heath

371 (U*) POS-D17 -- Quantification of Sensitivity and Specificity in a Laser-Induced Breakdown Spectroscopy Diagnostic Assay for Pathogenic Bacteria Detection and Classification

Laser-induced breakdown spectroscopy (LIBS) is a laser-based spectrochemical technique that allows a near-instantaneous measurement of the elemental composition of a target by making time-resolved spectroscopic analyses of laser-induced ablation plasmas. Utilizing nanosecond laser pulses and a broadband high-resolution Echelle spectrometer, high signal-to-noise optical emission spectra can be obtained from almost any desired target.

When the ablation target contains bacterial cells, the inorganic elements present in the bacterial cells (phosphorous, magnesium, calcium, and sodium) can be used to discriminate the bacteria on the basis of their atomic emission spectrum alone. Currently, we deposit bacterial cells onto a nitrocellulose filtration medium by centrifuging very low titer liquid specimens through a custom-fabricated centrifuge tube insert device. Prior to centrifugation, the bacteria cells are obtained by swabbing abiotic surfaces upon which a known number of bacteria cells have been deposited. The cells are then shaken off the disposable pathology swabs into a water suspension in a vortex mixing instrument.

Spectra from five different bacterial pathogens and pathogen surrogates (Staphylococcus epidermidis, Escherichia coli, Mycobacterium smegmatis, Pseudomonas aeruginosa, and Enterococcus faecalis) and sterile water control specimens have been obtained along with spectra from sterile deionized water control specimens.

This presentation will detail our efforts to identify and optimize chemometric algorithms for the autonomous classification of unknown spectra. Algorithms such as principal component analysis (PCA), discriminant function analysis (DFA), partial least squares discriminant analysis (PLSDA), and artificial neural networks (ANN) have been investigated. Rates of sensitivity and specificity have been determined and will be presented for the various techniques. Efforts to use chemometric algorithms to discriminate low-titer suspensions from blank water specimens and thus calculate limits of detection and limits of identification will also be discussed.

Speaker: Emma Blanchette (University of Windsor)

372 (G*) POS-D18 -- Investigating normalizing methods for X-ray fluorescence measurements of Zinc in nail clippings using TOPAS Monte Carlo code

Development of portable X-ray fluorescence devices has made it easier to quickly assess trace elements such as zinc in human tissue. Zinc deficiency can have serious implications on growth and development of the human body. From recent studies zinc content in nail clippings has been suggested to be an effective biomarker for zinc status. In this study, a simulation approach was used to investigate the use of a portable X-ray fluorescence system for detecting the variation of zinc signal with respect to nail thickness and was compared with the experimental results. The portable X-ray device was modelled using the available information from the manufacturer using the TOPAS Monte Carlo code (Geant4 simulation software).The simulations were carried out for varying nail phantom thickness (0.2 mm – 1.2 mm) with concentration of 1000 ppm zinc. Each simulation was run for 10^9 histories and the statistical uncertainty was less than 3.5%. The obtained energy spectra from different measurements were analyzed and three different normalization techniques (Coherent, Compton and Entire) spectrum were investigated to account for the variation of sample interrogated by the X-ray beam. Close agreement between simulation and experimental trends were observed indicating successful benchmarking of the simulation. Compton and Coherent normalization followed a slightly negative trend. One other important observation was coherent normalization can be a robust normalization procedure to improve the accuracy of elemental quantification in order to reduce the variability in nail thickness by ~8%. Overall the simulation approach can provide additional insights into elemental analysis in keratin based nail phantoms.

Speaker: Mr Utsav Sharma (Ryerson University)

13:49 WITHDRAWN : POS-D19

373 (U*) POS-D20 -- 3He/129Xe MRI as a Tool to Track Emphysema Progression in Alpha-1 Antitrypsin Deficiency Patients

RATIONALE: Hyperpolarized gas MRI is a powerful tool to track lung progression using biomarkers (ADC and mean linear intercept estimate (Lm)). Sometimes, longitudinal observations can lead to problematic values, as the disease progression can lead to increasing unventilated lung areas, which likely excludes the largest3 ADC/Lm values. We hypothesize that this morphometry method can provide an accurate assessment of the progression. For this work, we used the SV & ADC/Lm data acquired using the traditional approach (3He data, 2014) and our method (129Xe data, 2018).
METHODS: 4 AATDs provided written informed consent to an ethics board approved protocol and underwent two visits, four years apart that included CT, spirometry, plethysmography, DLCO and MRI including anatomical 1H, 3He/129Xe diffusion-weighted (DW) & SV imaging. 3D 3He/129Xe MRI-based ADC and lung morphometry maps were generated using the stretched-exponential-method4 which was extended and adapted for both 3He/129Xe to provide clinically-relevant biomarkers of emphysema.5
RESULTS: 3He/129Xe MRI-based lung morphometry data were converted to the VDP/ADC/Lm maps. The global VDP/ADC/Lm estimates for all subjects and both contrast agents (3He (2014) and 29Xe (2018)) were computed from the correspondent maps. The VDPHe/VDPXe & LmHe/LmXe values were compared directly.
DISCUSSION: Over the four-years, we showed that ADC/Lm can be used to estimate emphysema progression. These biomarkers showed decrease in lung health over the term. There was some notable decreases in ADC/Lm between 2014 and 2018, which would indicate an overall decrease in emphysema progression (p<0.01) contradicting the human being physiology. To resolve this contradictory, one can normalize the ADC/Lm biomarkers by corresponding VDP values, taking into account decreased lung volume. The feasibility of such approach has been recently demonstrated using the 3He SV & DW data. For future work, we plan to normalize the 129Xe ADC/Lm estimates by 129Xe VDP for an accurate assessment of the emphysema progression.

References
1 Mugler, J. P. et al JMRI 37, (2013).
2 Driehuys, B. et al. Radiol 262, (2012).
3 Kirby M et al. Radiol 265 (2012).
4 Westcott A et al JMRI 49 (2018).
5 Ouriadov A et al MRM 84 (2020).

Speaker: Elise Woodward (Western University)

374 (G*) POS-D21 -- Trade-offs between fluctuations and efficiency in stochastic complex formation processes

Understanding the physical limitations and trade-offs related to suppressing fluctuations in stochastic cellular processes is of great importance for systems and synthetic biology applications. We show that a generic class of complex formation processes in which two subunits associate to form a complex is constrained by a trade-off between the subunit fluctuations and the efficiency of complex formation. Previously this trade-off has been demonstrated in the special case that the subunit production rates are equal regardless of closed-loop feedback control. Here, we extend this result for asymmetric subunit production and arbitrary complex formation kinetics. We show that this trade-off can only be overcome with closed-loop feedback control in this case. However, preliminary numerical results suggest that the subunit fluctuations are supressed by the control mechanism at the expense of increasing fluctuations in the controlling variables, suggesting a general uncertainty principle in stochastic processes.

Speaker: Brayden Kell (University of Toronto)

375 (G*) POS-D22 -- Effect of Lung Surfactant Protein B Fragment, SP-B1-9 on Model Lipid Bilayer.

Effect of Lung Surfactant Protein B Fragment, SP-B1-9 on Model Lipid Bilayer.
Abinu, MHK, ISV, MRM

Lung surfactant is a mixture of protein and lipid that reduces surface tension at the air-water interface in the lungs and thus reduces the work needed to breathe. Two hydrophobic proteins, SP-B and SP-C, are thought to facilitate the re-spreading of fresh and recycled surfactant material from bilayer and multilayer reservoirs. In an earlier deuterium NMR study of bilayer model membranes containing either the SP-B fragment SP-B(1-25, 63-78) or the fragment SP-B(8-25, 63-78), it was found that lipid acyl chain orientational order was perturbed more strongly by SP-B(1-25, 63-78). Both fragments contain the first and last SP-B helices but differ in whether or not the insertion motif, SP-B1-7, is present, suggesting that the insertion motif might play a role in the capacity of SP-B to promote the bilayer reorganization implicit in lung surfactant function. To gain more insight into the interaction of the insertion motif with surfactant lipids, we have studied the effect of SP-B1-9 on lipid acyl chain order in DPPC-d62 /POPG(7:3) bilayers using deuterium NMR and GROMACS molecular dynamics simulations.
Using deuterium NMR at a peptide: lipid ratio of 0.065, we find that the peptide tends to disorder acyl chains in the liquid crystalline bilayer phase suggesting that it promotes an increase in average lipid headgroup separation. MD simulation of a bilayer model containing SP-B1-9 at a peptide: lipid ratio of 0.031 also shows a decrease in chain orientational order. The MD simulations also provide information about the average peptide orientation and conformation. These findings may provide a better understanding of the extent to which the insertion motif may contribute to the capacity of SP-B to promote reorganization of bilayer surfactant material.

Supported by NSERC Discovery Grants to MRM and ISV.

Speaker: Abinu Jyothini (Memorial University of Newfoundland)

13:57 WITHDRAWN : POS-D23

376 (G*) POS-D24 -- Simulation of collective motion in surface colonies of twitching bacteria using a dynamical self-consistent field theory for self-propelled rods

We use dynamical self-consistent field-theory simulations of interacting, self-propelled rods to study the fascinating time-dependent, inhomogeneous structures observed during the growth of a colony of twitching Pseudomonas aeruginosa bacteria confined at the interface between a glass substrate and agar. These collective patterns in colony growth are relevant to early-stage biofilm formation, to the spread of infection, and to our understanding of the surface-motility mechanism of these bacteria. Our focus is on colony fingers, which are long-lived, compact, dense domains of aligned bacteria which form at, and grow out from, the leading edge of the growing bacteria colony. We investigate how the strength of the self-propulsion and the density of bacteria affect the shape and speed of the fingers, as well as the degree of bacteria alignment within the fingers. In the presence of self-propulsion, a perturbation of an initially flat colony edge will evolve into a long finger. By introducing a random spatial variation of the glass-agar adhesion strength into the simulation, we produce finger structures and dynamics similar to what is seen in experiment.

Speaker: Drake Lee (University of Guelph)

377 POS-D25 -- Simulations of DNA-carbon nanotube interactions for the design of field-effect transistors biosensors

Bioanalytical sensors based on field-effect transistors (bioFETs) are emerging as promising tools to measure the kinetics of biopolymers such as proteins and DNA strands. This class of biosensors is based on an ultra-miniaturized electronic circuit whose conductance is very sensitive to the variations of the electrostatic potential in its environment caused by conformational changes in the biopolymer. Here, we investigate the working of a specific bioFET made of a single carbon nanotube to which is covalently grafted a single DNA strand of the G-quadruplex motif. More specifically, we use advanced sampling techniques based on molecular dynamics simulations to unveil the interactions and kinetics between the biopolymer and the carbon nanotube. We observed that, while the structural stability of the G-quadruplex motif is not significantly altered by the carbon nanotube, some interactions could modify its folding kinetics. We also investigated the origin of the device’s sensitivity by characterizing the electrostatic potential around the nanotube as a function of the biopolymer’s conformational ensemble. Our conclusions from computational simulations complement the experimental measurements obtained by our collaborators who characterized the same setup. Together, they support the development of this promising biosensor for monitoring the kinetics of biopolymers.

Speaker: Sébastien Côté (Université de Montréal)

378 POS-D26 -- Multi-Modality Comparison of Wrist and Ankle joints: A Feasibility Study

A prototype medical device has been developed and built at Western University to image adolescents with hemophilic arthropathy. The device consists of a plastic cylindrical tub able to rotate freely about a base plate. A 10 MHz linear array ultrasound transducer by Canon Medical Systems is mounted to the inside of the tub pointed toward its center. The tub is filled with water to act as a medium between the ultrasound transducer and the skin. The leg or arm is fixed, while a clinical ultrasound probe rotates over 360 degrees. 2D US images are recorded every 0.5 degrees, and reconstructed into a 3D volume in an inverse fan geometry. The 3D image provides a viewpoint that is unreachable in conventional 2D ultrasonography. The prototype design, study protocol workflow, and preliminary results will be presented; specifically showing corresponding anatomical landmarks between 3D ultrasound and MR images. The future work for the study is a clinical trial at SickKids Hospital in Toronto; whereby, ultrasound / MRI data from each subject will be viewed by two experienced musculoskeletal radiologists who are blinded to the other aspects of the study. Interpretations from both modalities will gauge the feasibility of this approach for use in imaging of hemophilic arthropathy in target joints.

Speaker: David Tessier (The University of Western Ontario)

379 (U*) POS-D27 -- Moving toward faster measurements of micron-sized axon diameters in vivo

Autopsy studies indicate that the distribution of axons throughout the brain could differ in brains with and without schizophrenia. MRI has inferred axon diameters and distribution in the brain, typically for axons larger than 5 μm in diameter. The goal of this work is to modify these methods to adapt oscillating gradients (OG) to target small axons (1 to 2 μm range) which constitute the majority of cortical connections and shorten the data acquisition time so that the method can be used to measure axon diameters in vivo.
Methods to determine micron-sized axon radii using oscillating gradients were too time-consuming for in vivo mouse imaging. The methods use many gradient frequencies, and a geometric model called AxCaliber which uses intracellular and extracellular compartments. Through simulations, we found that fewer gradient frequencies for data provided a good fit to the intracellular model, and in some cases, fewer frequencies led to a better fit to the model than more frequencies. A moderate correlation was found between the predicted axonal radius from the model and the actual axonal radius used in the simulations. In conclusion, reducing the number of gradient frequencies and gradient strengths appears to be possible, in theory, to reduce the imaging time by a factor of 4.16 without a significant change in the precision of the inferred axon radii. The method proposed here requires a priori knowledge of the desired cell sizes to be inferred. Imaging data, as well as electron microscopy data, need to be collected after reopening the lab after the pandemic to verify the theoretical predictions. This work is the first step to reducing the imaging time so that OG can be used with the AxCaliber model to infer 1-2 μm axon sizes.
The authors wish to acknowledge funding from Mitacs and NSERC.

Speaker: Mr Kaihim Wong (University of Winnipeg, Winnipeg, MB, Canada; University of Manitoba, Winnipeg, MB, Canada)

380 POS-D110 -- Radical pairs in the brain: xenon-induced anesthesia and lithium effects on hyperactivity

The human brain is a magnificent system with highly complex functionalities such as learning, memory, emotion, and subjective experience. Over the past decades, it has been proposed that quantum physics could help answer unsolved questions in life science. Here we present a quantum model that could shed light on the mechanisms behind xenon-induced anesthesia and the lithium effects on hyperactivity. It has been shown that the process of xenon-induced general anesthesia involves electron transfer, and the potency of xenon as a general anesthetic exhibits isotopic dependence. It has also been observed that lithium’s effects are isotope-dependent. Based on these findings, here we propose that xenon and lithium exert their effects by influencing the recombination dynamics of a naturally occurring radical pair involving oxygen. We develop a simple model inspired by the radical-pair mechanism in cryptochrome in the context of avian magnetoreception. Our model reproduces the observed isotopic dependence in the xenon anesthesia and the lithium treatment of hyperactivity. It predicts a magnetic-field dependence of the effectiveness of lithium on hyperactivity and the potency of xenon anesthetic,which provides one potential experimental test of our hypothesis. Our findings show that Nature might harness quantum entanglement for the brain’s cognitive processes.

Speaker: Hadi Zadeh-Haghighi (University of Calgary)

W-POS-E #28-40 Poster Session (DAMOPC) / Session d'affiches (DPAMOC))

Convener: Nisha Rani Agarwal (University of Ontario Institute of Technology)

381 POS-E28 -- Holographic optical manipulation of trapped ions for quantum simulation

Trapped ions can offer a functional platform for quantum simulation of many-body Hamiltonians modeled by spin-systems. Programmable, arbitrary and precise control over each ion is required in order to tune ion-ion interactions, which translate to diverse parameters of the system under study. Current technologies suffer from scalability issues to large ion chains, and from ``cross-talk'' due to micron-level inter-ion separation. Here, we report our development of a holographic optical ion-addressing setup for Yb$^+$ ions ($\lambda = 369.5$ nm) using a Digital Micromirror Device (DMD). This technique uses a reprogrammable hologram to modulate the wavefront of the addressing beam and thus engineer the amplitude and phase profile of light across the ion ensemble to better than $\lambda/20$. We implement a novel Iterative Fourier Transform Algorithm (IFTA) to compute the desired hologram. This algorithm efficiently compensates for optical aberrations and produces $<10^{-4}$ intensity cross-talk error in arbitrary pair-wise addressing profiles, suitable for over fifty ions. This scheme relies on standard commercial hardware, can be readily extended to over a hundred ions, and adapted to other ion-species and quantum platforms. Such high-precision optical control will enable the simulation of arbitrary and dynamic lattice geometries of spins to be realized in a 1D chain of ions. This technique will also allow us to investigate problems in quantum quench, quantum phase transitions, and physics of higher dimensional systems such as the creation of topological states.

We acknowledge financial support from University of Waterloo, US ARO, NSERC Discovery and NFRF grants, TQT (CFREF), and the Ontario Government.

Speaker: Roland Hablutzel (UWaterloo)

382 (G*) POS-E29 -- Simple Measurement for Field Reconstruction

Simple Measurement for Field Reconstruction

The temporal resolution of pump-probe experiments is determined by the duration of the excitation and measurement pulses. A major constraint on femtosecond ($1$ fs = $10^{-15}$ s) and attosecond ($1$ as = $10^{-18}$ s) science is how well we can control and compress these pulses. However, such ultrashort pulses require a broad spectrum with careful phase control across its bandwidth to minimize the duration. The temporal characterization of these pulses is crucial in establishing ultrafast experiments. For this reason, several pulse characterizing techniques have been developed, each with their own strengths and weaknesses [1].

In this paper, we discuss a new optical measurement technique that can directly measure the electric field that constitutes the laser pulse. We find that compared to other techniques for electric field measurements, our method is relatively inexpensive and robust in characterizing pulses up to 100 fs in duration. This method requires only a commercially available CCD camera as opposed to spectrometers or other expensive instruments and provides the ability to reconstruct the field without ambiguities [2]. In this way, we can directly measure the temporal evolution of the field amplitude and phase [3]. We find that the measurement is in good agreement with established characterization techniques.

References

[1] J. C. Diels and W. Rudolph. Ultrashort Laser Pulse Phenomena, chapter Diagnostic Techniques,pages 452–466. Elsevier, 2006.

[2] T. J. Hammond, A. Korobenko, Y. Naumov, M. Villeneuve, P. B. Corkum and D. H. Ko. Near-field imaging for single-shot wave form measurements.Journal of Physics, 51, February 2018

[3] E. Goulielmakis, M. Uiberacker, R. Kienberger, A. Baltuska, V. Yakovlev, A. Scrinzi, T. West-erwalbesloh, U. Kleineberg, U. Heinzmann, M. Drescher and F. Krausz. Direct measurement of light waves.Science, 305(5688):1267–1269, August 2004.

Speaker: Chathurangani Jayalath Arachchige (University of Windsor)

383 (G*) POS-E30 -- Quantum Gates in a Cold Atom System

Quantum computing requires the ability to prepare and manipulate arbitrary quantum states and read out results. Cold atom systems are a proven and highly versatile platform for the study of quantum computing and other aspects of quantum physics. They have been used to develop quantum memories, to study adiabatic quantum computing, and for quantum simulation.

In this work, we explore a variety of quantum computing operations that are possible in this cold-atom system, including those with non-trivial topological character. To work with qubits, we label particular $m_F$ states as $|1\rangle$ and $|0\rangle$. Our cold atoms also provide direct and convenient multi-qudit manifolds for study including qutrits (3 levels: e.g., the $m_F$ states in an $F=1$ hyperfine state) and ququints (5 levels: e.g., in an $F=2$ hyperfine state). In our system, this dimensionality can be dynamically adjusted as interactions with some levels can be suppressed by higher detuning (via the quadratic Zeeman shift) or by destructive interference between optical transition pathways.

Our apparatus uses ultracold atoms of ${}^{87}$Rb to simulate a wide array of Hamiltonians by coupling atomic states via optical, microwave, and modulated magnetic fields. Two-photon coupling between states is achieved by sending in two laser beams with a frequency difference $\Delta \omega_L$ matching the states’ energy difference, $\omega$. Microwave sources are used to directly couple between hyperfine levels. Meanwhile, the separation between Zeeman sublevels is controlled by changing the strength of an external magnetic field.

After state preparation and quantum operations are performed, we measure the output via the populations in each $m_F$ state by Stern-Gerlach imaging. To fully characterize a state, the phases of $m_F$ states need to be determined. In some cases, this information can be found by re-generating the state, then applying operators which have a known effect. For example, by applying a tuned $\frac{\pi}{2}$ rotation to a qubit before imaging, information about the x- and y-populations can be discerned in addition to the z-populations. Because of the wide array of tools available for the manipulation of ultracold atomic systems, they are a powerful platform for the study of quantum computing.

Speaker: Joseph Lindon (University of Alberta)

384 (G*) POS-E31 -- Quantum Simulation of the Quantum Kicked Top

The connection between quantum entanglement and classical chaos has puzzled physicists for decades. To understand chaos in the quantum context, it is necessary to explore signatures of chaos in the deep quantum regime, where the quantum-classical correspondence cannot be invoked. A common approach is to study the quantum kicked top, which is a finite-dimensional quantum system that displays chaotic dynamics in the classical limit. Few experimental realizations of the quantum kicked top have been achieved for small number of time steps and low chaoticity parameters. However, the problem of accurate experimental realization of long-term dynamics and large range of chaoticity parameter in the quantum kicked top is still unsolved. In this work we propose and demonstrate an exact simulation of the 2-qubit quantum kicked top on a universal quantum computer. Our proposal allows for arbitrary time steps and chaoticity parameter without compromising experimental fidelity. Using the IBM 5-qubit quantum chip we physically demonstrate the theoretical connection between delocalization and entanglement. We obtain a phase space plot of time-averaged entanglement in the deep quantum regime, which surprisingly reflects the classical phase space structure. Since chaos is known to generate entanglement in the quantum kicked top, our proposed method could be useful in Quantum Information Processing.

Speaker: Sayan Gangopadhyay (University of Waterloo)

385 POS-E32 -- Optical design challenges of subnivean camera trapping under extreme arctic conditions

Camera trapping is widely used in different ecological studies and is particularly important for remote locations and extreme environments. However, due to certain optical challenges of adapting this approach to small rodents, combined with the logistical and environmental issues, it was not possible to use camera traps for subnivean observation during the arctic winter before. The frost formed on each lens of the camera preventing it from working continuosly during the whole winter season.

In this work we propose an optimized camera trap design, that allowed us to obtain the first videos of lemmings in winter, when direct observations are impossible. We also suggest a design of tunable liquid-crystal lens that has a potential to considerably improve the image quality. This lens can provide a range of optical powers from around 1 to 10D and is fully controlled by an external electric field application, so it does not require any mechanical movement. This lens has a low power consumption and can be adapted to the temperature change during the year (from around -20°C to +20°C). Using such a lens with an autofocus algoritm will help to obtain enough details on each animal for individual recognition.

Speaker: Anastasiia Pusenkova (Université Laval)

386 POS-E33 -- Light-induced dissociation dynamics of Br2

When a chemical bond breaks, all valence electrons in the bond will re-arrange and transfer as the nuclei are separating. The dynamical information of such electronic re-arrangement processes will be encoded in the kinetic energy of the ions if the breaking neutral molecule is ionized, allowing us to follow the entire electronic re-arrangement process by only observing the ions. Here, using Cold Target Recoil Ion Momentum Spectroscopy (COLTRIMS) and a pump-probe experiment in the bromine molecule. we show how the single ionization reveals the bond breaking while the double ionization measures the separation distance of the neutral dissociating bromine molecule. In addition, we also studied the vibrational wave packet dynamics of bromine single ion, which is pumped by a strong 800nm pulse and probed by another weak 400nm pulse.

Speaker: Mr Tian Wang (university of Ottawa)

387 POS-E34 -- Photonic Cooperativity and Coherence in Tubulin Architectures

From cytoskeleton to centriole, we investigate the photonic inner workings of the living cell. The cytoskeleton provides the structural organization of the cell, as the supporting architecture for all known forms of life. A major structural unit of this architecture is the cellular “microtubule,” a hollow tubular body composed of individual units of the protein “tubulin” organized in an array of spiral-shaped components. Recently, it was proposed that microtubules may exhibit useful photonic properties, as well as a myriad of known structural features. In this work, we explore the role that photonic super-radiance may play in facilitating excitonic transport and communication within the cellular architecture, from the cytoskeleton to the eukaryotic centriole—and beyond.

Speaker: Nathan Babcock (Howard University)

388 (G*) POS-E35 -- Novel Methods for Pulse Compression

Strong field physics, femtosecond (1 fs = $10^{-15}$), and attosecond (1 as = $10^{-18}$) science require intense ultrashort laser pulses for excitation and measurement. Although fs pulses can be generated directly from a laser amplifier, durations necessary for ultrafast science require spectral broadening and compression. The most common spectral broadening technique exploits the nonlinear interaction of intense pulses focused into gas-filled hollow-core fibres [1]. These fibres allow for a long interaction length to generate octave-spanning spectra while maintaining a near Gaussian spatial distribution. However, these fibres can be 1 – 3 metres on an optical table with additional 1 m focusing and collimating optics, and require continuous backfilled gas flow. More recently, the self-phase modulation in thin crystals broadens the spectrum and uses a self-focusing relay to maintain the beam quality [2]. A combination of solids and gases to generate a supercontinuum has been used to generate attosecond extreme ultraviolet (XUV) pulses [3]. Ultrashort pulses can have a wide variety of applications, including disrupting biological processes for medical procedures, observation of electronic processes on an attosecond scale, and generating XUV and soft X-ray pulses via high harmonic generation or terahertz via difference frequency generation [4]. Here, we compare numerically and experimentally the spectral broadening in solvents and crystals to demonstrate the potential for a compact setup for generating octave spanning pulses for ultrafast experiments.

We find that passing a beam through several cm of methanol produces a supercontinuum spectrum that can support few-fs pulses. Similar to the multi-plate thin crystal method, we place a series of 1 cm cuvettes of methanol around two foci in order to reduce self-focussing effects and to avoid filamentation within the material. We compress these pulses using dispersion compensating mirrors, and characterize the resulting pulses using frequency resolved optical gating (FROG) and a novel measurement scheme. Our simulations and models predict a sub-10 fs bandwidth-limited pulse resulting from two subsequent compressions using a total of 4 cm of methanol to generate a supercontinuum. Using this method, experimentally, we have achieved a broad spectrum capable of supporting sub-30 fs pulses.

[1] E. Haddad, R. Safaei, A. Leblanc, R. Piccoli, Y.G. Jeong, H. Ibrahim,B.E. Schmidt, R. Morandotti, L. Razzari, F. Légaré, P. Lassonde. "Molecular gases for pulse compression in hollow core fibers," Optics Express (2018).

[2] Y.-C. Cheng, C.-H. Lu, Y.-Y. Lin, and A. H. Kung, "Supercontinuum generation in a multi-plate medium," Optics Express (2016).

[3] T. J. Hammond, S. Monchocé, C. Zhang, G. Vampa, D. Klug, A. Y. Naumov, D. M. Villeneuve, and P. B. Corkum "Integrating solids and gases for attosecond pulse generation," Nature Photonics (2017).

[4] M. Cheng, A. Reynolds, H. Widgren, and M. Khalil, "Generation of tunable octave-spanning mid-infrared pulses by filamentation in gas media," Optics Letters (2012).

Speaker: Jacob Stephen (University of Windsor)

389 (G*) POS-E36 -- On the origin of the coherence of sunlight on the earth

We show that the observed far-field behavior of sunlight on the earth’s surface, located in the near-field region, is due to the small angular width it subtends at the center of the sun. The sun is modelled as an incoherent spherical source. The cross spectral density at the surface of the source is described by a Dirac delta function. The asymptotic far zone behavior of the cross spectral density function for small angle is then inferred from a Schrodinger like differential equation with an inverse square potential.

Speaker: Mr Sriram Sundaram (McMaster University)

390 (G*) POS-E37 -- Advanced modelling in computational nanophotonics

With advances in nanofabrication, modelling the optical properties of nanoscale systems is critical.

The optical response of nanostructures can be simulated using the bulk permittivity of the constituent materials (1). The permittivity is generally assumed time-invariant and spatially dispersionless. While these approximations are enough for the simulations of most systems, in some cases the physics must be modelled more precisely.

We present three recent projects on the modelling of complex optical properties with implications in active nanophotonics (2), ultrafast physics and nonlinear plasmonics. The algorithms we developed are unavailable in commercial or open-source software.

1.) Nonlocal models: for small nanostructures (< 10 nm) spatial dispersion cannot be neglected, and we need to account for the electron degeneracy pressure (3).

2.) Nonlinear hydrodynamics: The hydrodynamic plasma model is required to properly model conduction electron dynamics in strong optical fields (4).

3.) Time-variant permittivity: Electrodynamics combined with two-temperature modelling is required to calculate the optical response induced by nonlinearity in ITO under strong optical fields (5).

Our models combined with high-performance computing allow us to achieve accurate results and significant agreement to experiments.

References

1. Pernice, W. H. P. Finite-Difference Time-Domain Methods and Material Models for the Simulation of Metallic and Plasmonic Structures. J. Comput. Theor. Nanosci. 7, 1–14 (2010).

2. Shaltout, A. M., Shalaev, V. M. & Brongersma, M. L. Spatiotemporal light control with active metasurfaces. Science 364, eaat3100 (2019).

3. Baxter, J., Lesina, A. C. & Ramunno, L. Parallel FDTD modelling of nonlocality in plasmonics. ArXiv200506997 Phys. (2020).

4. Bin-Alam, M. S. et al. Hyperpolarizability of plasmonic meta-atoms in metasurfaces. ArXiv200705142 Phys. (2020).

5. Alam, M. Z., Schulz, S. A., Upham, J., De Leon, I. & Boyd, R. W. Large optical nonlinearity of nanoantennas coupled to an epsilon-near-zero material. Nat. Photonics 12, 79–83 (2018)

Speaker: Joshua Baxter (Department of Physics and Center for Research in Photonics, Uni)

391 (G*) POS-E38 -- Toward a spin-tensor-momentum coupled Bose-Einstein condensate

The spin state of an electron has a 3-dimensional vector representation. In spin-orbit coupling (SOC), an electron’s external momentum becomes linked to its spin vector. This phenomenon appears in many different systems, including atomic and crystal band structure, (quantum) spin-Hall systems, and topological insulators. Previous experiments have used Raman coupling to generate and study several forms of SOC in pseudospin-1/2 ultracold gases. A similar method has been proposed to couple a quantum gas’ linear momentum with a spin tensor - a representation of a higher (spin-1+) state. While possessing a rich ground state phase diagram, this spin-tensor-momentum coupled system also provides an opportunity to directly observe a dynamical supersolid-like stripe phase with a tunable stripe period. This poster reports our experimental progress toward producing and characterizing this novel state of matter using a Rb-87 Bose-Einstein condensate.

Speaker: Benjamin Smith

392 POS-E39 -- Photoelectron distributions of synthetically chiral light

Chiral enantiomers are notoriously difficult to differentiate as they have the same chemical and physical properties. Circularly polarized light has been shown to be able to distinguish between them, but the sensitivity is low, on the order of a few percent signal difference. However, in 2019 [1], an ultrafast multi-pulse scheme has been developed which can theoretically elicit responses of up to 100% signal difference between enantiomers, a remarkable jump from the past. This technique relies on measuring the harmonics produced by the chiral molecules. Our work instead focuses on measuring photoelectrons produced by this pulse scheme, comparing targets of increasing complexity, from simple atoms to chiral molecules.

[1] Ayuso et al, Nature Photonics, 13, 866–871, (2019)

Speaker: Zack Dube (National Research Council Canada)

393 POS-E40 -- Accurate numerical method for the calculation of the doubly excited states in atoms

We investigate in the present work the doubly excited states (DES) in the Helium-like O6+ and F7+ ions. The interaction of these systems with X-ray laser pulses can cause the DES to appear in their energy spectra due to the strong correlation between the electrons. The formation of the DES can be followed by a decay by electron emission (autoionization) causing the parent ion to lose its electrons.
The recent advent of free electron lasers (FELs) sources capable to generate laser pulses of durations comparable to the ultrashort lifetimes of the autoionizing DES in atoms will open the opportunity to investigate the autoionization mechanisms and to understand the importance of the role the DES play in the ionization process. Accurate theoretical knowledge of where these states can be located in the energy spectrum of the targeted system and their precise lifetime decay will be a support to the future experiments on the laser-atom processes involving the DES.
To date, theoretical data of the energy position E and the lifetime decay τ for the DES in the O6+ and F7+ ions and other heavier systems are still lacking. In order to locate and investigate the DES in the energy spectrum of an Helium-like ion, we have developed an efficient method based on the numerical resolution of the Schrödinger equation with a B-splines discretization technique [1,2] combined with the complex rotation method [3]. Our method has the numerical advantage to generate the parameters (E, τ) in a single calculation. It also allows the identification of the DES that share similar angular correlation pattern, which helps in their classification into distinct series.
We present our recently published results on the detection of DES in the O6+ion [4] and other recent results of our investigation of the DES in the F7+ ion. The theoretical results generated in this work will be of great interest to the future experiments on the O6+ and F7+ with X-ray FELs laser pulses.
[1] S. Barmaki, M.-A. Albert, S. Laulan, Chem.Phys. 517, 24 (2019)
[2] S. Barmaki, M.-A. Albert, S. Laulan, J. Phys. B: At. Mol. Opt. Phys. 51, 105002 (2018)
[3] M.- A. Albert, S. Laulan, S. Barmaki, Radiat. Phys. Chem. 166, 108453 (2020)
[4] S. Barmaki, M.- A. Albert, S. Laulan, Phys. Scr. 95, 055403 (2020)

Speaker: Marc-André Albert

W-POS-F #41-56 Poster session (DCMMP) / Session d'affiches (DPMCM)

Convener: Michel Gingras

394 (G*) POS-F41 -- A Study of Silicon Dangling Bond Pairs in Search of a True Random Number Generator

Hydrogen terminated silicon has seen a recent resurgence in popularity due to several works demonstrating its use for ultra-dense memory, atomic electronics, and quantum devices. On this surface, individual hydrogen atoms can be removed with atomic precision through STM pulses, leaving a dangling bond (DB) behind. DBs are quantum dot-like entities that can hold either 0, 1, or 2 electrons, with their discrete energy levels in the bandgap. We are studying DBs to achieve true random number generators (RNG) on the atomic scale. Two DBs patterned in close proximity to each other on a highly n-doped crystal host a net extra electron, which can quantum mechanically tunnel to reside on either side. Through measurement of the extra electrons’ spatial location in the pair, it is expected that the electron will be found on either side with equal probability in the absence of any biasing effects. This opens the possibility of using the system as a true RNG, where the bits are generated by probing the electrons’ spatial location. Quantum processes are most desired for RNG because the randomness can be such that no common naturally occurring or imposed noise will alter the number generation. We study these DB pairs by DFT methods to establish the effect of geometry, external fields, and nearby dopants on charge localization and consequent RNG bit generation.

Speaker: Furkan Altincicek (University of Alberta)

395 POS-F42 -- Exact Diagonalization on Pyrochlore System with Lattice Distortion

Exact diagonalization is a powerful method to analyze a crystal system. In our research, we apply the exact diagonlization method on 16 site spin 1/2 Pyrochlore system. The Hamiltonian of this system can be expressed as a 65536 times 65536 matrix, then we use point group D_3 and FCC translational group to block diagonalise this matrix. Finally, we apply Lapack subroutine to get the eigenvalues and eigenstates of this 16 sites system. Moreover, we also consider a lattice distortion which reduce the full spce group Fd3m to F43m. With small varying of the exchange constants J_{ij}, we can analyze the ground state energy and the total system energy changing through the lattice distortion. Moreover, using the result from exact diagonalization, we are also able to find the quantum entanglement between different sites in the system with lattice distortion.

Speaker: chen wei (Memorial University)

396 (U*) POS-F43 -- Finite Difference Simulation of Interacting Resonance and Pulse Waves in a Nonlinear Material

The field of nonlinear acousto-elastic behaviour in materials such as rocks is an area of active research, applicable to phenomena such as earthquakes or material fatigue. This nonlinearity arises from the rock microstructure, notably through cracks, and appears in the form of a nonlinear relation between the stress and strain fields within the rock. We study how this nonlinearity manifests when the sample is in either a resonant or a non-resonant state. To do this, we numerically model a sample including a crack and broadcast a low frequency pump wave and a high frequency probe wave through the sample. We use a fourth order finite difference scheme to model the evolution of wave velocity, stress, and strain, then use a form of averaging to represent the cracked, heterogeneous model with an effective homogeneous model [1]. Calculating the nonlinear interactions between the two waves allows us to compare the resonant and non-resonant behaviour. We demonstrate differences in the effective wave velocity, and in the travel time delays between effective velocities with and without a pump source.
[1] Heru Rusmanugroho, Alison E. Malcolm, Meghdad Darijani, A numerical model for the nonlinear interaction of elastic waves with cracks. Wave Motion 92, 102444 (2020). DOI: 10.1016/j.wavemoti.2019.102444

Speaker: Matthew Williams

397 (G*) POS-F44 -- Electronic properties of pure and iron(III) doped TiO2 nanomaterials

In the past few decades, scientists discovered that TiO2 was capable of purifying polluted water without any addition of strong oxidants. Active hydroxyl radicals can be produced through photodegradation process when TiO2 is illuminated under water, and such process is viewed as a favorable method for on-site decomposition of organic compounds. However, the main drawback of this process suffers from the range of wavelength TiO2 can absorb, which lies in Ultraviolet region. In previous studies, Fe (III) doping was used to broaden the band gap of titania and allow the material of absorb into the visible region. Yet, in our own work, the doping of TiO2 with iron does not provide the expected improvement during methylene blue photodegradation under simulated sun light illumination.

In this study, we characterized pure and Fe(III) doped TiO2 nanopowders using SEM, EDS, XRD, valence band XPS and UPS, to learn about the phase, particle size, chemical composition, and more importantly the influence of Fe (III) dopants on the valence band structure of TiO2 nanoparticles synthesized through Sol-Gel method. The relationship between the valence band structure and the material’s photocatalytic properties will be discussed.

Speaker: Mr Tuochen Gong

398 POS-F45 -- Optimizing ZnO overlayer for surface acoustic wave devices

Golnaz Azodi and James Stotz

Queen’s University, Kingston, Ontario, Canada

A piezoelectric substrate is key for generating surface acoustic waves. The high electromechanical coupling factor of Zinc Oxide (ZnO) makes it a suitable material for this purpose. Among various techniques, we use physical vapour deposition (PVD) to obtain a uniform and well-orientated film. In this study, we used both RF and DC sputtering with a ZnO source and compare the quality of the resulted film. For both of the methods, we vary several parameters and repeat the deposition process to study the impact on the quality of the deposited film. The parameters we studied included the substrate temperature, pressure of the deposition chamber, as well as the types and ratio of the gases involved in the sputtering process. To quantify the film quality, we use x-ray diffraction and evaluate the orientation of the c-axis. We additionally measure the film thickness with a profilometer to study and estimate the growth rate. As the final step of characterization, a pair of Aluminium interdigitated transducers are fabricated on the surface of ZnO to confirm the propagation of the surface acoustic waves through the medium. This was done by measuring the frequency response of the transducers by a network analyzer. Through our three steps characterization, we find the best parameter configuration that can lead to a high-quality film for surface acoustic wave devices.

Speaker: Golnaz Azodi Aval (Queen's University)

13:55 WITHDRAWN

399 (G*) POS-F47 -- Microwave resonators for global control of electron spins qubits

Electron spins confined to quantum dots are a promising platform for scalable quantum computation. A necessary component of such a quantum processor is a microwave magnetic field (B$_1$) that implements single-qubit gate operations via electron spin resonance. A common method for generating a B$_1$ field is to place a micro-stripline close to the device. A second method is to place a micromagnet near the device and apply local voltage pulses to induce electric dipole spin resonance. Both methods involve elements that are bulky (> 1 µm) compared to the scale of an individual quantum dot (~60 nm), and are placed on the surface of the chip, taking up valuable space and preventing scalable, dense packing of qubits. Furthermore, the B$_1$ produced by both methods is local, limiting single-qubit rotations to only a few quantum dots per micro-stripline or micromagnet.

We have investigated a centimeter-scale bowtie-shaped microwave resonator design that produces a global B$_1$ field with minimal electric field over a relatively large area (~mm$^2$), which could enable single-qubit rotations for thousands of qubits. The design ensures that the magnetic field is maximal near the center of the resonator, whereas the electric field is expelled towards the edges of the resonator. A minimal electric field in the active area is necessary to prevent photon-assisted tunneling of the confined electrons. The resonator can be vertically integrated above the quantum device layer, removing the need for microwave interconnects or bulky components in the device layer. Individual qubits can be tuned in and out of resonance with this global B$_1$ field using the Stark effect, wherein the electronic $g$-factor shifts slightly as a function of applied electric field. Coupling an external microwave source to the resonator is achieved by an excitation stripline on the opposite side of a dielectric substrate. The resonator and stripline dimensions are optimized for operation at ~15 GHz, corresponding to a DC magnetic field of 0.53 T for a $g=2$ electron spin. At this field and a temperature of 100 mK, the spin qubit is initialized by relaxing into its ground state with a probability of 99.9 %. Our experimental implementation of lateral quantum dots in silicon will be discussed, along with progress in testing and integrating the global B$_1$ field resonator.

Speaker: Stephen R. Harrigan (University of Waterloo)

400 (G*) POS-F48 -- Evolution of Shadowed Triplet Superconductor to Spin-Density Wave in Sr2RuO4 and Sr3Ru2O7

The superconducting order parameter of Sr$_2$RuO$_4$ has again become a topic of great interest after recent NMR experiments have contradicted the once popular $p_x\pm i p_y$ spin-triplet superconducting state. We have previously explored a microscopic route to inter-orbital spin-triplet superconducting pairing with spin-orbit coupling to explain recent experimental data in Sr$_2$RuO$_4$ [1-3]. Here, we extend this microscopic theory to Sr$_3$Ru$_2$O$_7$, the bilayer version of Sr$_2$RuO$_4$ to explain why Sr$_3$Ru$_2$O$_7$ does not exhibit superconductivity, but spin-density wave order under a magnetic field.

[1] C. M. Puetter and H.-Y. Kee, EPL 98, 27010 (2012).
[2] A. W. Lindquist and H.-Y. Kee, PRR 2, 032055 (2020).
[3] J. Clepkens, A. W. Lindquist, and H.-Y. Kee, PRR 3, 013001 (2021).

Speaker: Austin Lindquist

401 POS-F49 -- Theory of Hysteretic Behaviour of Doped Quantum Paraelectric-Insulator Interfaces

Until recently, there has been a general belief that carrier doping destroys spontaneous polarization in ferroelectric materials. However, a small number of materials have been discovered in which ferroelectricity persists into the metallic state. Motivated by this, we study a theoretical model for a MOSFET-like system comprising an insulating polar cap layer and a metallic ferroelectric thin film. We find that adding electrons screens the depolarizing fields and allows for a ferroelectric transition below the insulating film’s critical thickness. We show that one may obtain hysteretic behaviour as a function of applied field and that switching the polarization induces a metal-insulator transition at the interface. Depending on the bias voltage, we find both “low-polarization” and “high-polarization” states, similar to what is obtained in insulating ferroelectrics. Our most surprising finding is that the low-polarization state, which has a nearly vanishing average polarization, comprises two domains with large and opposite polarizations, separated by a conducting domain wall. The high-polarization state, on the other hand, contains no such domains. In this case the local polarization is determined by the electron density, where the electrons are confined to either the interface or the back wall depending on the polarization. In both low- and high-polarization states the free charge compensates for the bound charge in the film, making the interior electrically neutral.

Speaker: Kelsey Chapman

402 POS-F50 -- Studying Advanced Materials at the REIXS Beamline

Advanced materials, including: superconductors, light emitting materials and battery materials, play an ever increasing role in society today. Studying these materials is key to reducing overall energy consumption for everyday technology. Soft x-rays have the ideal energy for probing the electronic properties of typical elements in these materials; x-ray absorption spectroscopy (XAS) and x-ray emission spectroscopy (XES) are robust techniques to measure the electronic structure in general. More advanced techniques, resonant inelastic x-ray scattering (RIXS) and resonant soft x-ray scattering (RSXS) are invaluable for studying electron correlations in novel materials. In addition, resonant x-ray reflectometry (RXR) allows one to probe the electronic structure of interfaces in layered materials. The Resonant Elastic and Inelastic X-ray Scattering (REIXS) beamline at the Canadian Light Source (CLS) is a soft x-ray beamline specializing in photon-in/photon-out techniques including those mentioned above. There are many opportunities at REIXS for material scientists wanting to fully explore the electronic properties of their advanced materials. We will showcase the current capabilities offered at REIXS as well as discuss some future advancements.

Speaker: Dr Teak Boyko (Canadian Light Source)

403 POS-F51 -- Non-linear elastic wave interactions: pump-probe experiments in rocks

During earthquakes, the travelling speeds of seismic waves can change due to the heterogeneous nature of the earth’s crust. However, it remains an open question which factors most influence seismic wave speed changes. In this context, we use lab-scale experiments to study how heterogeneities such as cracks and ambient humidity affect the way that elastic waves interact in porous sandstone. We focus on non-linear wave interactions that allow us to track changes in wave travelling speeds, which can indicate changes in material (rock) properties. We demonstrate that strong pump wave pulses soften sandstone more in humidified conditions than they do in dry conditions, and that this effect is repeatable and reversible.[1] Furthermore, our pump-probe experiments detect rock softening changes easily and repeatably using an experimental design that does not rely on resonance conditions. Building on previous simulations [2], we assess wave speed differences between resonant and non-resonant pumping conditions.

