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LASNPA & WONP-NURT 2017 will be devoted to the discussion of current problems in various fields of applied and fundamental research.
The LASNPA (Latin-American Symposium on Nuclear Physics and Applications) is a traditional symposium which takes place every two years since 1995 in different countries of Latin America. For the next symposium, Cuba was chosen to hold the LASNPA. This series of symposia is attended by the most important nuclear physicists of Latin America and has the participation of several scientists from the USA, Europe and Asia. The XII LASNPA is being organized in cooperation with the International Atomic Energy Agency (IAEA) and the International Union of Pure and Applied Physics (IUPAP).
The WONP and the NURT (Workshops on Nuclear Physics and Nuclear Related Techniques) are key Cuban Scientific Meetings in the field of Nuclear and High Energy Particle Physics and peaceful applications of nuclear techniques in the economic and social life. WONP-NURT Symposia has a biannual frequency, hosting delegates and invited scientists from more than 40 countries from all over the world. Since 2009 a pre-conference school is also organized. In this edition the Symposium NURT is celebrating its 20th Anniversary.
Invited Talk (45 min + 10 min) will be held at “Aula Magna”, Colegio Universitario San Gerónimo de La Habana.
Our knowledge of the states of nuclear matter under extreme conditions has advanced significantly in recent years through developments along numerous interrelated paths. This talk will describe this progress by focusing on new understanding of the densest matter in the universe, that deep inside neutron stars. Recent advances driving a better picture of neutron star interiors include observations of heavy neutron stars with masses just twice that of the sun; ongoing observational simultaneous determinations of neutron star masses and radii; an emerging understanding in QCD of how nuclear matter can turn into deconfined quark matter in the interior; and the creation of new states of quantum matter in the laboratory, including quark-gluon plasmas in ultrarelativistic heavy ion collisions, and new Bose and Fermi superfluids in ultracold trapped atomic clouds. The importance of a better understanding of dense nuclear matter is strongly underlined by the observational discovery of gravitational radiation, since merging of neutron stars with black holes or neutron stars will be a principal source of future gravitational radiation events.
The 1975 Nobel prize in Physics was awarded to Bohr, Mottelson, and Rainwater for the discovery of the connection between nucleon motion and the emergent collective behavior. They described nuclei geometrically as a shape and the oscillations of the nucleus around that shape. In deformed nuclei, they predicted low-lying quadrupole oscillations of the deformed shape with respect to projections on the symmetry axis as “$\beta$” and “$\gamma$” vibrations.
The “$\gamma$” vibration seems to be well characterized and exhibits a systematic behavior across the region of deformed nuclei with typical B(E2; 2+ γ → 0+ g.s. ) values of a few Weisskopf units (W.u.). The discussion on the “$\beta$” vibration however still continues today some forty years later and remains an open challenge to nuclear structure studies to large part to the lack of experimental data on the identification and characterization of 0$^+$ states. This has been changing recently with the discovery of numerous 0$^+$ states well below the pairing gap in several isotopes of Sm, Gd, Dy, Er and Hf in the rare earth region. We have been measuring lifetimes of low-lying excited states of K$_{\pi}$ = 0$^+$, 2$^+$, 4$^+$ states in this region of deformation and will present our results along with expected levels of collectivity.
This work was supported by the US National Science Foundation under contract number PHYS- 1419765.
The experiments at the Large Hadron Collider (LHC) at CERN are in need of major detector upgrades to cope with the increased luminosity of the High-Luminosity Upgrade of the LHC. In order to cope with the massive increases in track densities, event rates and radiation damage, the entire Inner Tracker of the ATLAS experiment will be replaced. This presentation outlines the huge challenges of this task, and discusses methods to increase the radiation hardness of silicon particle detectors. An overview of radiation-hard silicon detector technologies will be given.
The technological choices made for the ATLAS Upgrade will be shown and motivated, and the layout and expected performance of the new ATLAS Inner Tracker will be presented.
Exclusive processes at high momentum transfer, such as Deeply Virtual Compton Scattering (DVCS) access the Generalized Parton Distributions (GPDs) of the nucleon. GPDs offer the exciting possibility of mapping the 3-D internal structure of protons and neutrons by providing a transverse image of the constituents as a function of their longitudinal momentum.
