Description
The Poster Session is held on Wed and Thu. All posters are to be presented on both days. However, due to technical reasons, the contributions are only listed in the timetable of Wed.
A new and promising technique to study the dynamics on an atomic scale in hard condensed matter uses high flux coherent X-ray radiation. The technique is called Atomic scale X-Ray Photon Correlation Spectroscopy (aXPCS). Since new X-Ray sources have become more powerful in recent years the question of influence of X-rays on materials is becoming more important. Here the effect of the beam on...
Two well studied compounds $Sr_{3} Cr_{2} O_{8}$ and $Ba_{3} Cr_{2} O_{8}$ are insulating dimerized antiferromagnets with magnetic ions. These ions are located in hexagonal bilayers with a strong intradimer antiferromagnetic interaction, that leads to a singlet ground state and gapped triplet states We report on the effect on the structural and magnetic properties of the...
In this work, we present calculation of the Y NMR shielding in
intermetallic compounds. (YM, YMX, YM$_{2}$X, YM$_{2}$X$_{2}$, Y$_{2}$MB$_{6}$ and Y$_{2}$MSi$_{3}$ where M represents various transition metals and X refers to Si, Ge, Sn). The total shift $\sigma$ of this selection varies by about 2500 ppm and correlates very well with the experimentally observed shielding except for YMg and...
We studied the $T$&doping-dependence of the energy-loss function of bilayer and trilayer Bi-cuprate by ellipsometry to obtain information on the energy stored in the Coulomb interaction between the conduction electrons,on the $T$-dependence thereof,and on the change of Coulomb interaction when Cooper-pairs are formed. As $T$ drops through $T_c$,the loss function's integral $\leq2eV$ displays...
Both matter and language are dynamic systems constantly in motion. Language dynamics can lead to so-called language shift when people give up use of their language for another. We show that it is possible to study language shift on a large scale by using methods from diffusion physics. We present a microscopic model for language diffusion [1] and its application to data on minority languages...
The Brill transition is a phase transition process in polyamides, that has been related with structural changes between the hydrogen bonds of the lateral functional groups (C=O) and (N-H). In this study we show the potential of Raman spectroscopy for exploring this phase transition in polyamide PA66 (nylon 6,6). Raman spectra were collected during a step by step heating and cooling process of...
The main goal of the Interreg Italy-Austria ITAT1023 InCIMa project (2017-2019), as cooperation between Elettra Sincrotrone Trieste, University of Salzburg and Salzburg University of Applied Sciences, is the establishment of a cross-border infrastructure for the synthesis and characterization of functional smart materials, through the exploitation of spectroscopic techniques that employ...
Samples of totally natural rigid foams, derived from byproducts of wood industries, have been characterized through the exploitation of state-of-the-art spectroscopic techniques combined with imaging and mapping options employing a wide range of electromagnetic radiation from far infrared to X-rays. The synergistic complementation of several analytic techniques available through the beamlines...
Detailed characterization by means of confocal Raman microscopy of interfaces present in the raw material formulations of several PLA 3D printing filaments, as well as in 3D shaped bodies, have been performed in order to gain information on polymer/polymer interfaces, these having a decisive influence on the mechanical properties as well as the formability or the homogeneity of the final...
Surface-enhanced Raman spectroscopy (SERS) is a promising characterization technique for biomedical diagnostics usable for quick identification of cells, tissue and bacteria. The aim of our study is to analyze the SERS performance of new, promising SERS substrates and to compare their performance with commercial ones.
Large area prototypes of homogenous SERS substrates were created from...
Crystalline films of small semiconducting organic molecules on two-dimensional materials like graphene or ultrathin hexagonal boron nitride (hBN) offer attractive potential for fabricating organic solar cells, organic light emitting diodes, and organic field effect transistors on flexible substrates. Here, we report on the growth of the polar, acene-like molecule dihydrotetraazaheptacene...
Combined hydration/dehydration processes of oxide/hydroxide systems - e.g. CaO/Ca(OH)2 - can be used for storage of industrial excess heat. Exothermal hydration of CaO is fast and complete at ambient temperature; however, dehydration requires high temperatures. A system operable at lower temperatures would be desirable.