[1] Somayeh Khajehpour Tadavani, Kristin M. Poduska, Alison E. Malcolm, and Andrey Melnikov. A non-linear elastic approach to study the effect of ambient humidity on sandstone. J. Appl. Phys. 128, 244902 (2020). DOI: 10.1063/5.0025936

[2] Heru Rusmanugroho, Alison E. Malcolm, Meghdad Darijani, A numerical model for the nonlinear interaction of elastic waves with cracks. Wave Motion 92, 102444 (2020). DOI: 10.1016/j.wavemoti.2019.102444

Speaker: Kristin Poduska (Memorial University of Newfoundland)

404 POS-F52 -- Theoretical study of strain and superconductivity in Sr2IrO4

Several parallels can be drawn between the perovskite iridate Sr$_2$IrO$_4$, and the high Tc cuprates. Although the low energy spectrum of Sr$_2$IrO$_4$ includes the three t$_{2g}$ bands, strong spin-orbit coupling splits the bands such that one can write an effective one-orbital J=1/2 model, in analogy with the single orbital of the cuprates. This has led to predictions of d-wave superconductivity in Sr$_2$IrO$_4$ upon electron doping. A three-orbital Hubbard model finds that the pairing is dependent on the interorbital interactions, therefore, an effective one orbital model may be insufficient in describing the superconducting state. In this work we investigate the multiorbital properties of Sr$_2$IrO$_4$, both with and without doping, under compressive epitaxial strain. Strain modifies lattice constants and bond orientations. The strain is modeled by modifying the orbital dependent hopping amplitudes and can therefore tune the bandwidths of the different bands. By applying a multiple order parameter, self-consistent mean-field approach we study the magnetic structure and pairing symmetry of Sr$_2$IrO$_4$ under strain and carrier doping. We comment on ways to increase the chance of superconductivity.

Speaker: Lena Engström (McGill University)

14:09 WITHDRAWN

405 POS-F54 -- Transport of Majorana zero modes in 1D topological superconductors

Majorana zero modes (MZM) have been a focal point of the condensed matter physics
community in recent times due in part to their potential applications in quantum computation.
Most notably, the exotic exchange statistics of MZMs form the basis of
topologically protected quantum gates. The physical exchange, or braiding, of MZMs is often modeled in networks of 1D topological superconducting wires. A key ingredient of these braiding protocols is the transport of MZMs across a superconductor. We consider a “piano key model” of transport, where segments of a superconductor are adiabatically tuned between the topologically trivial and the topologically non-trivial phases via electric gates. We examine the time scales over which the piano key tuning should be performed in order to minimize the likelihood of unwanted excitations of the ground state. We also examine the dynamical phase accrued by the ground state, which is of importance in the context of braiding.

Speaker: Bill Truong (McGill University)

406 POS-F55 -- Toward an understanding of the interplay between quantum magnetism and electron transport in magnetic topological insulators

Motivated by magnetotransport experiments on magnetic topological insulators, a theoretical study of Dirac cone electrons coupled to magnetic moments has been done [1]. That work showed that the electronic response is determined by the magnetic configuration - the electronic spectrum is gapped in a region of the ferromagnetically ordered moments, but the gap vanishes at domain walls. This vanishing gap gives rise to one-dimensional channels of conductance. Taking the interplay between Dirac electrons and magnetic moments further, we wish to study a coupled system where the magnetic moments are treated quantum mechanically. A quantum-mechanical treatment may provide a more complete understanding of the role that the domain-wall bound states play in the behavior of the magnetoconductance in magnetic topological insulators and in heterostructure. For example, domain walls may be delocalized due to quantum fluctuations while still coupling to the Dirac fermions. The generalization of the classical model to the quantum regime could help in the development of spintronics applications and sensors of magnetic excitations.

[1] K. L. Tiwari, W.A. Coish, and T. Pereg-Barnea Phys. Rev. B. 96, 235120 (2017).

Speaker: Ivan Martinez (McGill)

407 POS-F56 -- Solitons of the higher spin Haldane spin chain

We consider the antiferromagnetic anisotropic Haldane model with large spins, in a region where a perturbative treatment is indicated. The Néel order is frustrated by periodic boundary conditions imposed on an odd-numbered chain, resulting in a highly degenerate groundspace spanned by solitons. We study the pertrubative groundstate entropy of entanglement for different scenarios, and compare with recent results.

Speaker: Christian Boudreault (Royal Military College Saint-Jean/U de Montréal)

W-POS-G #57-74 Poster session (Mag.North) / Session d'affiches (Nord mag.)

Convener: Bruce Gaulin (McMaster University)

408 POS-G57 -- Imaging Magnetic Dynamics on the Atomic Scale

The ability to image magnetodynamics has proved key to the advancement of spintronics technology [1]. As technological size scales reduce and speeds increase, there is a need to provide commensurate advancement in experimental tools to image magnetodynamics down to the atomic scale with ultrafast time resolution. In pursuit of this goal, we are developing a custom designed scanning tunneling microscope which will be paired with a THz light source to create a THz-STM that achieves ultrafast time resolution [2]. THz-STM experiments require significant acquisition time and present an extreme challenge. To make such an instrument practical, the STM must be designed with optical access, long-term stability, and rigidity in mind. Progress on the design and construction of a variable temperature scanning tunneling microscope purpose built for the observation of magnetodynamics will be presented.

1 https://science.sciencemag.org/content/294/5546/1484
2 https://www.nature.com/articles/nphoton.2013.151

Speaker: Sangeev Selvaratnam (Department of Physics and Astronomy, University of Manitoba)

409 POS-G58 -- Collective dynamics of antiferromagnetic domain walls in an optical cavity

Recently, there has been an increasing interest in the study of optical/microwave cavity-confined photon-magnon interaction due to their potential applications in quantum information processing and spintronics [1,2]. In those studies, a number of unique features have been observed at frequencies in the GHz range. On the other hand, less is known about the dynamics of antiferromagnets, which are characterized by frequencies in the THz range [3].

We report results from an analytical study of the coupling of an antiferromagnetic domain wall to optical photons via the inverse Faraday effect. We consider spin canting and complex spin textures in antiferromagnetic materials that can arise from Dzyaloshinskii-Moriya interactions (DMI) [4]. DMI is not easily measurable and is often inferred from other quantities. In this work, we find that the presence of DMI enables spin interactions with cavity photons in a geometry which otherwise allows no magneto-optical coupling. This result may be used to measure the DMI constant in optomagnonic experiments by measuring the interaction of antiferromagnetic resonances to optical modes in a cavity.

Keywords: optomagnonic, DMI, antiferromagnet, domain wall, spin texture

This work was supported by NSERC, CFI-JELF, Research Manitoba and the University of Manitoba, Canada.

References
1. Harder, M. & Hu, C. M. Cavity Spintronics: An Early Review of Recent Progress in the Study of
Magnon–Photon Level Repulsion. in Solid State Physics - Advances in Research and Applications (eds. Camley, R. E. & Stamps, R. L.) vol. 69 47–121 (Academic Press, 2018).
2. Bozhko, D. A., Vasyuchka, V. I., Chumak, A. V & Serga, A. A. Magnon-phonon interactions in
magnon spintronics (Review article). Low Temp. Phys. 46, 383–399 (2020).
3. Kampfrath, T. et al. Coherent terahertz control of antiferromagnetic spin waves. Nat. Photonics 5, 31–34 (2011).
4. Conzelmann, T., Selzer, S. & Nowak, U. Domain walls in antiferromagnets: The effect of Dzyaloshinskii-Moriya interactions. J. Appl. Phys. 127, 223908 (2020).

Speaker: Oluwanisola Iyaro (University of Manitoba)

410 POS-G59 -- Investigation of the dynamics of twisted bilayer artificial spin ice structure

Geometrical frustration arises in systems whose structures support multiple degenerate ground states. Artificial spin ice (ASI), has been built in diverse configurations which allows us to control frustration by experimentally tuning suitable parameters[1]. We present computational results on ASI systems consisting
of planar arrays of nanosized elongated ferromagnetic islands where geometrical frustration takes place at the vertices due to dipolar interactions between elements. To date, most studies have employed two-dimensional geometries in order to study magnetic charge dynamics, phase transitions, vertex-based frustration, and other interesting effects[2]. Recently, there has been a surge of interest in realizing three-dimensional artificial spin ice[3]. The use of a third dimension allows increased configurability and optimization of the magnetostatic interaction between different elements of the system. The work mentioned here concerns non-
equilibrium dynamics of a bilayer artificial spin ice structure consisting of two identical arrays separated by some distance and rotated at an angle between the two array axes. Introducing an angle between the layers enables the observation of novel, emergent phenomena as it changes the nature of the interactions between
the spins. We consider pinwheel variants of a square ice geometry for each
array[4]. Using different Monte Carlo techniques, we examine ground state ordering as a function of the interaction strength between layers for different relative orientations. Avalanche processes are also investigated and contrasted with those found in single-layer arrays.

References:
[1] RF Wang, C Nisoli, RS Freitas, J Li, W McConville, BJ Cooley, MS Lund, N Samarth, C Leighton, VH Crespi, et al. Artificial `spin ice' in a geometrically frustrated lattice of nanoscale ferromagnetic islands. Nature, 439(7074):303{306, 2006.
[2] Cristiano Nisoli, Vassilios Kapaklis, and Peter Schi?er. Deliberate exotic magnetism via frustration and topology. Nature Physics, 13(3):200{203, 2017.
[3] Gia-Wei Chern, Charles Reichhardt, and Cristiano Nisoli. Realizing three-dimensional artificial spin ice by stacking planar nano-arrays. Applied Physics Letters, 104(1):013101, 2014.
[4] R. Mac^edo, G. M. Macauley, F. S. Nascimento, and Robert L. Stamps. Apparent ferromagnetism in the pinwheel artificial spin ice. Physical Review B,
98(1):014437, 2018.

Speaker: Rehana Begum Popy (University of Manitoba)

411 (G*) POS-G60 -- Large Magnetic Anisotropy in Spinel Vanadate Thin Films

Bulk spinel vanadate crystals are structurally cubic and ferrimagnetic, with biaxial anisotropy along the cubic axes. However, for thin film Cobalt Vanadate, an orthorhombic crystal structure leads to very different and stronger magnetic anisotropies. Data from torque magnetometry shows a uniaxial anisotropy with the magnetic easy axis shifting from out-of-plane at high temperatures, to in-plane upon cooling. At low temperature, the out-of-plane magnetic hard axis is shown to not saturate until ~20T, whereas the in plane magnetic hard axis does not saturate even at 30T. Comparing the torque data to previous zero field neutron diffraction measurements [1] suggest that a field dependent structural distortion may be responsible for the large anisotropies.

[1] Thompson, C. J., Reig-I-Plessis, D., Kish, L., Aczel, A. A., Zhang, B., Karapetrova, E., Macdougall, G. J., & Beekman, C. (2018). Spin canting and orbital order in spinel vanadate thin films. Physical Review Materials, 2(10). https://doi.org/10.1103/PhysRevMaterials.2.104411

Speaker: Sangsoo Kim (Florida State University)

412 (G*) POS-G61 -- $\mu$SR study of superconducting Re-B compounds

The discovery of time-reversal symmetry(TRS) breaking in elemental Re has ignited fresh interest in the Re based superconductors. The recent studies show that role of Re concentration and crystal symmetry is crucial in understanding the unconventional superconductivity of these compounds. Therefore, we studied two Re-based superconductors Re$_3$B (<var>T_C</var> = 5.19 K) and Re$_7$B$_3$ (<var>T_C</var> = 3.2 K) having a centrosymmetric and non-centrosymmetric crystal structure, respectively. In this talk, we will present a comprehensive study on superconducting properties of Re$_7$B$_3$ and Re$_3$B through specific heat, magnetic susceptibility, resistivity, and transverse and zero-field muon rotation/relaxation ($\mu$SR) experiments. This will include the temperature dependence of penetration depth using transverse-field $\mu$SR measurements, which will be used to determine the symmetry of the superconducting gap. To further explore these materials, we performed the zero-field $\mu$SR measurements, which show the evidence for TRS preserving superconducting state for both materials in the limits of our measurements.

Speaker: Sudarshan Sharma (McMaster University)

413 (G*) POS-G62 -- Extent of Frustration in the Classical Kitaev-$\Gamma$ Model

The Kitaev model on the honeycomb lattice recently attracted considerable attention. However, in candidate materials, other interactions are present, and
among them the off-diagonal $\Gamma$ interaction has been particularly challenging. While several numerical studies on a minimal Kitaev-$\Gamma$ $(K\Gamma)$ model found multiple quantum disordered phases, definite conclusions on existence of quantum spin liquids remain elusive due to various numerical limitations. Here we present a classical phase diagram of the $K\Gamma$ model in the presence of the bond-anisotropy, which reveals intriguing competing phases and extended frustration. The stability of the classical phases to quantum fluctuations using a linear spin wave theory will be also discussed.

Speaker: Ahmed Rayyan (University of Toronto)

414 POS-G63 -- The ground state of the disordered triangular lattice

The simplest example of geometric frustration is found in the two-dimensional triangular lattice. While the ground state of the Heisenberg model in this lattice is known to be Néel ordered, some recent low-temperature experiments on various triangular lattice compounds have unambiguously demonstrated the presence of short-range ordering, continuous excitation spectra, and non-trivial spin dynamics. These studies highlight the roles played by frustration and quenched disorder present in laboratory samples to engender a competition between prospective spin liquid and spin glass ground states. Inspired by these observations, this presentation focuses on a set of results that clarify the nature of the true ground state of the disordered triangular lattice.

Speaker: Santanu Dey (University of Alberta)

415 POS-G64 -- The Kosterlitz-Thouless transition in a finite 2D magnetic film with fourfold anisotropy

The Kosterlitz-Thouless (KT) transition is a topological transition in a model where magnetic vortex and antivortex spin structures are created in an infinite, isotropic, 2D magnetic system. The transition occurs when bound vortex-antivortex pairs unbind due to thermal energy at the temperature $T_{KT}$, and is marked by a magnetic susceptibility that diverges at low temperature, and decreases exponentially with temperature above $T_{KT}$. When the infinite system has fourfold in-plane anisotropy, the transition is no longer of the KT type, but has non-universal critical exponents that depend upon the strength of the anisotropy. More recent work has shown that the logarithmic dependence of vortex sizes and energy scales imply that real 2D isotropic magnetic films will exhibit a finite-size KT transition instead. The susceptibility then displays a broad peak that rises above $T_{KT}$ and then falls with the characteristic exponential form predicted for the infinite system. Our recent experimental measurements on Fe/W(100) films have confirmed this high temperature behaviour.
In order to understand the behaviour of the susceptibility across the broad transition, the renormalization group equations have been re-solved for the case of a system of finite size L with fourfold anisotropy $\lambda = K/J ~10^{-3}-10^{-2}$ appropriate to metallic magnetic films. The anisotropic film continues to exhibit a finite-size KT transition, with an effective exchange coupling that moves to zero asymptotically, and an anisotropy that is exponentially screened by the formation of a free vortex gas. The resulting susceptibility compares very well with experiment across a wide temperature range, and allows quantitative fitting of the finite size L of the experimental system. Questions remain concerning the relative size of the low temperature spin wave and high temperature vortex contributions to the susceptibility.

Speaker: Jordan Atchison (McMaster University)

14:01 WITHDRAWN

416 (G*) POS-G66 -- Dynamical Backaction Magnomechanics

Dynamical backaction resulting from radiation pressure forces in optomechanical systems has proven to be a versatile tool for manipulating mechanical vibrations. Notably, dynamical backaction has resulted in the cooling of a mechanical resonator to its ground-state, driving phonon lasing, and observing the optical-spring effect. In certain magnetic materials, mechanical vibrations can interact with magnetic excitations (magnons) via the magnetostrictive interaction, resulting in an analogous magnon-induced dynamical backaction. This talk will discuss the direct observation of magnon-induced dynamical backaction and its effect on a spherical magnetic sample's mechanical vibrations. Moreover, dynamical backaction effects play a crucial role in many recent theoretical proposals; thus, our work provides the foundation for future experimental work perusing many of these novel theoretical proposals. foundation for future experimental work perusing many of these novel theoretical proposals.

Speaker: Clinton Potts (University of Alberta)

417 (G*) POS-G67 -- Unconventional singularity in anti-parity-time symmetric cavity magnonics

By engineering an anti-parity-time (anti-PT) symmetric cavity magnonics system with precise eigenspace controllability, we observe two different singularities in the same system. One type of singularity, the exceptional point (EP), is produced by tuning the magnon damping. Between two EPs, the maximal coherent superposition of photon and magnon states is robustly sustained by the preserved anti-PT symmetry. The other type of singularity, arising from the dissipative coupling of two antiresonances, is a zero-damping condition (ZDC). At the settings of ZDCs, the coupled system exhibits infinite discontinuities in the group delay. We find that both singularities coexist at the equator of the Bloch sphere, which reveals a unique hybrid state that simultaneously exhibits the maximal coherent superposition and slow light capability.

Speaker: Ying Yang (University of Manitoba)

418 (G*) POS-G68 -- The Einstein-de Haas Effect in Yttrium Iron Garnet at 3 MHz

The classical Einstein-de Haas (EdH) effect [1] is a AC mechanical torque arising from a time rate of change of net magnetization, and represents the intrinsic relationship between magnetism and mechanical angular momentum. Nanofabrication of torque sensing devices is opening new avenues for exploration and applications of the EdH effect. The scale-up of resonance frequencies with continued miniaturization of mechanical torque sensing resonators enhances EdH torques, which increase linearly with drive frequency, relative to frequency-independent magnetic cross-product torques. Previously, miniaturized EdH experiments have been performed at the microscale using mechanical modes in the audio frequency range (13 kHz) [2]. The present work brings the measurements to radio frequencies.

Single-crystal Yttrium Iron Garnet (YIG) disks with magnetic vortex ground states are mounted on nano-scale mechanical resonators with a torsional resonance mode close to 3 MHz. For DC bias fields below about 200 A/m the maximum cross-product torques remain smaller than the EdH torques [3]; no control of the field geometry to null cross-product torques is required. Quadrature lock-in measurements allow cross-product and EdH torque signals to be recorded simultaneously, owing to a 90$^{\circ}$ relative phase shift arising between the driving torques, and referenced to the phase of the driving field. The simultaneous measurement scheme enables determination of the magnetomechanical ratio, $g\prime$, without requiring separate experimental inputs. Results from measurements around the full vortex hysteresis loop, and comparisons with micromagnetic simulations of cross-product and EdH torques, also will be discussed.

[1] A. Einstein and W.J. de Haas, Proceedings - KNAW 18, 696 (1915).

[2] T.M. Wallis, J. Moreland, and P. Kabos, Appl. Phys. Lett. 89, 122502 (2006)

[3] K. Mori, M.G. Dunsmore, J.E. Losby, D.M. Jenson, M. Belov, and M.R. Freeman, Phys. Rev. B 102, 054415 (2020)

Speaker: Michael Dunsmore (University of Alberta)

419 (G*) POS-G69 -- Three-axis torque magnetometry for study of interfacial exchange coupling in ferromagnetic/antiferromagnetic bilayers.

Studies of exchange coupling at interfaces in permalloy/cobalt oxide bilayer microdisks are made possible by measurements of a full AC magnetic torque vector [1]. Magnetic cross-product torque involves a linear combination of perpendicular moment and magnetic susceptibility, yielding the rotational magnetic anisotropy or stiffness of the spin texture in response to torque. Single-axis torque measurements are most common and are useful for hysteresis measurements of thin film structures where, in particular, high shape anisotropy yields a near-proportionality of in-plane magnetic moment and magnetic torque along the perpendicular in-plane axis. Three-axis torque measurement provides a platform for obtaining standard hysteresis curves while simultaneously measuring in-plane anisotropies, with no requirement to reorient the sample or the field generators.

Our three-axis methodology uses a modified, single-paddle, silicon-on-insulator, resonant torque sensor. The torsion mechanical susceptibilities to x- and z-torques are maximized by clamping the sensor at a single point. Mechanically-resonant AC torques are driven by an RF field containing frequency components for each fundamental torsional mode. The displacements are read out interferometrically. The sensors are prepared by silicon micromachining and the sample fabrication is completed by lithographic patterning of the active magnetic layers [2].

Investigations of a permalloy/cobalt oxide bilayer sample show an absence of single-vortex behaviour at cryogenic temperatures, in contrast to the well-characterized single-vortex behaviour at both ambient and cryogenic temperatures in permalloy-only samples [3]. In-plane torque measurements yield shifted hysteresis loops consistent with standard exchange bias. Unexpectedly, however, the dominant contribution to the out-of-plane torque observed in the cooled bilayer samples, when measured in strong bias fields, has a rotational symmetry inconsistent with unidirectional anisotropy. This suggests that the AC torsion stiffness, arising from interfacial exchange coupling in these samples, does not hinge on uniform alignment within the antiferromagnetic layer.

[1] K.R. Fast et al., AIP Advances 11, 015119 (2021)

[2] Z. Diao et al., J. Vac. Sci. Technol. B. 31, 051805 (2013)

[3] J.A.J. Burgess et al., Science 339, 1051-1054 (2013)

Speaker: Ms Katryna Fast (University of Alberta)

420 POS-G70 -- Implementation of skyrmion cellular automaton using Brownian motion

The quantum dot cellular automaton (QCA) is a device that uses the interaction between confined electrons in aligned cells to transfer and process information. In QCA architecture, two antipodal arrangements of two electrons confined in square shaped cell are defined as digital “0” and “1”. QCA requires no electrical current for its operation therefore, extremely low power computing can be realized.[1] However, the operation of QCA is limited at cryogenic temperature.[2,3] In this study, we demonstrated a device similar to QCA utilizing magnetic skyrmion instead of electron at room-temperature. Ta/CoFeB/Ta/MgO/SiO2 thin films were deposited on thermally oxidized silicon substrates at room-temperature through magnetron sputtering. Skyrmions observed in our films showed Brownian motion at room-temperature. This Brownian motion of skyrmions was utilized to transfer and process information. Square-shaped cells containing single skyrmion or pair of skyrmions were implemented by controlling the magnetic anisotropy of the continuous magnetic film.[4] At first, we fabricated neighbored two cells containing pair of skyrmions and found the correlation coefficient between the y-coordinate of the skyrmions near the gap was negative. The negative correlation coefficient indicates that the repulsive interaction between the skyrmions works across the two isolated regions. Next, we investigated interaction between single fixed skyrmions and pair of free skyrmions skyrmions confined in different cells. By changing distance between two cells, we clarified magnitude of repulsive interaction between skyrmions depended on distance. These results show that the Brownian motion of skyrmions has the potential to realize a novel computing architecture similar to QCA. Detailed experimental method and results will be discussed at the presentation.

[Acknowledgements]
This work was supported by JSPS KAKENHI (S) Grant Numbers JP20H05666 and JST CREST Grant Number JPMJCR20C1, Japan.

[1] C. S. Lent, et al., Nanotechnology 4, 49 (1993)
[2] G. L. Snider, et al., Semicond. Sci. Technol. 13, A130, (1998)
[3] I. Amlani, et al., Science 284, 9 (1999)
[4] Y. Jibiki, et al., Appl. Phys. Lett. 117, 082402 (2020)

Speaker: Ryo Ishikawa (ULVAC Inc.)

421 (G*) POS-G71 -- Hidden diffusion and perpetual motion of the skyrmions

Since the magnetic skyrmion is a topologically protected particle-like domain in the ferromagnetic film, it can survive under thermal agitations and shows Brownian motion. The skyrmion system can be an ideal platform to design unconventional computers like stochastic/Brownian computers. Therefore, investigation of the Brownian motion of the magnetic skyrmion is now the subject of scientific and technical interest [1,2].
In this talk, experimental proof of a non-vanishing x-velocity to y-coordinate correlation will be shown. The result is explained by the Thiele equation including a stochastic field [3,4]. Description of the phenomena introduces the gyro-diffusion constant [5] that is special for the diffusion of the chiral particles like skyrmions. The existence of the x-velocity to y-coordinate correlation also evidences the perpetual rotation motion of the skyrmion. Theory shows that the result does not conflict with the 2nd law of thermodynamics and the van Leeuwen theorem.
Acknowledgments
The authors acknowledge Mr. Y. Jibiki of Osaka University, Dr. S. Auffret, Dr. C. Baraduc, and Dr. Hélèn Béa of Spintech, France for their initial contributions. The authors also acknowledge Dr. M. Oogane and Dr. K. Saito. This research and development work was supported by the ULVAC, Inc., the Ministry of Internal Affairs and Communications, Basic research S (20H05666) of JSPS, and CREST (Non-classical Spin project) of JST.
References
[1] Y. Jibiki et al., Appl. Phys. Lett. 117, 082402 (2020).
[2] L. Zhao et al., Phys. Rev. Lett. 125, 027206 (2020).
[3] A. Thiele et al., Phys. Rev. Lett. 30, 230 (1973).
[4] C. Schuette et al., Phys. Rev. B 90, 174434 (2014)
[5] E. Tamura et al. https://arxiv.org/abs/2005.04860.

Speaker: Mr Soma MIKI (Osaka University)

422 POS-G72 -- Multi-frequency torque magnetometry: contribution of the Einstein-de Haas effect, and direct detection of overlapping magnetic and mechanical resonance modes

High-finesse optical nanocavities coupled with nanomechanical torque sensors have enabled highly sensitive and broadband readout of magnetic torques, from timescales involving quasi-static hysteresis response to radio-frequency magnetic susceptibility [1-3]. The extension of torque magnetometry to higher mechanical frequencies will grant further access to spin dynamics, including mechanical investigations of spin-lattice relaxation times.

For nanomechanical torque magnetometry measurements into radio frequencies, the contribution of the Einstein-de Haas (EdH) effect can become comparable to, and even exceed, the conventional magnetic torque (cross-product of magnetic moment and applied field) signal [4]. Extending sensitive optomechanical detection across a ladder of higher-order mechanical modes is a natural way to extract further information, through examination of the relative scaling of EdH and cross-product torques.

Sufficiently high-order mechanical modes have application to co-resonant detection of magnetic resonances. Magnetic vortex resonances intersecting the mechanical resonance spectrum will be described, and allow for the observation of dynamic vortex core interactions with magnetic inhomogeneities.

[1] M. Wu et al. Nat. Nanotechnol. 12, 127 (2017).
[2] G. Hajisalem et al. New J. Phys. 21, 095005 (2019).
[3] J. Losby et al. J. Phys D. 51, 483001 (2018).
[4] K. Mori et al. Phys. Rev. B. 102, 054415 (2020).

Speaker: Dr Joseph Losby (University of Alberta)

423 POS-G73 -- Pure-spin-current diode-like effect at the Au/Pt interface

Asymmetric charge transport at the interface of two materials with dissimilar electrical properties, such as metal/semiconductor and p-n junctions, is the fundamental feature behind modern diode and transistor technology. Spin pumping from a ferromagnet into an adjacent non-magnetic material is a powerful technique to generate pure-spin-currents, wherein spin transport is unaccompanied by net charge transport. It is therefore interesting to study pure-spin transport at the interface of two materials with different spin transport properties. Here we demonstrate asymmetric transport of pure-spin-currents across an interface of dissimilar non-magnetic materials Au/Pt. We exploit Py/Au/Pt/Co structures where spin pumping can generate pure-spin-current from either Py or Co independently. We find that the transmission of pure-spin-current from Au into Pt is more than twice as efficient as transmission from Pt into Au. Experimental results are interpreted by extending conventional spin-pumping/spin-diffusion theory to include boundary conditions of reflected and transmitted spin-current at the Au/Pt interface that are proportional to the established spin chemical potentials on either side of the interface.

Speaker: Pavlo Omelchenko

424 POS-G74 -- Observation of Magnon-Photon Coupling in a THz Scanning Fabry-Pérot Cavity

Hybridization of disparate physical systems is a key area of research in harnessing quantum technologies. Exploiting hybridized states can mitigate perturbative effects of reading out quantum states or even enable new devices based on new material properties associated with hybrid quasiparticle excitations. In the area of magnetism a particularly prominent area of progress is the exploration of magnon-photon hybridization in electromagnetic cavities which results in the emergence of a cavity magnon-polariton (CMP) [1]. Extensive work has been performed examining CMPs in microwave systems but little work has explored coupling with THz light. THz frequency magnon modes are prevalent in antiferromagnetic and ferromagnetic materials which themselves offer promising platforms for magnonic and spintronic technologies. In this experiment, we explore the coupling of THz light to electromagnons in multiferroic Bisthmuth Orthoferrite (BiFeO3) by suspending BiFeO3 powder on nearly THz transparent sample holders in a scanning Fabry-Pérot cavity. Characteristic splitting of the cavity modes is observed when the cavity modes are tuned to be coincident with the electro-magnons suggesting a THz scale CMP has been observed and pointing towards a new avenue to develop THz spintronic technologies.

[1] H. Huebl et al. Phys. Rev. Lett. 111, 127003

Speaker: Aimé Braconnier (University of Manitoba)

W-POS-H #75-79,109 Poster session (DTP) / Session d'affiches (DPT)

Convener: Mark Walton (University of Lethbridge)

425 (G*) POS-H75 -- Holographic and Localization Calculations of Boundary F for N=4 SUSY Yang-Mills Theory

$\mathcal{N}$=4 Supersymmetric Yang-Mills (SYM) theory can be defined on a half-space with a variety of boundary conditions preserving scale invariance and half of the original supersymmetry; more general theories with the same symmetry can be obtained by coupling to a 3D SCFT at the boundary. Each of these theories is characterized by a quantity called "boundary F", conjectured to decrease under boundary renormalization group flows. In this paper, we calculate boundary F for U(N) $\mathcal{N}$=4 SYM theory with the most general half-supersymmetric boundary conditions arising from string theory constructions with D3-branes ending on collections of D5-branes and/or NS5-branes. We first perform the calculation holographically by evaluating the entanglement entropy for a half-ball centered on the boundary using the Ryu-Takayanagi formula in the dual type IIB supergravity solutions. For boundary conditions associated with D3-branes ending on D5 branes only or NS5-branes only, we also calculate boundary F exactly by evaluating the hemisphere partition function using supersymmetric localization. The leading term at large N in the supergravity and localization results agree exactly as a function of the t' Hooft coupling λ.

Speaker: Christopher Waddell (University of British Columbia)

426 (G*) POS-H76 -- Continuous-variable entanglement in a ring resonator: An analytic solution

We prove that the state created via spontaneous parametric downconversion in a two-mode lossy cavity is a squeezed thermal state. We examine the case of generation in a side-coupled ring resonator.

In the context of quantum optics, two-mode squeezed states are routinely used as a source of continuous-variable (CV) entanglement for applications in the field of quantum information [1]. They can be generated via a nonlinear interaction such as spontaneous parametric downconversion (SPDC), where a strong coherent pump field interacts with a material that has a $\chi^{(2)}$ nonlinearity. The resulting squeezed light exhibits correlations between the quadratures of photons in the two modes.

In this work, we model the nonlinear generation of a squeezed state inside a lossy multimode cavity using the Lindblad master equation and show that the exact solution to this model is a two-mode squeezed thermal state, with time-dependent squeezing amplitude and thermal photon number in each mode. We also derive an analytic expression for the entanglement between the modes, and calculate the degree of entanglement in a side-coupled ring resonator.

These results will be of use to researchers that are trying to optimize CV entanglement in lossy cavities when the losses of each mode are different.

[1] Samuel L Braunstein and Peter Van Loock. Quantum Information with Continuous Variables.Rev. Mod.Phys., 77:513, 2005.

Speaker: Colin Vendromin

427 (G*) POS-H77 -- Brownian motion on a stochastic oscillator chain

Molecular dynamics simulations are, in principle, numerically exact, but severely restricted with respect to the accessible time- and length-scale of the system studied. Stochastic simulations offer an alternative modeling method that overcomes these limitations. Unfortunately, the relation between the properties of the original system and the parameters used in stochastic modeling is not always clear. We address this problem by studying the diffusion of a Brownian particle along a chain of coupled stochastic oscillators. We show that stochastic simulations of the Brownian particle alone may be in quantitative as well as in qualitative disagreement with the result of the full-scale molecular dynamics simulations. As a remedy, we propose to simulate a small part of the chain together with the Brownian particle, which now becomes ``dressed''. We introduce a recipe to perform the stochastic simulations of the part of the chain. We show that the diffusion coefficient of the Brownian particle in this type of stochastic modeling is practically the same as in the molecular dynamics simulations in a broad parameter range.

Speaker: Mr Amir Kaffashnia (Memorial University of Newfoundland)

428 POS-H78 -- Revisiting the Unruh effect with modified dispersion relations

The detected spectrum in the Unruh effect is Planckian for massless fields. The reason is that the latter display a linear dispersion relation. It is also well known that for massive fields, the detected spectrum in the Unruh effect would lose its Planckian profile. Remarkably, the relativistic Doppler shift approach to the Unruh effect shows that, just like with massive fields, fields with nonlinear dispersion relations also lead to a departure from a Planckian spectrum. The approach even applies to the case of modified Lorentz transformations. The big advantage of the approach, however, lies in the fact that it offers a very intuitive explanation for the reasons behind such results, and applies even to analogs of the Unruh effect. Detecting such a departure from thermality using water surface waves is very promising.

Speaker: Fayçal Hammad (Bishop's University)

429 (G*) POS-H79 -- Homonuclear diatomic molecule properties from an orbital-free-related density functional theory

An orbital free related density functional theory based on the principles of polymer self-consistent field theory is used to calculate the electron densities, bond energy, bond length and fundamental vibrational frequency of homonuclear diatomic molecules. A simple exchange-correlation functional that neglects correlations is used, and the Pauli potential is based on Edwards–Flory-Huggins interaction taken from polymer physics. Other approximations include a Fermi-Amaldi correction for electron-electron self-interactions and cylindrical averaging to reduce the dimensionality of the problem. Expected bonding characteristics are observed for the first 7 elements in the periodic table. Specifically, quantitatively accurate bond lengths and qualitatively accurate bond energy structure for hydrogen and nitrogen molecules. Bond energy and fundamental vibrational frequency are discrepant up to a factor of two when compared with accepted values. Other elements do not exhibit bonding as expected.

Speaker: Spencer Sillaste (University of Waterloo)

430 POS-H109 -- Fourier transform of gravitational wave signals from a pulsar

Gravitational Wave (GW) detection from continuous sources such as pulsars is an anticipated discovery. However, due to exceedingly weak signals, detection is challenging. In this presentation, we detail the derivation of a Fourier transform of a continuous wave signal amenable for detection of the GW signal from a pulsar. We also present an easy to implement algorithm for computing peak heights and frequencies from analytical results arising from features in frequency evolution of gravitational wave signals. Our approach can handle gaps in data, allowing longer
coherence lengths. While the presentation focuses on GW detection from pulsar, our results are general and can be applied to any monochromatic signals of this form.

Speaker: Farrukh Ahmed Chishtie (University of Western Ontario)

W-POS-J #80-107 Poster session (PPD) / Session d'affiches (PPD)

Convener: Marie-Cécile Piro (University of Alberta)

431 (U*) POS-J80 -- Automated Feature Detection and Camera R&D for Photogrammetry in Super-K and Future Water Cherenkov Neutrino Detectors

To allow for precision measurements of neutrino interactions in water Cherenkov neutrino detectors, reducing the position uncertainty on the photomultiplier tubes (PMTs) and calibration sources is necessary. This can be achieved with the photogrammetry technique. Detected PMTs in images of the detectors can be used to reconstruct a 3D model of their positions. This photogrammetry technique is being applied in the current Super-Kamiokande (Super-K) detector, and there are plans for its application in the next generation of water Cherenkov detectors, Hyper-K and its intermediate water Cherenkov detector (IWCD).
This talk discusses detection and identification of PMT features from a drone photographic survey of the Super-K detector, and camera calibration and R&D for a built-in photogrammetry camera system in the upcoming IWCD and Hyper-K detectors.

Speaker: Michael Sekatchev (TRIUMF)

sekatchev_photogrammetry.jpg

sekatchev_photogrammetry.pdf

432 (G*) POS-J81 -- Study of External Crosstalk in Light-only Liquid Xenon (LoLX) experiment

The Light-only Liquid Xenon experiment aims to investigate scintillation and Cherenkov emission in Liquid Xenon (LXe). This is a small experiment set up consisting of 24 Hamamatsu Silicon Photomultipliers (SiPM), giving a total of 96 channels arranged in an octagonal cylinder. 92 of these channels are covered with 225 nm high pass filters which help measure Cherenkov and VUV scintillation light, by blocking Xe scintillation. This experiment is designed in part to gain a clear understanding of the phenomena that contributes to misreconstruction of the scintillation light flashes for the future experiments, nEXO, DarkSide-20k and ARGO. One such factor is External Cross-talk. External cross-talk is a phenomenon in which a signal in one SiPM produces signals in neighboring SiPMs, making observed signal higher than the actual count. Crosstalk may seriously limit the photon-counting resolution of SiPMs.
This talk will discuss results of simulation of external cross-talk in the setup produced by using GEANT4, and its characteristics.

Speaker: Mayur Patel (Simon Fraser University)

433 POS-J82 -- Constraining ultralight dark photons with galactic center gas clouds

We demonstrate that dark matter heating of gas clouds, hundreds of parsecs from the Milky Way Galactic Center, provides a powerful new test of dark sector interactions. As an example, we constrain ultralight dark photon dark matter, which requires a simple extension of the Standard Model (SM) by a U(1) gauge group. We place new bounds on ultralight dark photon dark matter for m ≤ 10^10 eV. An ultralight dark photon, through its mixing with the SM photon, produces an oscillating electric field that generates a current and dissipation in
the gas cloud medium, which is not a perfect conductor. This altogether transforms dark photon potential energy into the kinetic energy of charged particles in cold gas clouds. This enables us to place leading constraints on ultralight dark photon interactions.

Speaker: Amit Bhoonah

434 (G*) POS-J83 -- Exploring dark matter detection using Solar capture and the Non-Relativistic Effective Operator formalism.

In the search for particle dark matter (DM), the most prominent model is the Weakly Interacting Massive Particle (WIMP). Should particle DM have some weak interaction with baryonic matter, the DM would interact with the matter found in the Sun and other massive bodies. When the DM scatters to velocities below the local escape velocity, this results in gravitational capture and subsequent annihilation into neutrinos, which can be seen at telescopes such as IceCube. This is complementary to direct detection experiments, as solar capture is sensitive to different types of interaction, mass ranges, and different parts of the DM velocity distribution. We use Non-Relativistic Effective Operators (NREO) to produce combined constraints from solar and direct detection searches for WIMPs. NREOs allow for the description of general interactions that can favour properties such as the spin-orbit coupling of nucleons in a nucleus. We combine the general solar DM constraints from IceCube with a variety of direct detection experiments such as Lux, Xenon1T, PandaX, Pico 60, Cresst II, CDMSlite, and Darkside 50 using GAMBIT, the Global And Modular BSM Inference Tool and perform a statistically consistent global analysis of the current state of DM detection using the NREO formalism.

Speaker: Neal Avis Kozar

435 (G*) POS-J84 -- The effect of single Coulomb scattering on Cherenkov emission

Cherenkov radiation plays a crucial role in particle physics experiments.
This is of particular importance in water-filled neutrino detectors, where electron neutrinos are observed through the Cherenkov radiation of ultra-relativistic secondary particles created in the detector's volume. Modern simulation methods of the process that describe Cherenkov emission assume coherence of the radiation throughout the particle’s path without accounting for the impact of scattering of the electrons in matter. Here we consider a more physically accurate calculation of Cherenkov radiation as a phenomenon of wave interference. We then apply this calculation to a simulation that accounts for single Coulomb scattering of the electron with the material.
The obtained angular distributions of the photons as they would be observed in a detector are compared to the ones predicted by standard simulation tools.

Speaker: Dmytro Minchenko (University of Alberta)

Poster_Cherenkov_CAP2021.pdf

436 (G*) POS-J85 -- SN0+ U-238 External Background Measurements using Radon Assay Technique

ABSTRACT:
SNO+ is large multipurpose detector located at SNOLAB, Canada, Sudbury filled with liquid scintillator. The scintillator will eventually be loaded with a tellurium isotope, allowing to look for neutrino-less double beta decay which is extremely rare. This will determine if the neutrino is its own antiparticle. One of the main concerns for these rare event experiments is the presence of backgrounds, which could mask the signals of interest. This presentation will focus on Rn222, one of the most common backgrounds due to its excessive prevalence in the mine environment. Radon decays into daughters where the energies lie within the region of interest for neutrino-less double beta decay. The detector is housed in a large cavity that is filled with ultrapure water and has a nitrogen cover-gas in order to avoid contamination. This presentation will focus on radon assays, a technique that was developed for the SNO experiment. Assays are performed frequently at different positions to monitor the radon levels. During a radon assay, radon is trapped with a ZnS coated lucas cell for a period of time and known amount of flow. This lucas cell can then be connected to a PMT, which detects the decayed alphas that are used to calculate the number of radon atoms in the cavity. This external technique is a crucial part of measuring and monitoring the low background for the experiment.

Speaker: Mr Syed M Adil Hussain (Laurentian University)

437 (U*) POS-J86 -- K40 Backgrounds in the SNO+ Neutrino Detector

SNO+ is a neutrino detector located 2 km underground at the deep clean lab facility - SNOLAB, in Vale’s Creighton Mine, in Sudbury ON. The primary goal of the SNO+ experiment is to search for an extremely rare, hypothesized phenomenon, neutrino-less double beta decay (0vbb) - the discovery of which will have a multitude of major implications in fundamental physics. Given the rarity of this phenomenon, it is paramount that all backgrounds in the detector be carefully measured and understood. In this poster, I will show the importance of background analysis and detail the method used to find a rate for K40 backgrounds – a signal that is especially difficult to measure. The techniques used in this analysis allowed for the first-ever estimate of the K40 background made directly from data taken with a detector partially filled with liquid organic scintillator.

Speaker: Parmesh Ravi (University of Waterloo)

Ravi_CAP_poster_2021_Final.pdf

438 (G*) POS-J87 -- Magnetic monopole production in heavy-ion ultraperipheral collisions at the LHC

The possible existence the magnetic monopole is strongly motivated by theories and extensively tested in experiments. Searches at the LHC have been exclusively conducted with proton-proton collisions. However, the LHC not only collides protons but also heavy ions. Highly relativistic ultraperipheral collisions (UPC), where the ion-ion impact parameter exceeds the ion’s diameter, act as a strong source of electromagnetic radiation. Characterized by minimal hadronic activities, the UPC creates a clean environment to study magnetic monopoles produced via photon-fusion processes. I will present a generator-level study of this production mode, including the modelling of the photon energy spectrum and the monopole interaction required to compute the production cross section at the maximal collision energy of the LHC.

Speaker: Wen Yi Song (York University (CA))

cap_2021_song.pdf

439 (G*) POS-J88 -- Searching for charged Higgs bosons in W+photon final state

The Higgs boson was observed at the Large Hadron Collider (LHC) at CERN in 2012. Its existence confirms the Higgs field which explains how some particles have mass while others do not. Since 2012, an important task has been to search for the neutral Higgs boson’s charged siblings. In the Standard Model (SM), the Higgs boson is a massive neutral particle observed at a mass near 125 GeV. The Georgi-Machacek (GM) model extends the SM to have a fiveplet Higgs sector with singly and doubly charged Higgs particles. Our search of the charged Higgs boson uses the 2015-2018 Run-2 data from the LHC as well as simulated samples to model the processes. Machine learning algorithms are used on simulated samples to achieve optimal signal selection. The status of the current analysis will be presented.

Speaker: Zhelun Li (McGill University, (CA))

440 (U*) POS-J89 -- Modelling bubble nucleation efficiency in superheated liquid argon

Astronomical and cosmological observations strongly suggest the existence of dark matter in the Universe. The favourite candidate is the WIMP (Weakly Interacting Massive Particles) and can be detected directly via elastic scattering on the target nuclei. Physicists are relying on more innovative and sensitive detectors in hope of capturing the nuclear recoil created by this mysterious particle. One of those detectors is the bubble chamber, which is made up of an outer shell filled with superheated liquids (argon, xenon, fluorocarbons etc). Once incoming particles collide with the liquid molecules, they deposit energy and can cause bubble(s) to form: this is named the nucleation. Therefore, by understanding the conditions of bubble formation and how this process is efficient, we can gain information about the incoming particles, and potentially gather evidence about the existence of dark matter particles. After describing the method used to model the bubble formation, I will present the current results we have obtained to extract the nucleation efficiency of nuclear recoils in superheated liquid argon and compare with the observed bubble nucleation efficiency in the detector. Finally, I will discuss how it can improve the sensitivity of the bubble chambers to potential dark matter particles.