A vigorous experimental program is currently pursued at Jefferson Lab (JLab) to study GPDs through DVCS and meson production. New results from Hall A will be shown and discussed. Special attention will be devoted to the pplicability of the GPD formalism at the moderate values of momentum transfer. In addition, we will report on results for L/T separated pi0 electroproduction cross sections off the proton, the neutron and the deuteron. A large transverse response for both the proton and neutron cases is found, pointing to a possible dominance of higher-twist transversity GPD contributions. For the first time, a flavor decomposition of the u and d quark contributions to the cross section will be shown.
We will conclude with a brief overview of additional DVCS experiments under analysis and planned with the future Upgrade of JLab to 12 GeV.
We report the generation of a pseudovector electric current having imbalanced chirality in an electron-positron strongly magnetized gas in QED. It propagates along the external applied magnetic field B as a chiral magnetic effect in QED. It is triggered by a perturbative electric field parallel to B, associated to a pseudovector longitudinal mode propagating along B. This mode is associated to the chiral charge density in a massive charged medium in the context of QED. We do not introduce a chiral chemical potential, this term usually used in the literature is not well defined, because the axial charge is not conserved. However, an electromagnetic chemical potential was introduced, but our results remain valid even when it vanishes. A nonzero fermion mass was assumed, which is usually considered vanishing in the literature. In the quantum field theory formalism at finite temperature and density, an anomaly relation for the axial current was found for a medium of massive fermions. It bears some analogy to the Adler-Bell-Jackiw anomaly. We obtain that the pair creation process, due to longitudinal photons (out of light cone), induces an imbalanced chirality and contributes to the chiral current along B. We also discuss about the introduction of a chiral chemical potential in the quantum field theory formalism at finite temperature and density, specifically in the frame of electroweak theory.
If Boron Neutron Capture Therapy is to become a practical option, accelerator-based sources of high fluxes of epithermal neutrons are essential. Generation of low energy neutron can be achieved by $^7$Li(p,n)$^7$Be reaction using accelerator-based neutron source. Much work has been performed on development of high-flux compact proton accelerators, but a doselimiting component remains design of the neutron production target. Specifically, lithium has a low melting point (180ºC) and low thermal conductivity (44 W/mºC). In this study, therapeutic gain and tumor dose per target power, as parameters to evaluate the treatment quality, were calculated. Energies near the reaction threshold for deep-seated brain tumors were employed. These calculations were performed with the Monte Carlo N-Particle (MCNP) code. As a result, a good therapeutic gain was obtained with a simple but effective beam shaping assembly. Also, heat transfer evaluations of a lithium target designed were performed by ANSYS software. The target designed show that the peak lithium temperature can be held below 150ºC with indalloy flowing by a cooper microchannels plate.
In this work we calculated the self-shielding factor, $G$, as a function of the neutron energy, which is important to consider in precise neutron activation experiments.
Twelve samples of pure metallic materials were simulated using the Geant4 Monte Carlo toolkit[1,2] and the MCNP[3] code.
The self-shielding factor is defined as the ratio between the neutron flux inside the sample volume and the flux in the surface of the sample,
$$ G = \left( \int_{E_1}^{E_2}dE\Phi_V \right) \div \left( \int_{E_1}^{E_2}dE\Phi_S \right). $$ We have simulated the behaviour of the self-shielding factor for neutron energies from 10$^{-5}$ eV to 20 MeV. Results obtained by running 10$^{6}$ neutron events in MCNP6 using the ENDF-B/VII.1, JEFF 3.2 and TENDL2014 neutron cross section libraries, shows that the self-shielding factor is relevant to include in neutron activation analysis experiments for thermal neutron energies and for sample thickness greater than 10$^{-4}$ m, as seen in the recent calculation of the neutron flux at the RECH-1 nuclear reactor[4].