A candidate is the system MgO/Mg(OH)2. However,...
An amorphous ultra thin W foil with a thickness of 2 nm was deposited on an amorphous 3 nm carbon foil by electron beam- physical vapor deposition. The specimen was analyzed in an aberration corrected scanning transmission electron microscope (STEM) under ultra high vacuum condition. During the observation the amorphous structure of W converts to a partially nanocrystalline structure. The...
Compared to bulk systems, in the two-dimensional realization of electron liquids, correlation effects are much more pronounced, key examples being the collective modes such as plasmons and magnons. Taking care of these effects leads to substanially lower excitation energies. For highly dilute semiconductor quantum wells it is mandatory to account for dynamic multi-particle fluctuations, which...
The photodissociation cross section of different CsnIn-1+ (n < 8) clusters is measured in a commercial Bruker 9.4 T ICR, where the fragmentation is obtained by directly irradiating the CsI clusters in the ICR cell with a tunable EKSPLA NT 342B UV/VIS OPO. A wavelength range of 225 to 350 nm is covered, where dissociation is found from 225 up to 260 - 290 nm (depending on the cluster size)....
Gas phase studies have provided significant contributions to the understanding of activated CO$_\text{2}$. The metastable CO$_\text{2}^{\bullet-}$ is stabilized by a solvation shell and CO$_\text{2}^{\bullet-}$(H$_\text{2}$O)$_\text{n}$ can be studied readily by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. An EKSPLA NT277 optical parametric oscillator system is coupled...
As sodium chloride is the main component of marine aerosols, the present study shows experimental investigations with theoretical support on the photodissociation cross section of sodium chloride clusters doped with glyoxylate ([Na$_n$Cl$_{n-2}$(C$_2$HO$_3$)]$^+$, n = 5-11). It was found that that the glyoxylate can be photolyzed into HCO and a carbon dioxide radical anion, which is known to...
Hydrated singly charged metal ions doped with carbon dioxide, $M(CO_2)(H_2O)_n~^+$ $(M=Co,~Mg;~n<50)$ in the gas phase are valuable model systems for the electrochemical activation of $CO_2$. These systems are studied by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry combined with laser spectroscopy. Since mass spectrometry does not yield direct structural information,...
Ethyl tert-butyl ether (ETBE) is an upcoming groundwater pollutant in Europe whose environmental fate has been less investigated, thus far. In the present study, we investigated the in situ biodegradation of ETBE in a fuel-contaminated aquifer using compound-specific stable isotope analysis (CSIA), and in situ microcosms in combination with total lipid fatty acid (TLFA)-stable isotope probing (SIP).
Along with the evolution of the laser technologies, the idea to develop a new type of lightning protection based on lasers has emerged in recent years. The goal of the European funded [LLR][1] project is to investigate and develop a lightning protection based on the use of upward lightning discharges initiated through a high repetition rate multi terawatt laser. The feasibility of the novel...
The treatment of radiative heat transfer in arc simulation is difficult due to the large temperature inhomogeneity. Line-by-line integration of the radiative transfer equation is prohibitive due to the large computational effort needed. Therefore, the spectrum (e.g. $10^6$ wavelengths) has to be reduced to a suitable number of bands (order 10). As the temperature variation is large, scaling...
The scrape-off layer (SOL) sets the boundary conditions of a tokamak, determining the plasma confinement, the heat exhaust, the impurity levels, and controlling the fuelling of the device. Therefore, a first principles understanding of the physical mechanisms governing SOL turbulence is crucial on the way towards fusion energy. We describe SOL simulations carried out by using GBS, a...
The non-adiabatic response of passing electrons near low order Mode Rational Surfaces (MRSs) lead to fine radial structures on ion-scale microinstabilities. It has been shown that these structures persist in the non-linear turbulent regime and lead to the corrugation of density, temperature and zonal flow profiles. This effect significantly affects the turbulent fluxes of heat and particles as...