Speaker: Freyja Wang (University of Alberta)

CAP Poster .pdf

441 (G*) POS-J90 -- Analysis and identification of alpha events for NEWS-G

The NEWS-G experiment uses a spherical proportional counter filled with gas in order to detect potential dark matter particles that can ionize the gas after a nuclear recoil. The detector works by attracting the free electrons towards the center of the sphere where there is a high voltage anode inducing a radial electric field. Near the anode, the accelerated electrons then cause a Townsend avalanche that produces many drifting ions, which creates an identifiable electrical signal. Since this method has been most efficient at energies below 1 GeV, that is where keeping the background contamination at minimum is of upmost importance. However, there is approximately 20 mBq of alpha particles coming from impurities in the copper surface of the sphere that create a sudden influx of events close to the region of interest for up to five seconds. These alphas also lead to fluctuations in the electric field, which in turn alters the time taken for electrons to reach the anode at the center. This presentation aims to show how the consequences of alpha particles in the detector can be characterized, as well as how those consequences can be used to better identify alpha events in order to remove the correlated influx of low energy events.
*On behalf of the NEWS-G collaboration

Speaker: Jean-Marie Coquillat (Queen's University)

CAP 2021 poster final.pdf

442 POS-J91 -- Crosstalk and fiducial volume study with the ACHINOS sensor for the NEWS-G experiment

The NEWS-G experiment aims for the direct detection of low mass Weakly Interacting
Massive Particle (WIMP) dark matter using Spherical Proportional Counters (SPC). At the center of the SPC, a small sensor held at high voltage drives the drift of the primary ionization and provide the amplification needed to detect sub-keV nuclear recoils down to single electrons. The ACHINOS is a novel multi-channel sensor at the center of the SPC that allows for high amplification and better primary ionization collection thanks to enhanced electric fields at larger radius. The current implementation of ACHINOS in the NEWS-G SPC has two channels that separate the active volume in to distinct volumes, namely north and south. An improved version of ACHINOS sensor with three channels is set to be used for the NEWS-G experiment at SNOLAB in Spring 2021. Future implementation of ACHINOS with multi-channel readout could allow for the directional measurement of dark matter in a large, low-pressure SPC. In this talk, the operating principle of the ACHINOS sensor will be presented together with the study of cross-talk and fiducial volume.

Speaker: George Savvidis (Queen's University)

443 (G*) POS-J92 -- Analyzing the behavior of a Candidate SiPM and Signal Amplifier for MATHUSLA

MATHUSLA (MAssive Timing Hodoscope for Ultra-Stable neutraL pArticles) is a long-lived particle (LLP) detector which would be constructed on the surface above CMS and is currently in its planning stages. This large-area detector would be composed of several layers of solid plastic scintillator, with wavelength-shifting fibers connected to silicon photomultipliers (SiPMs), allowing us to monitor an empty air-filled decay volume. The purpose of this research is to examine the behavior of a candidate SiPM and signal amplifier for this detection array. The SiPM in question is the SensL MicroFB-30035 and the amplifier is the Broadcom AFBR-S4E001. This goal was accomplished by simulating these components in Ngspice, an electronic circuit simulator. Using this simulation method, we were able to measure the amplified signal output and produce voltage-time plots for it. We will next build this setup in the lab and compare our results to other candidate SiPMs. This research will be useful in developing other aspects of the detection array, the triggering system, and the readout system.

Speaker: Lucas Perna

_Final_Lucas_Perna_Poster.pdf

444 (G*) POS-J93 -- Validating misalignment measurements between particle detectors for the ATLAS New Small Wheels

The major ongoing upgrade of the ATLAS detector at the Large Hadron Collider at CERN consists in the replacement of parts of its muon spectrometer. The so-called New Small Wheels (NSWs) will be covered with two detector types that must trigger on and track outgoing particles - one type is small-strip thin gap chambers (sTGCs) assembled into modules of four layers. Canadian-built sTGC modules are characterized at McGill University using cosmic rays before being shipped to CERN for integration into the wheels. To achieve the design tracking performance, misalignments between sTGC layers must be corrected for. The charge profile left by an x-ray gun and coordinate measuring machine (CMM) measurements of quadruplet layers are being used to define these parameters. Work on using cosmic ray data to validate misalignment parameters derived using the above-mentioned methods will be presented.

Speaker: Lia Frances Formenti (McGill University, (CA))

formenti_CAP2021_poster.pdf

445 (G*) POS-J94 -- Study of Wyy tri-boson production in proton-proton collisions with the ATLAS detector

From 2015 to 2018, the Large Hadron Collider (LHC) collided protons at an unprecedented center of mass energy of s=√13 TeV. The ATLAS detector recorded an integrated luminosity of 139fb$^{-1}$ of these collisions. This offers an unprecedented opportunity for physicists to test the Standard Model by measuring predicted but yet unobserved rare processes. The triboson W$\gamma\gamma$ production is one of these unobserved processes. Its sensitivity to the electroweak trilinear and quartic gauge couplings make it a great probe of new physics phenomena as Beyond Standard Model processes could affect the effective strength of these couplings. The dominant source of background to the search for W$\gamma\gamma$ production are jets being misidentified as photons. The advanced data-driven technique used to estimate this background will be presented. Furthermore, preliminary studies of the dominant systematic uncertainties impacting the expected significance of the measurement will be presented.

Speaker: Auriane Canesse (McGill University, (CA))

acanesse_poster.pdf

14:15 WITHDRAWN: POS-J95

446 (G*) POS-J96 -- Drift Time and Charge Trapping in P-Type Point-Contact HPGe Detectors

P-type point contact (PPC) high-purity Germanium detectors have gained substantial interests in the search for neutrinoless double beta decay (0νββ) due to their background-rejection capabilities and excellent energy resolution. The drift time of charge carriers in the detector can be used in determining the position of an energy deposition and identifying sources of the background. One can also use drift time to look for evidence of charge trapping by impurities in the germanium crystal and correct the degraded energy resolution. Here we will discuss charge trapping in detail and present an optimized method for measuring the drift time in PPC detectors.

Speaker: Tianai Ye (Queen's University)

447 (G*) POS-J97 -- Optical reflectors in an ARICH detector for a hadron production experiment

EMPHATIC (Experiment to Measure the Production of Hadrons At a Testbeam In Chicagoland) is a low-cost, table-top-sized, hadron-production experiment located at the Fermilab Test Beam Facility (FTBF) that will measure hadron scattering and production cross sections that are relevant for neutrino flux predictions. High statistics data will be collected using a minimum bias trigger, enabling measurements of both interacting and non-interacting cross sections. Particle identification will be done using a compact aerogel+heavy gas hybrid ring imaging Cherenkov (RICH) detector, a time-of-flight (ToF) wall, and a lead glass calorimeter array. The ARICH focuses on the kaons, pions and protons separation with multi-track capability up to 8 GeV/c. This presentation is about the implementation of optical reflectors in the ARICH system to reflect Cherenkov light outside of the PMT array acceptance onto the PMT array increasing the angular acceptance of the experiment with a low cost improvement.

Speaker: Mr Bruno Ferrazzi (University of Regina)

CAP_bferrazzi.pdf

448 (G*) POS-J98 -- A search for neutrino absorption with 40Ar using the DEAP-3600 detector

The highest energy range of the solar neutrino spectrum is dominated by $^8$B neutrinos produced in the pp-chain in the Sun and by hep neutrinos. R.S. Raghavan, K. Bhattacharya, and others have predicted that neutrino absorption with $^{40}$Ar is a possible interaction for neutrinos with energies above 3.9 MeV. In this case, neutrino induced nuclear transitions from $^{40}$Ar to $^{40}$K are feasible. One possible transition produces a delayed coincidence signature with a mean lifetime of 480 ns. A search for this process relies on understanding the backgrounds for this search, specifically neutron capture gammas. These neutrons include both radiogenic neutrons from PMTs and detector materials and cosmogenic neutrons from muon interactions with the surrounding rock. We propose to search for this process using 3 years of data from the DEAP-3600 dark matter experiment and present the latest efforts in this on-going study. DEAP-3600 is a liquid argon (LAr) direct dark matter experiment based at SNOLAB that is designed to detect WIMP-nucleon scattering in argon. The experiment's ultra-low background, high sensitivity and its large target mass could make it possible to observe this process for the first time.

Speaker: Emma Ellingwood (Queen's University)

14:23 WITHDRAWN : POS-J99

449 POS-J100 -- Multi-Interacting Massive Particles in DEAP-3600

DEAP-3600, hosted at SNOLAB, has been designed for the search of WIMPs, Weakly Interacting Massive Particles; its target of 3.3 t of liquid argon is the largest direct detection experiment. In addition to its sensitivity to WIMPs, DEAP-3600 is sensitive to super-massive dark matter candidates with masses up to the Planck scale. At dark matter-argon cross-sections above 10^{-24} cm^2 and dark matter masses above 10^{16} GeV, dark matter particles are expected to reach an underground experiment and give a detectable signal in liquid argon; indeed particles at lower masses and such high cross-sections are eventually stopped by the overburden. Moreover, due to the large cross-section, all MIMPs that enter the detector are expected to produce signals; as a consequence, the sensitivity to high masses depends on the cross-sectional area of the detector. The expected signal in DEAP-3600 is a collinear sequence of nuclear recoils in the same acquisition window, giving a very clear and unique signature;hence, we refer to them as MIMPs, Multi-interacting Massive Particles. In the present talk, the search for MIMPs in three years of data-taking is presented, showing the first search for multi-scattering dark matter in noble liquids ever performed.

Speaker: Michela Lai (University of Cagliari)

poster_mimp.pdf

450 POS-J101 -- Constraining contributions from Kr-85 in DEAP-3600

DEAP-3600 is a liquid argon detector designed to directly detect dark matter by searching for nuclear recoil (NR) events caused by elastically scattered weakly interacting massive particles, a prime candidate for dark matter. Pulse-shape discrimination properties of the argon allow for significant separation between electromagnetic recoil (ER) events and NR events. The majority of the events in the ER spectrum are beta decays of Ar-39, which is an isotope naturally present in argon. Several efforts are underway to study the Ar-39 spectrum in DEAP-3600. In order to perform these studies, we must have an extensive understanding of the possible background in the ER spectrum. A possible background contribution to this spectrum are events from Kr-85, a radioactive isotope that can potentially bypass the purification methods used to fill the detector with argon. Trace amounts of Kr-85 are produced in the atmosphere via interactions with cosmic rays and Kr-84, which could be present in atmospheric argon. Given that the beta spectrum endpoint (Q-value) of Kr-85 is slightly higher than Ar-39, excess events in the region just above the Q-value of Ar-39 are expected if there is any contamination by Kr-85. A full spectrum fit was done to search for potential contributions from this isotope.

Speaker: Sean Daugherty (Laurentian University)

Constraining contributions from Kr-85 in DEAP-3600.pdf

14:29 WITHDRAWN : POS-J102

451 (G*) POS-J103 -- Search for Dark Matter Produced in Association with a Dark Sector Higgs Boson in Proton-Proton Collisions with the ATLAS Detector

Longstanding evidence from observational astronomy indicates that non-luminous "dark matter" constitutes the majority of all matter in the universe, yet this mysterious form of matter continues to elude experimental detection. The study presented in this talk is part of an ongoing programme to search for dark matter production in high-energy proton-proton collisions at the Large Hadron Collider (LHC) at CERN. This search targets a model in which dark matter is produced in association with the emission of a hypothesized heavy Higgs boson in the dark sector, which then decays to a pair of W bosons. The final-state signature of this model would be an excess of missing transverse energy in the detector due to undetected dark matter production, along with two reconstructed W bosons. A search was recently performed targeting this final state in the 'hadronic' decay channel, wherein both W bosons decay to a pair of quarks. The semi-leptonic WW decay channel, in which one of the bosons instead decays to a lepton and neutrino, will complement and extend the reach of the existing search in the hadronic channel. A dark matter search in this semi-leptonic WW decay channel is presented.

Speaker: Danika MacDonell (University of Victoria (CA))

DMacDonell_CAP_2021_Poster.pdf

452 (G*) POS-J104 -- Low Background Neutron Counters for HALO-1KT

The last supernova near our galaxy was in 1987. HALO-1kT will be a low background galactic Supernova detector that uses 1kT of lead as the target for supernova neutrinos and helium-3 neutron counters to detect neutrons produced from the neutrino-lead interactions. The neutrons are then effectively captured by He-3 and converted to electrical signals by the proportional counters.

As with many experiments that want to detect particles coming from space, HALO- 1kT needs to have low ”backgrounds”. The term backgrounds refers to any ambient particles, or noise, which are unrelated to the supernova signal that the counters could pick up. Some backgrounds cannot be controlled, like the amount of neutrons in the lab at any given time, but there are backgrounds that can be minimized, like choosing the lowest background materials possible for building the counters. As HALO-1kT is planned to have 4.3 km of helium-3 counters, they need to have as low backgrounds as possible.

My research is testing the protype proportional counters to make sure their backgrounds are low enough to avoid regular false positives. The first way of testing them was to take the 4 counters underground at SNOLAB to collect 3-4 months of data as well as a 2-day calibration run to see what the base background rate is. After that two of counters were attached to electrostatic counters and counted for two months to determine the background of the wall material. Initial background rates show the prototype counters have 50x too much background. The ongoing research will help narrow down which part of the counters those backgrounds are coming from so that the materials used to make the actual counters will be cleaner allowing the counters to meet the background goals.

Speaker: Esther Weima (Laurentian University)

EstherWeimaCapPoster.pdf

453 POS-J105 -- Dark matter, axion quark nugget, and mysterious bursts observed by telescope array

Telescope Array experiment has recorded several short time bursts of air shower like events. These bursts are very distinct from conventional single showers, and are found to be strongly correlated with lightnings. We proposed these bursts represent the direct manifestation of the dark matter annihilation events within the so-called axion quark nugget model. We discuss how to test this proposal by searching for the radio signals in frequency band (0.5−200) MHz which must be synchronized with the Telescope Array bursts.

Speaker: Xunyu Liang (The University of British Columbia)

454 (G*) POS-J106 -- Search for New Physics Inside Boosted Jets at the ATLAS Detector Using Anomaly Detection

Since the discovery of the Higgs boson at the LHC in 2012, no sign of new physics beyond the Standard Model has been found. The SUSY and exotic particles searches have not uncovered signs of new physics, as the model-dependent searches. In recent years, multiple unsupervised machine learning methods have been proposed to search for new physics at the LHC. This poster will explore the use of a variational auto-encoder (VAE) to perform a general search in proton-proton collisions at the LHC using large radius jets in ATLAS simulation data. To test our workflow, we trained the algorithm on low-level jet information to differentiate between the dominant QCD background and a chosen test signal corresponding to top quark jets. The most anomalous jets predicted by the VAE were selected to plot the invariant mass spectrum and to find the top quark mass peak. Our study found an important correlation between the jet invariant mass and the loss function of the VAE, resulting in a sculpting of our background and preventing the apparition of the top peak. We successfully used a mass-decorrelation method based on Outlier Exposure to prevent this sculpting.

Speaker: Mrs Jacinthe Pilette (Montreal)

455 (U*) POS-J107 - Radioactive Background Characterization of the Cryogenic Underground TEst Facility (CUTE)

The Cryogenic Underground TEst Facility (CUTE) is fully operational underground at SNOLAB. The facility can host up to six of the next generation SuperCDMS cryogenic detectors, and allows for the opportunity to search for low-mass dark matter while testing the new detectors. The SNOLAB cleanroom laboratory provides a low-background and low-cosmogenic-activation environment for CUTE operations. Estimating the background from radioactive processes with Geant4 simulations becomes a crucial task in informing the background budget for the experiment. This presentation will describe the radioactive background characterization of the CUTE facility, and discuss its validation through comparison with acquired data.

Speaker: Melissa Baiocchi (SNOLAB)

CAP_Poster_J107_Melissa_Baiocchi.pdf

W-POS-K #108 Poster session (DNP) / Session d'affiches (DPN)

456 POS-K #108 -- Time-reversal test in radiative beta decay: progress

We are developing a time-reversal breaking test in radiative $\beta$ decay, using just the momenta of three outgoing particles. This type of time reversal is independent of nuclear spin, so explores time reversal-breaking physics unrelated to electric dipole moments (though there are model-dependent constraints at 1-loop order from null measurements of the neutron EDM). The scalar triple product of three momenta $\vec{p_1}\cdot \vec{p_2} \times \vec{p_3}$ provides a unique time-reversal odd observable, but trivially vanishes in ordinary $\beta$ decay when the three momenta sum to zero. So we need the fourth outgoing particle in radiative $\beta$ decay, considering the correlation between $\beta$, $\nu$, and $\gamma$. We add $\gamma$-ray detectors (GAGG scintillator with SiPM readout) to TRIUMF's magneto-optical trap for beta decay (TRINAT), which includes a uniform electrostatic field for efficient recoil ion detection. Explicit models produce this observable with an antisymmetric Chern-Simons term from QCD-like new interactions, interfering with the standard model vector electroweak interaction within the nucleon [S. Gardner and D. He, Phys. Rev. D 87 116012 (2013)], and among the predicted features are a quite different gamma-ray spectrum than normal bremsstrahlung. We will show initial data from the decay of 92Rb, a case without vector interactions not yet testing the explicit models.

Speaker: John Behr (TRIUMF)

behr_CAP_2021_TRV.pdf

14:45 15 Minute Break

W-PLEN-3 Alessandra Lanzara, Lawrence Berkeley National Laboratory (DCMMP/DPMCM)

Convener: Michel Gingras

457 Leveraging local symmetry breaking to engineering novel materials.

The 20th century has been dominated by the realization that symmetry and symmetry breaking influence the forces that govern our universe and are keys to much of the novel phenomena observed in materials today. Recently it has been realized that, even if the global symmetry of a system is retained, a local symmetry breaking can still drive a variety of novel fascinating behaviors. In this talk I will present the effect that local breaking of inversion, translational and rotational symmetry can have in defining fundamental properties of matter from topological phases to superconductivity and how it can be used as a tuning parameter to control novel properties in van der Waals heterostructures.

Speaker: Prof. Alessandra Lanzara (University California, Berkeley)

15:30 15 Minute Break

W3-1 Quantum Information: Theory (DAMOPC) / Information quantique: théorie (DPAMPC)

Convener: Jens Lassen (TRIUMF)

458 (I) Quantum Information Processing With Superconducting Circuits

By exploiting effects such as quantum superpositions and entanglement, quantum computers could solve problems that are intractable on standard, classical, computers. While building a full-scale quantum computer capable of rivalling with today’s supercomputers remains a challenge, the last few years have seen tremendous improvements in our ability to build small superconducting quantum processors and run simple algorithms on these processors. In parallel to these advances towards quantum information processing, much effort has been invested in using superconducting qubits as artificial atoms to explore the physics of quantum optics in novel parameter regimes. I will discuss recent developments and future challenges that lie ahead.

Speaker: Prof. Alexandre Blais (Universite de Sherbrooke)

459 (I) Realizing a perfect quantum transduction by applying a bad transducer twice

To utilize the advantages of different quantum platforms, we need an interface (transducer) to transfer quantum information from one to another. Unfortunately, realistic transducers are imperfect due to, e.g. weak interaction strength or unwanted coupling. In this talk, I will present a surprising strategy to remedy the transduction imperfections: by applying a bad transducer twice [1]. I will first introduce a novel characterization of all coherent transducers by their analogous position and momentum noises. I will then show how destructive interference and measurement can be employed to eliminate the unwanted noise. I will also illustrate how the remaining noise can be corrected by using bosonic codes. Our proposal can relax the stringent technological requirement of implementing perfect transducer, and potentially enhance the speed of information transfer.

[1] Hoi-Kwan Lau and Aashish A. Clerk, npj Quantum Information 5, 31 (2019)

Speaker: Prof. Hoi-Kwan (Kero) Lau (Simon Fraser University)

460 (G*) High-performance information engine.

Information engines are the modern realization of the Maxwell demon, a thought experiment that revealed that information is also a thermodynamic quantity. We build and study a simple information-to-work engine, which consists of a heavy bead, in a water bath, trapped by optical tweezers. The bead undergoes Brownian motion due to the thermal fluctuations in the bath. The position of the bead is tracked at a high sampling rate (50 kHz) using a quadrant photodiode. Occasionally, when the bead fluctuates “up,” the position of the trap is also raised, thus converting information about the system’s position into stored energy. The engine can also be designed to produce directed motion. Optimizing the feedback parameters, we found that maximum performance is obtained for continuous ratcheting. Also, the velocity is maximized for small bead diameters, whereas stored power is maximized for large bead diameters. Increasing the trap stiffness increases both. These observations are well explained by a recently developed theory based on mean first-passage times. By optimizing the feedback algorithm and experimental parameters, we have observed rates of energy storage of 1000 $k_\rm{B}$T/s and directed velocities of 190 µm/s, numbers that are comparable to those observed in biological systems such as bacteria.

Speaker: Mr Tushar K. Saha (Simon Fraser University)

461 (G*) Accurate numerical method for the calculation of the doubly excited states in atoms

We investigate in the present work the doubly excited states (DES) in the Helium-like O6+ and F7+ ions. The interaction of these systems with X-ray laser pulses can cause the DES to appear in their energy spectra due to the strong correlation between the electrons. The formation of the DES can be followed by a decay by electron emission (autoionization) causing the parent ion to lose its electrons.
The recent advent of free electron lasers (FELs) sources capable to generate laser pulses of durations comparable to the ultrashort lifetimes of the autoionizing DES in atoms will open the opportunity to investigate the autoionization mechanisms and to understand the importance of the role the DES play in the ionization process. Accurate theoretical knowledge of where these states can be located in the energy spectrum of the targeted system and their precise lifetime decay will be a support to the future experiments on the laser-atom processes involving the DES.
To date, theoretical data of the energy position E and the lifetime decay τ for the DES in the O6+ and F7+ ions and other heavier systems are still lacking. In order to locate and investigate the DES in the energy spectrum of an Helium-like ion, we have developed an efficient method based on the numerical resolution of the Schrödinger equation with a B-splines discretization technique [1,2] combined with the complex rotation method [3]. Our method has the numerical advantage to generate the parameters (E, τ) in a single calculation. It also allows the identification of the DES that share similar angular correlation pattern, which helps in their classification into distinct series.
We present our recently published results on the detection of DES in the O6+ion [4] and other recent results of our investigation of the DES in the F7+ ion. The theoretical results generated in this work will be of great interest to the future experiments on the O6+ and F7+ with X-ray FELs laser pulses.
[1] S. Barmaki, M.-A. Albert, S. Laulan, Chem.Phys. 517, 24 (2019)
[2] S. Barmaki, M.-A. Albert, S. Laulan, J. Phys. B: At. Mol. Opt. Phys. 51, 105002 (2018)
[3] M.- A. Albert, S. Laulan, S. Barmaki, Radiat. Phys. Chem. 166, 108453 (2020)
[4] S. Barmaki, M.- A. Albert, S. Laulan, Phys. Scr. 95, 055403 (2020)

Speaker: Marc-André Albert

462 (G*) Waveguide QED toolboxes for universal quantum matter

The simulation of quantum systems is inherently difficult due to the exponentially scaling of the state that must be simulated for a general system. One clear way to get around this problem is to utilize the properties of the quantum physics it’s self, ergo simulate quantum physics on quantum physics. An exciting frontier in quantum information science is the realization and control of complex quantum many-body systems for just this. Within this realm, we here harness the engineered coupling between spin and quantum motion of neutral atoms in a 1D photonic crystal waveguides for the realization of analog quantum simulation. In particular our platform realizes analog simulation of synthetic quantum material for universal 2-local Hamiltonian graphs. To do this, we develop a low-energy theory for the external motional states of the trapped atoms in the bandgap regime of waveguide QED, then generalize our microscopic theory to the development of dynamical gauge fields. In the spirit of gauge theories, we investigate emergent lattice models for strongly coupled SU(n)-constrained excitations driven by an underlying multi-body interaction. As a minimal model in the infrared, we explore the realization of an archetypical strong coupling quantum field theory, SU(n) Wess-Zumino-Witten model, and discuss a diagnostic tool to extract the entire conformal data of the field theory by the static and dynamical correlators of the fluctuating photons in the guided mode.

Speaker: Mr Jacob Taylor (Institute for Quantum Computing University of Waterloo)

463 (U*) Quantum Control of Trapped Ions using Stimulated Raman Adiabatic Passage

Trapped-ion quantum states are well-known to be good candidates for qubits in quantum computing. I will study the application of an adiabatic method known as STIRAP to achieve qubit switching. Stimulated Raman Adiabatic Passage (STIRAP) is a method of quantum control that utilizes a specific atomic structure known as a 3-Level Lambda System (3LLS). The system consists of two ground states that are coupled to an intermediate excited state via two counter-intuitively ordered pulses known as the Stokes and pump pulses. STIRAP is a notable method of population transfer because not only is it robust against small experimental variations, but it also has the unique property to allow the complete transfer of population between the two ground states without ever suffering population loss due to spontaneous emission from the excited state. STIRAP can be extended to other chain-wise connected multi-level systems such as those that are present in the trapped-ion. In this study, I will numerically determine the optimal pump and Stokes pulses that will maximize qubit switching in 3, 5, and 7-quantum states of the trapped-ion, and discuss the potential applicability of this method in quantum computing.

Speaker: Zach Manson (University of Windsor)

464 (G*) Wigner negativity in spin-j systems

The nonclassicality of simple spin systems as measured by Wigner negativity is studied on a spherical phase space. Several SU(2)-covariant states with common qubit representations are addressed: spin coherent, spin cat (GHZ/N00N), and Dicke (W). We derive an upper bound on the Wigner negativity of spin cat states that rapidly approaches the true value as spin increases beyond $j \approx 5$. We find that spin cat states are not significantly Wigner-negative relative to their Dicke state counterparts of equal dimension. We also find, in contrast to several entanglement measures, that the most nonclassical Dicke basis element is spin-dependent, and is not in general the equatorial state $|j,0\rangle$ (or $|j,\pm 1/2 \rangle$ for half-integer spin). These results underscore the influence that dynamical symmetry has on nonclassicality, and suggest a guiding perspective for finding novel quantum computational applications.

Speaker: Jack Davis (University of Waterloo)

465 Broadband quantum memory in a cavity via zero spectral dispersion

We seek to design experimentally feasible broadband multiplexed optical quantum memory with near-term applications to telecom bands. Specifically, we devise dispersion compensation for an impedance-matched narrow-band quantum memory by exploiting Raman processes over two three-level atomic subensembles, one for memory and the other for dispersion compensation. Our proposed broadband quantum memory employs three-level atoms with atomic density, cavity quality, and Raman-laser power and detuning chosen such that inverse cavity lifetime equal so ptical depth, the delay-bandwidth product exceeds $10^6$, power efficiency exceeding 90% and at least one second of storage time, thereby leading to $10^6$ modes for multiplexing. Our design will lead to significant multiplexing enhancement for quantum repeaters to be used for telecom quantum networks.

Speaker: Arina Tashchilina

16:19 Group discussion

W3-10 Candidates for Dark matter and Dark sector I (PPD) / Candidats pour matière et secteur sombres I (PPD)

Convener: David Morrissey (TRIUMF)

466 (I) New evidence for a dark sector? – Search for the X17 resonance

Nuclear transitions provide a means to probe light, weakly-coupled new physics and portals into the dark sector. Particularly promising are those transitions that can be accessed through excited nuclear states that are resonantly produced, providing a high-statistics laboratory to search for MeV-scale new physics. In this talk the so-called X-17 anomaly will be discussed, which is a 7σ discrepancy reported by the ATOMKI group in the observation of the decays of excited 8Be and 4He nuclei to their ground states via internal e+ - e- pair creation. The anomaly can be explained by the emission of a neutral boson with a mass of about 17 MeV/c2. The ATOMKI results and their interpretations are discussed, as well as follow-up experiments, among which an ongoing project at the Montreal tandem accelerator facility.

Speaker: Viktor Zacek (Université de Montreal)

Zacek_CAP_W3.pdf

467 Searches for Dark Photons at Belle II

Belle II is a B-Factory experiment designed to produce precision measurements of CP violation in the weak sector as well as search for Beyond the Standard Model particle physics. The $e^{+}e^{-}$ collisions are created by the SuperKEKB accelerator which has achieved a world record of instantaneous luminosity of $2.4 \times 10^{34} {\text{cm}^{-2}}{\text{s}^{-1}}$. One of the highest priorities for the early data of the experiment is the search for dark photons that decay to dark matter. A dark photon is a mediator within the dark sector which mixes with the Standard Model (SM) photon. The experimental signature is a single energetic photon observed in the detector. A dark photon would produce an excess of events in the single photon recoil mass. A particularly challenging case is when the visible photon carries the full beam energy, which corresponds to a low-mass dark photon. There is a significant background from the SM process $e^{+}e^{-}\rightarrow \gamma\gamma$, where one of the photons is missed due to detector imperfections. This has motivated us to study the structure of the sub-detectors and compare the data and Monte Carlo response. By understanding the photon detection sensitivity of the sub-detectors, we will estimate the background for dark photon studies. This talk will discuss the ''single photon search'' and the approach to quantifying this background.

Speaker: Ms Miho Wakai (University of British Columbia)

MihoWakai_CAP2021.pdf

468 Migdal effect as an inelastic channel in dark matter direct detection

The Migdal ?effect in a dark-matter-nucleus scattering extends the direct search experiments to the sub-GeV mass region through electron ionization with sub-keV detection thresholds. In this talk, I'll present a rigorous and model-independent "Migdal-photoabsorption" relation that links the sub-keV Migdal process to photoabsorption. This relation is free of theoretical uncertainties as it only requires the photoabsorption cross section as the experimental input, and can be applied for most common detectors in the market.

Speaker: Dr Chih-Pan Wu (University of Montreal)

CAP2021_CPWu.pdf

W3-11 History of Physics I (DHP) / Histoire de la physique I (DHP)

Convener: Patrick Clancy (McMaster University)

469 (I) Synchrotron Radiation as a Tool in Paleontology – Search for Soft Tissue Preservation

Studies in paleontology have been fast developing with the recent employment of new technologies. Among these new tools, the use of dedicated synchrotron radiation facilities to probe specimens long extinct have added a new layer of contribution to the knowledge of how those animals lived, died and, in some cases, evolved into the diversity of life that we witness nowadays.

In this talk, I will cover the work that I have been developing in searches for soft tissue structure preservation, and how to use this towards valuable contributions to evolutionary studies. I will cover a recent discovery of dinosaur cell layers and how they compare to extant specimens. I will also discuss a few selected ongoing projects including exceptionally well-preserved insect amber inclusions and dinosaurs such as T. rex, hadrosaurs and others.

Speaker: Prof. Mauricio Barbi (University of Regina)

16:15 Discussion Period

W3-12 Magnetic North VII - Session 7 / Nord magnétique VII - session 7

Convener: Ted Monchesky (Dalhousie University)

470 (I) Skyrmions in Chiral Cubic Magnets

Skyrmions are a topologically non-trivial state that has been observed in a number of different magnetic materials, such as the chiral cubic magnets Cu2OSeO3, FeGe, and MnSi. In these non-centrosymmetric systems, competition between the symmetric exchange interaction and Dzyaloshinskii-Moriya interaction results in the formation of non-trivial incommensurate spin textures, such as skyrmions. In bulk crystals, skyrmions typically only appear in a small pocket of field and temperature close to the critical temperature. These skyrmions can be manipulated by small electrical currents (in metallic systems) or electric fields (in insulators), allowing the possibility of their use in low energy storage applications.

In addition to the importance of the DMI and exchange interactions, various anisotropy energies are also highly important for the stabilization of skyrmions and other spin textures in these materials. For example, surface and shape anisotropies lead to a dramatically enhanced region of stability for skyrmions in lamella thinned out of bulk crystals, uniaxial anisotropy is thought to play a large role in the stabilization of skyrmions in epitaxially grown thin films, and cubic anisotropy has been shown to help stabilize a second isolated region of ‘low temperature skyrmions’ in Cu2OSeO3.

In this talk, I will discuss our recent work on skyrmions in bulk and thin lamella of FeGe and Cu2OSeO3. We have investigated these materials using x-ray and neutron scattering, as well as magnetic X-ray imaging techniques. We show the effects of various perturbations on the stability and metastability of skyrmions in these materials, including the application of electric fields, chemical substitutions, the contrast between thin lamella and bulk samples, and temperature dependent anisotropies.

Speaker: Murray Wilson (Durham University)

471 Two views of the dynamical conductivity in MnSi

I will present terahertz time-domain spectroscopy measurements of the dynamical conductivity of MnSi, and compare them to Fermi liquid theory at low temperatures and low frequencies. I will also describe a new methodology for terahertz time-domain data analysis, developed to perform this comparison, which has higher sensitivity to fit quality than earlier methods. Within the extended Drude model framework, the conductivity scattering rate exhibits quadratic dependence on both frequency and temperature, as expected in Fermi liquid theory. However, the joint dependence of the scattering rate on frequency and temperature deviates from the standard functional form associated with Fermi liquid theory, as observed previously in other materials. We find better agreement with two alternative models, which are also motivated by Fermi liquid theory but which rely on different assumptions. These observations offer a way to reconcile Fermi liquid theory with the observed conductivity of real materials.

Speaker: Laleh Mohtashemi (Simon Fraser University)

W3-2 Mathematical and Theoretical Physics (DTP) / Physique mathématique et physique théorique (DPT)

Convener: Thomas Creutzig (University of Alberta)

472 (I) Chaos and the spectrum on Moduli space

We numerically analyze the spectrum of the Laplacian on the moduli space of a genus zero Riemann surface with four punctures via a perturbative expansion of the path integral of Liouville theory. Our results furnish evidence that the eigenvalues obey the statistics of a random matrix in the Gaussian Orthogonal Ensemble. We comment on possible implications for the quantum geometry of Riemann surfaces and quantum gravity in anti–de Sitter space. Based on work with A. Maloney and T. Numasawa.

Speaker: Prof. Sarah Harrison (McGill University)

473 (G*) Generalized Unitarity and the Poincaré Duals of Feynman Integrals

We elucidate the vector space (twisted relative cohomology) that is Poincar\'e dual to the vector space of Feynman integrals (twisted cohomology) in general dimension. These spaces are paired via an inner product called the intersection number -- an invariant which can be computed algebraically. In this language, reduction of an integrand modulo integration-by-part identities is simply its projection onto a chosen basis. The dual-forms turn out to be far simpler than their Feynman counterparts; they are uplifts of lower-dimensional forms supported on the maximal cuts of various sub-topologies (boundaries). The intersection numbers are then computed by taking residues around cuts where various subsets of propagators become on-shell, giving a systematic approach to generalized unitarity. Moreover, the dual integrals satisfy the transposed differential equation to their Feynman counterparts. Since the dual-forms are localized to cut the transposed differential equation is a much simpler to construct.

Speaker: Andrzej Pokraka (McGill University)

474 The offset logarithm function and some applications in physics: A generalization of the Lambert W function

We describe the offset logarithm function and illustrate its applications to physics. The offset log can be considered an extension of the logarithm function, and it can also be considered as a generalization of the Lambert W function.
The offset log function shows up in a variety of physical and biological models, such as the mean field model (Weiss model) of ferromagnetism, and models of carbon nanoribbons. It provides a convenient framework for describing phenomena in which the behaviour of a physical variable at one location or time, has an exponential or logarithmic relationship to the value of attribute at a displaced location or time.

The offset logarithm function of order $k$ is the multivalued function $w = L_k(z)$ of the complex variable $z$, which satisfies the equation
\begin{equation} \frac{ w-k }{w+k}e^w = z \qquad(1) \end{equation}
Each of $k$, $z$, and $w$ can be in general a complex number. However, for this, we consider $k$, $z$ and $w$ as real numbers. Approximate solutions to Equation (1) can be calculated numerically, but a study of the analytic properties of that equation can provide insight into the system being described.

The offset log function is multi-branch. Each branch of $L_k(z)$ is an analytic function for certain regions of $ k$ and $z$ values. We present the main characteristics of the $L_k(z)$ function. For each domain of the $k$ parameter, the properties of $L_k$ in terms of the branches are given. We show that the number of solutions of Equation (1) depends upon the domains of $k$ and $z$. For these domains we give the number of solutions and we give the interval where each solution lies. We identify the cases where a solution is a multiple solution. We give a symbolic formula for the multiple solutions.

Speaker: Aude Maignan (university Grenoble Alpes)

475 Implementing the Gradient Descent Method in an Infinite Dimensional Hilbert Space

Approximation of the ground state wave function and energy of a quantum system is often achieved using perturbation theory or the variational method. The former approach suffers from the requirement that the Hamiltonian perturbation be small enough for the series to converge while the variational method is only as good as the choice of functions used in the expansion, providing only an approximate ground state whose mean energy is an upper bound to the ground state energy. The method of gradient descent, typically used for optimizing functions over finite dimensions, may be generalized to the infinite-dimensional Hilbert space of a quantum mechanical system to avoid both previous limitations. One may find the ground state of a quantum system by minimizing the energy functional of the wave function of the system via iterative calculation of better approximations using the gradient of the functional. This can be achieved in an infinite-dimensional setting by careful bookkeeping of only the non-zero components of the state vector in the chosen basis of expansion and those matrix elements of the Hamiltonian in that basis required to calculate the next iterative approximation via gradient descent. The sparse nature of the Hamiltonian matrix elements in a chosen basis for many quantum systems ensures that subsequent iterations of the state vector have only a finite number of non-zero components, thereby making the method computationally tractable.

The gradient descent method will be formulated for a quantum system with a time-independent Hamiltonian. The algorithm will be illustrated with a simple quantum system. The impact of symmetry in the choice of initial state vector will be discussed. Limitations of the method and potential improvements (e.g. conjugate gradient) will be considered.

Speaker: Robert Petry (Campion College at the University of Regina)

476 A Quantum-Classical Isomorphic Interpretation of Quantum Foundations Based on Density Functional Theory and Polymer Self-Consistent Field Theory

The Feynman quantum-classical isomorphism between classical statistical mechanics in 3+1 dimensions and quantum statistical mechanics in 3 dimensions is used to relate classical polymer self-consistent field theory to quantum density functional theory. This allows the theorems of density functional theory, which connect single particle density descriptions of quantum systems to wave function descriptions, to relate non-relativistic quantum mechanics back to a classical statistical mechanical derivation of polymer self-consistent field theory for ring polymers. In turn, this allows for a quantum-classical isomorphic interpretation of quantum foundations which may require fewer postulates than standard approaches to quantum mechanics, while preserving all quantum predictions.

Speaker: Russell Thompson (University of Waterloo)

477 The Collapse of the Manifold

THESIS: The ontology of spacetime should not be modelled as a single universally-shared 4D spacetime manifold.

THE CONSENSUS SPACETIME ONTOLOGY: The accepted ontology of classical spacetime is of a 4D differentiable manifold of events. Although different observers may assign different coordinate labels to events, it is conventionally asserted that the underlying reality is that of a single spacetime manifold.
This single classical manifold ontology prohibits nonlocality, because there is no possibility for any form of physical interaction, except those occurring along paths in the manifold. Consequently, Bell nonlocality (EPR) remains mysterious [1].

DIAGNOSIS: The existence of an invariant distance measure (the spacetime interval), and smooth coordinate manifolds has been taken to imply the existence of a universally-shared smooth spacetime manifold. However, this move involves an improper conflation of two different modes of description.
The causal structure possesses invariant properties, but lacks the smooth neighborhood properties required for a manifold, whereas exactly the converse is true of the coordinate manifolds. Manifolds are smooth, but not invariant. We cannot borrow invariance from the causal structure and glue it to coordinate manifolds to create an invariant manifold.

GR: The tensor calculus of GR is "coordinate-free" in the sense that it gives consistent results, irrespective of coordinate system. However, the existence of coordinate mappings between spacetime manifolds does not imply the physical existence of a universal shared manifold. By analogy, the existence of an atlas of the human brain (allowing anatomical mapping between individual brains) does not imply the physical existence of a shared `universal brain’. A mathematical mapping does not imply a physical process.

CONCLUSION: To move beyond classical GR, it is necessary to abandon the image of spacetime as a single deformable 4D entity, and to replace it with a structure acknowledging the reality of the multiple coordinate manifolds. See [2] for such a `many-spaces’ proposal, including an account of quantum nonlocality.

REFERENCES

[1] Nicolas Brunner et al. “Bell nonlocality”. In: Rev. Mod. Phys. 86 (2 Apr. 2014), p. 419.

[2] J. C. Sharp. One Universe, Many Spaces: A Non-Local, Relativistic Quantum Spacetime
https://doi.org/10.20944/preprints201805.0003.v1

Speaker: Jonathan Sharp (University of Alberta)

16:05 Questions/Answers and Discussion Period

W3-3 High School Physics (DPE) / Physique du secondaire (DEP)

Convener: Daria Ahrensmeier (Simon Fraser University)

478 (I) The fast and the furious: special relativity for high school students

One of the problems educators often confront is the lack of preparedness and engagement of physics students as they enter university. Two potential causes are 1) some students think physics is about tedious descriptions of balls rolling down ramps, 2) students may have no motivation for learning algebra. Special relativity (SR) is no weirder for high school students than for university students (or faculty for that matter) and perhaps less so in that high school students have not yet been fully indoctrinated into the Newtonian paradigm. Doing problems in SR requires only high school algebra. Introducing SR at the high school level may address the two issues mentioned above by 1) getting students excited about the weirdness of physics, and 2) providing an exciting new arena in which algebra is useful. In this talk I will first show how to use simple thought experiments (and a bit of algebra) to derive from first principles SR and its main consequences. Time permitting, I will present a couple of simple but intriguing and/or relevant examples that students can tackle.

Speaker: Gabor Kunstatter (University of Winnipeg)

479 The Development of Astroparticle Educational Resources for High Schools

High School physics programs across the country all include outcomes related to subatomic particles and their interactions with matter and fields. Despite this, many high school teachers have received little training in particle physics and are often unaware of the contributions Canadian Physicists are making in this area. To help bridge the gap between university research and high school physics education we are developing citizen science projects, classroom resources and professional development opportunities that will highlight current and past particle physics research in ways that support curricular integration. These resources will/are being developed in collaboration with McDonald Institute researchers and will incorporate real world data, research questions and procedures.

Classroom resources will include links to curriculum and possible assessment ideas as well as teacher guides. Important topics of discussion will be how to present astroparticle data to students, teacher training and ways to connect current Canadian research to curriculum.

Speakers: Ian Doktor (University of Alberta), Marie-Cécile Piro (University of Alberta)

W3-4 Molecular and Cellular Biophysics (DPMB) / Biophysique moléculaire et biophysique cellulaire (DPMB)

Convener: Melanie Campbell (University of Waterloo)

480 (G*) How did first life emerge on terrestrial planets?

How did the first genetic code and the first forms of cellular appear in the early life, about 3.5 billion years ago, of terrestrial and Earth‐like exoplanets? This question has become especially timely with the discovery of an ever‐increasing number of rocky exoplanets where liquid water is present and the successful landing of Perseverance, the latest of NASA’s Mars rovers to search for signes of molecular life on the red planet.

We investigated how specific conditions on terrestrial planets, such as water, temperatures, radiation, atmospheres, and the presence of certain minerals and organic molecules, can potentially drive polymerization of RNA‐like polymers. Experiments were conducted using the Planet Simulator, a custom-built simulation chamber.

Our current results show that the formation of the first genetic assemblies would have occurred in shallow wells that undergo hot-cold and wet-dry cycles. Nucleic acids may have evolved in contact with salt, such as ammonium chloride, and in particular phospholipids and simple membranes, for the formation of protocells when the concentration of those elements would have been optimal. We found that long RNA polymers form spontaneously in the presence of membranes in these warm little ponds and that these polymers are spontaneously incorporated into liposomes. We observe RNA-chains of hundreds of nucleotides whose length depends on the exact temperature and humidity cycles due to daily and seasonal change. Together these results may present a pathway to the formation of first prebiotic life.

Speaker: Alix Dujardin (McMaster University)

481 MD Simulation and Topological Data Analysis of High Temperature Activity of an Enzyme

Applying a novel computational technique to the structure of Candida Antarctica Lipase B, which is an efficient catalyst with a wide range of applications, this study investigates the potential for its industrial applications owing to its activity under extreme conditions. We examined themolecular effects of distinct solvents on the stability of CalB at high temperatures, aiming to con-tribute to its unusual performance. Applying the persistent homology tool from algebraic topologywe proposed to recognize the relationship between the topology-function of these macromoleculesand uncover how local modifications in the amino acid interaction network structure correlate toactivity at the scale of the entire protein network. Originally, MD simulations were carried out toaddress the molecular impacts of different solvents on the structural stability of CalB at a range oftemperatures. We tracked conformational changes of an alpha helix (alpha-5), which its functionpreviously is considered as the lipase lid and is thought to be responsible for the activity of the pro-tein both in polar(water), and nonpolar(glycerol) solvents at high temperature. Notably, the nativelipase fold was maintained in a non-polar solvent (glycerol) even at high temperatures, representingthe enhancement of lipase’s thermostability in glycerol. Topologically we distinguish the topologicalfeature this conformational change emerge in the amino acid network in its active state and com-pared its topology to inactive network. Hence, we noted the presence of a relationship betweenlocal topological features of the network and the global activity of the protein

Speaker: samin tajik (brock university)

482 (U*) Protein Conformational Ensembles for a Disordered Protein Restricted by Separate Biophysical Experiments

We combined information from Fluorescence Correlation Spectroscopy (FCS), Nuclear Magnetic Resonance (NMR), Small-Angle X-ray Scattering (SAXS) and Single-Molecule Förster Energy Transfer (smFRET) to calculate conformational ensembles for the neuronal transcription factor initiation protein 4E-BP2. This is a 120-residue intrinsically disordered protein which toggles between an active, non-phosphorylated (NP) state and an inactive multi-phosphorylated (5P) state. An initial pool of 4E-BP2 structures was generated using Trajectory Directed Ensemble Sampling (TraDES) (Feldman & Hogue, Proteins: Structure, Function, and Bioinformatics, 46, 8-23, 2002). The ENSEMBLE method (Krzeminski et al, Bioinformatics, 29, 398-399, 2013) was used to search and select conformations within the initial pool that are consistent with the experimental data. NMR and SAXS data were used as restraints for the conformational search and FCS and smFRET data were used as validation.

The NP 4E-BP2 ensemble calculated with SAXS-only restraints showed a bimodal distribution of protein global dimensions such as the radius of gyration and the end-to-end distance. The back-calculated FRET efficiency and the hydrodynamic radius for this ensemble were lower than the respective experimental values. These inconsistencies are likely due to lack of short-range (5-20 Å) distance restraints, which are currently addressed by acquiring Paramagnetic Resonance Enhancement (PRE) data. Such data is available for the phosphorylated state (5P 4E-BP2), however this is partly folded, with a 4-stranded beta domain spanning residues 18-62. To address this challenge, we used the FastFloppyTail (FFT) program (Ferrie & Petersson, The Journal of Physical Chemistry B, 124, 5538-5548, 2020) to generate structures in the initial pool. As such, the folded region was modelled using the 5P 4E-BP2 folds from the Protein Databank, while the disordered tails were generated through the FFT algorithm. By incorporating the more realistic FFT-built prior in ENSEMBLE calculations, more accurate conformational ensembles of both phospho- and non-phospho- variants of 4E-BP2 were obtained. Analysis of these ensembles in terms of polymer physics and contact maps reveal new molecular level details lead to new insights into the biological function of 4E-BP2.

Speaker: Mr Thomas Tsangaris (University of Toronto)

483 (U*) Quantitatively Analysing Evolutionary Effects in the Transition From Non-Genetic to Genetic Drug Resistance

Antimicrobial drug resistance is a growing health threat that is predicted to kill 10 million people per year globally by 2050 unless preventative measures are put in place. The first step in implementing these measures is to gain a better understanding of the fundamental processes involved in antimicrobial drug resistance through quantitative approaches from fields such as biophysics, molecular biology, computational biology, bioinformatics, and synthetic biology. With this in mind, this study aimed to quantitatively analyse evolutionary effects by studying the interplay between non-genetic antimicrobial resistance due to gene expression noise and resistance due to genetic mutation. This was done using numerical simulations of deterministic mathematical models along with the corresponding stochastic simulations to investigate cellular and population dynamics in various drug conditions. The results of these simulations were quantitatively analyzed to determine the establishment and fixation times of genetic mutations within the cell population for varying levels of relative fitness between non-genetically drug-resistant and genetically drug-resistant subpopulations to investigate the evolutionary interplay between these processes. Counterintuitively, we found that gene expression noise can prolong the establishment and fixation of genetic mutations for populations exposed to cidal and static drugs.

Speaker: Mr Joshua Guthrie (University of Alberta)

484 (U*) The quantitative analysis of gel electrophoresis data using a cloud-based smartphone application

Separating and analyzing DNA, RNA or proteins is often done through gel electrophoresis. This simple technique is conducted millions of times in labs every day world-wide. Analysis of the gels is typically done visually on a photo by comparing measured intensities with a well-defined reference ladder. Using digital photography and image analysis, we have developed a technique to quantitatively analyze standard gel images to determine exact sized distributions. This information can then be used to compare experimental data to theoretical models and predictions. The software consists of a smartphone-based application with an easy-to-use GUI to analyze images of any quality, dimension, or type. Within seconds, the user can sign in, choose ladder specifications, and select the image for analysis. They can then tap on the ladders of interest and send the image for analysis. The cloud-based analysis uses an exponential model to characterize the propagation of molecules within the gel and automatically measures the size and relative quantity of detectable solutes. I will provide direct evidence that the software allows measurement of RNA molecule lengths with resolution down to a single monomer. The entire analysis process takes under 10 seconds, after which the results are automatically emailed to the user. The novel way in which this data is processed and presented to the end-user in a seamlessly integrated workflow with possibilities for additional integration makes this a major step forward over existing solutions. Enabling, supporting, and promoting this research by creating easy-to-use and powerful tools has the potential to promote change in physical and biological research.

Speaker: Udbhav Ram (McMaster University)

485 Ratcheting charged polymers through nanopores: Designing a low pass molecular filter for DNA

When nanopores are used to capture and translocate DNA molecules through a wall or membrane, the resulting capture rate is essentially independent of their molecular size, making the process incapable of changing relative concentrations in a mixture. Using Langevin Dynamics simulations, we show that it is possible to use pulsed fields to ratchet captured semiflexible molecules so that only short chains successfully translocate, thus transforming translocation into a low pass molecular filter. Two different modes of operation are investigated. One of these modes allow for the ratchet to be run with many pores in parallel, which increases its potential usefulness.

Speaker: Gary W. Slater (University of Ottawa)

486 Concentration and Mobility of Activator and Repressor Morphogens in live early Drosophila Embryos

Morphogens (often acting as transcription activators or repressors) govern pattern formation and cell differentiation during early embryogenesis. Abnormal distributions of morphogens can result in developmental defects or even death. Oftentimes, thresholds of concentrations of morphogens behave like an ON/OFF switch for the activation or repression of downstream genes. Thus accurate measurements of morphogen concentration and mobility in space and time can help tackle the puzzle of how exactly cascades of hundreds of morphogens coordinate their targets precisely and promptly amidst crowded and complicated cellular environments.

In principle, Fluorescence Correlation Spectroscopy (FCS) allow for accurate measurements of both protein dynamics and concentration. Here, we demonstrate how to use FCS and confocal imaging to achieve extremely low (~ nM) concentration measurements in live Drosophila embryos expressing recombinant fluorescent morphogens, by carefully taking account background noise and photobleaching effects. The dynamics of both an activator and a repressor morphogens were further studied using FCS and Fluorescence Recovery After Photobleaching. We found that both type of morphogens are very mobile in nuclei, explaining how that are able to turn on or off gene expression in only a few minutes.

Speaker: Lili Zhang (McMaster University)

487 Measurement of elements in toenail clippings using portable X-ray fluorescence

The analysis of human nail clippings to determine the concentration of certain elements of interest is now fairly common. Results can be used to assess exposure to various elements and their absorption into the body. When nail clippings are used as a biomarker in this way, they are typically analyzed by a method such as inductively coupled plasma-mass spectrometry (ICP-MS) or instrumental neutron activation analysis. Our group has recently explored the use of a portable X-ray fluorescence (pXRF) technique as an alternative approach to assessing elements within nail clippings. The pXRF method allows rapid measurement using a single nail clipping. We report on results from single toenail clippings from 60 individuals living in Atlantic Canada. Samples were obtained through the Atlantic PATH initiative, part of the Canadian Partnership for Tomorrow’s Health. Energy spectra resulting from irradiation of the clippings were analyzed for characteristic X-rays from zinc, arsenic, and other elements. Following non-destructive assessment by pXRF, the clippings were measured for elemental concentrations using ICP-MS. Results will be presented from the pXRF detection of zinc and arsenic in the clippings, and correlations examined between the pXRF and ICP-MS measurements. Overall, the results suggest that pXRF is a sensitive and accurate method when used with a single nail clipping. Limitations and challenges relating to the pXRF technique will also be reviewed.

Speaker: David Fleming (Mount Allison University)

W3-5 Plasma processes for material synthesis I (DPP) / Procédés de plasmas pour la synthèse de matériaux I (DPP)

Convener: Ahmad Hamdan (Université de Montréal)

488 (I) Plasma characterization in gaseous and liquid dielectric barrier discharge systems for nanoparticle synthesis and nanostructured thin film deposition

Atmospheric pressure discharges in a dielectric barrier configuration, resulting in non‐local thermodynamic equilibrium (nLTE) plasmas, are used in photovoltaics, photocatalysis, solar cells, water treatments and depollution, as well as for modifying the surface of wood. They can also be used to generate nanoparticles (NPs) and nanocomposites. They can be also integrated for novel approaches in biomedical devices, such as the fabrication of biodegradable systems.

At this moment in their development, the chain of physico-chemical processes occurring between the atmospheric pressure plasma discharges and the molecules of precursors contained in the plasma-treated systems, were yet to be elucidated for the most part. Many attempts to model the chemical reactions occurring in the plasma have shed a new light on these complex processes and their kinetics. At the moment, these theoretical models must be reconciliated with experimental measurements confirming the nature of the chemical and elemental species contained by the plasma, as well as their respective concentrations.

This presentation will describe various atmospheric pressure plasma discharge systems and configurations, as well as their different regimes of operation, as well as different plasma characterization methods adapted to each one of them. Their respective advantages and limitations will be presented.

The first part of the presentation is focused on a plasma-assisted chemical vapor deposition systems based on a dielectric barrier discharge (DBD). This technology was used in both glow and filamentary plasma regimes to generate polymer as well as silica and gold nanoparticle-containing nanocomposites. Frequency Shift Keying (FSK) double modulation was used to successfully deposit polymers and NPs. In each one of these experiments, the nature of polymers and deposited NPs was varied by changing plasma excitation frequency.
Plasma was characterized using FTIR spectroscopy (of the plasma and gas), and the thin films were analyzed by AFM, SEM, profilometry and UV-vis spectrometry. Concurrently, these investigations have shown the importance of the discharge regime on the thickness, polymerization level and homogeneity of the thin film, as well as how the size-dependent nanoparticle transport is controlled by the plasma frequencies.

The second part of the presentation will describe a DBD system used to directly treat fluid surfaces (water). In-solution plasma filamentary discharge has been used for synthesizing metal NPs. It is a reliable method, allowing for the synthesis of surfactant-free NPs. Control of the size and shape of the NPs could be possible by a better optimization of the plasma parameters. In this project, optical emission spectroscopy (OES) was used to measure and analyze electron temperature and density, as well as the concentration of reactive species present in different gas mixture plasma regimes. Power measurements were also performed to correlate the species analysis with the energy that is injected into the system.

In conclusion, using different plasma characterization techniques in conjugation, allows a great control of the parameters of the deposited layers, and created nanoparticles.

Speaker: Natalia Milaniak (Laval University)

489 Energetics of reactions in a dielectric barrier discharge with argon carrier gas: Halocarbons

The novel method we developed for understanding energy exchanges between argon (Ar) carrier gas and precursor molecules in a large-area (216 cm$^2$) dielectric barrier discharge (DBD) reactor has resulted in a series of articles, each relating to a different family of organic compounds. This communication focuses on two new groups, perfluorocarbons, ($C_xF_y$), and perchlorocarbons, $(C_xCl_y)$, and compares results with earlier ones for hydrocarbons, ($C_xH_y$)[1] and hydrofluoromethanes, ($CH_xF_y$)[2].
The precursors (in parts per thousand concentrations) were mixed with Ar in a 20 kHz, 8 kV (peak‐to‐peak) DBD. For each separate compound, the energy absorbed per molecule ($E_m$, in eV), was determined from measurements of the time resolved discharge current, $I_d$, and the gap voltage, $V_{gap}$. Plotting $E_m$ as a function of precursor flow rate, $F_d$, and also $1/F_d$, allows for the identification of the maxima, $(E_m)_{max}$, identifying the boundary between the so-called “monomer-lean” and “monomer-rich” operating regimes. It has been highly instructive to plot $(E_m)_{max}$x values as a function of atomization enthalpy ($H_f$) or alternatively molar mass (MM): in the case of saturated hydrocarbons, for example, this results in straight-line plots with rising MM or $H_f$, while the trend was not as clear cut for halocarbons.
The process generally led to thin “plasma polymer” (PP) deposits (e.g. on Si wafer substrates). Their characteristics, like their $C/F$ or $C/Cl$ composition ratios from XPS measurements, strongly correlated with $E_m$ and $F_d$, as did PP deposition rates and water contact angles.

[1] B. Nisol et al., Plasma Process Polym, 2016;14:e201600191.
[2] S. Watson et al., Plasma Process Polym, 2020;17:e201900125.

Speaker: Dr Cédric Pattyn (Polytechnique Montreal)

16:25 Open discussion period

W3-6 Exotic Matter II (DNP) / Matière exotique II (DPN)

Convener: Baishan Hu (TRIUMF)

490 Laser Cooled Antihydrogen

We present the first laser cooling of antimatter, and results of precision spectroscopy performed with laser-cooled antihydrogen atoms. The ALPHA collaboration at CERN is engaged in precision testing fundamental symmetries between matter and antimatter using antihydrogen. Recently, we have made advances in the production, collection, storage, and laser addressing of antihydrogen. These efforts have culminated in the demonstration of laser cooling of hundreds of antihydrogen atoms using a narrow-width nanosecond pulsed laser source at 121.6 nm, tuned to a cycling transition in the 1S-2P line in antihydrogen. Although the cooling laser is only applied in one dimension, we demonstrate reduction in temperature in all three dimensions, using both time-of-flight data and the narrowing of 1S-2P spectroscopic line. We also show that the cooling has an effect of narrowing the 1S-2S line in antihydrogen by a factor of 4 over the our earlier result, the most precise spectroscopic measurement in antihydrogen. Laser cooling should allow us to rapidly approach the precision of hydrogen spectroscopy, and dramatically broaden the scope of possible experiments in antihydrogen. We discuss the laser system used to achieve the cooling, the diagnostic tools used to verify it, and the prospective uses of cold, dense samples of antihydrogen to drastically improve our understanding of the antimatter world.

Speaker: Alexander Khramov (BCIT)

491 HAICU: Developing an (anti)hydrogen fountain and quantum interferometer

Over the last decade, The ALPHA experiment at CERN produced a series of ground-breaking results, having demonstrated the first ever trapping and laser cooling of antihydrogen atoms, and precisely measured many of their physical properties, including the 1s-2s transition and hyperfine splitting. A new ALPHA-g apparatus is being built to precisely measure the gravitational mass of antihydrogen. Comparing these properties with the well-studied hydrogen atom offers a sensitive test of matter-antimatter symmetry, and may yield insight into physics beyond the Standard Model.

The achievable precision of the measurements at ALPHA is, however, limited by the innate magnetic inhomogeneity of the magnetic minimum trap used to confine the anti-atoms (e.g. due to Zeeman splitting). An atomic fountain can help overcome this limit by interrogating the anti-atoms during free-fall in a field-free volume. A practical antihydrogen fountain requires cooling the anti-atoms to micro-Kelvin energies, such that the volume of a free-falling bunch remains small enough for interrogation (usually via a laser or microwave pulse).

This presentation outlines the recent progress made towards the development of HAICU, a next-generation experiment aiming to create a fountain interferometer compatible with both hydrogen and antihydrogen. A sophisticated, superconducting magnetic trap is designed to capture anti-atoms synthesised by mixing antiprotons with positrons, magnetically compress them into a mm-scale volume, cool them using three orthogonal Doppler cooling lasers, transfer them to a large volume trap, adiabatically expand them to achieve micro-Kelvin energies, and finally magnetically launch them into a fountain volume. The radial confinement in the trap system is provided by a novel canted cosine theta (CCT) coil, whose multipole moment changes from octpolar, compatible with the initial synthesis of antihydrogen, into quadrupolar, capable of much stronger radial compression. The transition is achieved while maintaining continuous radial confinement. The strong compression volume is created by four azimuthally offset pancake coils, which are arranged to provide perpendicular optical access to the trap anti-atoms. Magnetic and particle tracking simulation are used to demonstrate the performance of the system, and provide a proof-of-concept for further experimental development work.

Speaker: Chukman So (TRIUMF (CA))

492 Extracting twist-three GPDs from deeply virtual Compton scattering

Observables in the hard exclusive leptoproduction of real photons can be cleanly expressed in terms of the compton amplitudes involving generalized parton distributions (GPDs). This process can be factorized into the product of a short-distance partonic subprocess with a long-distance, off forward hadronic matrix element. They involve nonlocal quark and gluon operators and are naturally expressed in terms of GPDs; quantities which may carry crucial information about the nucleon's intrinsic properties. In this talk, I will be providing an overview of the theoretical formalisms of these processes and a detailed look at some of the relevant asymmetry observables is given to twist-three accuracy. In particular, the relevant twist-two and -three GPDs which complete a newly-found nucleon spin sum rule in the transverse polarization plane are discussed.

Speaker: Kyle Shiells (University of Manitoba)

493 (G*) In situ magnetometry using electron plasmas for gravitational experiments with antihydrogen.

The Antihydrogen Laser Physics Apparatus (ALPHA), at the European Centre for Nuclear Research (CERN) antiproton decelerator facility, uses low energy antiprotons in a bound state with a positron to produce and trap antihydrogen [1]. Given the long history of atomic physics experiments with hydrogen, spectroscopy experiments with antihydrogen offer some of the most precise tests of quantum electrodynamics and charge-parity-time symmetry [1]. A test of the weak equivalence principle is also on the horizon with a major addition to the ALPHA experiment, ALPHAg, aiming to measure the free fall of antihydrogen.

For the spectroscopy and gravity experiments in ALPHA, precise measurements of the magnetic field inside the apparatus are essential [2]. A technique developed in ALPHA determines the in situ magnetic fields by measuring the cyclotron frequency of an electron plasma. Microwave pulses on resonance with the electron cyclotron frequency, which is magnetic field dependent, heat the plasma [3]. A campaign to characterize the precision and accuracy of this technique in a high magnetic field gradient is required before a successful measurement of the effect of Earth’s gravity on antimatter can be made.

I will discuss recent progress made towards realising this goal using the ALPHA2 apparatus. This will include the first application of this measurement in a strong magnetic field gradient and methods used to experimentally distinguish the cyclotron frequency from a sideband structure. I will move on to show development the ALPHA Penning-Malmberg traps and microwave injection system ahead of the recommissioning of ALPHAg in mid 2021.

1. Characterization of the 1S–2S transition in antihydrogen, ALPHA Collaboration, Nature, 557, 71, (2018)
2. Description And First Application Of A New Technique To Measure The Gravitational Mass Of Antihydrogen, ALPHA Collaboration, Nature Communications 4, 1785 (2013)
3. Electron Cyclotron Resonance (ECR) Magnetometry with a Plasma Reservoir, E. D. Hunter and A. Christensen and J. Fajans and T. Friesen and E. Kur and J. S. Wurtele, arXiv 1912.04358 (2019)

Speaker: Adam Powell (University of Calgary Dep. of Phys. and Astronomy (CA))

W3-7 Mesons I (DNP) / Mésons I (DPN)

Convener: Mark McCrea (University of Winnipeg)

494 (I) Search for exotic quantum-number mesons in the GlueX experiment

The GlueX Experiment at Jefferson Lab has been collecting high-energy photoproduction data since 2016 as part of its search for hybrid mesons, mesons in which the
gluonic field has been excited. An over views of the GlueX experiment and its physics program, including first results and the ongoing searches for hybrids will be presented.
These results include studies of photoproduction measurements utilizing the linearly polarized photons in GlueX as well as near threshold photoproduction of the J/ψ. In
addition, ongoing studies of final states seen as key in the search for hybrids will be presented.

Speaker: Prof. Curtis A. Meyer (Carnegie Mellon)

Meyer-CAPS-Presentation.pdf

495 Light Exotic Mesons in the GlueX Experiment

The primary goal of the GlueX program is to explore the spectrum of light-quark mesons for excitations with explicit gluonic degrees of freedom, as predicted by Quantum Chromodynamics. These particles are termed hybrid mesons and some are predicted to possess exotic JPC quantum numbers. Lattice QCD predicts patterns of hybrid states with masses in the 2-GeV/c^2 range, which can be accessed in photo-production through simple t-channel exchanges. GlueX's unique production mechanism in photon-proton collisions may be effective in this search. The experiment incorporates a high-intensity, linearly-polarized, tagged, real-photon beam and a multipurpose large-acceptance spectrometer with charged and neutral particle detection capability. The first phase of running has finished with a luminosity of over 300 pb^-1 above 8.1 GeV. The key features and selected results of this compelling physics program will be presented.

Speaker: Zisis Papandreou (University of Regina)

CAP_ContributedTalk_2021_GlueX_zpapandreou.pdf

496 (G*) The charged kaon electromagnetic form factor at Jefferson Lab

The Kaon LT experiment (E12-09-011) at Jefferson Lab, USA was designed to study the LT separated cross-section of the reaction $^1H(e, e'K^+ )Λ / Σ^0$ and to attempt to extract the $K^+$ electromagnetic form factor. The measurements for the $K^+$ electromagnetic form factor are important, as they allow us to better understand the role of the strange quark ($s$) in the $K^+$ structure. This experiment ran over fall 2018 and spring 2019 in the Hall-C at Jefferson Lab. The scattered electron ($e'$) and the produced $K^+$ were measured in the two magnetic spectrometers called High Momentum Spectrometer (HMS) and Super High Momentum Spectrometer (SHMS), while the $Λ$ or the $Σ^0$ are identified on the basis of their masses in the missing mass spectrum. The high precision nature of the experiment is required an in depth understanding of the behaviour of the detectors that are utilised in the experiment. In this talk, I will briefly outline the experiment, the experimental facility and the preliminary results of the studies that have been completed.

Speaker: Mr Vijay Kumar (University of Regina)

W3-8 Physics Focused on the Pandemic (DAPI) / Physique dirigée vers la pandémie (DPAI)

Convener: Steffon Luoma

497 (I) The MVM Ventilator: Particle physicists, National Labs and Industry

In response to the needs for ventilators for critically ill Covid-19 patients a collaboration of international particle physicists, engineers, software specialists, industry and medical specialists came together to create rapidly a simple, low-cost, open-source ventilator tailored specifically for such patients. The project was initiated by Professor Cristian Galbiati, spokesperson of the DarkSide-20k experiment designed to use about 55 tons of low-radioactivity liquid Argon to search for high-mass WIMPS as Dark Matter candidate particles at the Gran Sasso underground laboratory. This experiment is a successor to the DEAP experiment and pre-cursor to the proposed ARGO experiment at SNOLAB. It was realized that the expertise in gas handling and computer control that has been developed for these experiments could be used to develop the Mechanical Ventilator Milano (MVM). The Italian group was immediately joined by Canadian scientists and engineers from TRIUMF laboratory, CNL Chalk River, SNOLAB and the McDonald Institute and other international collaborators. A prototype was working in the lab within 10 days, papers were published openly for the design, industrialized versions were developed and the collaboration won a Canadian government contract that has now resulted in the delivery of over 6000 ventilators to the Canadian stockpile following Health Canada Interim Authorization. Donation to other countries in need is another possibility under discussion. A description will be provided of how this highly motivated team pivoted their work to make a contribution to the COVID-19 pandemic.

Speaker: Dr Art McDonald (Queen's University)

CAP McDonald Ventilators June 2021 7 min.pdf

498 (I) Innumeracy compounding an already difficult situation

Like many, a combination of curiosity, self-preservation, and dissatisfaction with what the news was calling "analyses", drove us to begin our own analyses of publicly available COVID-19 data. I will present some of the simple approaches we came up with, and our more interesting observations regarding the effectiveness of restrictions and the variations over time in the mortality rate per COVID-19 confirmed cases, across various areas and countries. Some of the shortcomings of COVID-19 reporting, including the issues of presenting data to the general public on a linear scale; and of performing 7-day rolling arithmetic averaging of daily counts to smooth over the noise, will be highlighted.

Speaker: Catherine Beauchemin (Ryerson University & iTHEMS @ RIKEN)

499 (I) Statistical Physics & Human Mobility in COVID-19

In the past 20 years, large-scale datasets of cell phone traces have emerged as a key proxy to study human movement patterns, and how those patterns change in response to exogenous events such as natural disasters or terrorist attacks. These data have proven especially useful to understand the effects of public policy in the current COVID-19 pandemic, where "lockdowns" and other mobility-based restrictions have served as the main intervention deployed by governments in the absence of a vaccine. In this talk, I will give an overview of how tools from information theory and statistical physics have been applied to high-resolution mobile phone data to understand the (in)effectiveness of physical distancing measures in reducing human mobility over the past year. In particular, I will discuss our own efforts to quantify heterogenity in human contact patterns and so-called "superspreading events"--both outsize drivers of epidemic spread.

Speaker: Sean Cornelius (Ryerson University)

W3-9 Contributed Talks III (DCMMP) / Conférences soumises III (DPMCM)

Convener: Michel Gingras

500 Using symmetric qubit clusters to protect quantum computation

We propose to use 4-level systems with an additional symmetry to encode pairs of coupled qubits. The chosen symmetry allows clusters to perform universal quantum computation on their encoded qubits, and gives full control over their energy spectrum. Each level can be dynamically decoupled from its immediate environment, modelled by its tunneling-coupling to a semi-infinite lead, turning the clusters into memory units when needed. We show that cluster quantum operations are symmetry-protected against unbiased noise, even when dynamically coupled to the leads. Finally, we discuss possible physical implementations, and a scalable scheme of resonator-coupled clusters.

Speaker: Christian Boudreault (Royal Military College Saint-Jean/U de Montréal)

15:48 Questions & answers

501 Optical properties of Ge-Sn nanoparticles grown by ion-implantation

We are exploring solid state precipitation methods to grow high-quality Ge-Sn nanoparticles with controlled compositions and band gaps. There have been decades of research to produce semiconductor nanoparticles using wet chemistry synthetic techniques, however many of these approaches are not compatible with current CMOS device manufacturing. Si-Ge-Sn alloys offer great new material properties, such as a direct bandgap, but there are challenges in their fabrication.[1]
We present experiments showing the advantages of ion implantation to grow high-quality GeSn nanoparticles, with morphology, composition, and size distribution controlled by implantation dose, temperature, and defect engineering. In particular, He bubbles are used as templates to nucleate and grow GeSn nanoparticles. Previously we were able to establish conditions favourable for He bubble formation and determine isotopic effects related to this process[2]. GeSn nanoparticles have been fabricated by ion implantation at energies of 30-90 keV, at 300K into Si(001) substrates, placing Ge and Sn into the same depth region. Growth of the GeSn nanoparticles has been characterized using I-V analysis, ellipsometry, Rutherford Backscattering Spectroscopy, Raman Spectroscopy, X-ray Photoelectron Spectroscopy (XPS) and X-ray diffraction (XRD). Preliminary results indicate the enhancement of diffusion in the presence of He bubbles leads to formation of nanoparticles with different sizes and morphologies. Achieving direct bandgap Sn-based materials strongly depends on the applied strain within the epilayers, our work leads to ways to control and modify the strain, especially the plastic strain relaxation of Ge-Sn nanoparticles grown in Si substrates.

1. Wirths, S., D. Buca, and S. Mantl, Si-Ge-Sn alloys: From growth to applications. Progress in Crystal Growth and Characterization of Materials, 2016. 62(1): p. 1-39.
2. Moutanabbir, O., et al., Influence of isotopic substitution and He coimplantation on defect complexes and voids induced by H ions in silicon. Physical Review B, 2007. 75(7): p. 11.

Speaker: Jake Erickson (Western University)

15:53 Questions & answers

502 Exploring properties of SiGeSn alloys fabricated by ion implantation

Numerous advances have been made in the field of Si photonics, attractive in terms of cost, power consumption and performance in comparison to conventional technologies. Photodetectors which converts light to electrical signals are vital parts of Si photonics system. Advances in materials science have led to photodetectors that operate in the short infrared wavelength range (1.3 - 2.5µm). This advancement is owed to the role alloy compositions and strain play. SixGe1-x-ySny ternary alloy is a promising candidate for photodetector applications. In this research, a set of SixGe1-x-ySny ternary alloy was fabricated by ion implantation in what we refer to as a matrix of SiGeSn compositions containing a mix of different atomic percent of Si, Ge and Sn (Si, x = 0.7 - 1.0, Sn, y = 0 - 0.08) for operation at wavelengths of 1.2 – 1.5µm. This approach has rarely been applied before for ternary alloy fabrication, and we exploited the low temperature growth, control, and wide range of concentration advantages of ion implantation to make tunable bandgap semiconductor materials for optoelectronics. The fabricated sample was annealed at 400oC for 10 - 15 minutes to minimize defects from low temperature growth. The fabricated SiGeSn matrix was characterized using Rutherford Backscattering Spectroscopy (RBS), X-ray Photoelectron Spectroscopy (XPS), and optical spectroscopic ellipsometry to determine its structural, compositional and optical properties. RBS results confirmed that the desired implantation dose is in the range of the simulations, the reduction in defects through the surface was observed for annealed SiGeSn compared to the unannealed sample, with little or no crystallization before and after annealing. The optical ellipsometry results showed how the optical properties of Si was changing as Ge and Sn were introduced to it. Finally, from the XPS results, we were able to determine different core electronic states associated to SiGeSn, we were also able to determine that there was no Sn segregation at low Sn concentrations. From these results, possible optimization strategies will be employed in fabricating new sets of samples. This research will, therefore, provide a route for developing new infrared detector technologies for applications in optoelectronics.

Speaker: Chinenye Ekeruche (University of Western Ontario)

15:58 Questions & answers

503 Size and Stiffness Reduction of Phytoglycogen Nanoparticles Through Acid Hydrolysis

Phytoglycogen occurs naturally in the form of compact, 42 nm diameter glucose-based nanoparticles in the kernels of sweet corn. Its highly branched, dendritic structure leads to interesting and useful properties that make the particles ideal as unique additives in personal care, nutrition and biomedical formulations. The properties of phytoglycogen nanoparticles can be altered through chemical modifications such as acid hydrolysis, which not only reduces their diameter but also alters their internal structure, producing significant changes to the interactions between particles in solution. As the acid hydrolyzed particles are packed beyond their glass transition volume fraction, the dependence of the zero-shear viscosity on the effective volume fraction abruptly changes from behaviour well-described by the Vogel-Fulcher-Tammann equation to more Arrhenius-like behaviour, with the transition marked by a pronounced kink in the data. This result is consistent with a reduction in stiffness for acid hydrolyzed phytoglycogen nanoparticles with a corresponding reduction in their fragility index.

Speaker: Hurmiz Shamana (University of Guelph)

16:03 Questions & answers

504 Stretching wormlike chains of finite length

The problem of stretching flexible polymers was covered in a seminal paper by John F. Marko and Eric D. Sigga in 1995, where they used the wormlike chain model to calculate the force required to stretch long segments of DNA. Their approach used a ground state dominance method to solve the modified diffusion equation, applicable to long (flexible) chains only. Here, using the same Green’s function approach, we go beyond their work and present the force extension relations for a full range of chain lengths, from rodlike molecules through to semiflexible and flexible polymers. In addition, we calculate the variance in extension, as well as the mean squared perpendicular displacement for all lengths. For each of the properties, we provide analytic results for the rodlike limit. Numerical methods were used to directly solve the modified diffusion equation for semiflexible polymers, with the ground state dominance theory again applied to the long chain limit. By covering all three regimes, this work completes the understanding of the stretching of ideal polymers from the wormlike-chain perspective.

Speaker: Nigel T. Andersen (University of Waterloo)

16:08 Questions & answers

505 Scanning Tunneling Microscopy and Spectroscopy of MnBi$_2$Te$_4$

It was recently demonstrated that the layered van der Waals bonded material MnBi$_2$Te$_4$ is an intrinsic antiferromagnetic topological insulator. The opening of an electronic gap in the surface state, originating in the presence of exchange interaction, was experimentally verified by ARPES. However, the presence and magnitude of this gap are still under debate. To develop a comprehensive understanding of this class of materials and ultimately achieve control over their topological phases, more experimental characterization of their spatial heterogeneity is needed.
In this talk we discuss low-temperature scanning tunneling microscopy and spectroscopy measurements of MnBi$_2$Te$_4$. We first use topographic maps to identify the surface profile, including steps which reflect the septuple-layer structure. Using scanning tunneling spectroscopy, we probe the local density of states and identify a bandgap with the same magnitude as some recent ARPES reports. We observe spatial inhomogeneity in the DOS which could be responsible for the reported differences in the size of this surface state gap. Using spectroscopic maps we characterize the electronic states associated with the presence of edges in the surface.
*We acknowledge funding from NSERC Discovery Grant RGPIN-2016-06717

Speaker: Ryan Plumadore (University of Ottawa)

16:13 Questions & answers

506 Stability Of Binary Colloidal Crystals Immersed In a Cholesteric Liquid Crystal

We model a number of both closed-packed and non-closed-packed crystals inside a cholesteric liquid crystal (LC) with different pitch values and nematic LC through the Landau–de Gennes free-energy method[1]. We investigated the anisotropic interactions between particles with heterogeneous boundary conditions inside both nematic and cholesteric liquid crystals[2]. The results show that it is energetically favorable for the particles to remain in a plane parallel to the far-field director in a nematic liquid crystal, while for particles immersed in a cholesteric there are multiple energy minima not all located in the same plane. Therefore, We became interested in investigating the stability of binary crystals [3]. The results indicate that body-centered-cubic (BCC) crystals have a lower-energy lattice defect structure than the diamond crystal. Furthermore, it is shown that a pair of binary colloids can be self-assemble into a stable face-centered- cubic lattice structure inside a nematic LC, as it has the lowest energy comparing to diamond and BCC crystals.

1-P.G. de Gennes and J. Prost, The Physics of Liquid Crystals (Oxford University Press, Oxford, 1993)
2-Phys. Rev. E 95, 052703 – Published 30 May 2017
3-Phys. Rev. E 99, 052701 – Published 13 May 2019

Speaker: Setarehalsadat Changizrezaei (University of Western Ontario)

16:18 Questions & answers

16:30 15 Minute Break

W4-1 Quantum Information: Experiments (DAMOPC) / Information quantique: expériences (DPAMPC)

Convener: Jens Lassen (TRIUMF)

507 (I) Quantum Cryptography Beyond Qubits with Structured Photons

Photons, the quanta of light, possess several different degrees of freedom, e.g., frequency, polarisation, spatial and temporal modes, which can be used as platforms for quantum information applications. Polarisation, corresponding to the vectorial nature of light, is bi-dimensional and can represent ‘0’ and ‘1’ in the digital world. Unlike, polarisation, transverse and temporal modes would provide an unbonded vector space and could be used to extend the alphabet beyond the ‘0’ and ‘1’s to any arbitrary integer numbers. Photons in superposition states of these different degrees of freedom are known as Structured Photons. In the classical regime, structured light has found tremendous applications, e.g., overcoming the diffraction limit (STED microscopy), for optical spanners, communication multiplexing, and generating non-trivial 3D topologies such as Möbius and Knots. In the quantum domain, structured photons may be used to realise higher- dimensional states, and thus are used for quantum communication, computation, and simulations. The recent progress, challenges, and applications of structured photons, beyond qubits, in quantum communication, will be the subject of my talk.

Speaker: Prof. Ebrahim Karimi (University of Ottawa)

508 (I) Quantum electromechanics: photon conversion, nonreciprocity, and entanglement

Here I discuss the possibilities to use nanomechanical resonators to converter information between microwave and optical domains. Additionally, I demonstrate an on-chip magnetic-free circulator based on reservoir-engineered electromechanical interactions. Directional circulation is achieved with controlled phase-sensitive interference of six distinct electromechanical signal conversion paths. Finally, I show that a parametrically driven mechanical oscillator can entangle electromagnetic fields. We observe stationary emission of path-entangled microwave radiation from a micro-machined silicon nanostring oscillator, squeezing the joint field operators of two thermal modes by 3.40 (37) ~ dB below the vacuum level.

Speaker: Prof. Shabir Barzanjeh (University of Calgary)

509 Millimeter Wave Quantum Optomechanics

Despite incredible experimental progress in quantum optomechanics, the intrinsically weak coupling between light and motion remains a bottleneck for accessing the full potential of these systems. While a strong pump field can parametrically enhance the optomechanical coupling, it also acts to obscure the fundamental nonlinearity of the interaction and hinders integration with single photon devices like detectors or qubits. Here, I will present theory, design and preliminary experiments detailing our approach to address these issues by introducing a new regime of optomechanics whereby mechanical oscillators are coupled to millimeter wave (~30 GHz) photons. Based on previous vacuum gap capacitor designs, these novel devices integrate the small electromagnetic mode volume of lumped elements with the increased photon energy provided by millimeter waves to generate larger optomechanical vacuum coupling rates. Combined with enhancements to the mechanical quality factor, these devices should allow access to the quantum regime with pump fields of less than a single photon on average, providing a novel quantum information resource, as well as a platform for fundamental studies of quantum mechanics at the mesoscale.

Speaker: Dr Bradley Hauer (NIST Boulder)

510 (G*) Demonstration of a model for AFC cavity quantum memory

Optical quantum memory that has the ability to store and on-demand, recall the quantum states of light with high efficiency and fidelity which has several applications in linear-optical quantum computation, single-photon detection, quantum metrology, tests of the foundations of quantum physics is one of the essential elements in distribution of quantum entanglement for long distance quantum communication based on quantum repeaters.
Amongst all the proposed protocols for implementation of quantum memory, atomic frequency comb (AFC) quantum memory is a promising candidate in quantum repeater applications because of the capability to store and read out multiple temporal modes that could enhance the performance of quantum repeater via faster entanglement generation. Also, opposed to other quantum memory protocols, in AFC technique the number of temporal modes that can be stored in a sample is independent of the optical depth of the storage material. To achieve high efficiency in quantum memories, large optical depth is needed. However, in practice large optical depth is difficult to gain specifically for rare-earth ion doped crystals.
To overcome this issue, it was proposed to put the memory inside an asymmetric optical cavity. By applying the impedance matching condition, unit efficiency can be obtained with an effective optical depth of one and the memory efficiency is only limited by intrinsic atomic dephasing.
So far, there have been several experiments carried out based on impedance matched proposal using atomic frequency comb technique. However, measuring the AFC properties e.g. optical depth within the cavity is formidable due to the change in cavity mode structure caused by strong dispersion effect originates from the absorption engineering of the ions to create the comb inside the cavity. As yet, there is only an estimation of the AFC structure properties e.g. optical depth inside the cavity by performing the measurements outside the cavity but the comb properties inside the cavity are not exactly known.
Here, we demonstrate a model for AFC memory inside an asymmetric cavity by broadening the scope of impedance-matched proposal which leads to better understanding of the AFC structure properties inside a cavity. We compare the results of our theory to the obtained results of the experimental data of an asymmetric cavity AFC quantum memory and we show agreement to some extent between our theory and the measurements for AFC cavity quantum memory which enables us to make predictions for comb properties i.e optically depth inside a cavity.

Speaker: Ms Shahrzad Taheri (University of Calgary)

511 (G*) Exceptional points in helically structured thin films

Thin film deposition on substrates inclined with respect to the flux of evaporated materials can be used to produce anisotropic porous nanostructures displaying effective anisotropic optical properties at the wavelength scale. When the orientation of the substrate is changed during the deposition process, sculptured thin films are grown, whose optical properties can be continuously controlled during the deposition along the direction normal to the substrate. Helically structured thin films are an example of such material. They give rise to a circular Bragg resonance at a soecific wavelength λ. Here we report about the existence of exceptional points (EPs), where the eigenpolarization states in reflection coalesce into a single state at specific orientations of the k vector of the incoming beam. Such EPs were previously reported for metasurfaces; here we show that they can also be realized by using conventional thin film deposition methods and thus lend themselves to low cost manufacturing. Laser mirrors based on helically structured thin films with EPS can be used to create only one eigenstate of polarization inside a resonator and thus eliminate dual polarization states, or to eliminate spatial hole burning in standing wave resonators.

Speaker: Mr Gabriel J. Gallant (Université de Moncton)

512 (G*) Towards a Radioactive Barium Atomic Source for an Open-access Trapped Ion Quantum Information Processor

Trapped ions for quantum information processing has been an area of intense study in the past twenty years due to the extraordinarily high-fidelity operations that have been achieved experimentally, and the recent microfabricated traps that offer a potential path to scaling the technology. Specifically, the Barium-133 trapped ion has been shown to have some of the highest fidelity operations of any qubit. Barium-133 is readily available as a salt, which can be ablated by a low pulse-energy ($<$ 1 mJ) 532 nm nanosecond laser. We present progress towards a method for preparing and testing barium salt atomic sources that will be used for loading different barium isotopes. The impact of different heat treatments applied to the ablation targets are investigated and the efficiency and longevity of the source are estimated by collecting barium neutral atom fluorescence from the ablation plume after nanosecond pulses. Furthermore, a mechanical design is presented, which will produce a highly collimated atomic beam, reducing contamination on current chip-trap architectures.

Speaker: Noah Greenberg (University of Waterloo)

513 (G*) Towards a large scale fully programable trapped ion quantum simulator

A programmable quantum simulator can simulate models of quantum many-body systems that may otherwise be impossible to be modeled with conventional computers. Simulation of such many-body quantum systems may further advance our understanding of exotic quantum materials, fundamental forces of nature, molecules for drug discovery, etc. Laser-cooled and trapped atomic ions serve as an ideal platform for the simulation of interacting quantum spin models. In this talk, we describe the development of a large-scale quantum simulator based on a multi-segmented blade electrode ion trap capable of trapping a large (>50) chain of Ytterbium ions in a near uniformly spaced configuration. A high numerical aperture (NA) holographic optical addressing system will be used for aberration-corrected addressing of the trapped ions with minimal ‘crosstalk error’ [1]. This would usher the capability to engineer dynamic many-body Hamiltonians with control over the individual ion-spins and the interactions between them. A high NA imaging system would allow us to detect the spin states of individual ions simultaneously with high precision, including the capability to perform partial measurements without necessarily decohering rest of the system. The trap will be housed inside an XHV vacuum system to keep the ions free from background collisions. Optimal vacuum system engineering has allowed us to design a vacuum vessel with simulated pressures of at least one order of magnitude lower than current room temperature trapped ion quantum simulators.
[1] C.-Y. Shih, S. Motlakunta, N. Kotibhaskar, M.Sajjan, R. Hablützel, R. Islam npj Quantum Information (in press, 2021)

Speaker: Nikhil Kotibhaskar (Institute for Quantum Computing)

17:15 Group discussion

W4-2 Theory and Condensed Matter (DTP/DCCMP) / Théorie et matière condensée (DPT/DPMCM)

Convener: Joseph Maciejko (University of Alberta)

514 (I) Magneto-optical Kerr effect and signature of the chiral anomaly in a Weyl semimetal in magnetic field

One striking property of the Landau level spectrum of a Weyl semimetal (WSM) is the existence of a chiral Landau level in which the electrons propagate unidirectionnaly along the magnetic field. This linearly dispersive level profoundly influences the optical properties of the WSM especially if it originates from a tilted Weyl cone. In this talk, we compare the behavior of the magneto-optical Kerr effect (MOKE) in a WSM with that of a normal (i.e. non-topological) metal. We obtain the Kerr angle from the optical conductivity tensor σ_{αβ}(ω) using the minimal model of a WSM developed in Ref. [1] which has four tilted Weyl nodes related by mirror and time-reversal symmetry. In the Voigt configuration, a large peak of the Kerr angle occurs at the plasmon frequency. We show that the blueshift in frequency of this peak with increasing magnetic field is a signature of the chiral anomaly in the MOKE.

[1] S. Bertrand, Jean-Michel Parent, R. Côté, and I. Garate, Phys. Rev. B 100, 075107 (2019).

Speaker: Prof. René Côté (Université de Sherbrooke)

515 (I) Domain and Skyrmion bound states on the surface of magnetic topological insulators

A 3D topological insulator (TI) hosts an odd number of Dirac cones as its 2D surface states spectrum. The states are exponentially localized to the surface and their (pseudo)spin is locked to the surface momentum direction due to spin-orbit interaction. If the TI is also magnetic there are fixed magnetic moments on the surface, co-existing with the itinerant Dirac electrons. The magnetic moments interact with each other both directly (exchange) and indirectly (RKKY) and may form a ferromagnetically ordered state. The magnetic state couples to the Dirac electrons and serves as a Dirac mass which, when uniform, opens a gap in the spectrum. When the ordering of the magnetic moments is modified by excitation such as skyrmions, the Dirac electrons see a landscape of spatially dependent mass. A skyrmion texture binds an electronic state to it which we call a skyrmion-bound state.
In this talk we will see how the bound states can be detected by a surface conductivity measurement and how the skyrmion-skyrmion interaction is altered due to the presence of Dirac electrons. We will also discuss a skyrmion solid background to Dirac electrons.

516 An Analytical study of the role of lattice conductivity in the enhancement of the thermoelectric figure of merit

In an earlier study on the Wiedemann–Franz Law and the thermoelectric figure of merit (FoM), we studied the electronic effects in detail. We briefly investigated the role of the lattice thermal conductivity in enhancing the FoM and derived the characteristic equations in the form of an offset-logarithmic function (a special case of the generalized Lambert W function) [1]. This work follows up with analytical and numerical solutions to the offset-log function and provides better insight into the materials parameter space. We find the extrema of the lattice thermal conductivity and comment on its role in optimizing the figure of merit.

[1] Yadav, A., Deshmukh, P. C., Roberts, K., Jisrawi, N. M., & Valluri, S. R. (2019). “An analytic study of the Wiedemann–Franz law and the thermoelectric figure of merit”, Journal of Physics Communications, 3 (10), 105001.

Speaker: Dr Najeh Jisrawi (King's University College, University of Western Ontario)

517 Kerr Nonlinearity and Energy Transport in Quantum Dots and Metallic Nanoparticles

Recently, there has been considerable interest to study the nonlinear properties of ensembles of
metallic nanoparticles and quantum dots [1,2]. Nonlinear optical properties can be used for
processing the information content of data images, on which the research can potentially induce a
revolution in electronic as well as photonic nanotechnology and nanomedicine. We have studied
the energy transport due to the Kerr nonlinearity in plasmonic nanohybrids. The Kerr coefficient
has been calculated by using the quantum density matrix method in the dipole-dipole coupling
between quantum dots. Induced dipoles are created when the probe photon falls on the metallic
nanoparticles. These metallic nanoparticles interact with each other via dipole-dipole interaction.
We showed that the power is transferred from the metallic nanoparticles to the quantum dots
through surface plasmon polaritons. During this process, enhancement in the energy transfer in the
quantum dots is found. We have also predicted that the power spectrum peak would split into two
peaks due to the strong coupling between excitons and the dipole-dipole interaction. Considering
one peak as ON position and two peaks as OFF position, the present findings can be applied to
fabricate nanoswitches. The Kerr nonlinear plasmonics in metallic nanohybrids can also be used
for medical applications since there will be no damaging effect on the body.
[1] J Guo, K Black, J Hu, M Singh, Journal of Physics: Condensed Matter 30 (18), 185301 (2018).
[2] M.R. Singh; Phys. Rev. A102, 013708 (2020).