The ATLAS experiment is planning a major upgrade of its tracking detectors during the Phase-II LHC shutdown, to better take advantage of the increased luminosity of the HL-LHC. To this end, new CMOS sensors are being developed. The Edge-Tracient Current Technique (eTCT) measurement method and its latest subsequent preliminary results on the TowerJazz 180nm CMOS technology sensor are presented....
The prospects of an implementation of Lloyd's Mirror with very-cold neutrons at the Institut Laue-Langevin are investigated. Lloyd’s Mirror is a free-space interferometer similar to the double-slit experiment, but with a vertical mirror on the beam axis.
This interferometer was suggested to probe physics beyond the standard model of particle physics i.e. dark matter and dark energy models....
One class of gravity experiments within the qBounce project focuses on the realization of a Quantum Bouncing Ball, in particular a measurement of the time evolution of a neutron bouncing above a horizontal plane.
We measured the spatial probability distribution of this Schrödinger wave packet for different observation times with a spatial resolution of about 1.8μm.
We illustrate the role of...
Physics beyond the Standard Model (SM) is required to understand many unexplained features, both of particle physics and of cosmology. Precision measurements in neutron beta decay allow searching for physics beyond the SM.
The PERKEO III collaboration performed a measurement of the proton asymmetry C, which describes the angular correlation between the momentum of the decay proton and the...
Proton-proton collisions at LHC can be used to study Central Exclusive diffractive Production (CEP). In CEP the scattering protons remain intact, but exchange sufficient energy to create a new particle X at central rapidity. Experimentally these events are identified by their rapidity-gap topology, with particle production at small rapidities and particle voids at larger rapidities. The...
The AEgIS Collaboration at CERN will perform the world’s first direct measurement of the Earth´s gravitational acceleration on antimatter, by sending an antihydrogen beam through a classical deflectometer.
I will present a detector for a first measurement of the gravitational effects on an antimatter system. The detector consists of pure Caesium Iodide crystals and commercially available...
The Future Circular Collider (FCC) design study plans a high-energy frontier particle accelerator of 100 km circumference to succeed the Large Hadron Collider. Ongoing work on hadronic and leptonic options for the beams of the accelerator are supported by a common software framework (FCCSW) developed at CERN. Great emphasis is put on collaboration and synergies, as for example with the...
Although radioactivity is generally assumed to be explained by a Poisson process, with no dependence on atmospheric or cosmological conditions, there have been some indications of time-dependent decay rates and theories including neutrino-induced rate variations. We have developed an experiment dedicated to the long-term measurement of beta decays using NaI(Tl) detectors. Two detectors for...
DAMPE is a satellite-borne experiment in operations since December 2015, capable of detecting high energy cosmic rays and gamma rays. Its calorimeter, corresponding to about 31 radiation lengths allows to study electrons up to 10 TeV, making it the deepest calorimeter in space to date. A major complication at these energies is the discrimination between protons and electrons, as both particles...
The LHCb detector will be upgraded during the second long shutdown of the LHC. The current tracking sub-systems will be replaced by the Upstream and the Scintillating Fibre (SciFi) trackers, composed of high-granularity silicon micro-strip planes and scintillating fibres read out by silicon photomultipliers, respectively.
The SciFi tracker consists of three stations each composed of four...
Muonium, which is the bound state of an antimuon and an electron (mu+e-), is an ideal system to perform fascinating measurements, e.g. fundamental constants, bound-state QED, and the gravitational interaction of antimatter. This poster presents an efficient approach to form muonium using superfluid helium proposed at the Paul Scherrer Institut. This is the first step towards a high-brightness...
The Paul Scherrer Institute Neutron Electric Dipole Moment (PSI nEDM) experiment is a room temperature experiment using the Ramsey technique of separated oscillating fields. The PSI nEDM experiment aims to achieve a sensitivity of $d_n\sim<1\times10^{-26}$e$\cdot$cm. Since the main magnetic and electric fields applied to the stored neutrons are flipped regularly, constant residual fields are...
Relativistic heavy-ion collisions produce hot and dense strongly interacting matter. Dielectrons (e$^{+}$e$^{-}$) offer a way to investigate, e.g. the temperature of this medium and signatures of chiral-symmetry restoration.