Speaker: Ningyan Fang (University of Western Ontario)

17:01 Questions/Answers and Discussion Period

W4-3 Labs I (DPE) / Laboratoires I (DEP)

Convener: Chitra Rangan (University of Windsor)

518 Roles in Collaborative Introductory Lab Activities

In order to give our students the opportunity to learn collaboratively in our introductory physics labs, we developed a series of hour-long collaborative activities that students engaged with via Zoom using the IOLab lesson player. We envisioned and developed the activities to revolve around four student roles (experimentalist, theorist, archivist, and manager) to help students share their work equally. By connecting student interviews with reports from 245 students who were randomly assigned to groups of 4 in each of 11 weeks for our activities, we find that roles helped to improve the sharing of collaborative work online. However, there are two caveats. First, the students did not allocate the roles equally. Second, write-ups from the groups with an isolated minority student (i.e., groups with one woman and three men) were significantly less than groups of any other configuration. These findings provide quantitative evidence to support longstanding advice that instructors should avoid forming groups with isolated minority students in physics.

Speaker: Danny Doucette (University of Pittsburgh)

519 Virtual Laboratories for Remote Teaching

The pandemic timeline has turn out to be much longer than initially expected, and the need for a remote teaching still remains. The immediate switch to the remote teaching that happened due to COVID-19 in March 2020, not surprisingly, had the greatest detrimental effect on laboratory components of physics courses. Smaller courses during summer time allowed us to test different approaches and more adequately prepare for large-enrollment classes for the Fall 2020 semester. The main decisions was to choose between the labs using real data and simulations-based labs. I will touch upon the challenges and successes of running the live lab sessions on teleconferencing platforms such as Zoom. Some elements, like pre-recorded introductions to the labs, methods of lab reports collections and grading online will remain well beyond the pandemic.

Speaker: Dr Tetyana Antimirova (Ryerson University)

520 Scaling the Investigative Science Learning Environment (ISLE) Online

I will share my experiences and lessons learned implementing the Investigative Science Learning Environment (ISLE) approach in a large online introductory class of hundreds of students. The ISLE approach is based on two intentionalities (Brookes, Etkina, & Planinsic 2020): (1) We want students to learn physics by thinking like physicists; by engaging in knowledge-generating activities that mimic the actual practices of physics and using the reasoning tools that physicists use when constructing and applying knowledge. (2) The way in which students learn physics should enhance their well-being.

Speaker: Carolyn Sealfon (University of Toronto)

W4-4 Application of Atmospheric Pressure Plasmas II (DPP) / Applications des plasmas à pression atmosphérique II (DPP)

Convener: Lenaic Couedel (University of Saskatchewan)

521 (I) Atmospheric pressure synthesis of chemical fuels by high frequency plasmas: an outlook

Chemical synthesis of fuels using sustainable energies is one of the main challenges for the development of a circular economy. In recent years, because of their flexibility and capability of not using any rare earth materials or noble metals, atmospheric pressure plasmas have been the focus of intense research activities for the reduction of stable molecules such as CO2 and N2. In this contribution, we will discuss the current status of plasmas for synthesis of chemicals and some of the main challenges ahead. To compare the potential of plasma technology with other technologies such as electrochemical and thermochemical reduction methods, many aspects need to be taken into account. This contribution focuses, as an example, on the reduction of CO2 using high frequency discharges (namely radio-frequency and microwave plasmas).

Depending on plasma parameters such as the electron density and temperature, the gas and vibrational temperatures, the dissociation and recombination pathways of molecules are completely different in atmospheric pressure plasmas. To enhance the energy and conversion efficiencies , the experimentalist has a number of tools to achieve this goal, mainly while controlling the reduced electric field and deposited power density, both through the applied frequency and applicator geometry, and via the input gas flow.

Energy efficiency is currently the main metric used for assessing the performance of the CO2 dissociation (plasma) process. It is however required to consider also the separation step to have pure CO and, the lower the initial CO yield, the higher is the energy cost per kg of produced CO. Although non-equilibrium plasmas are inherently attractive due to higher energy efficiencies (when achievable), their typically low conversion yields are detrimental for any industrial upscaling. Thermal plasmas, when energy recycling is possible, may prove to be a better alternative. Also, the power coupling efficiency as well as the energy losses due to transformers should be accounted. Such parameters, together with the assessment of employed materials, the reactor compactness, its flexibility to handle fluctuating renewable energy supplies and its integrability into a process chain need to be considered while considering new technologies for chemical synthesis of fuels.

Speaker: Prof. Emile Carbone (Institut National de la Recherche Scientifique)

522 (U*) Statistical analysis of pulsed spark discharges in dielectric liquids

Currently, the focus of plasma discharges in liquid is mainly to produce nanoparticles, to remove pollutant from water or to transform liquid fuels. In this paper, we aim to put forward a statistical study of the influence of various discharge parameters (e.g. applied voltage, pulse width, nature of liquid and electrode geometry) on the discharge characteristics, such as the discharge probability, the breakdown voltage, the discharge current and others. These characteristics are monitored as a function of time, until the moment when no discharges occurred. Although the mechanisms that lead to a gas breakdown are well-reported, those describing a breakdown in liquid are far to be completely understood. This is partially due to multiple phenomena that are not present in gas, such as phase change, presence of impurities, or the presence of microbubbles. In this paper, the time evolution of the discharge is mainly due to electrode erosion that induces i) an increase of the interelectrode gap, a modification of the electrode geometry, and a change in liquid properties. Each experiment lasted between 400 and 38 000 discharges, depending on the four parameters mentioned previously. This study goes beyond a qualitative analysis as we will introduce predictive models of the injected charges as a function of the average current and the discharge delay (or a model of the injected energy as a function of the average power and the discharge delay). The findings allowed further understanding of the discharge behavior based on its voltage-current characteristics. Furthermore, our results can be utilized in the context of the production of nanoparticles, where a control of the discharge characteristics is required.

Speaker: Naomi Bourbeau (University of Montreal)

17:25 Open discussion period

W4-5 Theory I (DNP) / Théorie I (DPN)

Convener: Jason Holt (TRIUMF)

523 (I) Nuclear many-body problem at zero and finite temperature

Recent developments of the relativistic nuclear field theory (NFT) on the fermionic correlation functions will be presented. The general non-perturbative equation of motion framework is formulated in terms of a closed system of non-linear equations for one-body and two-body propagators. The present formulation provides a direct link to ab-initio theories and extends the explicit treatment of many-body correlations beyond the standard NFT level. The novel approach to the nuclear response, which includes configurations with two quasiparticles coupled to two phonons (2q⊗2phonon), is discussed in detail for electromagnetic excitations in medium-mass nuclei. The proposed developments are implemented numerically on the basis of the relativistic effective meson-nucleon Lagrangian and compared to the models confined by 2q and 2q⊗phonon configurations, which are considered the state-of-the-art for the response theory in nuclear structure calculations. The results obtained for the dipole response of 42,48-Ca and 68-Ni nuclei in comparison to available experimental data show that the higher-complexity configurations are necessary for a successful description of both gross and fine details of the spectra in both high-energy and low-energy sectors.

The approach confined by the 2q⊗phonon configurations has been extended recently to the case of finite temperature for both neutral and charge-exchange nuclear response. Within this approach, we investigate the temperature dependence of nuclear spectra in various channels, such as the monopole, dipole, quadrupole and spin-isospin ones, for even-even medium-heavy nuclei. The temperature dependence of the Gamow-Teller and spin dipole excitations will be discussed in the context of its potential impact on the astrophysical modeling of supernovae and neutron-star mergers.

Speaker: Elena Litvinova (Western Michigan University)

524 Ab-initio calculations of structure factors for dark matter searches

We present the first ab-initio calculations of the structure factors for elastic spin-dependent WIMP scattering off $^{19}$F, $^{27}$Al, $^{23}$Na, $^{27}$Al, $^{29}$Si, $^{73}$Ge, $^{127}$I and $^{129,131}$Xe. A set of established two- (NN) and three-nucleon (3N) interactions derived from chiral effective field theory (EFT) are used for nuclear interaction, including N$^3$LO-level NN + N$^2$LO-level 3N, N$^4$LO-level NN + N$^2$LO-level 3N, and N$^2$LO-level NN+3N with the $\rm{\Delta}$(1232)-isobar degrees of freedom. Within the same chiral EFT framework, we employ corresponding WIMP-nucleus currents at the one-body level and also include the effects from axial-vector two-body currents. We then apply the ab-initio in-medium similarity renormalization group to construct valence-space Hamiltonians and consistently transformed operators of nuclear responses. By combining the newly developed frameworks, natural orbitals and expressing the 3N force with a very large basis size, we obtain basis-space converged structure factors in heavy nuclei. This work paves the path toward a true first-principles calculation of the structure factor for WIMP scattering in all nuclei relevant for ongoing searches. All results are publicly available in a Jupyter notebook.

Speaker: Dr Baishan Hu (TRIUMF)

525 (G*) Scattering and Reaction Calculations for the 8Be Composite System

We apply the no-core shell model with continuum technique to investigate nuclear reactions involving p+7Li and n+7Be with 8Be as the composite system. This method enables accurate description of both bound states and the continuum using chiral nucleon-nucleon and three-nucleon forces as input. We report phase-shifts, astrophysical S-factors and cross-sections for a suite of scattering and reaction processes.

The production and destruction of 7Li through these channels is the main contributor to the prediction of cosmological Lithium abundance of which current estimates differ significantly from measurements. Through first-principles calculations of 7Li(p, $\gamma$)8Be and 7Li(p, e+ e-)8Be capture, we also examine the nuclear processes relevant for the ATOMKI anomaly (which posits the existence of a new boson with a mass of 17 MeV).

Speaker: Mr Peter Gysbers

W4-6 Exotic Matter II (DNP) / Matière exotique II (DPN)

Convener: Christopher Chambers (McGill University)

526 (I) Status of the Ultracold Neutron Source and nEDM Experiment at TRIUMF

Ultracold neutrons are neutrons that exhibit the peculiar behavior of being able to be stored in material bottles for periods ranging up to their beta-decay lifetime (~15 min). They present an attractive avenue for performing fundamental neutron experiments such as: searching for a non-zero neutron electric dipole moment (nEDM), precise measurement of the neutron lifetime, and precision measurements of neutron-beta-decay correlation coefficients to name a few. These measurements have important consequences for extensions to the standard model of particle physics which could help explain the baryon asymmetry of our universe.

The TUCAN (TRIUMF Ultra-Cold Advanced Neutron) collaboration, with researchers from Japan and Canada, aims to measure the nEDM with a sensitivity of 1E-27 ecm, which is a factor of 10 more precise than the best nEDM measurement to date. Key to this realization is the installation of a high-intensity UCN source, currently being fabricated, and a new-room temperature Ramsey-resonance-based measurement device. This talk will introduce UCN fundamentals and present the status of the TUCAN source and nEDM experiment.

Speaker: Russell Mammei (The university of Winnipeg)

527 (G*) Optical magnetometry for the TUCAN nEDM experiment

The TUCAN collaboration aims to provide an ultra-precise measurement of the neutron electric dipole moment, resulting in a planned sensitivity of 10-27 ecm. EDM experiments of this kind require measuring changes in the precession frequency of ultracold neutrons as they are subjected to parallel and anti-parallel electric and magnetic fields. In order to reach the planned sensitivity, precise control of these magnetic fields and their gradients is required. To this end, the group is developing an array of optical (Cs based) magnetometers and analysis software sensitive enough to accurately characterize magnetic-field dependent systematic uncertainties to better than 10-28 ecm.

Operation of the first fibre optic coupled prototypes is demonstrated in this presentation, as well as the work done in optimizing the deployment of the system in order to identify magnetic field dependent systematic effects to the required precision.

Speaker: Wolfgang Klassen (University of Manitoba)

2021_06_07_CAP_WKlassen_presentation.pdf

528 (G*) Bound-state beta-decay of Thallium-205 for low-energy neutrino flux

Bound-state beta-decay ($\beta_b^-$-decay) is an exotic $\beta^-$-decay mode where the electron is emitted directly into a bound orbital of the daughter nuclei. The electron is emitted into the K- or L-orbitals so this decay mode is only possible for highly charged ions. The first experimental confirmation of $\beta_b^-$-decay was achieved 30 years ago at the Experimental Storage Ring (ESR) at GSI Darmstadt. Thallium-205 as a neutral atom is stable but the bare ion $^{205}Tl^{81+}$ is unstable to $\beta_b^-$-decay, so removing all electrons from $^{205}Tl$ literally changes its stability. The capture of solar-neutrinos onto $^{205}Tl$ to produce $^{205}Pb$ is the lowest energy threshold neutrino-induced reaction known at just 53 keV, allowing us to probe a completely new region of the solar-neutrino spectrum. The LORandite EXperiment (LOREX) aims to extract a time-averaged flux measurement from the thallium-bearing mineral Lorandite ($TlAsS_2$) by determining the $^{205}Pb$ content of the mineral deposit. However, the neutrino-capture reaction rate is highly uncertain because the nuclear matrix element (which is identical to the $\beta$-decay matrix element) is unknown as neutral $^{205}Tl$ is stable. The measurement of the $\beta_b^-$-decay half-life, and hence the $\beta$-decay matrix element, is crucial for the LOREX experiment to succeed.

The $\beta_b^-$-decay measurement of $^{205}Tl^{81+}$ was conducted at the GSI Heavy Ion Facility in March 2020. A $^{206}Pb$ primary was impacted onto a beryllium target to produce a $^{205}Tl^{81+}$ beam at 400 MeV/u that was stored in the Experimental Storage Ring. During storage, the beam is electron cooled and monitored by resonant Schottky detectors that identify ion species and intensity by their revolution frequency in the ring. An Argon gas target was used to remove the bound electron from the $^{205}Pb^{81+}$ daughter ions so they could be counted. The $^{205}Tl^{81+}$ injections were stored for a variety of times, and the growth of the $^{205}Pb^{82+}$ signal was directly attributable to $\beta_b^-$-decay. From the linear growth over time, the decay rate was calculated. The authors aim to present the motivation, storage ring methods, and some preliminary results.

Speaker: Mr Guy Leckenby (TRIUMF)

W4-7 Candidates for Dark matter and Dark sector II (PPD) / Candidats pour matière et secteur sombres II (PPD)

Convener: David Morrissey (University of Michigan)

529 (G*) Dark matter model constraints using a fast simulation of the ATLAS detector

Data collected at the LHC are analyzed by the ATLAS collaboration for evidence of dark matter. In this talk, a fast simulation of the ATLAS detector response using the Delphes software is assessed for dark matter models with a leptonically decaying $Z$ boson and a pair of dark matter particles ($\chi\bar{\chi}$) in the final state. Limits for the Two Higgs Doublet plus pseudoscalar (2HDMa) dark matter model are obtained using simplified systematics, and compared to limits obtained using the more complex standard ATLAS analysis.

Speaker: Samantha Taylor (University of Victoria (CA))

STaylor_CAP2021_updated.pdf

530 (G*) FORMOSA - Looking Forward to Millicharged Dark Sectors at the LHC

We identify potentially the world's most sensitive location to search for millicharged particles in the 10 MeV to 100 GeV mass range: the forward region at the LHC. We propose constructing a scintillator-based experiment, FORward MicrOcharge SeArch (FORMOSA) in this location, and estimate the corresponding sensitivity projection. FORMOSA, placed $\sim 500 \, \rm m$ downstream from ATLAS, would take advantage of enhanced MCP production in the forward direction. We show that FORMOSA can discover millicharged particles in large and unexplored parameter space, and study strongly interacting dark matter that cannot be detected by ground-based direct-detection experiments. The newly proposed LHC Forward Physics Facility (FPF) provides an ideal structure to host the full FORMOSA experiment.

This talk is based on arXiv:2010.07941.

Speaker: Mr Saeid Foroughi-Abari (University of Victoria)

CAP Millicharged Dark Sector .pdf

531 U(1)_{Lμ-Lτ} charged fermionic dark matter at weak scale

The existence of dark matter is widely accepted, with a well motivated theoretical candidate being a class of particles known as WIMPs (weakly interacting massive particles), which appear in the spectra of many extensions to the standard model.

We explore a particular WIMP-like model in which fermionic dark matter weakly couples to the muon/tau sectors of the standard model through a new vector boson Z’, in addition to electrically charged particles through kinetic mixing of the Z' with the SM photon. As well as the model providing a candidate dark matter particle, the hypothetical Z’ could potentially aid in explaining the discrepancy between the predicted and observed value of the anomalous magnetic dipole moment of the muon.

Cosmological observations of the dark matter relic density along with findings from direct detection attempts allow us to tightly constrain the parameter space of the model. By initially assuming a momentum independent kinetic mixing parameter, it is difficult for the resulting parameter space to satisfy the restrictions imposed by both sets of experimental results. In this talk, we focus on the work done to remedy this disagreement. Our work involves an attempt at softening the direct detection constraint by considering the general case in which the mixing parameter is momentum dependent. We construct it in such a way that it vanishes in the zero-momentum transfer limit, which results in a viable parameter space. Our goal is then to compare model derived quantities including interaction cross sections and early universe annihilation rates to well established experimental bounds to determine if the resulting parameter space is consistent with the constraints imposed by both direct detection and relic abundance.

Speaker: Timothy Hapitas (Carleton University)

CAP CONGRESS TALK TIMOTHY HAPITAS.pdf

CAP CONGRESS TALK TIMOTHY HAPITAS.pptx

532 Closing the window for WIMPy inelastic dark matter with heavy nuclei

The kinematics of WIMP dark matter-nuclear scattering is drastically altered in the presence of inelastic dark matter, where the dominant dark matter component is up-scattered to a heavier state with certain mass splitting. With hundreds of keV mass splitting inelastic dark matter will evade the search in most direct detection experiments, where the momentum transfer is limited either by the mass of target nuclei, or by the detector response. We propose a novel way to search for inelastic dark matter in nuclear decay searches. In such experiments, inelastic dark matter scattering may excite the isotopes to an excited state and the deexcitation gamma ray leaves detectable signals in the gamma ray detector. We illustrate the kinematics of inelastic dark matter in light of heavy nuclear targets, and derive the bound on inelastic dark matter from the induced excitation of hafnium and osmium isotopes. We also set the limit on inelastic dark matter nuclear scattering from the alpha decay search with CaWO$_4$ and PbWO$_4$ crystals, which extends to a mass splitting of 640 keV, much beyond the current limits from XENON1T and CRESST.

Speaker: Ningqiang Song (Queen's University)

IDM_CAP.pdf

W4-8 Membrane Biophysics and Drug Delivery (DPMB) / Biophysique des membranes et administration de médicaments (DPMB)

Convener: Melanie Campbell (University of Waterloo)

533 (U*) The Effects of Resveratrol, Caffeine, 𝜷-Carotene, and Epigallocatechin Gallate (EGCG) on Amyloid-𝜷25–35 Aggregation in Synthetic Brain Membranes

Alzheimer’s disease is a neurodegenerative condition marked by the formation and aggregation of amyloid-𝜷 (A𝜷) peptides. It is the most common cause of dementia worldwide, with numbers expected to double each year, reaching 81 million by 2040. There exists, to this day, no cure or effective prevention for the disease; however, there is evidence that a nutritious diet and certain food compounds can slow down first occurrence and progression of the disease. Here, we prepared synthetic membranes that contained A𝜷 aggregates and investigated if certain food compounds could partition into the membrane and interact with such aggregates using optical and fluorescence microscopy, X-ray diffraction, UV–vis spectroscopy, and molecular dynamics simulations. The compounds studied were resveratrol, a polyphenol commonly found in the skin of grapes, 𝛽-carotene, a naturally occurring carotenoid found in carrots, EGCG, an antioxidant abundantly found in green tea, and caffeine, the principal pharmacologically active component in coffee [1].

Evidence suggests that all compounds are membrane active and spontaneously partitioned in the membrane. While resveratrol and caffeine lead to membrane thickening and reduced membrane fluidity, 𝜷-carotene and EGCG preserved or increased fluidity. Our findings show that resveratrol and caffeine did not reduce the volume fraction of peptide aggregates while 𝜷-carotene significantly reduced plaque size. Additionally, EGCG dissolved peptide aggregates and significantly decreased the corresponding cross-𝜷 and 𝜷-sheet signals. The results of this paper provide a mechanism by which food compounds may affect amyloid-𝜷 aggregation and may be useful in future research by providing candidates that target the membrane environment and in turn, potentially inhibit or reverse the formation of amyloid aggregates.

[1] Gastaldo, Isabella P., Sebastian Himbert, Udbhav Ram, and Maikel C. Rheinstädter. "The Effects of Resveratrol, Caffeine, 𝜷-Carotene, and Epigallocatechin Gallate (EGCG) on Amyloid-𝜷25–35 Aggregation in Synthetic Brain Membranes." Mol. Nutr. Food Res 2000632 (2020).

Speaker: Isabella Gastaldo

534 (U*) Curcumin and homotaurine suppress amyloid-b25-35 aggregation in synthetic brain membranes

More than 30 million individuals worldwide are living with Alzheimer’s Disease. To further the current understanding on this neurodegenerative disease, we developed a technique to create amyloid peptide clusters in synthetic, brain-like membranes, which mimic the senile plaques found in the brains of Alzheimer's patients. I compared the molecular functioning of homotaurine, a peptic anti-aggregant that binds to amyloid peptides directly, and curcumin, a non-peptic molecule that can inhibit aggregation by changing membrane properties. By using microscopy, x-ray diffraction, and UV-vis spectroscopy, we found that both curcumin and homotaurine significantly reduce the number of small, nanoscopic amyloid aggregates and the corresponding β- and cross-β sheet signals. This research shows that membrane active drugs can be as efficient as peptide targeting drugs in inhibiting amyloid aggregation in-vitro [1]. The findings can open new pathways for the developments of drugs to slow down first occurrence and progression of the disease.

[1] Xingyuan Zou, Sebastian Himbert, Janos Juhasz, Samantha Ros, Harald D. H. Stover, and Maikel C. Rheinstädter, “Curcumin and homotaurine suppress amyloid-b25-35 aggregation in synthetic brain membranes”, under review with ACS Chemical Neuroscience, Manuscript ID: cn-2021-00057r

Speaker: Xingyuan (Kate) Zou (McMaster University)

535 (G*) Diffusion in a membrane in the presence of immobile obstacles: the role of disorder

How diffusivity (e.g., of proteins in the plane of biomembranes) is impacted by obstruction has been explored using Lattice Monte Carlo methods for random and periodic obstacle configurations. However real systems are neither periodic nor totally random. We present a study of transient and steady-state molecular diffusion in two-dimensional ”Fuzzy” systems of immobile obstacles, \textit{i.e.,} systems which bridge the gap between the ideal periodic and random limits. In particular, we examine whether there are ”diffusion phase transitions”, i.e., abrupt quantitative and/or qualitative changes at some critical degree of disorder. For instance, while the crossover length $r^*$ (describing the transition from anomalous to normal diffusion) decreases when the concentration of obstacles, $\phi$, increases in a periodic system, it is the opposite for random systems. Interestingly, $r^*(\phi)$ can become a very weak function of $\phi$ in some fuzzy systems. We investigate several ways of creating tunable disorder leading to different behaviour, and we introduce a parameter describing how the disorder in fuzzy systems impacts diffusion. Furthermore we introduce a new relation between the crossover length $r^*$, and the properties of the (anomalous) transient regime, including the excess diffusivity that it generates. Finally we propose new connections between the properties of the transient and steady-state regimes, most notably the possibility of estimating the steady state diffusion coefficient using early time (transient) data.

Speaker: Nicholas Ilow (University of Ottawa)

536 FUNCTIONAL AND FUNCTIONALIZED MEMBRANES

Cell membranes are complex dynamic structures, and their composition and structure are major determinants of pathology. It is now commonly accepted that the membranes’ physical properties, such as fluidity and thickness, are determining factors for permeability, partitioning of drug molecules, and protein aggregation. Membrane-interacting molecules can in some instances be expected to have a greater therapeutic potential than traditional therapies targeting receptors or enzymes. I will provide a perspective on the basic mechanisms how physical membrane properties can affect diseases, and the therapeutic potential of changing membrane properties to target certain diseases. Red blood cell based liposomes with antiviral and antibiotic properties have great therapeutic potential because of their biocompatibility. We use these ideas also in our start-up (www.synth-med.com ) that develops smart membrane-based sensors for water and food safety.

Speaker: Maikel Rheinstadter (McMaster University)

537 THE NANOSCOPIC BENDING RIGIDITY OF RED BLOOD CELL MEMBRANES

Blood banks all around the world store blood for several weeks ensuring the availability of blood for transfusion medicine. Although the storage conditions have been optimized for decades it has become evident that red blood cells (RBC) undergo numerous changes when being stored.
We investigated the effect of storage on the nanoscopic bending rigidity of RBC membranes with a combination of Molecular Dynamics simulations, inelastic neutron scattering and diffuse X-ray scattering [1]. Coarse grained (CG) models of RBC membranes were created by matching experimental lipidomic analysis. It was found experimentally that the concentration of fatty acids and cholesterol changes during storage and aged membranes were mimicked by adjusting the lipid composition accordingly.
Solid supported membrane stacks of fresh and stored RBC samples were prepared. X-ray diffraction experiments were then conducted at high relative humidity allowing to reconstruct the membrane surface fluctuations from diffuse scattering signals using a GPU accelerated workstation. These experiments were complemented by Neutron Spin Echo measurements on RBC vesicles which probe the membrane fluctuations directly. Bending moduli of 1.8 kBT and 15.4 kBT were measured in excellent agreement with the simulation data.
[1] Himbert et al., “The Nanoscopic Bending Rigidity of Red Blood Cell Membranes”, in preparation

Speaker: Sebastian Himbert (McMaster University)

538 A Kinetic Monte Carlo Algorithm for Swelling Drug Delivery Systems

Due to their highly tunable physical properties and their biocompatibility, hydrogels-based drug delivery systems have sparked huge interests over the past twenty years. One of the reasons of this interest lies to the ability to encapsulate drug particles inside the porous hydrogel structure. In addition, by adjusting the density of cross-links in the gel matrix, it is possible to modify the diffusion coefficient of the drug particles and thus to control the drug release in order to maintain the dose of drugs delivered within a therapeutic window. Furthermore, the hydrogel structure can swell during the drug release process when surrounded by an aqueous environment due to their hydrophilic affinity. Consequently, it leads to a non trivial competition between the diffusion and the swelling processes; and therefore can strongly affect the release dynamics.

Mathematically, even for simple geometries, finding an analytical solution for the drug concentration evolution remains very complicated or even impossible. For this reason, it is necessary to tackle this problem numerically. Therefore, we have developed a Lattice Kinetic Monte Carlo (LKMC) method which allows to simulate the release dynamics from swelling delivery systems.

Our results show that our LKMC method perfectly reproduces the expected release properties and can be used over a large variety of swelling systems. Finally, we compare our numerical result to the rare existing analytical solution: the adiabatic release.

Speaker: Maxime Ignacio (University of Ottawa)

539 (G*) The Limits of Polymer Single File Dynamics: A phase diagram

We use Langevin dynamics (LD) simulations to investigate single file diffusion (SFD) in a dilute solution of flexible linear polymers inside a narrow tube. The transition from single-file diffusion, where the mean-square displacement scales like $\langle x^2 \rangle \sim t^{1/2}$, to normal diffusion with $\langle x^2 \rangle \sim t$, is studied as a function of the system parameters, such as the width of the channel, the polymer concentration and the polymer size. Based on our simulation results and scaling arguments, we propose a phase diagram describing the different diffusion regimes. We also map this problem onto a one-dimensional Lattice Random Walk algorithm where the diffusing object represents the polymer's center of mass. In order to model the polymers entanglement and disentanglement processes we allow several objects to temporarily share the same lattice site and diffuse together. Extension of our work to polydisperse polymer solutions, one-dimensional electrophoresis, ring polymers and DNA mapping are discussed.

Speaker: Hanyang Wang (University of Ottawa)

W4-9 Magnetic North VII - Session 8 / Nord magnétique VII - session 8

Convener: David Venus (McMaster University)

540 (I) Magnetic polaritons or strong photon-magnon coupling in arrays ferromagnetic nanowires

Magnetic polaritons have been known and observed for decades in ferromagnetic resonance spectroscopy experiments. A revival of interest and reinterpretation of these classical experiments, over the last decade, have focussed on the strong interaction between microwave photons and the collective spin excitations of ferromagnetic specimens in resonant cavities. Some of these studies have brought new insights on strong coupling phenomena, along with developing a variety of emerging fields, such as: cavity electromagnonics, cavity spintronics, cavity optomagnonics, cavity magnomechanics, quantum magnonics and so on. These systems are very much like ensembles of paramagnetic objects strongly coupled to a microwave field, as studied in quantum electrodynamics, but with some major differences. The very dense population of exchange-coupled spins in ferromagnets collectively couples with microwave cavity fields with ridiculously high efficiencies, but collective magnetic excitation is degenerate with a sea of spin waves modes, leading to additional complexity. Understanding the effect of dipolar coupled ferromagnetic objects and collective resonance modes on the strong photon-magnon coupling is important in order to exploit these systems for new technologies. We built on our recent work on two dipolar coupled ferromagnetic spheres in a resonant cavity to investigate and explain the strong coupling exhibited in arrays of CoFeB ferromagnetic nanowires, measured at frequencies ranging from 26 to 110 GHz.

Speaker: David Menard (Polytechnique Montreal)

541 Magnon confinement

Magnetic structures are known to possess magnetic excitations confined to their surfaces and interfaces, but these spatially localized modes are often not resolved in spectroscopy experiments. We developed a theory to calculate the confined magnon spectra and its associated spin scattering function, which is the physical observable in spectroscopy based on neutron and electron scattering, and a proxy for Raman and infrared optical experiments. We apply our theory to simple ferromagnetic and antiferromagnetic models to show that confined magnons are qualitatively different in these two systems. The theory shows that extra magnetic anisotropy at the system's edge quantitatively impacts magnon confinement in all cases. Our results provide insights on how to interpret magnetic spectroscopy experiments in nanostructures, and how their confined spectra is affected by surrounding materials.

Speaker: Prof. Rogério de Sousa (Centre for Advanced Materials and Related Technology, University of Victoria)

W-POS-A #1-4 Poster session (DPE) / Session d'affiches (DEP)

W-POS-B #5-8 Poster session (DPP) / Session d'affiches (DPP)

Convener: Lenaic Couedel (University of Saskatchewan)

W-POS-C #9-16 Poster session (DAPI) / Session d'affiches (DPAI)

Convener: Steffon Luoma

W-POS-D #17-27,110 Poster session (DPMB) / Session d'affiches (DPMB)

Convener: Emily Heath

W-POS-E #28-40 Poster Session (DAMOPC) / Session d'affiches (DPAMOC))

Convener: Nisha Rani Agarwal (University of Ontario Institute of Technology)

W-POS-F #41-56 Poster session (DCMMP) / Session d'affiches (DPMCM)

Convener: Michel Gingras

W-POS-G #57-74 Poster session (Mag.North) / Session d'affiches (Nord mag.)

Convener: Bruce Gaulin (McMaster University)

W-POS-H #75-79,109 Poster session (DTP) / Session d'affiches (DPT)

Convener: Mark Walton (University of Lethbridge)

W-POS-J #80-107 Poster session (PPD) / Session d'affiches (PPD)

Convener: Marie-Cécile Piro (University of Alberta)

W-POS-K #108 Poster session (DNP) / Session d'affiches (DPN)

Convener: Corina Andreoiu (Simon Fraser University)

Thursday 10 June

R-PLEN-1 NSERC Community Update - C. Harrison (NSERC) , S. Ellison (Evaluation Group Chair) and Rituparna Kanungo (Chair of CAP-NSERC Liaison Committee) / Information sur la communauté du CRSNG - C. Harrison (CRSNG) et S. Ellison (président du groupe d’évaluation) et Rituparna Kanungo (président du comité de liaison ACP-CRSNG)

Convener: Ubi Wichoski (Laurentian University)

R-PLEN-2 Chanda Prescod-Weinstein, U. New Hampshire - (CAP/EDI) (ACP/EDI) Sponsored by TRIUMF

Convener: Kevin Hewitt (Dalhousie University)

542 The Right to Know and Love the Night Sky

In this talk, I will argue that treating the marginalization of certain groups in science as a workforce problem ignores the deeper issue: that wondering about the universe is a fundamental right. I will discuss what it means to create the conditions in which we all have a chance to know and love the night sky and all of the particles that populate it.

Speaker: Prof. Chanda Prescod-Weinstein (University of New Hampshire)

11:30 15 Minute Break

R1-1 Progress towards Gender Equity in Physics (DGEP) / Progrès vers l'égalité des genres en physique (DEGP)

Convener: Chitra Rangan (University of Windsor)

11:45 Introduction of the panelists and overview of the session theme (live)

The Chair of the Division for Gender Equity in Physics, Prof. Chitra Rangan, will introduce the panelists and the overall theme of the session.

543 (I) Good IDEA! Promoting excellence in science through Inclusion, Diversity, Equity and Accessibility (flipped)

Scientists of all backgrounds and genders,have made important contributions in science, technology, engineering and mathematics (STEM), but the participation of women remains low in many areas of STEM, including physics. What can we do to build an inclusive STEM community? I'll discuss recent studies and data that shed light on where we stand today and what we can do to improve.

Speaker: Shohini Ghose (Wilfrid Laurier University)

544 (I) Equality and diversity in Physics: A UK perspective (flipped)

Physics is widely recognised as a subject which often does not recognise the diversity of the societies in which it is practised. There are differences between countries, but there are many parts of the world where female participation at all levels in Physics is 20% or below. In the UK specifically, there is also low participation by some groups either ethnic groups or lower socioeconomic groups. It is clear that for Physics to be a success and to build teams to solve the key challenges in Physics, we need the participants to fully represent the diversity of the society in which they are based.

I will present some of the activities of the Department of Physics at the University of York in the UK, in attempting to open up Physics to all. In particular, I will focus on actions intended to address gender imbalance and the recognised higher drop-out rate of women at all levels in Physics. At York, we hold Athena Swan Silver and Project Juno Champion status which are two schemes in the UK to recognise Physics departments in their equality activities. I will outline key aspects of our action plan to ensure a level playing field. These have been welcomed by all staff as they recognise issues such as work/life balance and part-time working which are of relevance to all. I will review aspects of recruiting and how avoiding unconscious bias is being put at the centre of our approach. I will review the data which shows the significance of this work and the impacts that it can achieve.

While there are many avenues to take in tackling challenges of inclusion, outreach can play a very strong role. I will discuss some aspects of our outreach programme. We engage with many different groups, at different levels and different ages. This starts with hands-on astronomy for schoolchildren at primary level and for local scouting groups such as cubs and brownies. Our outreach programme covers more advanced material for those in the final years of high school. For example, an online nuclear physics masterclass which has proven very popular and with audiences significantly more diverse than our own student cohort. I will also provide examples like the Physics outreach stand taken to the York Pride event. Finally, I will discuss a knowledge exchange programme with two historically disadvantaged universities in South Africa, supported by the UK Global Challenges Research Fund, which has seen many students from SA visit York for hands-on training and allowed the setting up of two detector development laboratories in South Africa.

Speaker: Dr David Jenkins (York University, UK)

545 (I) LGBT+ Climate in Physics (flipped)

In 2014 the Executive Officer of the American Physical Society (APS), Kate Kirby, created an Ad-Hoc Committee on LGBT Issues (C-LGBT) charged with reporting on the obstacles to inclusion of LGBT physicists, a term which for the purpose of this report refers to persons who self-identify as lesbian, gay, bisexual, transgender, queer, questioning, intersex, or asexual, as well as other sexual and gender minorities. The full charge was as follows: "The committee will advise the APS on the current status of LGBT issues in physics, provide recommendations for greater inclusion, and engage physicists in laying the foundation for a more inclusive physics community. More specifically, the committee will investigate LGBT representation in physics, assess the educational and professional climate in physics, recommend changes in policies and practices that impact LGBT physicists, and address other issues that affect inclusion." I will present the findings and recommendations of the C-LGBT final report, and discuss the future of APS efforts toward LGBT inclusion in physics with an intersectional lens.

Speaker: Dr Elena Long (University of New Hampshire)

12:16 Discussion, Q & A (live)

Discussion by the panelists, in which they respond to the other talks, and answer questions submitted by the audience.

R1-2 Labs II (DPE) / Laboratoires II (DEP)

Convener: Patricia Mitchler (Canadian Association of Physicists)

546 (I) Three advanced lab experiments on fluids and pattern formation

This talk will describe three new experiments recently developed for the advanced physics lab at the University of Toronto. Students work alone and have 18 class hours to complete a lab. [1] When a low viscosity fluid (in this case air) is pumped into a narrow gap between two plates filled with a more viscous fluid (here mineral oil), the resulting expanding bubble is unstable to the formation of fingers. Students measure the number and shape of the fingers, and compare this to theory. Strongly forced bubbles form fractal objects, like snowflakes, whose fractal dimension can be measured. [2] Solitons are localized nonlinear waves that keep their shape as they propagate. Using a long water tank and an automated soliton generating device, students create and collide solitons. They compare these waves to classic KdV solitons.[3] Granular materials (here bronze particles) form patterns when they are vibrated on an oscillating plate. Various very regular patterns are observed depending on the depth of the layer and the amplitude and frequency of the shaking. Students measure the wavelength of the pattern and the phase diagram of states observed. These are compared to theory and simulations.

Speaker: Stephen Morris (University of Toronto)

547 (G*) Dissipative coupling in a classical system

We experimentally demonstrate dissipative in a double pendulum system. Unlike the well-known spring coupled pendulum experiment, our experiment replaces the spring with the dissipative coupling device. Two pendulums are coupled by a device that employs Lenz's effect to dissipate energy through electromagnetic friction. To observe the influence of the dissipative coupling, we tune the natural frequency differences between two pendulums and observe the response of the system. This experiment contains both time and frequency domain results as well as additional relative phase analysis. Our work provides evidence of the dominant linear synchronization phenomenon. Synchronization arises from the dissipative coupling as it tends to re-establish the system’s degeneracy. While the coherent coupling (spring coupled pendulums) tends to break the system degeneracy. Our work also reveals the previously unstudied time-domain dynamics of two dissipative coupled pendulums. The study of the phase evolution of a dissipative coupling process could also deepen our understanding of synchronization. More importantly, this experiment is valuable for entry-level physics education. The dissipative coupling device is easy to manufacture, is budget-friendly, and the theoretical calculations are also suitable for the undergraduate level. Our experiment can serve as an excellent classical mechanics demonstration example.

Speaker: Chenyang Jerry Lu (University of Manitoba)

R1-3 Biophotonics I (DAMOPC/DPMB) / Biophotonique I (DPAMPC/DPMB)

Convener: Nisha Agarwal (University of Ontario Institute of Technology)

548 (I) Quantitative label-free vibrational spectroscopic imaging and analysis in medical physics

Label-free vibrational spectroscopic imaging based on inelastic (Raman) light scattering represents a rapidly emerging platform for biology and medicine. My research program in Medical Physics and Biomedical Engineering develops novel instrumentation and analysis methods based on Raman spectroscopy and Coherent Raman Scattering (SRS) imaging combined with other nonlinear optical imaging modalities such as Two-Photon Excitation Fluorescence (TPEF) and Second Harmonic Generation (SHG) imaging. This enables rapid chemical, structural and functional imaging with sub-cellular resolution, without the use of external chemical contrast agents. This talk will describe our recent work to advance new techniques that support the development of 1) quantitative optical imaging to measure the pathogen-specific single cell response, 2) high-resolution radiation dosimetry to assess exposure to ionizing radiation, and 3) optical biopsy to identify biomarkers of an aggressive variant of prostate cancer.

Speaker: Prof. Sangeeta Murugkar (Carleton University)

549 (U*) The Use of Silver Microparticles for Spectrum Emission Enhancement During Laser-Induced Breakdown Spectroscopy of Bacterial Specimens.

Laser-induced breakdown spectroscopy (LIBS) is a laser-based spectrochemical technique that allows a near-instantaneous measurement of the elemental composition of a target by making time-resolved spectroscopic analyses of laser-induced ablation plasmas. Utilizing nanosecond laser pulses and a broadband high-resolution Echelle spectrometer, high signal-to-noise optical emission spectra can be obtained from almost any desired target.

Recently it has been shown by others that ablation of a non-metallic target that has been coated with metallic (gold or silver) nanoparticles causes an increase in optical emission intensity due to the creation of a plasma with a higher temperature and higher electron density. This process is called “nanoparticle enhanced” LIBS or NELIBS. In our laboratory we have begun investigating whether cheaper and easier to acquire monodisperse metallic microparticles can be used to enhance the emission from bacterial cells when they are deposited upon a nitrocellulose paper filter medium.

This presentation will detail our efforts to build a small deposition chamber to reliably and reproducibly deposit a known mass of commercially obtained one micron silver microparticles. The silver microparticles must also be uniformly deposited over the surface of the 9 mm diameter filter medium (achieving a uniform surface mass density) to insure that the enhancement is consistent over the one millimeter diameter circular bacterial deposition area in the center of the filter.

A nominal surface coverage density of 0.026 μg/mm^2 of silver microparticles was achieved, resulting in a silver ablation mass of 110 pg per laser shot. Using this mass surface density, enhancement of the emission from the different elements present in the bacterial cells was observed and was found to not be consistent, varying from an enhancement factor of 1 up to 8. Efforts to exploit and further develop this phenomenon for detecting lower numbers of bacterial cells will be described.

Speaker: Haiqa Arain (University of Windsor)

R1-4 History of Physics II (DHP) / Histoire de la physique II (DHP)

Convener: Patrick Clancy (McMaster University)

550 (I) Hunting for Lost Nazi Uranium

1944 saw the height of the United States Manhattan Project efforts which was distributed between Los Alamos New Mexico, Oak Ridge Tennessee, and Hanford Washington. Since the Manhattan Project was spurred by the fear that Germany was building her own nuclear weapons, Allied anxiety continuously pondered the Nazi atomic progress. As Germany began to fall to the Allies, Gen. Groves commissioned the military and scientific intelligence mission code-named Alsos. It was to be at the forefront of the defeat so as to immediately assess the German advancement towards an atomic bomb.

Alsos uncovered what the Manhattan Project had feared, and had so rightly launched the American effort years earlier: the Germans had a two-year lead on the American nuclear program and being the birth place of nuclear fission, the Germans began with an incredible sprint of discovery. But then they found, just as the Americans were getting their feet wet, the German program miraculously had slowed to an amateur’s pace. In April of 1945 in the sleepy village of Haigerloch, Alsos found the culmination of the German nuclear program: a failed reactor experiment, named B-VIII. It was on the scale of Enrico Fermi’s successful Chicago Pile 1.

This incomplete nuclear reactor, built of 664 uranium cubes had come very close to criticality. What had happened? How did Germany miss the mark? The answer is straightforward: unlike the United States’ efforts, spearheaded by Groves’ singular defining military force, the German atomic program was not administered by a competent manager. Their adequate resources were distributed and not gathered, their superb intellect was competitive and not collaborative. The failure of their atomic program can be pinned to a critical mass of German confidence moderated by ego and arrogance. Had they had more humility and collaboration, history would have taken a different path. Instead, their reactor was scattered to history.

What happened to the German B-VIII reactor? The United States acquired it; and the question remains: what did they do with it?

Speaker: Prof. Timothy William Koeth (University of Maryland (US))

12:15 Discussion Period

R1-5 Theory II (DNP) / Théorie II (DPN)

Convener: Rituparna Kanungo (Saint Mary's University)

551 (I) A universal holographic wavefunction for light hadrons

I summarize recent work pointing towards the existence of a universal holographic light-front wavefunction for light mesons and nucleons. This holographic wavefunction, which describes simultaneously a bound state in light-front QCD and the propagation of string modes in a dilaton-modified 5-dimensional anti de Sitter spacetime, is a specific realization of the gauge-gravity duality. The modification of the holographic wavefunction by the spin structures specific to mesons and nucleons, leads to a remarkable simultaneous description of EM transition form factors of light mesons as well as the Dirac and Pauli form factors of nucleons.

Speaker: Prof. Ruben Sandapen (Acadia University)

CAP2021_Sandapen.pdf

CAP2021_Sandapen.pptx

552 (G*) Applications of ab initio nuclear theory to tests of fundamental symmetries

Ab initio approaches such as the no-core shell model with continuum (NCSMC) describe nuclei as systems of nucleons experiencing inter-nucleonic forces derived from the underlying Quantum Chromo-Dynamical (QCD) structure. This, along with the NCSMC's unified description of nuclear structure and reaction theory, provide a rigorous framework that can be applied to tests of fundamental symmetries of the standard model (SM) that involve nuclei. New global analysis of Fermi decays, and the corresponding $V_{ud}$ determination, reveal a statistical discrepancy with the well-established SM expectation for Cabibbo-Kobayashi-Maskawa (CKM) matrix unitarity. Theoretical confirmation of the discrepancy would point to beyond SM physics. Necessary for extracting $V_{ud}$ from experiment is calculation of corrections to Fermi transition matrix elements; computing the isospin symmetry breaking correction $\delta_C$ is the main effort of this work. By studying Fermi transitions in light-nuclei, such as the $^{10}\text{C} \rightarrow {}^{10}\text{B}$ beta transition, we may perform a precision calculation of $\delta_C$ within an ab initio framework. Further, there exists significant motivation from the nuclear physics community for understanding the structure of the aforementioned systems. In particular, $^{10}\text{C}$ is of great interest as little is known experimentally about its structure. We present nuclear structure results for the following systems (i) $^{10}\text{C} \rightarrow p + {}^{9}\text{B}$ (ii) $^{10}\text{B} \rightarrow (n + {}^{9}\text{B}) + (p + {}^{9}\text{Be}$) (iii) $^{10}\text{Be} \rightarrow n + {}^{9}\text{Be}$. A high-quality description of the first two of these systems is necessary to guarantee the accuracy of $\delta_C$, and the third system provides an additional check on the NCSMC. We present results for $^{10}\text{C}$ which indicate a good description of the $0^+$ ground-state for calculation of $\delta_C$. Importantly, we also present novel structure results for the $^{10}\text{B}$ system considered as two mass partitions, including the charge-exchange reaction. Lastly, we aim to present a preliminary result for the determination of $\delta_C$ in the NCSMC.

Speaker: Michael Gennari (TRIUMF)

553 (G*) Statistical studies of astrophysical reaction network calculations with correlated uncertainties of nuclear observables

The rapid neutron capture process ($r$-process) is a complex nucleosynthesis mechanism for heavy nuclei, which occurs under extreme astrophysical environments, such as binary neutron star mergers and core-collapse supernovae. It involves thousands of neutron-rich isotopes and the vast majority of them are not yet experimentally accessible. Therefore, the r-process abundance calculations have to rely on theoretical values of nuclear observables to determine various reaction rates. The choice of the nuclear physics models, as well as the uncertainty within the models themselves, can induce large uncertainties on the calculated abundance pattern. Mumpower et al. (2016, 2017) have opened up a way to perform a series of statistical studies on the r-process including uncertainty quantification, sensitivity analysis, and reverse engineering of the nuclear observables. In their work, a constant size of uncertainty on the baseline mass model was propagated by recalculating the nuclear reaction rates for each set of perturbed masses. This assumes no uncertainties on the reaction rate calculations, and in general, uncertainties on nuclear models are not available.

In this work, we develop a method to incorporate such uncertainties, especially in the presence of correlated observables, into various statistical inference tasks. Specifically, we estimate and explicitly model the uncertainties on the masses and $\beta$-decay half-lives, and their correlations in the rare-earth region ($A=150$-$180$), based on an ensemble of theoretical frameworks, including Skyrme-QRPA, relativistic QRPA, and pnFAM. Theoretical $\beta$-decay half-lives are calculated for a range of $Q_\beta$-values and their distributions are modelled with Gaussian processes. We then use these distributions to perform Monte Carlo uncertainty estimation for the r-process abundance pattern and variance-based global sensitivity analysis. Furthermore, we discuss emulation of the reaction network calculation code PRISM using artificial neural networks, which greatly reduces the computational cost. This is an essential tool for performing the reverse engineering of nuclear observables without constraining the form of the solutions. Applicability of this method for other reaction rates will also be discussed.

Speaker: Mr Yukiya Saito (The University of British Columbia / TRIUMF)

R1-6 Particle Theory (DTP) / Théorie des particules (DPT)

Convener: Yue Zhang (Carleton University)

554 Neutrino self-interactions and sterile neutrino dark matter

Sterile neutrinos with masses around a few keV have been postulated to be viable dark matter candidates. This is, however, mostly in tension with various astrophysical observations, the most stringent being the X-ray bounds. In this talk, I would like to present a testable sterile neutrino dark matter production mechanism in the early universe. The idea is to introduce secret self-interactions among the Standard Model neutrinos. Such interactions can enable the sterile neutrinos to be more efficiently produced in the early universe, thus alleviating the tensions. These new interactions are usually stronger than the weak interactions, and hence can serve as a well-motivated target for the upcoming experiments.

Speaker: Manibrata Sen

CAP_Talk_Sen.pdf

555 (G*) Exploring Direct Detection Suppressed Regions in a Simple 2-Scalar Mediator Model of Scalar Dark Matter

We explore regions of parameter space that give rise to suppressed direct detection cross sections in a simple model of scalar dark matter with a scalar portal that mixes with the standard model Higgs. We found that even this simple model allows considerable room in the parameter space that has not been excluded by direct detection limits.
While a number of effects leading to this result have been previously noted, our main new result explores interference effects between different contributions to DM annihilation when the DM mass is larger than the scalar portal mass. New annihilation channels open up and the parameters of the model need to compensate to give the correct DM relic abundance, resulting in smaller direct detection cross sections.
We find that even in a very simple model of DM there are still sizeable regions of parameter space that are not ruled out by experiment.

Speaker: Jérôme Claude (Carleton University)

556 (G*) NLO effects on light tetraquark mass estimates using QCD sum rules

Multiquark states have been of great interest among hadronic physicists, and despite the big breakthrough that came in 2003 with the discovery of the charmonium-like tetraquark candidate X(3872), their internal quark structure (e.g., molecular versus diquark clusters) are not well-understood yet. QCD sum-rule mass estimates for multiquark states can provide insights on possible internal quark structures. Previous research suggests that the next-to-leading order (NLO) corrections to QCD sum-rule mass determinations are quite different in heavy and light multiquark states.
The study of these multiquark systems can give us another approach to understand strong interactions at the elementary level and at different energy scales. The goal of this research is a detailed examination of the NLO corrections to mass estimates of the light scalar tetraquarks using QCD sum-rules.

Speaker: Barbara Cid Mora (University of Saskatchewan)

557 SU(2) lattice gauge theory on a quantum annealer

Lattice gauge theory is an indispensible tool for non-Abelian fields, such as those in quantum chromodynamics where lattice results have been of central importance for several decades. Recent studies suggest that quantum computers could extend the reach of lattice gauge theory in dramatic
ways, but the usefulness of quantum annealing hardware for lattice gauge theory has not yet been explored. In this work, we implement SU(2) pure gauge theory on a quantum annealer for lattices comprising a few plaquettes in a row with a periodic boundary condition. Numerical results are obtained from calculations on D-Wave Advantage hardware for eigenvalues, eigenvectors, vacuum expectation values, and time evolution. The success of this initial exploration indicates that the quantum annealer might become a useful hardware platform for some aspects of lattice gauge
theories.

Speaker: Emanuele Mendicelli (University of York (Toronto, Canada))

CAP_Emanuele_Mendicelli_15_minutes.pdf

558 Fixed target probes for the Higgs portal

High-luminosity fixed target experiments provide impressive sensitivity to new light weakly coupled degrees of freedom. In this talk, I will discuss the minimal case of a scalar singlet $S$ coupled to the Standard Model through the Higgs portal, that decays visibly to leptons for scalar masses below the dipion threshold. This UV-complete portal from the SM to a dark sector is of particular interest as one of the generic mediation channels for the interaction with dark matter. The existing dataset from the LSND experiment is found to impose the leading constraints within two mass windows between $m_S \sim$ 100 and 350 $\rm MeV$. In the process, we analyze a number of scalar production channels in the target, finding that proton bremsstrahlung provides the dominant channel at LSND beam energies.

Reference:
arXiv:2004.14515

Speaker: Mr Saeid Foroughi-Abari (University of Victoria)

CAP 2021 Higgs portal.pdf

12:00 Questions/Answers and Discussion Period

R1-7 Contributed Talks IV (DCMMP) / Conférences soumises IV (DPMCM)

Convener: Michel Gingras

559 Tuning the Electro-Optical Properties of Nanowire Networks

Conductive and transparent metallic nanowire networks are regarded as promising alternatives to Indium-Tin-Oxides (ITOs) in emerging flexible next-generation technologies due to its prominent optoelectronic properties and low-cost fabrication. The performance of such systems closely relies on many geometrical, physical, and intrinsic properties of the nanowire materials as well as the device-layout. Adequate comprehensive computational study is essential to make any device fabrication cost-effective. Here, we present a computational toolkit that exploits the electro-optical specifications of distinct device-layouts, namely standard random nanowire network and transparent mesh pattern structures. The target materials for transparent conducting electrodes of this study are aluminum, gold and silver nanowires. We have examined a variety of tunable parameters including network area fraction (AF), length to diameter aspect ratio (AR), and nanowires angular orientations under different device designs. Moreover, the optical extinction efficiency factors of each material are estimated by two approaches: Mie light scattering theory and finite element method (FEM) algorithm implemented in COMSOL® Multiphysics software. We studied various nanowire network structures and calculated their respective figures of merit (optical transmittance versus sheet resistance) from which insights on the design of next-generation transparent conductor devices can be inferred.

Speaker: Koorosh Esteki (University of Calgary)

11:48 Questions & answers

560 (U*) Simulation of Two Polymers Confined to a Box-Like Cavity: The Effect of Anisotropies in Polymer Length and Confinement Dimensions

The behaviour of confined polymeric systems has been the topic of much recent research. The information from these studies may help guide the development and optimization of nanofluidic devices and understand the segregation of DNA chromosomes in prokaryotic cells. Some recent experiments examined two DNA molecules confined to a box-like cavity with strong confinement in one dimension. The researchers looked at the effect of using an anisotropic cross-sectional box geometry and of having non-identical polymers. In this study, we use computer simulations to examine the effect of such anisotropies on the behaviour of the confined-polymer systems. We employ Metropolis Monte Carlo simulations where the polymers are modelled as bead spring chains. We calculate probability distributions for the centre-of-mass positions of either polymer and for the centre-of-mass displacement between the polymers. These distributions are used to examine the effect of anisotropies in polymer length for two polymers confined to a square box-like cavity and anisotropies in box dimensions for two identical polymers confined to a box-like cavity. The information obtained from this study can then be used to have a better understanding of the trends seen in the experiments.

Speaker: Desiree Rehel (N/A)

11:53 Questions & answers

561 (G*) Raman response modelling in multiband superconductors with competing order parameter symmetries

Recent experimental studies in the hole-doped iron pnictide BaFe${}_{2}$As${}_{2}$ observed features in its Raman response that are consistent with the existence of particle-particle excitons, also known as Bardasis–Schrieffer (BaSh) modes. The presence of such collective modes indicates the existence of a strong d-wave subleading channel in an otherwise s-wave superconductor. In light of such results, a spin-fluctuation based pairing mechanism seems the most promising and some studies argue that the ground-state symmetry could become a pure d-wave state in some cases. To facilitate the connection between experiments and theory of the pairing mechanism in these systems with symmetry competition, we formulate a self-consistent framework to calculate the Raman response in multiband 2D superconductors using any pairing interaction of electronic origin, which is applicable to models with any Fermi surface geometry. Our unified framework not only reproduces all the known collective modes, like BaSh modes and Leggett modes in the appropriate symmetry channels, but also allows one to study the Raman response of models with an arbitrary number of bands. We will present our results for two-band models and discuss the implications for the five-band system Ba${}_{1-x}$K${}_{x}$Fe${}_{2}$As${}_{2}$.

Speaker: Igor Benek-Lins (Concordia University)

11:58 Questions & answers

562 (G*) Magic-angle orientation selectivity in two-pulse EPR COSY (correlation spectroscopy) sequence: Distance measurements in biological systems

Two-pulse COSY (correlation spectroscopy) EPR (Electron Paramagnetic resonance) sequence, utilized for distance measurements in biological systems using nitroxide biradicals, is investigated both analytically and numerically. The analytical expressions derived here for any orientations of the two nitroxide dipoles with respect to the dipolar axis, oriented at an angle \theta with respect to the magnetic field with respect to the dipolar axis joining the two nitroxide dipoles at the angle, \theta, show that, in general, the coherence transfer from p=0 to the single quantum p=1 state is peaked at the orientation \theta being the magic-angle, {54.7}^\circle, and its supplementary angle, {125.3}^\circle, with a narrow width, implying that there is produced orientational selectivity, by the first \pi/2 pulse. This results in the signal being predominantly determined by those biradicals, whose dipolar axes are at, or near, the magic and its supplementary angle. This is entirely a novel finding, not published in the literature. Furthermore, the analytical treatment shows that the Fourier transforms of the two-pulse COSY signal exhibit peaks at \pm d\times \left(3cos^2\theta-1\right); here d=\frac{2}{3}D, with D being the dipolar-coupling constant.). In addition, there occurs also structural sensitivity of the signal, i.e., its dependence on the orientations of the two nitroxide dipoles during to free evolution over the two coherence states p=+1 and -1. The powder (polycrystalline) averages over the unit sphere, accumulated over 20 sets of Monte-Carlo orientations of the two nitroxide dipole moments reveal that the Pake doublets occur at \pm d. It is concluded that the two-pulse COSY experiment is a preferred technique for distance measurements as compared to other multi-pulse (four, five, six) sequences, as well as two-pulse DQ (double quantum) and five-pulse DQM (double quantum modulation) sequences, because its Pake doublet is the most intense of all the other multi-pulse sequences.

Speaker: Hamidreza Salahi (Concordia University)

12:03 Questions & answers

563 (G*) Triangular Pair-Density-Wave in Confined Superfluid 3He

The prototypical superfluid, Helium-4 ($^4$He), transitions to its superfluid state below ~2 K. In contrast, its isotopic counterpart Helium-3 ($^3$He) has a transition temperature of ~2 mK. This thousand-fold disparity is due to the nature of the superfluid transition; while $^4$He Bose condenses directly, the fermionic $^3$He atoms must first form composite bosons through Cooper pairing. The $p$-wave, spin-triplet pairing of the $^3$He atoms gives rise to many possible superfluid phases, though only two distinct phases are realized in the bulk.

Recent experimental and theoretical advances have suggested that a third phase emerges when superfluid $^3$He is confined to a slab --- a pair-density-wave (PDW) phase. Analogous to a supersolid, the PDW phase is characterized by the spontaneous breaking of translational symmetry that coexists with superfluid order. The precise spatial structure of this "superfluid crystal" has been the subject of ongoing debate: existing theories favor a unidirectional PDW, the stripe phase, while recent nuclear magnetic resonance (NMR) experiments seem to indicate a two-dimensional PDW with square or hexagonal symmetry. In this talk, I will outline a mechanism, based on Landau's theory of weak crystallization, which stabilizes a two-dimensional PDW with the hexagonal symmetry of a triangular lattice.

Speaker: Mr Pramodh Senarath Yapa (University of Alberta)

12:08 Questions & answers

564 (G*) Quantum dots as probes for topological materials

Topological insulators are an interesting class of materials which host distinct zero/low-energy states at their boundaries. These symmetry-protected states can, for example, arise as Majorana zero-modes in various superconducting systems and have potential applications in quantum error correction. However, experimental study and verification of such zero-modes remains a challenge. Considering a toy-system based on the Su-Schrieffer-Heeger (SSH) model coupled to one end with a semi-infinite conducting lead, we propose a measurement method for gapped topological states through a study of the decoherence dynamics of a quantum dot or qubit. Decoherence rates along the length of the SSH chain vary proportionally to the edge states and allow for both the identification and spatial characterisation of such states.

Speaker: Nicolas Delnour (University of Montreal)

12:13 Questions & answers

565 (G*) Observation of synchronization and Bloch sphere state trajectories in dissipatively coupled electrical oscillators

Synchronization describes an interesting dynamical process of coupled oscillators.
Particularly, it refers to oscillators oscillating at the same frequency despite their
natural frequency difference. Besides, for a coupled two-oscillator system, its
hybridized eigenmodes can be mapped onto the Bloch Sphere.

We experimentally studied the relationship between synchronization and
hybridized modes on the Bloch sphere through dissipatively coupled two electric
oscillators. The circuit consists of two parallel LC oscillators with identical
linewidth, connected by a coupling resistor. Utilizing adjustable components
enables great tunability of the system. The setup also allows us to perform
comprehensive spectral and time-domain analyses on the essential consequences
of dissipative coupling.

We observed anti-parity-time-symmetry preservation/breaking, exceptional points,
trajectories of eigenmodes on the surface of the Bloch sphere, and the
synchronization zone accompanied by characteristic phase difference between two
oscillating waveforms. As a result, we confirm that the exceptional points enclose
the synchronization zone and the equator states on the Bloch sphere are nothing
more than a later twin.

Speaker: Mun Kim (University of Manitoba)

12:18 Questions & answers

R1-8 Test Facility II (PPD) / Installations pour tests II (PPD)

Convener: Silvia Scorza (SNOLAB)

566 (G*) Super-Kamiokande PMT characterizations using artificial magnetic field and robotic laser-equipped arms

Super-Kamiokande (Super-K) is a neutrino detector located in Japan used to study neutrinos from different sources (atmospheric, solar, supernovae and accelerator). Its research program includes search for proton decay and measurement of neutrino oscillations among others. It contains ~11,000 20 inches photomultiplier tubes (PMTs) surrounding a massive tank filled with 50 ktonne of ultra-pure water. A detailed understanding of the PMTs, as well as their response to environmental effects, is necessary for a precise understanding of the detector and consequent reduction of systematic uncertainties.This is also a very important contribution towards the future Hyper-Kamiokande detector which will be instrumented of ~40,000 PMTs, helping realize the best design, monitoring and calibration methods needed to achieve maximum sensitivity of the experiment.

I will present the measured non-uniformity of the PMT used in Super-K as well as the effects of the magnetic field on the PMT parameters. Moreover, I will describe the recent facility upgrades (motion monitoring, magnetic field simulation) implemented to improve the accuracy and reproducibility of the measurements along with a better understanding of environmental variables that can lead to undesired systematic uncertainties.

Speaker: Vincent Gousy-Leblanc (University of Victoria)

CAP_talk_VincentGousyLeblanc.pdf

567 (G*) Measuring Single Event Upset Cross Sections and Other Radiation Effects in Readout Electronics for the ATLAS Inner Tracker Upgrade

The ATLAS detector at the Large Hadron Collider (LHC) at CERN is in the process of upgrading its silicon charged-particle tracker as part of the Inner Tracker (ITk) upgrade, in parallel with the LHC’s own High-Luminosity upgrade (HL-LHC). With ten times the radiation dose expected at the HL-LHC as compared to LHC, the silicon technology used in the ITk must demonstrate an excellent radiation hardness to be performant over its lifetime. ATLAS Binary Chips (ABCs) are one such aspect of the ITk’s silicon technology, responsible for digitizing analog signals at the detector’s front-end. While generally resistant to total ionizing dose effects, ASICs like ABCs are susceptible to single event upsets (SEUs) whereby instances of radiation can flip a binary state, resulting in wrong outputs or even resets. We have measured the readout performance of ABCStars, the production version of ABCs, at testbeams using protons at TRIUMF and heavy ions at Louvain. The ASICs were irradiated up to doses of 4 Mrad. The total number of SEUs normalized to the total integrated fluence, the SEU cross section, was measured and found to be reduced when compared to earlier prototype ABCs, a result of protections implemented in the chip’s logic. Additionally, the measurements were used to quantify the increasing and then decreasing behaviour of the ASICs' digital currents with accumulated ionizing dose. This confirms the validity of pre-irradiating ABCStars to guard against high current loads during runtime. Overall, these studies indicate excellent readiness of the ABCs for use in the ITk upgrade.

Speaker: Matthew Basso (University of Toronto (CA))

210610_Basso_2021-CAP-Congress-PPD_ATLAS-ABCStar-SEU.pdf

568 (G*) INJECTION TEST: BUILDING A DATA INJECTOR FOR THE ATLAS LIQUID ARGON SIGNAL PROCESSOR

A test-bench is created that injects digital pulses that emulate ATLAS Liquid Argon (LAr) Front End Board electronic signal pulses in order to test prototypes. The prototypes are for new electronics for an upgrade to the CERN Large Hadron Collider that increases the rate of proton-proton collisions by an order of magnitude. This High-Luminosity Large Hadron Collider requires a completely new Trigger and Data Acquisition system to deal with information from detectors.

One system that is being developed is the Liquid Argon Signal Processor (LASP) which has an architecture based on Field Programmable Gate Arrays (FPGA). Validation of individual modules of the LASP is of key importance in the development cycle. Additionally, verification of module behaviour with simulated ATLAS pulses will allow the full system to be tested with realistic conditions before data taking.

The injector project is implemented on an Intel Stratix 10 FPGA, that uses optimised GbE Ethernet technologies to communicate with a workstation in order to transfer Monte Carlo simulation pulses to the FPGA. The pulses are then buffered and injected to the LASP, mimicking the operation of the Front End Boards (FEB2s). The user is in complete control of the data pulses injected which is a vital property that enables the test of LASP behaviour for different cases and possible failure modes. A complete overview of the injector design, its performance, as well as its benefit to the LAr-LASP is shown in this talk.

Speaker: Maheyer Jamshed Shroff (University of Victoria (CA))

cap-injector.pdf

569 (G*) The Light-only Liquid Xenon experiment - Status and Updates

The Light-only Liquid Xenon (LoLX) project aims to study the properties of light emission and transport in liquid xenon (LXe) using silicon photomultipliers (SiPMs). By investigating scintillation and Chernekov emission in LXe, LoLX will develop Cherenkov-scintillation separation with SiPMs as a background discrimination technique for low-background LXe experiments, e.g. searches for neutrinoless double beta decay. The first phase of LoLX consists of a baseball-sized octagonal cylinder that houses 24 Hamamatsu VUV4 SiPMs, a total of 96 readout channels. Covering 92 of these channels are 225 nm high-pass filters that block out the Xe scintillation light. These filters allow the long-wavelength components of the Cherenkov and scintillation light to go through, providing an independent measurement of their light yields. The initial goal of LoLX is to measure these light yields from $^{90}$Sr $\beta$-decays (Cherenkov + scintillation emission) and $^{210}$Po $\alpha$-decays (scintillation only) in LXe. These measurements will be used to validate optical transport simulations in GEANT4, and verify measurements of vacuum UV reflectivities being performed at TRIUMF. This talk will give an overview of the LoLX project and provide an update on its current status and latest results.

Speaker: Soud Al Kharusi (McGill University)

AlKharusi_LoLX_CAP2021.pdf

R1-9 Plasma processes for material synthesis II (DPP) / Procédés de plasmas pour la synthèse de matériaux II (DPP)

Convener: Lenaic Couedel (University of Saskatchewan)

570 (G*) Influence of pulsed gas injections on the stability of Townsend dielectric barrier discharges in nitrogen at atmospheric pressure

Nanocomposite (NC) thin-films are widely studied due to the multifunctional properties they can develop (optical, electrical, mechanical). A lot of methods are under development with a real attraction for processes at atmospheric pressure, such as dielectric barrier discharge (DBD).
Recently, a new process of nanoparticles injection in plasmas has been developed [1]. This method consists in synthesizing the nanoparticles prior to their injection in the plasma in a low frequency pulsed injection regime. However, the impacts of the gas pulsed injection on the DBD physics are still opening questions.
This work investigates the effects of pulsed gas injections on the physics driving Townsend dielectric barrier discharges in high-purity nitrogen at atmospheric pressure in laminar gas flows (residence time ~50 ms). For single-pulse injections of N2 with gas opening times lower than the gas residence time, current-voltage characteristics reveal that the discharge remains homogeneous with a single current peak per half-cycle of the applied voltage. However, a transition from homogeneous to filamentary discharge combined with a decrease of the discharge power at fixed amplitude of the applied voltage is observed for higher gas opening times due to an accumulative effect. This is further confirmed by multiple pulsed injections with repetition frequencies between 0.1 and 10 Hz. In such multi-pulse conditions, time-resolved optical emission spectroscopy measurements reveal longer time scale variations of the N2(A) and O(3P) populations compared to the expected residence time in a laminar gas flow. This suggests that recirculation of impurities due to the pulsed injections play an important role in the destabilization of Townsend discharges. The system’s conductance, calculated from pressure rise measurements over a wide range of operating conditions, confirms the instantaneous transition from laminar to turbulent gas flow due to the pulsed gas injections.

1. Kahn, M., Champouret, Y., Clergereaux, R., Vahlas, C. & Mingotaud, A.-F. Process for the preparation of nanoparticles. (2016).

Speaker: Ms Laura Cacot (University of montreal)

571 (I) Inductively-coupled RF plasma: a versatile tool to synthesize functional materials and advanced ceramics

Inductively-coupled RF thermal plasma have been known and used in the last three decades for the spheroidization of powders, for the synthesis of single cation ceramics or metallic nanoparticles as well as for the deposition of coatings. This electrodeless plasma produces pure materials at a high throughput. Over the years, the chemical precursors used have evolved from single gas or solid powder injected in inert, reducing or oxidizing gases, to mixtures of reactive gases and powders, to suspensions and solutions axially atomized within the plasma jet. The complexity of the plasma-precursors interactions is increasing and, if the chemically reactive environment of these plasmas have long been considered difficult to probe, the application of optical emission spectroscopy (OES) on molecular bands has opened new possibilities to follow diatomic species, in complement to atomic species. As such, OES should help in understanding and optimizing the synthesis of functional materials and advanced ceramics in RF thermal plasmas.

In this presentation, recent developments undertaken at the Université de Sherbrooke for the RF thermal plasma synthesis of active cathode and anode materials for lithium batteries will be presented. In particular, solid precursors were used to synthesize Li2S and silicon nanowires, whereas solutions precursors were chosen for the synthesis of LiFePO4.

In another field of application, tantalum ethoxide was put into sol, mixed with a solution of Ba and Mg salts, and injected in an oxidative plasma jet to form a complex, high melting point Ba(Mg2/3Ta1/3)O3 perovskite with vertical grains to be used as thermal barrier coatings. The synthesis of a simpler BaTiO3 perovskite was investigated using OES.

As a final example, the synthesis of graphene nanoflakes and other carbonaceous structures will be discussed in relation to operating parameters such as the C : H ratio and pressure, as well as to OES measurements.

Speaker: Prof. Jocelyn Veilleux (Université de Sherbrooke)

12:25 Open discussion period

12:30 15 Minute Break

R2-1 Group discussion: Do we still need to work on gender equity in Physics? / Discussion: doit-on toujours travailler à l'équité des genres en physique?

Convener: Chitra Rangan (University of Windsor)

12:45 Welcome and Networking

This session will be held via the Gather.Town interface. Please circulate, introduce yourself, and exchange LinkedIn information. Your goal is to meet 5 people you haven't met before.

13:00 Group discussion: Do we still need to work on gender equity in Physics?

Please join a table and discuss the need to work on gender equity in Physics. Do our efforts matter? Where should we put our efforts and why? After about 20 min, we will debrief as a group.

R2-10 History of Physics III (DHP) / Histoire de la physique III (DHP)

Convener: Patrick Clancy (McMaster University)

572 Early Alpha Scattering Results by Ernest Rutherford

Most physicists know that Rutherford proposed the presence of an atomic nucleus in 1911 when he was in Manchester based on the result of an alpha scattering experiment performed by Geiger and Marsden. However, the first results on alpha scattering were obtained much earlier, during the time Rutherford was at McGill. In a paper Rutherford published in 1906 entitled “Retardation of the alpha particle from radium in passing through matter” [1] a small section is titled “Scattering of the alpha rays”. In this experiment he observed that in passing through a foil of mica the alpha particles were scattered by a small angle. From that observation he estimated that the alpha particles were subject to an average transverse electric field of about 100 million volts per cm. He concluded by “Such a result brings out clearly the fact that the atoms of matter must be the seat of very intense electrical forces--a deduction in harmony with the electronic theory of matter." These were clearly the precursor to the experiments that led to the discovery of the atomic nucleus.

[1] Rutherford, E. (1906), Philosophical Magazine Series 6,12:68,134- 146

Speaker: Jean Barrette (McGill University)

573 Some Observations on Ethical Problems and Conundra for Scientists

In our time, when problems of population growth, consumption demands and climate change are matters of daily concern, I want to mention some of the ethical problems that have confronted scientists. The fact that any discovery may turn out to have both wonderful and disastrous consequences has been discussed many times before.
The discovery of nuclear fission brought us both the atomic bomb and nuclear power generation. One may lead to the end of human life on earth and the other may be the only way that we can avoid catastrophic global climate change.
Among the German Nobel laureates who worked on poison gas in WW1 were Fritz Haber, Walther Nernst, Otto Hahn, James Franck and Richard Wilstatter. Americans who worked on poison gas included James B. Conant, later president of Harvard and supervisor of the Manhattan Project.
There is no science that cannot be misused. The fertilizer that helps to feed millions and is made using Haber's Nobel-prize-winning process, is the main ingredient in home-made bombs, along with diesel fuel.
Often totally benign discoveries lead to consequences that society has been unprepared or unwilling to deal with. These include DDT and Penicillin, which led to wonderful reductions in infant and adult mortality, but caused population growth that made demands on food resources that were often unmet.
More mundane problems include decisions that we have to make about attending conferences in countries with serious human-rights abuses or governments whose policies and actions we may find abhorrent. The work of editors of scientific journals involves daily questions of ethics.

Speaker: Michael Steinitz (St. Francis Xavier University)

574 La contribution scientifique extraordinaire de Déodat de Dolomieu (1750-1801) au progrès de la volcanologie du Val di Noto

En 1781, le géologue français Déodat de Dolomieu visite le sud-est de la Sicile afin d’étudier les volcans éteints de la région du Val di Noto. Les résultats de ses recherches furent présentés dans un mémoire, publié en 1784, paru dans les Observations sur la physique, sur l'histoire naturelle et sur les arts par François Rozier (1734-1793). Dans ce mémoire, Dolomieu expose notamment, en premier, une théorie pour expliquer la singulière alternance de roches volcaniques et sédimentaires particulièrement frappante dans les escarpements près de Vizzini. Par ailleurs, Dolomieu témoigne d’un important effondrement de terrain, près de Sortino, associé probablement à une séquence sismique, survenue de mars à juin 1780, qui a affecté la côte ionienne du nord-est de la Sicile. Enfin, le mémoire se termine avec une description détaillée de l’activité paravolcanique observée au lac Palius, près de Mineo. Dans cette présentation, la contribution fondamentale de Dolomieu au développement de la volcanologie moderne ainsi que de la sismologie historique sera présentée.

Speaker: Dr Francesco Barletta (Centre matapédien d'études collégiales)

R2-2 Engaging students (DPE) / Implication d'étudiants(es) (DEP)

Convener: Patricia Mitchler (Canadian Association of Physicists)

575 (U*) Student preferences for pedagogic techniques

This is a report on a project to interview the student body of the Concordia University Physics Department concerning teacher-students interaction. The goal of this research is to establish an easily implemented guideline of teaching methods for a professor to use in the classroom. Students were asked to complete a questionnaire that included a request to describe the teaching style of their favourite physics professors. They were asked to describe what makes them excellent to the student. A variety of known and successful pedagogic techniques were also presented to ascertain their appeal to students. Follow-up interviews were conducted in order to fully develop the given answers.

Speaker: Ms Rose Delarosbil (Concordia University)

576 (U*) Student Response to the Integration of Online Education in High School Physics Classrooms

In response to the COVID-19 pandemic and the physical distancing requirements, high school classrooms in Quebec had to switch to a half in-person and a half-online attendance. With very few studies examining this education model at the high school level, this study aims to investigate the teacher and student response, as well as observe its impact on student engagement within the physics classroom. Ten students in the same grade 11 physics classroom participated in this study. Two surveys, completed respectively at the beginning and end of the semester, were used to evaluate the progression of the student’s physics interest, study habits, preferred learning methods and engagement in online and in-person settings over the course of the semester. Additionally, the instructor and five students volunteered to be interviewed. These interviews provided a deeper understanding of the survey data, as well as insight on the student’s emotional response to their new classroom setting. Results indicated that the reasons for taking the course and the overall perception of the course was independent of the student’s main learning type - be it visual, auditory, or kinetic. Moreover, while the majority preferred attending classes in-person rather than online, a significant portion mentioned advantages of the half/half model. Regardless of the classroom setting, students most often stressed the importance of going slower while introducing new material, rather than repeatedly review it later on. Technical difficulties, lack of live social interactions and the increased workload were the main reasons for the lower motivation to attend school online. However, most students enjoyed the increased efficiency, schedule flexibility, comfort and the ability to simultaneously cooperate with peers during teacher-led lectures when attending classes online. These findings are linked to theories of academic motivation, and implications for implementation of the model are discussed.

Speaker: Ms Samantha Clark

577 Reaching out while remaining isolated: how Lakehead Orillia increased its science outreach during the pandemic.

Changes brought about by the COVID-19 pandemic have challenged educators at all levels. While the University experience has not been ideal, our classes benefited from platforms like Zoom already being in place and virtual labs already having been available to us. Elementary and secondary school students have had to overcome much more uncertainty and more severe obstacles. The need for outreach opportunities that extend the science classroom experience has never been greater, but science outreach has also never been so difficult. Classes split between in-person and online learners, questions about the safety of students sharing equipment and restrictions to classroom access have all demanded that we change the way we carry out hands-on science outreach. In this presentation I will discuss the ways our small outreach site, Let’s Talk Science - Lakehead Orillia, managed to grow in spite of the difficulties presented by the COVID-19 pandemic. I will focus on the formation of partnerships that enabled equipment to get to individual students (both those learning from home and those in classrooms) and strategies we employed to connect more than 120 volunteers with thousands of students through more than 130 virtual classroom visits over the last year.

Speaker: Christopher Murray (Lakehead University)

R2-3 Biophotonics II (DAMOPC/DPMB) / Biophotonique II (DPAMPC/DPMB)

Convener: Ozzy Mermut (York University)

578 (I) In-vivo, non-contact, cellular resolution imaging of the srtucture and function of the human eye

Over the past 25 years, optical coherence tomography (OCT) technology has been used for clinical diagnostics of potentially blinding ocular (retinal and corneal) diseases because it offers a non-invasive approach, fast image acquisition rates and multi-functionality. However, clinical OCT systems lack the necessary resolution and imaging speed for in-vivo imaging of the cellular and sub-cellular structure of ocular tissues, as well as probing fast, light-induced functional changes in the retina.

This presentation will discuss a relatively novel line-scan OCT (LS-OCT) technology that combines ultra-broadband lasers with ultrahigh speed cameras to allow for in-vivo, non-contact imaging of individual cells in the human cornea and limbus. The same technology is able to map blood vasculature, measure ocular flow and potentially measure light-induced physiological changes in the retina. The LS-OCT technology has numerous clinical applications from early diagnostics of potentially blinding corneal and retinal diseases, including neurodegenerative conditions such as Alzheimer’s, Diabetes, etc, to aiding and monitoring the effectiveness of different therapeutic approaches (drug therapies, nano-caged drugs, ocular surgeries, stem cell transplantation, etc.)

Speaker: Prof. Kostadinka Bizheva (University of Waterloo)

579 Novel design of instruments to image the retina in a wide field of view

Wide field imaging of the retina at the rear of the eye is recommended yearly for those with diabetes to screen for sight threatening changes. We and others have shown that amyloid protein deposits in the retina appear early in Alzheimer’s disease (AD) and predict the severity of amyloid in the brain.
We wish to optimize a scanning laser instrument to image the retina for screening both diabetic complications, and amyloid protein deposits as a biomarker of early AD. We aim to image between 100 and 200 degrees of the retina, with sufficient resolution to detect small, sparse features, either amyloid deposits in AD or changes in blood vessels and small bleeds due to diabetes. Improved optical resolution could be achieved with the use of adaptive optics but this would increase complexity and cost in an instrument, intended for low cost screening in varied settings.
An analysis of individual eye models for over 1200 normal individuals, for whom optical aberrations had previously been measured as a function of age, showed that, as previously reported, these imperfections increase with age. But for each age group, an optimum pupil size could be found which gave the best image quality, defined by resolution. This optimum pupil decreased by on average 30% from the youngest to oldest age group with a 12% loss of resolution, but there was high variability across individuals.
A second approach which predicted the optimum pupil size for each normal individual from a single metric of their ocular image quality (root mean square (RMS) wavefront error), produced accurate estimates of the optimum pupil sizes (on average within 2% of an individual’s optimum). The required wavefront measurement would be a relatively low-cost change to the instrument.
Those with diabetes are known to have larger optical imperfections than age-matched normal eyes. This means that, for optimum image quality, they will need to be imaged at smaller pupil sizes, similar to those of older adults. A separate curve of optimum pupil size versus RMS wavefront error may need to be established. Extensions of this research also consider the impact of off-axis optical quality, imaging wavelength and the use of polarized light in imaging. The improved quality in the resulting retinal images will be important to early diagnosis of the retinal effects of both Alzheimer’s disease and diabetes.

Speaker: Melanie CW Campbell (Physics and Astronomy, School of Optometry and Vision Science and Systems Design Engineering University of Waterloo)

R2-4 Advances in Nuclear and Particle Theory (DTP/PPD/DNP) / Avancées en physique nucléaire et physique des particules (DPT/PPD/DPN)

Convener: Charles Gale (McGill University)

580 (I) From alpha clustering to homogeneous matter

Over the last few decades, the study of nuclei and neutron-rich matter from first principles has entered a new era. This has partly been driven by the development of novel interactions between two or three nucleons. In an attempt to produce a systematic expansion, several groups have produced Effective Field Theory (EFT) interactions, whether of finite range (chiral EFT) or zero range (pionless EFT). Pionless EFT has been quite successful in studies of cold-atomic Fermi gases. In this talk, I will present recent Quantum Monte Carlo calculations of 8-particle systems and discuss their impact on 8Be and the physics of alpha clustering. I will also discuss recent work on trying to connect ab initio theory with simpler qualitative pictures. Specifically, I will address the first ever systematic non-perturbative calculations of the single-particle excitation spectrum and of the static response (both for strongly interacting neutron matter). In addition to impacting light and neutron-rich nuclei, this work and this talk also touch upon the physics of ultracold gases and of neutron stars.

Speaker: Alexandros Gezerlis

581 (G*) Superfluid neutrons: from particles to matter

Superfluid neutron matter is a key ingredient in the composition of neutron stars. The physics of the inner crust is largely dependent on that of its $S$-wave neutron superfluid which has been connected to pulsar glitches and modifications on the neutron star cooling. An accurate description of these effects calls for a model-independent treatment of neutron superfluidity. Ab initio techniques developed for finite systems can be guided to extrapolate to the thermodynamic limit and attain this model-independent extraction of various quantities of infinite superfluid neutron matter. To develop a well-informed extrapolation prescription, we calculated the neutron $^1S_0$ pairing gap using the model-independent odd-even staggering in the context of the particle-conserving, projected Bardeen-Cooper-Schrieffer theory under twisted boundary conditions. While the practice of twisted boundary conditions is standard in solid state physics, and has been used repeatedly in the past to reduce finite-size effects, this is the first time it is employed in the context of pairing. We find that a twist-averaging substantially reduces the finite-size effects, bringing systems with $N>50$ within a $2\%$ error margin from the infinite system. This can significantly reduce extrapolation-related errors in the extraction of superfluid neutron matter quantities.

Speaker: Georgios Palkanoglou (University of Guelph)

582 Characteristics of early time gluon fields in relativistic heavy ion collisions

We present some analytic results that describe the gluon field, or glasma, that exists at very early times after a collision of relativistic heavy ions at proper time $\tau=0$. We use a Colour Glass Condensate approach, and perform an expansion in $\tau$. We show that the expansion to order $\tau^6$ can be trusted to about $\tau=0.05$ fm/c. We calculate the transverse and longitudinal pressures and show that for $\tau < 0.05$ fm/c they move towards their equilibrium values of one third of the energy density. We study the spatial eccentricity of the plasma, and the Fourier coefficients of the azimuthal momentum distribution. Our results for the Fourier coefficients are larger than  expected, which contradicts the usual assumption that anisotropy is mostly generated during the hydrodynamic evolution of the plasma. We  find a significant correlation between the elliptic flow coefficient and the eccentricity, which indicates that the spatial inhomogeneity introduced by the initial geometry is effectively transmitted to the azimuthal distribution of the gluon momentum field, even at very early times. This result is interesting because correlations of this kind are  characteristic of the onset of hydrodynamic behaviour. We also calculate the angular momentum of the glasma and obtain results that are many orders of magnitude smaller than the initial angular momentum of two ions colliding with non-zero impact parameter. This indicates that most of the angular momentum carried by the valence quarks is not transmitted to the glasma. The result is significant because it contradicts the picture of a rapidly rotating initial glasma state,  but agrees with the current lack of experimental evidence for a global polarization effect in the hyperons and vector mesons produced in heavy ion collisions.

Speaker: Margaret Carrington (Brandon University)

583 Constraints on Axions from GW170817

As you know, first gravitational wave event GW150914(binary black hole) has been oberved by LIGO on Sep. 14, 2015. And most importantly, first binary neutron star coalescence event GW170817 has been observed with a signal noise ratio upto 33, which alows us to make constraints on axion field! Here, we first time use axion charged binary neutron star waveform model to give a constaint on axion field.

Speaker: Zhenwei Lyu (University of Guelph)

584 (G*) Using Underground Nuclear Accelerators in the Quest for Dark Matter

The existence of dark matter is ubiquitous in cosmological data, yet numerous particle detectors have been thoroughly looking for it without any success. For strongly interacting dark matter, the bounds from these experiments are actually irrelevant; as dark matter enters the atmosphere, it scatters and slows down, such that it has a much lower velocity than the detector threshold when it reaches underground laboratories. In this case, however, it would accumulate within the Earth and reach a density much greater than that of the dark matter halo. Here, I will describe a scheme for adapting present-day underground nuclear physics experiments to detect dark matter within this context. In particular, I will show that accumulated dark matter can be up-scattered to resolvable energies using underground nuclear accelerators, such as LUNA in Gran Sasso, and captured in nearby located low-background detectors.

Speaker: Marianne Moore (University of British Columbia)

585 (G*) Diagrammatic Renormalization for QCD Sum-Rules

QCD sum-rule calculations contain loop-integration divergences associated with composite operators in correlation functions that must be renormalized to obtain physical predictions.  The standard approach to renormalization through operator mixing can present technical challenges in situations where the basis of operators becomes large (e.g., for multi-quark operators). The BPH renormalization method provides an alternative to the standard method of operator mixing and Lagrangian counter-term renormalization. The BPH method consists of dividing Feynman diagrams into subdiagrams and subtracting the divergent part of each subdiagram. In this talk, I will present the BPH diagrammatic renormalization method and show an example of its application to the correlation function of gluon and mesonic composite operators.

Speaker: Thamirys de Oliveira (University of Saskatchewan)

13:05 Questions/Answers and Discussion Period

R2-5 Theory III (DNP) / Théorie III (DPN)

Convener: Dr Johnson Liang (McMaster Univsersity)

586 (G*) Characterization and Calibration of the ALPHA-g Barrel Veto Detector

Since trapping the first cold antihydrogen atoms over 10 years ago, the ALPHA collaboration has established itself at the leading edge of antimatter science. Through a series of experiments located at the Antiproton Decelerator at CERN, the group has carried out a number of novel precision measurements, primarily on the spectral transitions of antihydrogen. ALPHA-g is the latest addition to the ALPHA experiment, a new apparatus which aims to measure the gravitational acceleration of antihydrogen at the 1% level.

After trapping and cooling a collection of antihydrogen atoms using established methods, ALPHA-g will perform a controlled and precise relaxation of some of the confining magnetic fields. The antihydrogen atoms will free-fall until they reach the walls of the trap, where they will annihilate. Reconstructing these annihilation vertices and times will allow ALPHA-g to determine the rate of gravitational acceleration.

ALPHA-g uses two main detector systems to observe these annihilations. A time projection chamber (TPC) allows for tracking of the annihilation products. A time-of-flight detector surrounding the TPC, called the Barrel Veto (BV), allows for much more precise timing measurements. The BV is composed of 64 bars of plastic scintillator which are instrumented with silicon photomultipliers. As well as providing timing and position data to complement the TPC, measuring time-of-flight will allow ALPHA-g to distinguish interactions occurring within the trap volume (annihilation events) from particles originating outside the experiment (cosmic rays).

Using a vertical slice set up at TRIUMF, I was able to characterize the cosmic ray background in the BV. Monte Carlo simulations show that a time resolution on the order of 100 picoseconds is required in order to reject cosmic ray background. I present the readout electronics for the BV, with special attention given to the calibration techniques used, and report on the progress to date on characterizing the time resolution of the detector.

Speaker: Gareth William Smith

587 Is New Physics Needed to Explain the ATOMKI Anomaly?

Do we really need a hypothetical gauge boson, "X17", to explain the famous ATOMKI measurements? Or can there be some interplay between the theoretical and experimental effects? We show that the bump in the $^8Be(18.15)\rightarrow ^8Be +e^++e^-$ decay data can be reproduced within the Standard Model by adding the full set of second-order corrections and the interference terms to the Born-level decay amplitudes, and demonstrate how experimental selection and acceptance bias exacerbate the apparent difference between the experimental data and the Born-level prediction.

Speaker: Prof. Aleksandrs Aleksejevs (Memorial University of Newfoundland)

Aleksejevs-CAP2021-RED.pdf

588 (U*) Ab initio calculations of electric dipole moments of light nuclei

In any finite system, the presence of a non-zero permanent electric dipole moment (EDM) would require both parity (P) and time-reversal (T) violation. The standard model predicts a very small CP violation and consequently any observation of the EDM would imply physics beyond the standard model. Thus, EDMs have long been proposed as a way to test these fundamental symmetries. Experimental studies have placed upper bounds on neutron, nuclear and atomic EDMs, while theoretical studies have calculated their magnitudes using a variety of methods. In particular, it has been found that nuclear structure in certain nuclei can enhance the EDM. Here, we use the ${\textit{ab initio}}$ no-core shell model (NCSM) framework to theoretically investigate the magnitude of the nuclear EDM. We calculate EDMs of several light nuclei using chiral two- and three-body interactions and a PT-violating Hamiltonian based on a one-meson-exchange model. We present a benchmark calculation for $^3$He, as well as results for the more complex nuclei $^{6,7}$Li, $^9$Be, $^{10,11}$B, $^{13}$C, $^{14,15}$N, and $^{19}$F. Our results suggest that different nuclei can be used to probe different terms of the PT violating interaction. These calculations allow us to suggest which nuclei may be good candidates in the search for a measurable permanent dipole moment.