The dominant background in the analysis of dielectrons originates from tracks produced via photon conversions in the detector material. Numerous observables allow for...
ALICE, the dedicated heavy-ion experiment at CERN—LHC, will undergo a major upgrade in 2019/20. In this work, we analyze low-mass dielectrons in Pb—Pb collisions after this upgrade. These $e^+e^-$ pairs are, for example, sensitive to the temperature of the collision system. Due to their small signal-to-background ratio, high-purity dielectron samples are required, which can be provided by...
Mu3e is a dedicated experiment for the rare lepton flavour violating decay $\mu^{+} \rightarrow e^{+}e^{-}e^{+}$. Its ultimate goal is to find or exclude this process if it occurs more than once in $10^{16}$ muon decays, a four orders of magnitude improvement.
A thin multi-layer scintillating fibre detector read out on both sides with silicon photomultiplier arrays provides a sub nanosecond...
Understanding the precise rigidity dependence of the carbon flux sheds light on the origin, acceleration and propagation of cosmic rays. The Alpha Magnetic Spectrometer (AMS-02) provides measurements of cosmic rays with high accuracy. Data analysis procedures, focusing on charge selection and efficiency calculations, together with the measurement of the carbon flux based on data collected by...
The LHC operation relies on a good knowledge of the optics, usually corrected in absence of beam-beam interactions. In a near future, both the LHC and the HL-LHC will need to cope with large head-on beam-beam parameters, the impact on the optics needs to be understood and, if necessary, corrected.
The T2K experiment is a long-baseline accelerator neutrino experiment using a near detector complex ND280 and a far detector Super-Kamiokande.
This contribution presents the results obtained with the simultaneous fit of muon neutrino disappearance and electron neutrino appearance, in neutrino and antineutrino mode.
A Markov Chain Monte Carlo method is used to obtain the posterior probability...
Observations at cosmological and astronomical scales indicate that the majority of matter in our Universe is in the form of non-relativistic and long-lived dark matter. Dual-phase xenon Time Projection Chambers (TPCs) are successfully operated in direct dark matter detection experiments. Silicon Photomultipliers (SiPM) are a favored candidate to detect the scintillation light in the next...
The Cherenkov telescope array (CTA) is the next generation of ground-based gamma-ray astronomy and will provide a deep insight into the non-thermal high-energy universe. CTA array will be composed of an array of up to 100 small sized telescopes in the Southern emisphere.
The SST-1M is one of the proposed prototypes for the sub-array.The SST-1M camera is under commissioning at the University of...
Silicon detectors built in high-voltage and high-resistivity CMOS technology are an interesting options for the pixel tracker needed for the ATLAS experiment upgrade for the high luminosity LHC program. They are less expensive and easier to produce with respect to standard hybrid silicon pixel detectors. This technology must be carefully tested and characterized. One of the techniques used for...
The Landau damping suppresses the development of coherent particle motion preventing instabilities. In particle accelerators the coupled motion of the circulating particles with the induced wake fields in the accelerator environment is Landau damped by a diversification of particle oscillation frequencies (tune spread). In colliders the tune spread can be generated by non-linear forces such as...
The ASACUSA collaboration at CERNs Antiproton Decelerator aims to measure the ground-state hyperfine splitting of antihydrogen to test CPT symmetry. The Rabi-type setup consists of an antihydrogen source and a spectroscopy apparatus made out of a microwave cavity and a sextupole magnet, terminating in a detector.
Previously, this detector consisted of a BGO crystal and two layers of...
The SHiP experiment is a new general purpose fixed target experiment proposed at the CERN SPS accelerator. The experiment will comprise a compact tau neutrino detector and a detector to search for hidden particles. Background rejection is ensured by use of background taggers and a dedicated timing detector. The timing detector will reduce combinatorial di-muon background by requiring incoming...
The IceCube detector has observed the first clear detection of a diffuse astrophysical high energy neutrino flux, however, the sources for these neutrinos have yet to be found. IceCube neutrino source searches involve looking for clustering of neutrinos or a strong correlation with known sources observed by other messengers also expected to emit a neutrino flux. The most recent updates will be...