Speaker: Paul Froese (TRIUMF)

589 Ab initio calculations of heavy nuclei

An ab initio nuclear many-body calculation needs the nucleon-nucleon (NN) and three-nucleon (3N) matrix elements as an input. The NN matrix elements can be prepared in a sufficiently large space, while the 3N matrix elements are significantly limited. Due to the limitation, it is challenging to obtain reliable results for the system heavier than $A \sim 100$. Since we usually do not use all possible 3N matrix elements in the calculations, it is possible to reduce the required RAM by computing only the matrix elements needed. In this talk, I will present a recently proposed storage method for the 3N matrix elements. This enables us to generate the 3N matrix elements in a large space well beyond the previous limit. Also, I will demonstrate some converged calculation results of the heavy nuclei.

Speaker: Takayuki Miyagi (TRIUMF)

R2-6 Contributed Talks V (DCMMP) / Conférences soumises V (DPMCM)

Convener: Michel Gingras

590 Fundamental study of plasma-graphene interactions in Argon/B2H6 plasma

Raman spectroscopy is an efficient method to characterize the graphene structure. The technique gives distinctive features for pristine, damaged and even doped graphene. Nonetheless, especially when graphene is grown on a polycrystalline substrate, strong discrepancies may appear on the macroscopic scale. Moreover, in the case of plasma irradiation of graphene, it is essential to understand the impact of the small heterogeneities in pristine graphene (local defects, grain boundaries, etc.) on the resulting graphene structure after treatment [1]. Hyperspectral Raman Imaging (RIMA for Raman Imaging) is a powerful method enabling the capture of qualitative as well as quantitative data on a macroscopic scale [2]. Grain Boundaries (GBs) reveal themselves being more resistant to plasma treatment than pristine graphene domains. After careful consideration of Raman parameters, it appears clearly that preferential self-healing of GBs and its surrounding is taking place, a phenomenon observed in 3D materials, yet to be observed in graphene. This mechanism is governed by carbon adatoms generated from impacts of low-energy argon ions with graphene film. Under constant irradiation from exited species (ions, metastable, VUV photons), carbon adatoms can easily migrate on graphene surface and, in particular, alongside GBs. Hence, defects created at GBs or present nearby might be healed by the adatoms influx [3]. Furthermore, another plasma conditions shown that energy fluence from Argon metastable deexcitation can be linked to an enhanced defect migration and self-healing at GBs [4]. Finally, the previous study in Argon plasma enable the determination of ideal operating conditions for Argon plasma with B2H6 trace. The exposition of graphene to such plasma reveals boron in-plane substitution combined with low-level hydrogenation and defect generation [5].

Speaker: Dr Pierre Vinchon (Université de Montréal)

12:48 Questions & answers

591 (G*) Semi-metal insulator phase transitions in graphene - the role of anisotropy

Graphene is an interesting system for condensed matter physicists because of many potential technological applications. It is interesting to theorists as an abelian strongly coupled system that has some of the interesting properties of QCD.

We are particularly interested in studying the effects of anisotropic strain of the graphene
lattice on the critical coupling, which determines the transition point for graphene
from a conductor to an insulator. We use a low energy effective theory and a Schwinger-Dyson approach. The full set of coupled equations is numerically very difficult to solve, and so previous calculations have made many simplifying assumptions in order to make the procedure tractable. These simplifications have led to disagreement about the effect anisotropy has on the critical coupling constant. We have studied the effect of some common approximations including polarization tensor approximations and vertex ansaetze. In this talk we discuss the motivation for several of these approximations, and show that in some cases their effect on the critical coupling is significant. We discuss more accurate ways to solve the non-perturbative low energy effective theory, and its ability to predict the critical coupling of the phase transition.

Speaker: Brett Meggison (University of Manitoba)

12:53 Questions & answers

592 (G*) N-heterocyclic carbene adsorption and self-assembly on Au(111): Fine-tuning the binding mode

Organic molecules capable of forming strongly bound self-assembled monolayers (SAMs) offer a promising route to surface modification and functionalization. Technological advances including the protection and stabilization of nanoparticles and the development of lab-on-chip sensors have been largely realized by the adsorption of alkanethiols. N-heterocyclic carbenes (NHCs) were recently introduced as alternative anchors in the preparation of SAMs on metal surfaces and may be superior to thiol-based systems. NHCs have important advantages compared to thiol-based systems, most notably their chemical tunability and ability to form strongly bound monolayers with improved stability. Given their novelty in the field of materials science, many fundamental properties of NHC-based SAMs are not well-understood, including factors that control the adsorption and self-assembly processes.

By means of scanning tunneling microscopy and further supplemented by ab initio (DFT) and Monte Carlo simulations, we investigate the mechanisms by which NHCs bind and self-assemble on Au(111). Our investigation demonstrates a critical dependence of the binding mode on NHC structure, surface coverage, and substrate temperature. The dependence on these factors arises due to the minimization of molecule-surface steric interactions, the production of Au adatoms by the effect of NHC adsorption on the underlying gold substrate, and the reactivity and stability of the ligand, respectively. The main effect on the adsorption process is a competition between upright attachment geometries and the formation of flat-lying bis-NHC-metal complexes. These species form a rich variety of self-assembled structures, including in particular a zig-zag lattice formed by adatom-bound NHCs and a non-porous chiral Kagome lattice containing trapped NHC monomers. These lattices are analyzed within our three-pronged methodology, providing valuable insights into molecule--molecule and molecule-substate interactions, as well as the role of surface modifications and on-surface chemical reactions in the formation of NHC SAMs. Efforts to understand these processes were crucial in advancing the chemistry and applications of thiol-based SAMs, and will similarly offer critical strategies for the design of upright NHC SAMs and their applications.

Speaker: Ryan Groome (Queen's University)

GroomeRyanCAP2021Oral.pdf

GroomeRyanCAP2021Video.pdf

12:58 Questions & answers

593 (G*) The Journey of a single polymer chain to a nanopore

The delivery of a polymer chain from the chamber of origin to the destination through a nano-scale pore (nanopore) is called polymer translocation. Transport of RNA and DNA inside and into cells, virus Injection, and drug delivery are only a few examples of biological processes that polymer translocation plays a key role in. Prior to translocation, however, the chain must first find the nanopore. This so-called polymer capture has a significant impact on the conformation of the translocation. Two possible capture conformations are considered single-file and single-folded (hairpin) conformations. Our molecular dynamics-lattice Boltzmann simulations show that the presence of hydrodynamic flow facilitates the finding process as well as fostering the single-file insertion by a hairpin-unravelling mechanism, namely, the pulley effect.

Speaker: Mr Navid Afrasiabian (University of Western Ontario)

13:03 Questions & answers

594 Tradeoffs for reliable quantum information storage from graph invariants

A central problem in quantum error correction is to develop good codes. This problem is often reduced to maximizing the number of logical qubits $k$, and the distance $d$ relative to the number of physical qubits used $n$. Bravyi-Terhal, and Bravyi-Poulin-Terhal developed techniques showing that good codes cannot be locally embedded in a low dimensional Euclidean space.

In this work, we use similar techniques to generalize their results to graph invariants of the factor graph. More generally we hope to draw attention on the potential applications of the tools developed in combinatorial geometry.

We prove for quantum LDPCs that $d$ is bounded by the treewidth of the factor graph. As a consequence we recover Bravyi-Terhal, and we obtain bounds on codes locally embedded in $D$-dimensional hyperbolic space $\mathbb{H}^D$. Namely we find $d \in O(log(n))$ for codes in $\mathbb{H}^2$ and $d \in n^{(D-2)/(D-1)}$ for codes in $\mathbb{H}^{D \geq 3}$.

Further, using graph separators, we prove tradeoffs between $k$ and $d$, notably $k \frac{d^2}{log(d)^2} \in O(n)$ for codes in $\mathbb{H}^2$ and $k d^{1/(D-1)}\in O(n)$ for codes in $\mathbb{H}^{D \geq 3}$.

Aside from these specific bounds, this work has experimental implications. The ability of a quantum computer to implement a good code is closely related to its ability to achieve complex couplings between qubits.

Speaker: Mr Nouédyn Baspin

13:08 Questions & answers

595 (G*) Effective Charges in Entropy Stabilized Oxides

Entropy stabilized oxides, containing a large number of different elements, exhibiting simple crystal structure have shown interesting properties such as colossal dielectric permittivity, superionic conductivity and enhanced exchange coupling.
To study how the ionic character can be tuned by using different mixtures of oxides, the effective charge for the rocksalt structure high entropy oxide (CuCoMgZnNi)O and medium entropy oxides including (CoMgZnNi)O, (CuMgZnNi)O, (CuCoZnNi)O, (CuCoMgNi)O were calculated by using Scott formula for effective charge and the data from infrared reflectance measurements. The data suggest that (CoMgZn Ni)O has the highest ionic character and the lowest ionic character belongs to (CuCoZnNi)O which has the the lowest effective charge.

Speaker: Tahereh Afsharvosoughi (Brock University)

13:13 Questions & answers

596 (G*) Negative Differential Resistance in Carbon-based Cryogenic Composite Nanomaterials

With the proliferating global concern for environmental issues, there is a growing demand for a renewable, cost-effective, and sustainable electronics [1]. Carbon-based composite nanomaterials (i.e. graphene, graphene oxide, carbon nanotubes, carbon quantum dots etc.) are a promising candidate for such applications due to their tunable electrical, optical, and mechanical properties [2]. Most importantly, carbon materials are generally lacking in toxicity making them highly ecofriendly. Graphene oxide (GO) is a two dimensional oxidized form of graphene with oxygen functional groups decorated within the sp2 basal carbon plane [3]. The physical properties of GO can be tuned with simple wet chemistry by the adjustment of surface functional groups and can be easily extend to large scale production making it an attractive material for studies in device fabrication, renewable energy, and medicine [4]. In this presentation, we present the study of multilayer GO composite of polyvinylidene fluoride (PVDF) : D-glucose synthesized by lyophilisation i.e. freeze drying. Preliminary studies of our GO composite material include scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX) and current-voltage characteristic measurements. From preliminary studies, our GO composite material shows a negative differential resistance in which the carrier transport mechanism can be associated with quantum mechanical tunneling.

[1] He, C., Jiang, Y., Zhang, X., Cui, X., & Yang, Y. (2020). A Simple Glucose-Blowing Approach to Graphene-Like Foam/NiO Composites for Asymmetric Supercapacitors. Energy Technology, 8(1).
[2] Berrio, M. E., Oñate, A., Salas, A., Fernández, K., & Meléndrez, M. F. (2021). Synthesis and applications of graphene oxide aerogels in bone tissue regeneration: a review. Materials Today Chemistry, 20.
[3] Wang, Y., Wang, L., Zhang, X., Liang, X., Feng, Y., & Feng, W. (2021). Two-dimensional nanomaterials with engineered bandgap: Synthesis, properties, applications. Nano Today, 37.
[4] Perrozzi, F., Prezioso, S., & Ottaviano, L. (2015). Graphene oxide: From fundamentals to applications. Journal of Physics Condensed Matter, 27(1).

Speaker: Victor Wong (Department of Physics & Astronomy University of Western Ontario)

13:18 Questions & answers

597 (G*) High carrier mobility and anisotropic electronic structure in double-helix SnIP nanowires

SnIP is an exciting new quasi-1D van der Waals semiconductor with a unique double-helix structure at the atomic scale that shows promise as a new material for flexible electronics. However, due to the high resistivity of as-grown SnIP its true potential is not clear. In this work, we study SnIP-nanowire thin films using time-resolved THz spectroscopy (TRTS), a powerful ultrafast optical tool that enables picosecond-resolution measurement of the complex photoconductivity spectrum. Modeling the dispersion of the conductivity allows us to extract the carrier scattering rate, however, the choice of model can yield different values. We discuss our results in terms of the two most common models in the field, the Drude-Smith model and the plasmon model, and show how fluence-dependent spectroscopic studies can be used to differentiate the two experimentally. Moreover, with knowledge of the effective mass, the scattering rate enables us to calculate the carrier mobility. We performed an ab-initio study of the electronic structure in SnIP and extracted the effective mass tensor for several bands near the Fermi level. Along with the carrier scattering rate, we find a carrier mobility as high as 280 cm^2 V^-1s^-1, which is remarkably high for such a soft and flexible material and suggests that it is ideally suited for flexible electronics. Moreover, we find a large anisotropy in the electronic structure, which is due to the low symmetry and unique bond arrangement in SnIP. In the effective mass approximation, the preferred transport direction is band dependent, with preferential electron and hole transport parallel and perpendicular to the double-helix axis, respectively. Furthermore, we show that over a wide range of energies the conduction band dispersion shows quasi-2D behavior and discuss possible experimental evidence of this in our TRTS data.

Speaker: David Purschke (University of Alberta)

13:23 Questions & answers

R2-7 Data Acquisition (DAPI) / Acquisition de données (DPAI)

Convener: Steffon Luoma

598 Real-Time Event Filtering in Complex Multi-Detector Systems

The quest to develop a fundamental understanding of the nuclear interaction is aided greatly through measurements made with complex, multi-detector systems. As these systems allow for both an increase in total efficiency due to greater angular coverage as well as correlation measurements in both time and space, the information which can be probed using these detectors is greatly increased over single-detector systems.

With an increase in both number of detectors and complexity of detector systems comes challenges in data acquisition. As each detector can obtain data independently, the required throughput of the data acquisition system also increases. To address this problem, real-time event filtering can be performed on the data to only process and store events with certain characteristics. Traditional methods for event filtering require large arrays of electronics to perform logic on unprocessed data. This approach comes with a large up front cost both in money and effort in order to purchase, set up, and test electronics. Finally, for small laboratories, the scaling of these approaches can be a limiting factor as an increasing number of detectors also increases the number of electronic modules, as well as the space and power consumption of the data acquisition system.

At the Nuclear Science Lab (NSL) at Simon Fraser University (SFU), we implement a single-unit, computer controlled XLM72S universal logic module to perform real-time event filtering. The XLM72S contains a field programmable gate array with two operational firmware developed for the NSL at SFU. The first of these performs both anti-coincidence logic and multiplicity filtering for up to twenty independent Compton Suppressed Spectrometers, as well as coincidence logic with up to four auxiliary detectors. The second is designed to perform coincidence logic on up to 128 individual inputs through the daisy-chaining of multiple XLM72S logic modules, a feature which can be achieved with both firmware. Through daisy-chaining of XLM72S modules, scaling real-time event filtering to large-scale, complex, multi-detector system is easily achievable.

Details of the module and the two firmware developed for and implemented in the NSL at SFU will be discussed in this talk.

Speaker: Matthew Martin (Simon Fraser University)

599 (G*) Development and Implementation of a Machine Learning Algorithm for Pulse Shape Discrimination

In any application where a radiation detector is utilized in a mixed radiation field, there is an inherent issue of separating the signal from the background. This research focuses on the separation of neutron and gamma-ray events in a liquid scintillator. The standard solution to this issue leverages the fact that the secondary particles generated in neutron and photon interactions are different; the former being nuclear recoils, typically protons in organic scintillators, and the latter being electrons or positrons in the case of pair production. The charge deposition characteristics of these secondary particles provide the basis for Pulse Shape Discrimination (PSD) as a means of event classification.

The work presented focuses on the development of a machine learning algorithm for use in the problem of pulse shape discrimination. The signals generated from gamma ray and neutron interactions inside the liquid scintillator used are comprised of three characteristic scintillation decay times: 3.16 ns, 32.3 ns, and 270 ns. The proportion of scintillation light generated from these three characteristic times is dictated by the stopping power of the particle traversing the scintillator, generating distinguishable signals for photon interactions relative to neutron interactions. Typically PSD is performed by allowing two different charge collection windows and comparing the amount of charge collected in both; tail-to-total integration. This work utilizes current generation machine vision algorithms for the task of event classification, where the PMT output from the scintillator will be utilized as the input to the machine vision algorithm. Current generation algorithms allow for feature extraction performed simultaneously at differing spatial extents, which enables the algorithm to extract valuable information about the signal from all three time scales present in the scintillator, 3, 30, and 300 ns. This new application of machine vision algorithms will be coupled with a current generation digitizer operating with 12 bit precision and sampling at 3.2 GS/s. This opens up the possibility of utilizing information from the rising edge of the signal, which is on the order of a few nanoseconds.

Training of this algorithm was performed in a supervised manner, which requires that labeled sets of data be provided for the algorithm to learn from. Any improperly labeled data utilized, diminishes the performance of the algorithm, making correctly labeled data paramount to success. Performing this for neutron and gamma-ray events in the scintillator is quite difficult due to the complications mentioned for event classification. The solution used in this project is to utilize an isotopic source of neutrons, PuBe. The PuBe source produces prompt gamma rays in conjunction with neutrons in some decays, with energies greater than 4 MeV. These prompt gamma rays can serve as an event trigger for detection of neutrons in a secondary detector, providing relative certainty that detected events within an appropriate time window are indeed neutron events. Producing a high degree of purity in the training data.

Speaker: Richard Garnett (McMaster University)

600 (G*) Development of a digital data acquisition system capable of pulse-pileup recovery for HPGe detectors

The versatility of gamma-ray spectroscopy has given rise to its many applications, from quantification of trace elements in a sample to maintaining nuclear material safeguards. Depending on the application and gamma-ray detector, there is often a compromise made between detection efficiency and energy resolution. While characterizing or quantifying trace radionuclide concentrations in an unknown sample, energy resolution is often the more important property. In these situations, high-purity germanium (HPGe) detectors are the detector of choice as they have a superior energy resolution which significantly reduce measurement uncertainties and improve minimum detection limits.

Applications using HPGe detectors are limited to counting rates on the order of a few tens of thousands of counts per second (cps) before the performance of the detector is severely diminished. The limiting factor for high counting rate measurements comes from the need to shape signals with a relatively long shaping time, on the order of 1-6 μs, to maintain good energy resolution. At higher counting rates however, if a signal is received while a previous signal is still being shaped, pulse-pileup occurs. Pulse-pileup distorts the energy measurement of the previous signal and entirely drops the measurement of the second signal. Traditionally, this situation is usually handled with a pileup rejection method. At ultra high counting rates, on the order of a million cps, the percentage of the pileup rejection is so high that the spectroscopy system suffers from extremely high deadtimes.

In order to solve this critical problem, the present study aims to develop a data acquisition system capable of deconvoluting pileup signals into two or more recovered signals in real-time. This technique has been applied for NaI(Tl) and silicon drift detectors, which showed very promising results. However, applications of this technique for HPGe detectors have been unsuccessful as it relies on a fixed signal rising edge shape, a feature which cannot applied for HPGe detectors due to the variation in the rising shape. Our study has been focused on developing a deconvolution algorithm to identify and recover piled-up signals using a planar HPGe. During this development stage, signal waveforms are analyzed offline, optimizing the algorithm over a range of counting rates while building a library of the rising edge shapes. Once completed, the deconvolution algorithm will be benchmarked for various high-rate measurements. The preliminary result of the pile-up deconvolution performance will be presented.

Speaker: Thomas Domingo (McMaster University)

601 (G*) Progress toward optimizing energy and arrival-time resolution with a transition-edge sensor

Superconducting transition-edge sensors (TESs) carried by x-ray telescopes are powerful tools for the study of neutron stars and black holes. Several methods, such as optimal filtering or principal component analysis, have already been developed to analyze x-ray data from these sensors. However, these techniques may be hard to implement in space. Our goal is to develop a lower-computational-cost technique that optimizes energy and time resolution when x-ray photons are detected by a TES. Current pulses, in TESs, exhibit a non-linear response to photon energy. Therefore, at low energies, we focus on the current-pulse height, whereas at high energies, we consider the current-pulse width, to retrieve energy and arrival time of x-ray photons. For energies between 0.1 and 30 keV and with a sampling rate of 195 kHz, we obtain an energy resolution (full-width at half maximum) between 1.32 and 2.98 eV. We also get an arrival-time resolution (full duration at half-maximum) between 163 and 3.85 ns. To improve the accuracy of these results, it will be essential to get a thorough description of non-stationary noise in a TES and develop a robust on-board identification method of pile-up events.

Speaker: Paul Ripoche (University of British Columbia)

602 The Vertical Slice Data Processing Scheme for DarkSide

DarkSide-20k is a planned two-phase liquid Argon time-projection-chamber (LAr-TPC) for direct WIMP search. The S1 and S2 light from the 20 ton fiducial volume is detected with Silicon photomultipliers and digitized. Due to the expected data rate of hundreds of MB/s it is impractical to record full waveform data continuously like in the smaller DarkSide-50 experiment, instead complex filtering and processing is required to select meaningful data. Since this processing needs to take into account all (above threshold) data channels at once, it cannot happen directly in the acquisition module, but all data has to be transferred to a processing farm, where processing time will likely exceed acquisition time. In order to address this, data will be compiled into time slices (on the order of a second), which get distributed to individual processing machines. The process is somewhat complicated by the fact that due to the long drift time in the TPC signals from the same physical event can be spread out over milliseconds, it is thus necessary for time slices to overlap enough to ensure each physical event is contained completely in one slice.
This presentation will give an overview of the DarkSide vertical slice scheme and show how it is implemented within a MIDAS-based data acquisition system.

Speaker: Lars Dieter Martin (TRIUMF)

R2-8 Backgrounds and modelling for rare event searches (PPD) / Bruit et modélisation pour la recherche d'événements rares (PPD)

Convener: Juan-Pablo Yanez (University of Alberta)

603 (G*) Muon-induced backgrounds in a new dark matter experiment: the Scintillating Bubble Chamber

Searching for low mass WIMPS has many challenges, the largest one being the discrimination between electron recoils and nuclear recoils within a given detector, the latter being a potential dark mater signal while the former is not. Many detectors cannot make this distinction and thus can only look so far in the low mass dark matter regime, but a new dark matter detector called the Scintillating Bubble Chamber (SBC) has a clever design to overcome this barrier. By having a target fluid of liquid argon that is both a bubble chamber and scintillator, scintillation from an electron recoil will distinguish the event from a lightless nuclear recoil allowing the detector to reach a 100 eV energy threshold. In addition to introducing the SBC, this talk will go over my personal contribution to the experiment, namely the study of another important background: neutrons from muon-induced spallation. Since it is impossible to know what caused a nuclear recoil just from the bubble it produces within the SBC, it is crucial to know how many neutron nuclear recoils we expect to see and their range of energies. Additionally, these events can potentially be vetoed by surrounding the SBC with a water shield. The surrounding water would cause an incoming muon to produce Cerenkov light detected by photomultiplier tubes within the shield, giving a signal that any nuclear recoils seen within the detector at that moment might be from a spallated neutron. Exactly how to build an effective water shield for SBC is the second focus of my talk. This work, studied through Monte Carlo simulations, will inform the data analysis and the water shield design of the SBC when it begins its data taking at SNOLAB in 2022.

Speaker: Patrick Hatch (Queen's University)

Muon-induced backgrounds in a new dark matter experiment - the Scintillating Bubble Chamber.pdf

Muon-induced backgrounds in a new dark matter experiment - the Scintillating Bubble Chamber.pptx

604 (G*) Detector response simulation for NEWS-G Dark Matter experiment

The spherical Proportional Counter (SPC) is used in NEWS-G to search for low-mass Weakly Interacting Massive Particles (WIMPs). UV laser and Ar37 calibration data was previously taken at Laboratoire Souterrain de Modane (LSM) with a 1.35m diameter SPC filled with pure CH4 gas. In order to verify our understanding of the detector behaviour and the physics model we use, a simulation of the SPC response to these two responses is needed. The primary electrons originating from the same event will drift toward the high voltage sensor and a current will be induced by the motion of secondary ions drifting away from the sensor. The signal amplitude characterized by the rise time of the amplitude of the integrated charge pulse, will increase with the diffusion time and consequently with the radial location of the event. After describing the method used to model the electron drift and how we obtain the rise time from the simulated events, I will present the different approaches used to match the model with the calibration data performed at LSM. Finally, I will discuss the implication of the simulation results in cut efficiencies and WIMP signal acceptance to further extract the dark matter cross-section exclusion limits.

Speaker: Yuqi DENG (University of Alberta)

CAP2021Congress_v3_Yuqi_UofA_NEWSG.pdf

605 (G*) Background characterization and detector model after hardware upgrades of the DEAP-3600 detector

DEAP-3600 is a dark matter experiment which uses liquid argon to search for spin-independent interactions of weakly interacting massive particles (WIMPs). The experiment has completed two WIMP searches using 4.44 and 231 live days with 3322 kg and 3279 kg of liquid argon, respectively. In addition to these two data sets, the detector has recorded WIMP search data from 2016-2020 and analysis of this cumulative data set is currently underway.

Characterization and understanding of backgrounds capable of mimicking a WIMP signal are essential to completing any dark matter search. To further understand and distinguish several backgrounds identified in DEAP-3600 data, upgrades to the detector hardware have been designed and are scheduled to be completed by the end of 2021.

This talk will outline details of the DEAP-3600 hardware upgrades and present analysis of detector backgrounds using an upgraded detector model and Monte Carlo simulation.

Speaker: Courtney Mielnichuk

CAP 2021 - C. Mielnichuk.pdf

606 (G*) Radon Mitigation Strategies for the NEWS-G Dark Matter Experiment

Contamination from radioisotopes are a major background source in rare-event experiments such as searches for dark matter and neutrinoless double beta decay searches. A common internal source of radioactive backgrounds that creates many challenges for these experiments is radon and its progeny. As a noble gas, it can easily enter the innermost part of the active target through diffusion, and can be continuously produced inside detector materials due to the decay of trace amounts of radium from uranium and thorium decay chains. The New Experiments With Spheres - Gas (NEWS-G) experiment currently being installed at SNOLAB, has launched a mitigation program to reduce the amount of radon produced by certain components. After describing the different strategies, the results obtained from different materials to remove radon will be discussed, along with the use of different target gases for NEWS-G detector. The reliability of these results are demonstrated through successfully trapping the radon. Finally, the integration of the radon removal system into the gas purification loop (a part of the gas handling system) for the NEWS-G detector will be discussed.

Speaker: Patrick O'Brien (University of Alberta)

PBO_UofA_CAP_2021_v3.pdf

R2-9 Neutrino experiment and related calibration (PPD) / Expérience sur neutrinos et calibration associée (PPD)

Convener: Claire David (York University (CA))

607 (G*) Ambient Background Modeling and Event Trigger Development for the Pacific Ocean Neutrino Explorer

At energies over 100 TeV, the universe becomes opaque to photons limiting the range of high energy gamma ray observations to roughly within the Milky Way. Neutrinos on the other hand do not suffer from this drawback which makes them ideal messengers for studying extremely energetic astrophysical phenomena across the cosmos. Recent observations using neutrino telescopes have thoroughly cemented the research potential of neutrino astronomy. However, multiple neutrino telescopes are needed to expand the observable skyline and increase the detection rate of extraterrestrial neutrinos. The Pacific Ocean Neutrino Explorer (P-ONE) is a proposed initiative to construct one of the largest neutrino telescopes deep in the northern Pacific Ocean off the coast of British Columbia. The detector itself will consist of an array of strings lined with digital optical modules (DOMs) which detect Cherenkov light from secondary particles produced in neutrino interactions within the detector. To date, two pathfinder missions have been deployed for studying the optical properties of Pacific Ocean seawater including scattering and absorption lengths as well as the ambient undersea background. The background consists of stochastic noise spikes due to various undersea bioluminescence along with a baseline of Cherenkov radiation produced by $\beta^-$ decay of radioactive isotopes, primarily $^{40}$K, in sea salt. This presentation will discuss modeling the response of a pathfinder DOM to the $^{40}$K background using Geant4 as well as the process of using this characterization of $^{40}$K to develop event triggers for P-ONE. Verifying the undersea ambient background simulation against in situ measurements confirms the accuracy of measured optical parameters and solidifies the understanding of noise within the detector. Not only is this important step of the site characterization essential for event trigger development as will be discussed, but accurate modeling of ambient $^{40}$K also proves to be useful for detector efficiency measurement and recalibration.

Speaker: Jakub Stacho (Simon Fraser University)

2021_CAP_JakubStacho.pdf

608 Study of neutrons associated with neutrino interactions in water with the IWCD detector

The Hyper-Kamiokande (HK) experiment, a next generation underground experiment in Japan, will have a broad physics program, including long-baseline neutrino oscillation measurements using an upgraded 1.3 MW beam produced at J-PARC accelerator, following the successful T2K experiment. To achieve the designed goal, an accurate prediction of neutrino interaction rates on the water target at the HK far detector is vital. For this aim, the Intermediate Water Cherenkov Detector (IWCD), which can vertically move changing the angle between the average beam direction and the direction of neutrinos impinging the detector, is planned as one of HK’s near detector. By measuring neutrino interaction rates at various vertical positions, IWCD will measure neutrino interactions’dependence on neutrino energy. It is also planned to operate the detector with Gd2(SO4)3 loading, enabling the measurement of neutrons associated with neutrino interactions in water. Since information about these neutrons will be utilized to improve various physics analyses at the HK far detector, the measurement at IWCD will be used to reduce uncertainties on the modeling of neutron production. This talk will present an overview of the IWCD detector design and its measurement program, and discuss the challenges associated with the measurement of neutron multiplicities, including reconstruction of neutron signal and backgrounds in the measurement.

Speaker: Dr Ryosuke AKUTSU (TRIUMF)

June102021CAP_RyosukeAkutsu_v1.pdf

609 Measuring the muon (anti-)neutrino induced charged-current coherent pion production cross sections on carbon using the off-axis T2K near detector

A neutrino (or an anti-neutrino) can interact with an entire nucleus coherently (this means that the target nucleus has to stay intact after the interaction) and produce a pion - we call such an interaction coherent pion production. The interaction can either be mediated by a Z boson (neutral current) or a W boson (charged current). This process is not well understood theoretically. Additionally, the neutral current channel can be a background source to the electron neutrino appearance measurements. The Tokai-to-Kamioka (T2K) experiment has previously published the first sub-GeV charged current coherent pion production (CC-COH) measurement using a 0.6 GeV muon neutrino beam. Since then, T2K has collected roughly twice the muon neutrino data and an equivalent amount of muon anti-neutrino data. The detector reconstruction and the modelling of neutrino interactions have also been greatly improved. An improved muon neutrino induced CC-COH measurement (compared to the previously published T2K result) and the first sub-GeV muon anti-neutrino induced CC-COH measurement are in progress. This talk will describe the challenges associated with measuring the muon neutrino and anti-neutrino induced CC-COH cross-sections and how T2K addresses these issues.

Speaker: Mitchell Yu (York University)

CAP2021_Jun_10_2021_Mitchell_Yu.pdf

610 Photogrammetry in Water Cherenkov Neutrino Detectors

Precision measurements of neutrino interactions being pursued in the current Super-K detector, the next-generation Hyper-K detector, and its Intermediate distance Water Cherenkov Detector (IWCD) necessitate improved calibrations. Photogrammetry will be used to reduce the position uncertainty on the photomultiplier tubes (PMTs) and calibration source locations within the detector. The positioning of PMTs within the detector and of calibration sources in the detector may slightly deviate from the design, and these deviations may cause biases in event reconstruction. Calibrating these positions through direct measurement can allow the related systematic errors to be constrained further than has been achieved previously. Photographs of the PMTs lining the walls of the detectors are used to create a 3D reconstruction of their positions, starting from the 2D PMT positions obtained in each image via image processing and machine learning methods. These positions, in combination with camera calibration parameters, are used to determine the location and orientation of the camera and reconstruct a 3D position for each PMT. This talk describes the photogrammetry efforts in Super-K, using an underwater drone survey to obtain images of all PMTs, as well as future applications to the Hyper-K and IWCD via a built-in camera and lighting system.

Speaker: Blair Jamieson (University of Winnipeg)

Photogrammetry_CAP_2021 pptx-converted-compressed.pdf

611 (G*) AmBe Source Calibrations in SNO+ Partial Scintillator Phase

SNO+ is a multipurpose neutrino experiment located approximately 2 km underground in SNOLAB, Sudbury, Canada. The second phase of the experiment is underway and consists of filling the detector with 780 tonnes of Linear Alkyl Benzene (LAB) scintillator. The fill is expected to be completed spring 2021. During this partial fill stage a number of external calibration campaigns have been completed in an effort to quantify the detector response. We look to accomplish our goals by analyzing a deployed neutron source, $^{241}$Am$^9$Be. A key component of this signal is the identification of the prompt and coincident signals comprised of 4.4 MeV and 2.2 MeV $\gamma$'s respectively. The characteristic energy spectrum allows for a verification of the energy reconstruction and photon light yield in scintillator. The 2.2 MeV $\gamma$ from the inverse beta decay neutron capturing on hydrogen allows for an in depth analysis of neutron capture efficiency. The low trigger threshold of the SNO+ detector allows for a substantial detection efficiency of these neutrons. The AmBe source mimics the reactor antineutrino signal within SNO+. In particular, we look to further constrain measurements on the reactor antineutrino energy spectrum and the neutrino oscillation parameters, $\Delta m_{12}^2$, and $\sin^2{\theta_{12}}$. This presentation outlines the effort on the AmBe calibration data and analysis during the partial fill phase.

Speaker: Jamie Grove (Laurentian University SNOLAB)

CAPtalk.pdf

13:30 15 Minute Break

R-SOCIAL Networking/Social Activities / Maillage et activités sociales

R-PPD Long Range Planning Discussion (PPD) / Échanges sur la planification à long terme (PPD)

Conveners: Marie-Cécile Piro (University of Alberta), Matthias Danninger (Simon Fraser University (CA))

612 LRP McDonald Institute

Speaker: Tony Noble (Queen's University)

MI-LongRangePlanning-Exercise.pdf

MI-LongRangePlanning-Exercise.pptx

613 LRP IPP

Speaker: Michael Roney (University of Victoria)

PPD-IPP-2021June10.pdf

614 Canadian Subatomic Physics LRP

Speakers: Adam Ritz, Brigitte Vachon (McGill University, (CA))

2021-06-10-CAP-PPD-slides.pdf

615 Development of the ARGO dark matter experiment

It has long been known that most of the matter in our Universe is dark. The direct detection of dark matter particle interactions is one of the most important topics in particle physics - a positive measurement would provide unambiguous evidence of the particle nature of dark matter in the Universe. In this talk we will present an overview of the phased approach to dark matter searches by the Global Argon Dark Matter Collaboration, including DEAP-3600, Darkside-20k, and an ultimate detector that will employ a 300-tonne sensitive target of liquid argon with sensitivity to the neutrino floor, ARGO. The status of R&D activities in Canada towards ARGO will be presented.

Speaker: Mark Boulay (Carleton University)

boulay_argo_CAP_2021.pdf

14:45 15 Minute Break

R-PLEN-3 Renée Horton, NASA (DGEP/DAPI) (DEGP/DPAI)

Conveners: Chitra Rangan (University of Windsor), Steffon Luoma

616 Friction Stir Welding in the Aerospace Industry

Abstract coming soon.

Speaker: Dr Renee Horton (NASA)

15:30 15 Minute Break

R3-1 Teaching and EDI (DPE) / Enseignement et EDI (DEP)

Conveners: Chitra Rangan (University of Windsor), Daria Ahrensmeier (Simon Fraser University)

617 (I) Exploring men’s and women’s roles in physics lab group work

While group work is common in most introductory physics labs, research in physics education has found that students' experiences in those groups are not necessarily in common. I'll discuss our recent work evaluating how students participate in the hands-on aspects of physics labs, particularly illuminating imbalances between men's and women's participation. I'll also describe how nuances in students' perceptions of these experiences and differences in single-gender versus mixed-gender groups motivate different types of instructional interventions (or even no intervention at all!).

Speaker: Natasha Holmes (Cornell University)

618 Exploring student perceptions of introductory physics

There is a large body of research suggesting that marginalized students hold negative attitudes and beliefs towards physics that manifest in high-school. These perceptions of physics can negatively impact student learning and have been repeatedly associated with the gender gap in performance in introductory physics courses at the university level. Many universities offer multiple streams of introductory physics, some can act as pre-requisites to upper year courses while others do not. As such, students self-select into cohorts based on their high-school perceptions of the subject. This decision potentially limits their ability to pursue physics, before ever taking a university level physics course. At McMaster University there are three streams of introductory physics that can each act as pre-requisites to upper year physics courses. Each course is marketed towards a different student interest group; life sciences, physical sciences and engineering, respectively. The goal of our study was to assess whether student perceptions of physics differed between the cohorts before and after taking an introductory level course. We hypothesized that marginalized students with more negative perception of physics would self-select into the life-sciences cohort, resulting in diversity differences at the introductory level that would persist into upper year courses. To test this hypothesis, we surveyed students’ perceptions and interest in physics before and after taking one of the three introductory physics courses. We focused on student feelings of preparedness from high-school for university. We also collected data on demographics, high-school education, career aspirations and degree program. Finally, we surveyed upper-year physics students to determine if introductory physics stream correlated with the propensity to pursue physics. The long-term goal of our study is to track how students’ perceptions of physics changes as they progress through their undergraduate training in the hopes of reducing barriers to entry into the program

Speaker: Dr Cayleih Robertson (McMaster Univerity)

R3-2 Ultrafast Processes (DAMOPC) / Procédés ultrarapides (DPAMPC)

Convener: Nisha Rani Agarwal (University of Ontario Institute of Technology)

619 (I) Signatures of light-induced potential energy surfaces in H2+ - beyond conical intersections

H2 continues to provide fundamental insights into the mechanisms of intense light-matter interactions [1]. Recently, there has been significant interest in so-called light-induced conical intersections (LICI) that arise from the angle dependence of the single-photon coupling of electronic states. Analogously to regular conical intersections, electronic and nuclear motions are strongly coupled in the vicinity of LICIs. As a signature of such rovibronic dynamics, weak modulations in the angular distribution of protons emitted from H2+ have been reported [2]. More generally speaking, infrared (IR) laser pulses couple the 1sg and 2pu electronic states of H2+ typically through several pathways involving an odd number of photons [1], which can produce complex light-induced potential energy landscapes, and consequently even richer dynamics.
In this talk we will present theory and experiment to show that the full complexity of such light-induced potential energy surfaces can be uncovered using a two-step scheme [3]. In this scheme a few cycle optical pulse projects a coherent wavepacket onto the ionic state of H2 and a weak, non-ionizing, mid-infrared, and perpendicularly polarized pulse creates the light-induced potential energy landscapes upon which the H2+ wavepacket can propagate. We observe a strongly modulated angular distribution of protons which has escaped prior observation. These modulations result directly from ultrafast dynamics on the light-induced molecular potentials and can be modified by varying the amplitude, duration and phase of the mid-infrared dressing field.

[1] H. Ibrahim, C. Lefebvre, A.D. Bandrauk, A. Staudte and F. Légaré. J. Phys. B 51, 042002 (2018).
[2] A. Natan, M.R. Ware, V.S. Prabhudesai, U. Lev, B.D. Bruner, O. Heber, and P.H. Bucksbaum, Phys. Rev. Lett. 116, 143004 (2016).
[3] M. Kübel, M. Spanner, Z. Dube, A.Yu. Naumov, S. Chelkowski, A.D. Bandrauk, M.J.J. Vrakking, P.B. Corkum, D.M. Villeneuve, and A. Staudte. Nature Communications 10, 1042 (2019).

Speaker: Prof. Andre Staudte (National Research Council and University of Ottawa)

620 (I) Coherent Ultrafast Electronic Dynamics in Molecules

The non-adiabatic coupling of nuclear and electronic degrees of freedom underlies many fundamental processes in Nature, including solar energy conversion and photosynthesis. The formation of electronic coherences by nuclear motion is a new aspect of such dynamics and requires new measurement techniques and methods of analysis. We will discuss Ultrafast Time-Resolved Xray Absorption and Time-Resolved Photoelectron Spectroscopy, powerful methods suited to addressing this problem. In particular, we present a new approach to fully separating electronic coherences from electronic population dynamics, a long-standing problem, based on the use and analysis of Time-Resolved Photoelectron Angular Distributions.

Speaker: Prof. Albert Stolow (University of Ottawa)

621 Clocking enhanced ionization of hydrogen molecule using molecular rotational wavepackets

Laser-induced rotational wavepacket of hydrogen molecules has been experimentally observed in real time by using two sequential 25-fs laser pulses (pump-probe scheme) and a COLTRIMs spectrometer. By measuring the time-dependent yield of the above-threshold dissociation and the enhanced ionization of the molecule, we observed a few-femtosecond time delay in between the two dissociation pathways for both H2 and D2. The delay was understood and interpreted by a classical model considering enhanced ionization requires extra interaction with the laser field. We demonstrate the molecule rotational clock in hydrogen molecule is a straightforward method for timing ultrafast molecular dissociation dynamics.

Speaker: Yonghao Mi (University of Ottawa)

622 (G*) Wavelength-dependent depolarization in fiber-based supercontinuum

Light possessing a broadband frequency spectrum, also known as a supercontinuum (SC), has facilitated a plethora of applications such as optical coherence tomography (OCT) and optical communication. In general, these spectra are produced by propagating narrow-band optical pulses through a highly nonlinear medium. Photonic crystal fibers (PCFs) are often used as the nonlinear medium for SC generation as their strong mode confinement capabilities over long distances lead to an increased nonlinearity. Although the polarization state of fiber-based SC sources can be crucial for the aforementioned applications, it is often overlooked due to the lack of proper experimental equipment operating over the entire spectrum. Here, we use a free-space, broadband, and polarization-resolving spectrometer to fully characterize the spectral intensity and linear polarization properties of a SC generated in a germania-doped silica PCF. More specifically, we investigate depolarization over more than two optical octaves as we vary the input polarization and pulse energy. We resolve self-phase modulation, self-shifted Raman solitons and dispersive waves within a set of orthogonal polarization states associated to the principal axes of the fiber as they contribute to generate a SC spanning from 450 to 2150 nm. We show that Raman soliton and dispersive wave generation remain axis-specific as they propagate in the PCF. Our experimental results feature a high degree of polarization at the edges of the spectrum in comparison to the region near the input pump wavelength. We show that this modulation is mostly caused by nonlinear spectral broadening. We also identify an additional depolarization mechanism preferentially acting on shorter wavelengths, indicative of a Rayleigh-like scattering effect due to the presence of intrinsic sub-wavelength defects in the fiber. Our results and experimental technique are a noteworthy step toward an improved standard for the characterization of broadband optical spectra and more efficient implementation of highly nonlinear fibers in a large range of polarization-sensitive applications like OCT.

Speaker: Nicolas Couture (University of Ottawa)

623 Multi-octave Parametric Amplification for Ultrashort Laser Pulses

Optical parametric amplifiers deliver intense ultrashort pulses with broadly tuneable frequencies, useful for strong field physics, high harmonic generation, and attosecond experiments. Currently, this nonlinear amplification scheme relies on the second order nonlinearity, $\chi^{(2)}$,which is made possible only by crystals without centro-symmetry. More recently, investigations into a non-collinear setup show an increase in the phase matching bandwidth, leading to the creation even shorter pulses [1]. In this presentation, we discuss our research involving non-collinear parametric amplification of ultrashort pulses using wide bandgap materials with centrosymmetry, previously reported as Kerr instability amplification (KIA) [2].

We find that by using these crystals that exploit the next order nonlinearity, $\chi^{(3)}$,we can choose our amplifying medium from a more general class of crystals and still can generate gain factors of g = 50 /mm, or amplification factors of > $10^{12}$ [3]. Without the constraint of centrosymmetry, we have a greater selection by varying the bandgap, thermal properties, and linear and nonlinear indices of refraction. We developed pulse propagation models to optimize the critical parameters for amplification, and we find that the amplified pulse duration is much shorter than the pump and can be independent of the seed. We test several high bandgap dielectrics to optimize our scheme. We experimentally demonstrate the octave spanning amplification, showing that KIA is closely linked to degenerate four-wave mixing. We also spectrally and temporally characterize the amplified pulses to show the agreement with theory.

References
[1] H. Fattahi et al, Third-generation femtosecond technology, Optica 1 45-63 (2014)
[2] G. Vampa, TJ Hammond et al, Kerr instability amplification, Science 359 673-675 (2018)
[3] M. Nesrallah et al, Theory of Kerr instability amplification, Optica 5 271-278 (2018)

Speaker: TJ Hammond (University of Windsor)

624 An exploration for new phenomena using high-harmonic generation in two-dimensional van der Waals materials

Attosecond science is a relatively new research field founded on high-harmonic generation (HHG) in atomic and molecular gases, which has recently transitioned to experiment in 3-dimensional solids. Most of the physics underlying attosecond pulse emission from 2-dimensional semiconductors is unknown. Following years of research focusing on HHG in bulk semiconductors, this project focuses on the mostly unstudied van der Waals materials ReS$_2$ and MoS$_2$. We measure the power of the emitted high harmonics for varying orientation of the crystallographic axis with respect to the linear polarization of the incident driving laser beam. Both crystals emit high harmonics in a very distinctive pattern which reveals the symmetry of the crystal as well as microscopic details about the orbitals involved in the emission. Our demonstration inches us closer to understanding high-field phenomena in van der Waals materials, and controlling high-harmonic emission with unprecedented precision thanks to the high degree of tunability of 2-dimensional materials and their heterostructures.

Speaker: Mr Chandler Bossaer (Joint Attosecond Science Laboratory, National Research Council and University of Ottawa)

R3-3 Quantum Theory (DTP) / Théorie quantique (DPT)

Convener: Hubert de Guise

625 (I) Markovian dynamics in open quantum systems

The state of a quantum system evolves according to the Schrödinger equation. Often, one is interested in the behaviour of parts of a whole system only. Such parts are called open quantum systems, as they exchange energy, matter, information with their surroundings. The dynamics of open systems is very complicated. They are a central topic of research in many theoretical and applied fields of modern quantum theory, such as quantum optics and quantum information, having applications to other sciences (chemistry, biology). One of the main tools for the analysis is the Markovian approximation, in which the open system dynamics is approximated by the so-called master equation. In some aspects, the latter is akin to the Schrödinger equation, in others it is crucially different due to the open nature of the system. Despite the ubiquitous use of the Markovian approximation, its rigorous justification turns out to be a difficult task.
In this talk we explain recent ideas and results of a mathematical approach proving the validity of the Markovian approximation, i.e., of the master equation. The talk does not require the listeners to have a deep background in quantum theory and should be accessible to a rather general audience.