We show that a refractive index varying continuously in space, e.g. due to optical excitation, may not be approximated by a rectangular function as it is common usage in the evaluation of pump-probe spectroscopy. For the example of a terahertz probe wave, we demonstrate the importance of the excitation depth and that approximative solutions may lead to an erroneous data interpretation.
In this work we designed and built an integrated waveguide three-path interferometer for measuring so-called higher-order interferences. These hypothetical higher-order interference do not occur in ordinary quantum mechanics or classical electrodynamics and thus the experiment tests the foundations of physics. Mechanical shutters could switch the interferometer arms on and off individually....
We are setting up an experiment which combines cavity-assisted measurements with a tunable Fermi gas of $^6$Li to study the transport properties of mesoscopic devices.
We will take advantage of a high-finesse cavity to implement a non-destructive measurements procedure to monitor in real time the dynamics of the system and to increase the sensitivity by reducing the preparation noise.
In my...
An ion held in a radiofrequency trap interacting with an ultracold buffer gas enables studying two- and many-body physics in a regime of intermediate interaction strengths, including collisions and chemical reactions at very low energy. During elastic ion-atom collisions energy is transferred between the thermal motion of the ion and the RF field, leading to multiplicative fluctuations of the...
The formation of positive and negative ions within doped clusters via electron ionization and electron attachment, respectively, opens a door to insights into cluster characteristics. For example, in case of electron attachment the stabilisation of the dopant anions by the cluster environment may occur. Furthermore, the understanding of the electron attachment process itself can be extended to...
Several experiments at CERN aim at testing the CPT-theorem and weak equivalence principle using antimatter, among them the AEgIS experiment. Here, antihydrogen - produced via resonant charge exchange - will be used for precision measurements where the achievable sensitivity is determined by the temperature of the antiprotons.
We are investigating laser-cooling of anionic molecules to...
The accurate modeling of transition-metal compounds (TMC) is essential for their deployment as electrodes of Li-ion batteries.
Allowing to capture the localization of electrons during charge/discharge, Hubbard-augmented DFT functionals (DFT+U) have become the standard choice for the modeling of TMC when computational efficiency is required. This work shows how an extended formulation of...
We measured the in-plane optical conductivity spectra between 0.01 and 4eV of (Sr1-xLax)2IrO4.Our data confirm that Sr2IrO4 is a Mott insulator with a gap onset at about 0.1eV.La substitution leads to a rapid collapse of the gap which is completed for x=0.05, and the emergence of a narrow-mode associated to free charge carriers. The intensity of this mode as compared to the nominal carrier...
We present an angle resolved photoemission spectroscopy study of the overdoped cuprate superconductor $La_{2-x}Sr_xCuO_4$. Using the symmetry properties of the photoemission matrix element effect, we present on this poster the orbital character of the band structure. With the obtained information, consequences for superconductivity and pseudogap physics is discussed.
High temperature superconductivity, colossal magneto-resistance and many other intriguing phenomena in correlated electron physics arise in doped Mott insulators. Here, we present the first angle-resolved photoemission (ARPES) study of electron-doped Ca$_{2}$RuO$_{4}$. The undoped parent compound of our study has been investigated intensely as a model system of a multi-band Mott transition....
In the past years, magnetism-driven ferroelectricity has been reported in a number of frustrated magnets with spiral magnetic orders. Such materials are of high current interest due to their potential for spintronics and low-power magnetoelectric devices. However, their low magnetic order temperatures (typically <100K) restrict their fields of application.
In this talk I will show that...
It is becoming clear that strong electron interactions with other electrons and with the magnetic excitations unify all iron-based materials, and probably, all unconventional superconductors in general. I will review the electronic self energy, determined from the angle-resolved photoemission spectroscopy (ARPES) for the 11, 111, 122, and 1111 families, and will compare it to the situation in...
The strength of the electron-phonon coupling in the superconducting mechanism of n-doped STO is still under debate. Interestingly, it has been proven that SrTiO$_3$ becomes ferroelectric at low temperature when $^{16}$O atoms are substituted by their isotope $^{16}$O. Using DC resistivity and AC susceptibly measurements we have determined the effect of $^{18}$O/$^{16}$O isotope substitution on...
Making connections between various domains of modern physic is an exciting opportunity. The spontaneous symmetry breaking of the crystal structure of hexagonal manganite creates an almost perfect Mexican hat potential. We have performed polarization resolved Raman spectroscopy of ErMn$O_3$ and two types of InMn$O_3$. In ErMn$O_3$, the phonons that have a substantial overlap with the Higgs...
We report a comprehensive investigation of the structural, electric transport, magnetic, and thermodynamic properties of Na2.7Ru4O9 and NaRu2O4 single crystals. The compounds are structurally different; Na2.7Ru4O9 crystalize in monoclinic (C 2/m) structure while NaRu2O4 crystalize in orthorhombic (P 21/ma) structure. We observed a first-order phase transition in the electrical resistivity at...
Regular arrays of single atom magnets represent model systems for information storage at the ultimate length scales. Individual rare-earth atoms on decoupling layers have recently received great attention for showing extraordinary magnetic stability; however, they still lack spatial order. Here we report a self-assembled superlattice of individual and noninteracting Dy atoms on graphene grown...
Recently it was shown that an end-user 3D printer can be used to print polymer bonded rare-earth magnets with a complex shape. The focus here is to manufacture polymer bonded NdFeB magnets for producing a tailored external field in a specific region outside the magnet. To determine the desired magnetization or shape of the printed magnet we developed an inverse stray field method and a...
Nanocrystalline Fe3O4 thin films were grown by adopting two different reduction approaches (1) vacuum annealing (2) wet H2 annealing. While vacuum annealed films shows Verwey transition with lower resistivity compared to the bulk Fe3O4, the same are not observed in electric transport properties of wet H2 annealed films. However, this transition was clearly seen in the temperature dependence of...
We report the formation and magnetic properties of metallic cobalt-core
and oxide shell structured nanoparticles upon oxidation of Co
nanoparticles with molecular oxygen under ultra-high vacuum conditions.
The presence of a core-shell structure was confirmed with HR-STEM while
x-ray photoemission electron microscopy shows that the core remained
metallic and magnetic at low oxygen dosage,...
A charge current flowing through a nonmagnetic conductor induces a spin current perpendicular to both the current direction and the spin polarization due to the spin Hall effect (SHE). Due to the nature of the SHE, most spin accumulation detection methods rely on the utilization of adjacent ferromagnets. We report here the first direct measurement of the current-induced interfacial spin...
Magnonic crystals (MCs) allow for tailoring the dispersion relation of spin waves (SWs) in nanopatterned ferromagnets. Local defects in MCs are expected to add further functionality. We prepared 1D MCs consisting of bistable magnetic stripes separated by sub-100 nm air gaps. By adjusting the magnetic history, we programmed ordered magnetic states with single stripes of opposed magnetization....
The chiral ferrimagnet Cu2OSeO3 hosts topologically protected spin textures known as magnetic skyrmions. It has been shown to provide novel functionality in microwave technology due to e.g. dichroism. We conducted broadband spin-wave spectroscopy on different single crystals of Cu2OSeO3 with magnetic fields applied in different orientations. In the field-polarized phase at 5K we observe...
The core-free magnetic configuration of ferromagnetic nanotubes leads to a controllable and fast reversal process and makes them promising candidates for high-density data storage, magnetic sensors, and logic device elements. We explore the magnetic configurations of different individual ferromagnetic nanotubes that we deposited on semiconductor nanowires of GaAs. Nanotubes prepared from...
Interconnected nanomagnets periodically arranged in one and two dimensions, called magnonic crystals, have been shown to provide tailored band structures for spin waves. The same has been found for antidot lattices. Aperiodic tilings and so-called artificial quasicrystals are far less explored. We fabricated nanopatternd holes in CoFeB thin films that were arranged in a Penrose tiling. Using...