Speaker: Marco Merkli (Memorial University)

626 (I) Schwinger pair production as a non-Hermitian problem

The creation and annihilation of particles is a fundamental feature of relativistic quantum fields. A famous example of this is provided by Schwinger’s 1951 prediction that the vacuum is unstable to particle-antiparticle production if a static electric field is applied to it. In this talk we examine the classical field limit of Schwinger pair production by mapping the Klein-Gordon equation with an electric field onto the non-relativistic Schrödinger equation with a 1/r^2 potential. This latter problem has two regimes depending on the depth of the potential: a sub-critical regime where PT symmetry is preserved and a supercritical regime where PT symmetry is broken and one finds ``fall-to-the-centre’’ where probability is absorbed at the origin. Schwinger pair production occurs in the latter regime and can be described in terms of non-Hermitian quantum mechanics.

Speaker: Duncan O'Dell (McMaster University)

627 (G*) Hawking radiation as a quantum caustic

In optics, caustics are bright, sharp lines and shapes created by the natural focusing of light. Some examples include rainbows, the wavy lines on the bottom of swimming pools and the patterns produced by gravitational lensing. The intensity at a caustic diverges in the classical ray theory, but can be smoothed by taking into account the wave nature of light. In this work we consider a new type of caustic that occurs in quantum systems due to phase singularities; because phase is such a central concept in wave theory, this heralds the breakdown of the wave description and is an example of a quantum caustic. In particular, we consider analogue black holes which can be formed in a flowing Bose-Einstein condensate (BEC) gas. Waves flowing near the event horizon (describing analogue Hawking radiation) appear to suffer a logarithmic phase divergence, which is known as the trans-Planckian problem for gravitational black holes. We describe the regularization procedure required to cure this quantum caustic in our BEC system, and make connections to catastrophe theory.

Speaker: Liam Farrell (McMaster University)

628 Gravitational tidal forces and the equivalence principle

Gravitational tidal forces conceal very interesting effects when combined with the extended nature of the wavefunction of a freely-falling quantum particle. The reason being that inertial properties of the particle get then mixed with the gravitational effects in such a way that, as in classical mechanics, the ratio between the gravitational mass and the inertial mass emerges. The equivalence principle in quantum mechanics then takes on a novel meaning thanks to the emergence of mass-independent dynamics during the free fall of the quantum particle.

Speaker: Fayçal Hammad (Bishop's University)

629 Beyond Semiclassical Physics: Consistent Hybrid Quantum-Classical Dynamics?

Combining quantum and classical degrees of freedom provides a useful approximation in many practical applications. Examples include the study of quantum particles in a classical external potential (textbook quantum mechanics), or quantum field theory on a classical curved background. In these examples, only the classical affects the quantum, but not the other way around. If these approximations can provide valuable insight, then what can we learn from a fully consistent framework capable of describing mutual interaction between quantum and classical systems?

Quantum and classical mechanics share a formal canonical structure. We investigate the possibility of leveraging this common structure to construct a consistent framework for ``quantum-classical'' dynamics. Previous attempts have been proposed and criticized in multiple no-go theorems. We generalize the procedure for constructing canonical hybrid dynamics and find a precise mathematical condition for the desired consistency. We show that the consistency requirement places constraints on the allowed interactions between quantum and classical systems.

Speaker: Mustafa Amin (University of Lehtbridge)

630 (G*) Gravitational scattering on quantum superposed states

This talk aim to discuss the scattering of particles on quantum superposed states. The fact that one of the initial states is in a superposition implies that the plane wave approximation is not valid anymore which is what we usually do. This will lead to the introduction of Wigner function and a formalism to describe this situation.
We will apply this new formalism to the question of gravitational scattering. The idea will be to put in evidence a quantum effect of gravity due to the superposition. We will compute the cross section and discuss the possibility to observe such a small effect.

Speaker: Mr Victor Massart (Université de Montréal)

16:07 Questions/Answers and Discussion Period

R3-4 Experimental Nuclear Physics II (DNP) / Physique nucléaire expérimentale II (DPN)

Convener: John Behr (TRIUMF)

631 (I) The Electron-Ion Collider: North America's Next Large Particle Collider

The Electron−Ion Collider (EIC) is a major new collider facility to be built on Long Island, New York, by the end of the current decade. At the EIC, polarized electrons will collide with polarized protons, polarized light ions, and heavy nuclei at luminosities far beyond what is presently available. The facility will answer several fundamental questions central to the understanding of atoms, and integral to the agenda of nuclear physics today: How does the mass of the nucleon arise? How does the spin of the nucleon arise? What are the emergent properties of dense systems of gluons? Canadian subatomic physicists have participated extensively in the planning of this new facility and have chartered the multi−institutional EIC Canada Collaboration. We anticipate that Canada will make significant contributions to detector systems, software, electronics, and the physics program of the EIC.

Speaker: Wouter Deconinck

632 (G*) High-precision experimental nuclear physics with the upgraded TITAN Penning trap

On behalf of the TITAN collaboration
Nuclear-physics studies are probing into nuclear structure, nucleosynthesis and fundamental interactions, for which high precision and accurate mass measurements are critical inputs. TRIUMF’s Ion Trap for Atomic and Nuclear science (TITAN) facility employs the Measurement Penning Trap (MPET) to measure masses of exotic nuclei ~1x10-8 accuracy. To improve the resolving power and reduce statistical uncertainty in the mass measurement, a higher charge state of the ions can be used. This and other benefits of charge breeding radionuclides in an electron beam ion trap, like improved beam purification, can only be realized at TITAN. To fully leverage these advantages, MPET is undergoing an upgrade to a new cryogenic vacuum system compatible with ions in charge states over 20+. The status of the new cryogenic upgrade will be presented.

Speaker: Ms Sakshi Kakkar (Department of Physics and Astronomy, University of Manitoba, Winnipeg, MB & TRIUMF - 4004 Wesbrook Mall, Vancouver, BC )

633 (G*) KDK: Measuring the unique third forbidden electron capture decay of K-40 for backgrounds in rare-event searches

Potassium-40 ($^{40}$K) is a long-lived, naturally occurring radioactive isotope. The decay products are prominent backgrounds for many rare event searches, especially those involving NaI-based scintillators (ex. DAMA, SABRE, COSINUS etc.). The branching ratio of the electron capture directly to the ground state of Argon-40 has never been experimentally measured and presents an unknown background directly in the 2 - 6 keV energy signal region which needs to be understood. This branching ratio also has important implications for nuclear physics and geochronology. KDK (Potassium (K) Decay (DK)) is an international collaboration dedicated to this measurement. The experiment is performed using a silicon drift detector with a thermally deposited, enriched $^{40}$K source inside the Modular Total Absorption Spectrometer (MTAS, Oak Ridge National Laboratory). MTAS is a large NaI detector whose high gamma-ray efficiency enables the proper discrimination between ground and excited state electron capture events. This setup has been characterized in terms of energy calibration, tagging efficiency and dead time (arXiv:2012.15232). We report on the analysis method and sensitivity for a 44-day $^{40}$K physics run.

Speaker: Matthew Stukel (Queen's University)

R3-5 Contributed Talks VI (DCMMP) / Conférences soumises VI (DPMCM)

Convener: Michel Gingras

634 Inferring potentials in a feedback-trap using machine learning

Optical tweezers are an essential tool in a broad range of fields, from biophysics to soft-matter and statistical physics. Using a feedback-based trap that can produce complex, time-dependent potential landscapes, we can experimentally realize situations in thermodynamics, such as finite-time bit-erasure, that were previously only thought experiments. To obtain quantitative results, however, it is crucial to know the optical tweezer’s original potential accurately. We use Gaussian process (GP) regression, a machine learning technique, to infer potentials in a feedback-trap. This method requires fewer data points to reach the same accuracy than more commonly used methods. GPs can estimate the potential without making prior assumptions on its shape and predict the sparsely explored regions. It also estimates the noise level in the data and provides uncertainties in the inferred potential. We trap a silica bead in different forms of potential using a feedback tweezer and record its displacement using two detectors simultaneously. We vary the amount of measurement noise in one of the detectors and then compare how accurately GP can estimate the potential in the presence of higher measurement noise. We find that GP performs better than standard methods to infer complex-shaped potentials in noisier situations.

Speaker: Prithviraj Basak (Simon Fraser University)

15:48 Questions & answers

635 (G*) Moiré patterns in graphene and transition metal dichalcogenide heterostructures

Vertically stacked heterostructures of two-dimensional materials provide a platform for realizing novel electronic states due to proximity effects. In particular, moiré patterns in two-dimensional material heterostructures have been shown to create flat bands that favor the occurrence of correlated electronic states. In this work, we use scanning tunneling microscopy and spectroscopy to study moiré patterns in mechanically assembled heterostructures of graphene and transition metal dichalcogenides. By comparing to a theoretical model, in the case of graphene - ReS2 heterostructures we find the presence of stripped moiré patterns, reflecting the different crystal symmetry of the two lattices.

The experimental work was supported by: National Sciences and Engineering Research Council (NSERC) No. RGPIN-2016-06717, No. 521420 and NSERC Scholarship program. Theory work was supported by Singapore Ministry of Education AcRF Tier 2 (No. MOE2017-T2-2-140).

Speaker: Laurent Molino (University of Ottawa)

15:53 Questions & answers

636 (G*) Towards 2D materials as Quantum Nano-Electromechanical Systems

Two dimensional (2D) materials are tempting for nano-electromechanical systems (NEMS), as they are atomically thin, have low mass and high flexibility. 2D materials have tunable optical and electronic properties, and can display other exotic properties, such as superconductivity. Over the last decade, scientists have begun stacking 2D materials into heterostructures that have desirable properties. One heterostructure is twisted bilayer graphene (TBG), which is comprised of two monolayers of graphene stacked at a rotated angle. If the angle of rotation is 1.1 degree, this material can display superconductivity at cryogenic temperatures.

The goal of this work is to model 2D drums, and to prepare sample fabrication techniques for NEMS devices. We developed analytic and numerical approximations for the motion of a 2D drum resonator. We use thin plate solutions due to a non-zero bending rigidity, and assumed low strain . We contrasted these solutions to linear and nonlinear membranes, where tension forces dominate. We consider nonlinearities inherent in the deflection driven by electrostatic forces and where strain dominates over rigidity. We also describe how finite element models can be constructed in Comsol, where the vanishing thinness makes conventional models impractical. These agree with the analytic plate approximations.

We use flake exfoliation, pick up and placement methods to fabricate heterostructures. We produce graphene flakes via mechanical exfoliation from low residue tape. We detail techniques for optimized cleanliness and monolayer production. The flake pick up is verified via optical and atomic force microscopy (AFM). Our eventual aim is to study a 2D material when it forms the top plate of a capacitor in an LC circuit – allowing a light mass resonator for quantum nanomechanics.

Speaker: Nathan Eddy (Queens University)

15:58 Questions & answers

637 Control of Aryldiazonium Reactions on Graphene Field-Effect Transistors

Introduction: Graphene is a promising nanomaterial for chemical sensors or biosensors, but functionalization of its surface is usually necessary to ensure specific interactions with the chosen analyte. Among functionalization strategies, covalent adducts are most likely to ensure stability of the functionalization during multiple flow cycles. In particular, aryldiazonium salts are known for their high reactivity with carbon allotropes. In single-walled carbon nanotubes, spontaneous covalent reactions with this reagent have been observed, notably via a strong diminution of conductance in electrical measurements and increase of D/G intensity ratio in Raman spectroscopy. However, results of this same reaction with graphene have been far less consistent, with mixed signatures of both chemisorption (covalent) and physisorption (non-covalent). This highlights the need to better understand and control aryldiazonium functionalization of graphene.

Methods and Results: Here we present novel experimental data to disambiguate the effect of aryldiazonium functionalization on graphene transport properties. We assembled an experimental setup to address an array of graphene field-effect transistors (GFETs), both simultaneously and individually. These GFETs were made of graphene grown by chemical vapor deposition (CVD), operated using a coplanar electrode in saline buffer, and functionalized with 4-carboxylbenzene diazonium tetrafluoroborate. The potential applied on the gate was varied during functionalization, which was monitored through electrical measurements and hyperspectral Raman imaging. We report a strong variation in the rate and yield of formation of covalent adducts with gate potential.

Conclusion and Significance: By incorporating past and recent experiments, we were able to explain and control graphene reactivity to the aryldiazonium chemistry with electrostatic potential. These results will be instrumental for improving the functionalization of graphene FETs with stable covalent adducts for chemical and biological sensing applications.

Speaker: Anouk Béraud (Université de Montréal)

16:03 Questions & answers

638 (G*) Theoretical study of strain and superconductivity in Sr2IrO4

Several parallels can be drawn between the perovskite iridate Sr$_2$IrO$_4$, and the high Tc cuprates. Although the low energy spectrum of Sr$_2$IrO$_4$ includes the three t$_{2g}$ bands, strong spin-orbit coupling splits the bands such that one can write an effective one-orbital J=1/2 model, in analogy with the single orbital of the cuprates. This has led to predictions of d-wave superconductivity in Sr$_2$IrO$_4$ upon electron doping. A three-orbital Hubbard model finds that the pairing is dependent on the interorbital interactions, therefore, an effective one orbital model may be insufficient in describing the superconducting state. In this work we investigate the multiorbital properties of Sr$_2$IrO$_4$, both with and without doping, under compressive epitaxial strain. Strain modifies lattice constants and bond orientations. The strain is modeled by modifying the orbital dependent hopping amplitudes and can therefore tune the bandwidths of the different bands. By applying a multiple order parameter, self-consistent mean-field approach we study the magnetic structure and pairing symmetry of Sr$_2$IrO$_4$ under strain and carrier doping. We comment on ways to increase the chance of superconductivity.

Speaker: Lena Engström (McGill University)

16:08 Questions & answers

639 Quantum Many-body Scars seen through the lens of Entanglement Spectroscopy.

According to the laws of thermodynamics, a closed many-body system is expected to follow a chaotic evolution and reach a state of thermal equilibrium. The issue arises when one asks for a quantum picture. Indeed quantum mechanics strictly prohibits chaotic dynamics, and some quantum systems have been discovered to resist thermalization.
To solve this paradox, entanglement is believed to be a key ingredient. We hope to adress these deep questions in the context of a phenomenon called "Quantum Many-body Scars" recently observed in trapped ions setup (Bernien et al., Nature 2017). In this experiment, starting from a very ordered unentangled state, strong local constraints give rise to a non-trivial quantum dynamics characterized by long-time oscillations and a very slow thermalization.
Using a simple model called PXP we are able to study this unusual dynamics at long times through the lens of entanglement. We use a random-matrix-based diagnosis of the entanglement structure called entanglement spectrum statistics which allows us to characterize both the scrambling and complexity underlying these quantum scars.

Speaker: Martin Schnee (Université de Sherbrooke)

16:13 Questions & answers

640 Electrostatically gated quantum dots in van der Waals materials

Quantum confinement and manipulation of charge carriers are critical for achieving devices practical for various quantum technologies. Atomically thin transition metal dichalcogenides (TMDCs) have attractive properties such as spin-valley locking, large spin-orbit coupling and high confinement energies which provide a promising platform for novel quantum technologies. In this talk, we present the design and fabrication of electrostatically gated quantum structures based on fully encapsulated monolayer tungsten diselenide (WSe2) aimed at probing the confined electron states in these structures. Furthermore, we show that laterally gated quantum point contacts successfully pinch-off the current across the device with gate voltages consistent with their lithographic widths. Finally, we discuss the origins of the observed mesoscopic transport features related to the emergence of the quantum dots through the WSe2 channel.

Speaker: Justin Boddison-Chouinard (University of Ottawa)

16:18 Questions & answers

R3-6 Detector Technology and Design (DAPI) / Technologie et conception de détecteurs (DPAI)

Convener: Ian Lawson (SNOLAB)

641 Water Cherenkov Test Experiment

Water Cherenkov Test Experiment (WCTE) is a proposed experiment at CERN that will study the response of a small water Cherenkov detector in hadron, electron, and muon low momentum beams. The aim of the experiment is to test new photosensor technologies such as multi-PMT modules and apply calibration techniques with known particle fluxes to validate $1\%$ level calibration at the GeV scale. Additionally, we will measure physics processes such as Cherenkov light production, pion scattering, and secondary neutron production. Precise calibration and accurate measurements of physical processes inside the detector are of utmost importance for the success of Hyper-Kamiokande, the next generation long-baseline neutrino experiment in Japan. This talk describes the WCTE physics program and detector design.

Speaker: Dr Matej Pavin (TRIUMF)

mpavin_WCTE_cap_long.pdf

mpavin_WCTE_cap.pdf

642 Measuring the absorption length of the deep Pacific Ocean: Results from STRAW, a pathfinder mission for the proposed P-ONE neutrino telescope

In the search for astrophysical neutrinos, neutrino telescopes instrument large volumes of clear natural water. Photomultiplier tubes placed along mooring lines detect the Cherenkov light of secondary particles produced in neutrino interactions, and allow us to search for possible neutrino sources in the sky. The P-ONE experiment proposes a new neutrino telescope off the shore of British Columbia.

To overcome the challenges of a deep-sea installation, we have developed prototype mooring lines in collaboration with Ocean Networks Canada, an initiative of the University of Victoria, which provides the infrastructure for many Oceanographic instruments. The STRAW and STRAW-b mooring lines, deployed in 2018 and 2020, provide continuous monitoring of optical water properties at a new possible detector site in the Pacific.

We present the measurements of the attenuation length, one of the defining properties of the site, based on data taken by the STRAW experiment.

Speaker: Andreas Gaertner (University of Alberta)

agaertner_cap.pdf

643 (G*) Characterization of wavelength shifters for background rejection in liquid argon dark matter experiments

Liquid Argon (LAr) is used as a target material by many WIMP dark matter search experiments for its high light-yield and excellent background rejection capability. LAr produces scintillation light at 128nm, which conventionally requires a wavelength shifting (WLS) material to be detected by photomultiplier tubes. Tetraphenyl-butadiene (TPB) is the WLS material of choice for most LAr detectors, including DEAP-3600 at SNOLAB, and is used to shift the primary scintillation light. Our work aims to characterize candidate thin films containing pyrene developed at Carleton University. Their long fluorescence time constant can be used for efficient rejection of pathological detector backgrounds. Fluorescence yield and mechanical stability in cryogenic conditions are also investigated. We describe the Queen's University cryogenic test facility which boasts good optical efficiency and a base temperature of 4K. We present results from pyrene thin films with various concentrations and purity as well as TPB as a reference.

Speaker: Hicham Benmansour (Queen's Univeristy)

644 (G*) High Voltage Breakdowns in Liquid Xenon

Liquid xenon (LXe) is frequently employed to build detectors for rare event searches due to many of its advantageous properties including high stopping power, high ionization and scintillation yields, and relatively high cryogenic operating temperature. Time projection chambers (TPC) with LXe allow for 3D event topology reconstruction and identification which is important for reducing backgrounds. Due to the high drift fields TPCs are operated at, it is crucial to model breakdown properties in LXe. Often, a high voltage (HV) discharge is able to damage the detector instrumentation, e.g. the photo-sensors array. We study the breakdown formation in the context of the EXO-200 experiment, the first generation 0νββ search experiment from the Enriched Xenon Observatory (EXO) collaboration that will be followed by a much higher sensitivity experiment called nEXO. In the EXO-200 detector, instabilities have been observed on the TPC HV line, each accompanied by scintillation VUV light which was detected by the EXO-200 Avalanche Photo Diode (APD) arrays. Using a setup designed to study LXe breakdowns we investigate the origin of the HV instabilities as well as the correlation between those HV glitches and fully formed breakdowns.

Speaker: Mohamed Elbeltagi (Carleton University)

645 (G*) Nuisance Processes in p-on-n SiPMs

Silicon Photo-Multipliers (SiPMs) have emerged as a compelling photo-sensor solution over the course of the last decade. SiPMs consist of an array of tightly packed microcells with each microcell acting as an avalanche photodiode that can behave in the Geiger mode regime when the device is reverse biased above a threshold voltage (breakdown voltage). In contrast to the widely used Photomultiplier Tubes (PMTs), SiPMs are low voltage powered, optimal for operation at cryogenic temperatures, and have low radioactivity levels with high gain stability over the time in operational conditions. For these reasons, large-scale low-background cryogenic experiments, such as DarkSide and nEXO plan to use this type of photodetector for their dark matter and neutrinoless double beta decay search. Despite their excellent Photon Detection Efficiency (PDE) SiPMs suffer however from Dark and correlated avalanche noise (After Pulse and Cross-Talk) that can reduce their pulse counting characteristics. In order to optimize the performances of new generation of SiPMs and to understand the noise characteristics of the existing ones in this talk we will propose a new physics motivated model to explain the over voltage dependence of the SiPM nuisance processes i.e. Dark Noise, After Pulse and Cross-Talk. The starting point is the extraction of the electron and hole avalanche triggering probabilities. Then we show that we can describe the over-voltage dependence of these three processes using a minimum set of parameters. In particular we will explain how it is possible to use the over voltage dependence to discriminate the type of carrier that initialise the avalanche and therefore extract the relative contribution of electrons vs holes in p-on-n SiPMs. In the talk we will show preliminary results for the characterization of the Hamamatsu VUV4 MPPC one Fondazione-Bruno-Kessler (FBK) SiPM.

Speaker: Giacomo Gallina (TRIUMF)

R3-7 Machine learning in HEP & Novel reconstruction techniques II (PPD) / Apprentissage automatique en PHE et nouvelles techniques de reconstruction II (PPD)

Convener: Eric Drechsler (Simon Fraser University (CA))

646 (I) Machine Learning Applications in Particle Physics: Present and Future

In this overview I'll present a selection of recent machine applications to event reconstruction and data analysis across the subfields of experimental particle physics. Strategies for treatment of experimental data and design of machine learning algorithms will be discussed. I will give a personal perspective on potential future particle physics applications of machine learning, including real-time evaluation for triggering and the deployment of generative models

Speaker: Wojtek Fedorko (TRIUMF)

ML_in_HEP.pptx

647 Pulse Shape Discrimination in DEAP-3600

DEAP-3600 is a sensitive single-phase liquid-argon detector of non-baryonic dark matter at SNOLAB. WIMP-nucleon scattering is distinguished from electromagnetic events by pulse shape discrimination (PSD) in the argon. Nuclear recoils, which have high ionization density, preferentially excite a singlet argon dimer state which decays via VUV emission in nanoseconds. Electromagnetic events, which have low ionization density, preferentially excite a triplet state which decays with a time constant of 1.445 microseconds. This difference allows for excellent separation of the two classes of events.

The liquid argon in DEAP-3600 is contained in a 85cm-radius acrylic sphere that is coated on the inside with 1,1,4,4-tetraphenyl-1,3-butadiene (TPB) which is as a wavelength shifter, efficiently absorbing the VUV light and re-emitting in the blue. The blue light travels through the acrylic vessel and acrylic light guides to 255 Hamamatsu R5912 HQE PMTs.

The pulse shapes and therefore the PSD is complicated by instrumental effects including the presence of long-lived states of TPB and PMT effects including late pulsing, after pulsing, and dark noise. Recent studies of the pulse shape and PSD will be discussed including the effect of removal of PMT effects in events before applying the PSD algorithms. Two PSD algorithms are discussed: 1) a prompt-fraction parameter and 2) a likelihood estimator. A comparison will be given.

Speaker: Chris Jillings (SNOLAB)

Jillings-DEAP-3600-PSD.pdf

648 Event Reconstruction in DEAP-3600 at SNOLAB

DEAP-3600 is a low-background, single-phase liquid argon (LAr) direct detection experiment looking for nuclear recoils from WIMP dark matter, operating 2 km underground at SNOLAB (Sudbury, Canada). The detector consists of 3279 kg of LAr contained in a spherical acrylic vessel. LAr is an excellent scintillator, transparent to its own scintillation light. Photomultiplier tubes detect the scintillation light, and pulse shape discrimination is applied to differentiate between nuclear recoils and electromagnetic interactions (the most abundant backgrounds, which predominantly come from the beta-decay of Ar39). The ‘Event Reconstruction’ methodology used to analyse events in the DEAP-3600 detector, significantly utilizes a detector model based on detailed optical and DAQ simulation. DEAP-3600 data is converted to a set of times and charges for pulses in each PMT. From that information, we have algorithms that reconstruct the position. One algorithm is based on the spatial distribution of the integrated charge in PMTs; the second algorithm is based on the time of flight in the first 40 nanoseconds of an event. The algorithms will be described and the performance compared. The algorithms give very consistent result for light due to scintillation events in the main detector volume; but disagreement is used to reject events that arise from shadowed geometries. I will present an overview of the event reconstruction methodology and will discuss the recent improvements in the pulse shape analysis techniques as well as time based event reconstruction techniques.

Speaker: Dr Sumanta Pal (University of Alberta)

CAP-2021-DEAP-SPAL.pdf

649 (G*) Using machine learning techniques to search for magnetic monopoles in ATLAS

Among the outstanding questions of particle physics, proof of the existence of a magnetic monopole is still one of great interest. Not only would the observation of a magnetically charged particle grant symmetry between electric and magnetic fields in Maxwell’s equations, but it would also explain the quantization of the electric charge. We are searching for TeV-mass magnetic monopoles in the ATLAS detector using the full set of data collected from 13 TeV pp collisions during Run 2 of the LHC. Detection is based on the particles’ characteristic high ionization, penetration distance and lack of calorimeter shower. The increase in the average number of collisions per bunch crossing during the last 2 years of Run 2 brought the challenge of isolating the monopole high energy depositions in the inner detector. In order to overcome this challenge, we introduce a random forest classifier trained on region of interest wedges of the transition radiation tracker (TRT) against a random wedge of the TRT in the same event - same pileup conditions. We achieve discrimination power equivalent to that of the traditional cut-and-count method applied in previous searches.

Speaker: Ana Maria Rodriguez Vera (York University (CA))

CAP_2021_HIP_AMRV.pdf

16:30 15 Minute Break

R4-1 EDI (DPE/DGEP) / EDI (DEP/DEGP)

Conveners: Chitra Rangan (University of Windsor), Daria Ahrensmeier (Simon Fraser University)

650 (G*) Closing the Gender Gap in Physics and Engineering: The Role of High School Physics

Recent decades have seen many advances towards gender parity in the fields of science, technology, engineering, and mathematics (STEM). But while biology, chemistry, and mathematics have all achieved >40% female undergraduate enrollment, there remains a significant dearth of women in physics and engineering. Both disciplines have plateaued at ~20% women since the mid-nineties. This issue, however, does not begin at university. Grade 10 science, the last mandatory science credit for most Canadian students, coincides with the single largest loss of potential female physicists. To better characterize the current state of Canadian STEM education, gendered, school-level enrollment data has been collected for all secondary schools across Ontario. This data was then combined with the Canadian census to provide detailed demographic information about each school catchment areas. Demographic factors such as socioeconomic status, immigrant status, and major employment sectors can all impact the gender gap at a given school. This talk will present the results from a statistical analysis of this novel data set, providing a detailed picture of who is and isn’t taking high school physics.

Speaker: Eamonn Corrigan (University of Guelph)

651 (I) Equity, Diversity, and Inclusion in Physics — a Career Perspective

Concern about the inclusion and fair treatment of all individuals wishing to pursue a degree in science is perhaps stronger now that it has ever been. Examples include studies related to pay equity, conferences for women in STEM disciplines, and NSERC’s new guidelines regarding Equity, Diversity, and Inclusion. The situation is regarded as particularly acute in Physics, where males still numerically dominate at all levels of post-secondary education.

I shall provide a somewhat personal perspective, describing how I have addressed these issues in my teaching and my research in my career, particularly with regard to graduate supervision and training. The goal is to open a dialogue as to how these issues might best be addressed in practical terms, and how we might distinguish the real issues from some current narratives that may have come from various theoretical studies.

Speaker: Robert Mann (University of Waterloo)

R4-2 Quantum Information: Theory (DTP) / Information quantique: théorie (DPT)

Convener: Barry Sanders (University of Calgary)

652 (I) Quantum Theory of Polarized Light

Polarimetry is a wildly-used measurement technique for inferring properties of a sample by observation of the changes in the polarization of the light transmitted or reflected by the sample. One of the impediments to wider use of the technique, especially in bio-medical applications such in-vivo biopsy, is that it can require very high laser intensities, leading to collateral tissue damage. As has been known for some time, by using quantum states of light, in which the individual photons are correlated rather than being independent of one another, one can in principle dramatically improve the signal to noise ratio in optical interferometry. Since polarized light can be understood as an interference phenomenon involving two light modes (i.e. the two orthogonal directions of field oscillation), it is natural to suppose that perhaps such a quantum advantage might apply to polarimetry as well.

In this presentation I will discuss my group’s recent work aimed at understanding, characterizing and exploiting the quantum polarization properties of light. The work is set in the context of leveraging the technology developed for quantum communications and quantum information processing and offers at least a chance for a truly useful and widely deployable application of the current revolution in quantum technologies.

Speaker: Daniel James (University of Toronto)

653 (I) Additive quantities cannot be more than asymptotically continuous

In this talk, we show that any non-constant quantity defined on density matrices that is additive on tensor products and invariant under permutations cannot be "more than asymptotically continuous."The proof is a direct consequence of generalizing a protocol for embezzling entanglement. Joint work with Andrea Coladangelo.

Speaker: Debbie Leung (University of Waterloo)

654 (I) Entanglement and Bell nonlocality are one and the same

Bell nonlocality describes a manifestation of quantum mechanics that cannot be explained by any local hidden variable model. Its origin lies in the nature of quantum entanglement, although understanding the precise relationship between nonlocality and entanglement has been a notorious open problem. In this talk, I will describe a resolution to this problem by developing a dynamical framework in which quantum Bell nonlocality emerges as special form of entanglement, and both are unified as resources under local operations and classical communication (LOCC). The framework is built on the notion of quantum processes, which are abstract quantum channels mapping elements between fixed intervals in space and time. Entanglement is then identified as a quantum process that cannot be generated by LOCC while Bell nonlocality is the subset of these processes that have an instantaneous input- output delay time. LOCC pre-processing is a natural set of free operations in this theory, thereby enabling all entangled states to activate some form of Bell nonlocality.

Speaker: Gilad Gour (University of Calgary)

655 (G*) Entanglement Amplification from Rotating Black Holes

The quantum vacuum has long been known to be characterized by field correlations between spacetime points. These correlations can be swapped with a pair of particle detectors, modelled as simple two-level quantum systems (Unruh-DeWitt detectors) via a process known as entanglement harvesting. We study this phenomenon in the presence of a rotating BTZ black hole, and find that rotation can significantly amplify the harvested vacuum entanglement. Concurrence between co-rotating detectors is amplified by as much as an order of magnitude at intermediate distances from the black hole relative to that at large distances. The effect is most pronounced for near-extremal small mass black holes, and allows for harvesting at large spacelike detector separations. We also find that the entanglement shadow – a region near the black hole from which entanglement cannot be extracted – is diminished in size as the black hole’s angular momentum increases.

Speaker: Matthew Robbins (University of Waterloo/Perimeter Institute)

656 (G*) Harvesting Entanglement inside a Black Hole

We carry out the first investigation of the entanglement and mutual information harvesting protocols for detectors moving on freely falling trajectories that cross the horizon of a black hole. We consider two pointlike Unruh-DeWitt detectors in different combinations of free-falling and static trajectories in (1+1)-dimensional Schwarzschild black hole spacetime and compare the results. We find that (i) correlations harvested between free-falling and static detectors are always less than those of the familiar two-static-detector case (ii) there is a large kinematic component to the correlations; (ii) correlations can be harvested purely from the quantum vacuum, with evidence that this is possible even when the detectors are causally disconnected by the event horizon; (iii) the previously known `entanglement shadow' near the horizon is indeed absent for the two free-falling-detector case since the relative gravitational redshift of the detectors remains finite as the horizon is crossed, in accordance with the equivalence principle.

Speaker: Kensuke Gallock-Yoshimura (University of Waterloo)

657 Quantum Temporal Superposition: the case of QFT

Quantum field theory is completely characterized by the field correlations between spacetime points. In turn, some of these can be accessed by locally coupling to the field simple quantum systems, a.k.a. particle detectors. In this work, we consider what happens when a quantum- controlled superposition of detectors at different space-time points is used to probe the correlations of the field. We show that, due to quantum interference effects, two detectors can gain information on field correlations which would not be otherwise accessible. This has relevant consequences for information theoretic quantities, like entanglement and mutual information harvested from the field. In particular, the quantum control allows for extraction of entanglement in scenarios where this is otherwise provably impossible.

Speaker: Laura Henderson (University of Waterloo)

17:09 Questions/Answers and Discussion Period

R4-3 Nuclei & Mesons (DNP) / Noyaux et mésons (DPN)

Convener: Alexandros Gezerlis

658 (I) The Pb Radius and Ca Radius Experiments (PREX and CREX)

In this talk I will provide motivation for determining the neutron radius of heavy nuclei, and why PREX II and CREX provide theoretically clean measurements in lead-208 and calcium-48. This will include a description of parity-violating electron scattering experimental design and efforts to minimize the systematic uncertainties. The neutron skin measurement on lead provides information about the neutron matter equation of state at nuclear densities, which is complemented by the measurement on calcium where ab initio nuclear structure calculations can be performed. These measurements are relatively free from strong interaction uncertainties because the electron probe does not interact via the strong force. The results at nuclear densities can be compared to astrophysical measurements of neutron star radii. I will present results for the PREX II experiment, and provide preliminary results from CREX.

Speaker: Juliette Mammei (Thomas Jefferson National Accelerator Facility)

659 (G*) Charged Pion Form Factor – A Unique Precision Experiment at Jefferson Lab

Hadronic structure is poorly understood as the properties of constituent quarks and gluons (e.g. spin, mass) do not explicitly add up to the properties of hadrons. The form factor describes the transverse position of partons inside a hadron. Perturbative QCD (pQCD) uniquely predicts the form factor at very high Q2, which is experimentally inaccessible. Different non-perturbative QCD models give the same prediction for the value of form factor at low Q2, but these predictions vary at moderate Q2 where published experimental data is limited. The pion is an excellent candidate for the study of the hadronic form factor as it is the lightest charged meson and has only two valence quarks. In this research, an exclusive reaction p(e,e′,𝜋+)n is studied at Thomas Jefferson National Accelerator Facility in Newport News, VA. The cross-section is dictated by the polarization of virtual photon. A unique technique, Rosenbluth Separation, is used to precisely separate the longitudinal and transverse components of the cross-section. The form factor is then extracted from longitudinal cross-section. The precision of separation of cross-section depends on accurate determination of small systematic uncertainties. This includes Particle Identification (PID), Particle reconstruction, dead time estimation etc. In this talk, I will discuss importance of the Rosenbluth separation technique and show the status of Pion form factor measurements performed at Jefferson Lab.

Speaker: Ali Usman (University of Regina)

CAP_2021.pdf

660 Probing New Physics Using $\eta$ Mesons at the Jefferson Lab Eta Factory

The $\eta$ meson offers the opportunity to probe a wide range of physics owing to its unique combination of additive quantum numbers, narrow mass width, and flavor-conserving decays. In particular, the $\eta$ meson provides a portal to look for beyond standard model (BSM) dark sector bosons, constraints to C-violating P-conserving physics, high precision tests of low-energy QCD descriptions, and access to the light quark mass ratio. The GlueX spectrometer at Jefferson Lab offers a high-statistics sample of photoproduced $\eta$ mesons and a unique degree of forward boosting in the lab frame ($p_{\eta}\approx 8$ GeV) to suppress wider-angle preferred backgrounds. Furthermore, the near-future Jefferson Eta Factory (JEF) experiment plans to improve photon position and energy resolution at small polar angles to improve sensitivity in key decay channels. We present the current status of $\eta$ measurements using the GlueX spectrometer and key objectives of the JEF experimental upgrade.

Speaker: Jonathan Zarling (University of Regina)

R4-4 Calibration and Analysis for rare event searches (PPD) / Calibration et analyse pour la recherche d'événements rares (PPD)

Convener: Juan-Pablo Yanez (University of Alberta)

661 (G*) Simulation-based Studies of Fiducialization and Potential Directionality for the NEWS-G Experiment

NEWS-G is a direct detection dark matter experiment specializing in low mass (sub ~1 GeV) WIMP (Weakly Interacting Massive Particles) searches. NEWS-G uses spherical proportional counters (SPCs) - gas-ionization detectors capable of observing signals from single-electrons through the use of a small (~1 mm radius) high-voltage anode sensor at their centre. With the increasingly complex nature of the sensory equipment used with large-scale SPCs, which use an improved 11-anode ACHINOS sensor, study of detector properties through simulation is needed to corroborate results of data analyses. The ACHINOS sensor groups anodes using 2-3 electronic channels, discriminating event signals by detector volume. Electronic drift simulation of the sensor-wise distribution of event-by-event primary electrons allows for the characterization of the fiducial volume for each channel. Improvements to ACHINOS sensors, supported by simulation, could allow for SPC detector directionality via finer volume discrimination. This talk will demonstrate the implications of using an 11-anode ACHINOS sensor within a large (~135 cm radius) SPC through simulation, focusing on detector fiducialization and the feasibility of SPC directionality with greater multi-channel ACHINOS sensors.

Speaker: Carter Garrah (University of Alberta)

Carter_Garrah_CAP_2021_Slides_Simulation-based_Studies_NEWS-G.pptx

662 Ionization yield for nuclear recoils in silicon at TUNL and Université de Montréal

SuperCDMS (Super Cryogenic Dark Matter Search) is an experiment for the direct detection of dark matter that uses cryogenic silicon and germanium detectors which can measure energy depositions as low as a few eV. The ionization yield for nuclear recoils is the ratio of the number of electron-hole pairs produced by a nuclear recoil over the number of electron-hole pairs produced by an electronic recoil of the same energy. The IMPACT experiment (Ionization Measurement with Phonons At Cryogenic Temperatures) uses a silicon SuperCDMS HVeV detector to measure the ionization yield of nuclear recoils in silicon below the recoil energies reached by previous calibrations. In order to do so, we used a 55.7 keV neutron beam on our detector at TUNL as well as 29 liquid scintillator detectors placed at various angles to the beam to detect the scattered neutrons. By comparing the energy deposited in our HVeV detector to the expected energy from the scattering angle at different voltages, we can measure the ionization yield for nuclear recoils in silicon for energies between 0.1 and 4 keV. No results currently exist for recoil energies < 0.7 keV. We plan on expanding the experiment at Université de Montréal with a 4.8 keV neutron beam and a borated liquid scintillator array.

Speaker: Emile Michaud (University of Montreal)

presentation_ACP_2021_v3.pdf

663 (G*) A Modern High-Precision Calculation of Deep Underground Cosmic Ray Muons

We present a new efficient calculation to propagate cosmic ray muons from the surface of the Earth to deep underground laboratories, allowing us to look at the physics and performance of various models of high-energy cosmic rays. The evolution of cosmic rays in the Earth's atmosphere is computed with MCEq (Matrix Cascade Equation), taking into account different combinations of primary and hadronic interaction models in order to calculate the muon flux at the surface. The latter serves as an input for the Monte Carlo code PROPOSAL (Propagator with Optimal Precision and Optimised Speed for All Leptons) to propagate the muons through the rock. A forward prediction for underground muon spectra at different slant depths, including the muon survival probabilities and underground energy spectra, is calculated with very high precision. The reliability of this state-of-the-art calculation was achieved by comparing the results obtained for the vertical muon intensity and total muon flux with the measured data at various underground sites with both flat overburdens and mountains. The implications of the results as well as the seasonal variation of the muon flux will also be discussed.

Speaker: Mr William Woodley (University of Alberta)

A Modern High-Precision Calculation of Deep Underground Cosmic Ray Muons.pdf

664 (G*) Alpha background rejection in DEAP-3600 using slow wavelength shifters

The DEAP-3600 experiment (Dark matter Experiment using Argon Pulseshape discrimination) at SNOLAB in Sudbury, Ontario is searching for dark matter by recording their interactions with a liquid argon target. It is designed to detect nuclear recoils induced by the elastic scattering of weakly interacting massive particles (WIMPs) - a leading candidate for dark matter.

Minimizing backgrounds is important for acquiring high sensitivity to dark matter. An example of a background source is an alpha decay which can produce a signal mimicking a dark matter signal. DEAP-3600 uses pulse shape discrimination (PSD) to distinguish between signal events and backgrounds. Prompt light (light coming early to the PMTs) versus total light in the pulse - called fprompt - is used as a discrimination parameter.

The detector setup includes a neck region that has flowguides made of acrylic. Alpha decays are produced in the flowguides from naturally occurring radioactive isotopes in the acrylic. These decays scintillate in the liquid argon (which is in the form of mist or condensate layer around the flowguides) and form a major background component in DEAP. In the upcoming hardware upgrades to DEAP-3600, the flowguides will be coated with a wavelength shifter having a slow time constant which could help move these neck alphas out of the WIMP ROI (region of interest) and increase our WIMP sensitivity. Monte Carlo simulations are used to model the ROI acceptance of the neck alphas with the slow wavelength shifter in place and in this talk, I will present the status of this work which includes measurements of the optical properties relevant for the simulations.

Speaker: Mr Shivam Garg (Carleton University)

ShivamGarg_CAPtalk_10June2021.pptm

ShivamGarg_CAPtalk_10June2021_upload.pdf

Congress Closing Session

F-PPD Annual Business Meeting (PPD) / Réunion d'affaires annuelle (PPD)

Convener: Marie-Cécile Piro (University of Alberta)

Friday 11 June

10:45 See 17h30 time slot below for Post-Congress scheduled events / meetings

F1-1 Joint CINP-IPP Session / Session conjointe ICPN-IPP

Zoom Meeting:
https://uvic.zoom.us/j/85895599784?pwd=dng3MG5nTDYwWTdHTWpvTytmN2tJdz09

Conveners: Garth Huber (University of Regina), Michael Roney (University of Victoria)

665 NSERC SAPES Chair Report (20 min + 5 min for questions)

Speaker: Alison Lister (University of British Columbia (CA))

CAP 2021 - Presentation by SAPES Co-Chair.pdf

666 CFI Report (10 min + 5 min for questions)

Speaker: Olivier Gagnon (Fondation canadienne pour l'innovation)

CFI CAP_June 2021.pdf

667 TRIUMF Director Report (20 min + 5 min for questions)

Speaker: Nigel Smith (TRIUMF)

2021-06-11 CINP-IPP TRIUMF.pdf

668 SNOLAB Director Report (15 min + 5 min for questions)

Speaker: Clarence Virtue (SNOLAB)

2021 CINP-IPP SNOLAB.pdf

669 McDonald Institute Update (10 min + 5 min for questions)

Speaker: Tony Noble (Queen's University)

MI Report to IPP AGM.pdf

MI Report to IPP AGM.pptx

670 SAP LRPC (25 min + 15 min for questions)

Speakers: Adam Ritz, Brigitte Vachon (McGill University, (CA))

2021-06-11-CAP-slides-v4.pdf

13:50 General Discussion period

14:10 Break

F2-1 CINP AGM

Convener: Garth Huber (University of Regina)

F-DAMOPC Annual Business Meeting (DAMOPC) / Réunion d'affaires annuelle (DPAMPC)

Convener: Nisha Agarwal (University of Ontario Institute of Technology)

F-DPP Annual Business Meeting (DPP) / Réunion d'affaires annuelle (DPP)

Convener: Lenaic Couedel (University of Saskatchewan)

F-DNP Annual Business Meeting (DNP) / Réunion d'affaires annuelle (DPN)

Convener: Corina Andreoiu (Simon Fraser University)

June 14 (Mon), 13h00-15h00 EDT - Annual Business Meeting (DTP) / Réunion d'affaires annuelle (DPT)

Convener: Mark Walton (University of Lethbridge)

June 15 (Tues), 13h00-15h00 EDT - Annual Business Meeting (DAPI) / Réunion d'affaires annuelles (DPAI)

Convener: Steffon Luoma

June 16 (Wed), 13h00-14h00 EDT - Annual Business Meeting (DHP) / Réunion d'affaires annuelle (DHP)

Convener: Patrick Clancy (McMaster University)

June 17 (Thurs), 13h15-15h30 EDT - 2021 CAP Best Student Oral Competition Finals and Award Presentations (16h30-17h30 EDT) / 13h15-15h30 HAE Finales du concours oral du meilleur étudiant de l'ACP 2021 et présentation des prix (16h30-17h30 HAE)

Conveners: Barbara Frisken (Simon Fraser University), Robert Thompson (University of Calgary)

June 21 (Mon), 16h00-17h30 EDT - Annual Business Meeting (DPMB) / Réunion d'affaires annuelle (DPMB)

Convener: Ozzy Mermut (York University)

June 23 (Wed), 14h30-16h15 - Annual Business Meeting (DGEP) / Réunion d'affaires annuelle (DEGP)

Convener: Chitra Rangan (University of Windsor)

June 28 (Mon), 13h00-15h00 EDT - Annual Business Meeting (DPE) / Réunion d'affaires annuelle (DEP)

Convener: Daria Ahrensmeier (Simon Fraser University)

June 29 (Tues), 14h30-16h15 EDT - CAP Annual General Meeting / Réunion annuelle générale de l'ACP

Convener: Robert Thompson (University of Calgary)