Magnonic crystals are a novel type of artificial crystals formed by the periodic arrangement of magnetic nanostructures and magnetic skyrmions [1] are topologically stable spin textures, generally stabilized by Dzyaloshinskii-Moriya interactions [2]. Key challenges regarding the skyrmion lattice are to stabilize and confine them. The aim of the present work is to stabilize and confine the...
One of our primary areas of research is artificial spin ice, which consists of specific arrangements of nanomagnets that display analogous behavior to their real crystal counterparts such as the rare-earth Pyrochlore compounds. We have earlier investigated static/quasi-static responses of well-known structures, such as artificial square and kagome spin ices, and our current efforts are on...
The control over the aggregation of magnetic ions in a non-magnetic semiconductor matrix constitutes a new way to realize semiconductor/ferromagnetic nanocomposites with yet unexplored but striking functionalities. In this work we show that it is possible to obtain a controlled and well-defined arrangement of single-phase magnetic Fe-rich nanocrystals embedded in a GaN matrix [1]. We observe a...
Artificially designed arrays of nanostructures with a microstructure at sub-micrometer length scales can exhibit unique functionality, especially when built from a combination of different classes of materials. We present an overview of a novel magneto-mechanical metamaterial, where the coupling between nanoscale magnets embedded in a soft polymer matrix is exploited to control its mechanical...
In contrast to well-known models such as the Heisenberg model, which just incorporate the notion of the nearest neighbour, the anisotropic dipolar interaction directly depends on the geometry of the lattice and therefore its symmetries. These symmetries should be reflected by the properties of a possible phase transition in that system. To study these effects we employ the Monte Carlo...
Correlations in low-dimensional magnetic systems result in interesting properties, especially if continuous spin degrees of freedom are involved. Here we observe the magnetic correlations of dipolar-coupled artificial XY moments (circular nanomagnets) on a square lattice as a function of temperature using low-energy muon-spin relaxation. For strong interactions between the nanomagnets, we...
In femtosecond optical transfection and nanosurgery, cell survival critically depends on phototoxicity. We demonstrated on fixed cells that the use of femtosecond third order phase pulses (Airy pulses) could modulate the photon-interaction in cells leading to a better membrane poration efficiency energy per pulse than bandwith limited femtosecond pulses.
We also discuss results from a live...
The Thin-TOF PET (TT-PET) project aims at the construction of a positron emission tomographer based on silicon sensors with very high time resolution. Using TCAD simulation, a monolithic silicon pixel sensor aimed at 30 ps time resolution was designed and the properties of several test chips were measured. The sensor characteristics and the first comparison of the lab measurements with the...
Optical biosensors based on photonic crystal surface waves offer a possibility to study binding interactions with living cells, overcoming a problem of a low penetration depth into the cells. Moreover, simultaneous excitation of s- and p-polarized surface waves is realized here, allowing for unambiguous separation of surface and volume contributions to the signal. In this work, we developed...
In a cyclotron-based proton therapy facility, the energy selection is performed by means of a degrader. The interaction of the proton beam
with the degrader creates low energy tails that alter the beam quality. The analysis of the degraded energy spectra is hence important,
not only to better understand the performance of an existing facility such as PROSCAN at the Paul Scherrer Institut...
The goal of the SAFIR project is to build a pre-clinical PET insert for an existing 7T MRI scanner, with a high temporal resolution of better than 5s per image.
The SAFIR PET insert was modeled by means of the Monte-Carlo tool Gate, and for a simplified mouse model different time dependent tracer activities were simulated. After coincidence sorting, the images were analytically reconstructed...
Polydisperse suspensions of pNIPAM microgel particles show a unique, spontaneous particle deswelling behavior. Beyond a critical concentration, the largest and softest microgels deswell and thereby reduce the polydispersity of the suspension. We have recently unraveled the mechanism of this spontaneous deswelling triggered by the percolation of the counterion clouds of the microgel particles,...
Rotationally tunable diffractive optical elements (DOEs) consist of two stacked
diffractive optical elements which are rotated with respect to each other around their central optical axis. The combined diffractive element acts as a highly efficient diffractive lens, which changes its optical power as a function of the mutual rotation angle. Here we show that the principle can be extended to...