Electronic devices are strongly influenced by radiation and the need for radiation tolerant devices is growing for applications in environments with high radiation dose [1]. The effects due to radiation on electronic components are mainly: Total Ionizing Dose (TID), Displacement Damage (DD), and Single Event Effects (SEE). TID is a cumulative effect that changes the characteristics of electronic devices. DD can change the arrangement of the atoms in the lattice, modifying also component electrical properties. SEE can be a transient effect in which free charge, generated by heavy-ions directly into the device, may provoke data corruption or even a permanent device failure. In order to study TID radiation effects in electronic devices subjected to proton beams, is used a 1.7 MV 5SDH Pelletron accelerator of São Paulo University, which can produce proton beams with energies up to 3.0 MeV [2]. In order to study SEE at the 8.0 MV São Paulo University Pelletron accelerator, a new beam line was mounted to test electronic devices with heavy-ion beams [2]. The heavy-ion beam characteristics follow the requirements to test electronic devices for SEE recommended by the European Space Agency (ESA). This setup is being currently used to provoke failures in integrated circuits and to test the performance of redundancy and correction algorithms in FPGAs.
The reaction $^7$Be(p,γ)$^8$B generates most of the high-energy neutrinos emanating from the pp-fusion chain in our Sun. Over the past twenty years there has been a substantial effort to measure its cross section at center-of-mass energies below 500 keV. One goal of this effort was accurate extrapolation of the astrophysical S-factor to solar energies. I will explain our treatment of this problem (Zhang et al., Phys. Lett. B 751, 535 (2015)), which uses an effective field theory (EFT) for $^7$Be(p,γ)$^8$B and Bayesian methods to perform the extrapolation. We find a zero-energy S-factor S(0)=21.3$\pm$0.7 eV–an uncertainty smaller by a factor of two than previously recommended. This improvement occurs because the EFT encapsulates all plausible low-energy models of the process, and so model selection for this problem can be accomplished in a rigorous and statistically meaningful way.
Proton-rich nuclei in the A$\sim$70 mass region relevant to the astrophysical rp-process manifest exotic structure and dynamics induced by shape coexistence and mixing, competition between like-nucleon and neutron-proton pairing correlations, as well as isospin-symmetry-breaking interactions. Recent results [1-4] concerning the interplay between isospin-symmetry-breaking and shape-coexistence effects on the structure and $\beta$-decay properties of N$\sim$Z nuclei obtained within the beyond-mean-field complex Excited Vampir variational model will be presented.
Reliable predictions on beyond experimental reach characteristics of these nuclei require realistic description of the experimentally accesible properties. Shape coexistence effects on terrestrial and stellar Fermi and Gamow-Teller $\beta$-decay properties of low-lying states and their influence on the effective half-lives of exotic nuclei at the high temperatures of X-ray bursts will be illustrated.
The evolution of the shell structure when moving away from the stability line is discussed in the present contribution. In particular, the effect of the tensor interaction in the appearance and disappearance of magic numbers and the specific case of $^{78}$Ni. To contribute to the understanding of the case, the level structure of $^{75,77}$Cu was studied in a $\beta$-delayed $\gamma$-spectroscopy experiment. The $\beta$-decay experiment was performed at the Radioactive Ion Beam Factory (RIBF) of the RIKEN Nishina Center. A secondary beam of nuclei in the region of $^{78}$Ni was produced by the in-flight fission of $^{238}$U projectiles on a $^{9}$Be target. After being selected and identified in the BigRIPS fragment separator, the nuclei of interest were implanted in the WAS3ABi active stopper, where the $\beta$-decay events were detected. The EURICA array, consisting of 12 germanium cluster detectors, was surrounding the active stopper for the detection of the $\gamma$-rays. The level schemes of $^{75,77}$Cu are presented together with the results of new shell model calculations.
Studies of the effects of different color reconnection (CR) choices for three different models implemented in Pythia 8 event generator is shown. Validation plots for the new tunes for the three main Pythia CR model, the MPI-based scheme, the new more QCD-based and the gluon-move model are shown. Four different Rivet validated analysis are presented, the CMS_2011_S9215166 which investigates the agreement of the tunes in the forward region, CMS_2012_PAS_QCD_11_010, which investigates the agreement of the tunes for strange particles, CMS_2015_I1356998 that investigates the agreement of the tunes for diffractive observables and ATLAS_2010_S8894728 which investigates the agreement of the tunes for UE observables.
The production of $t\bar{t}$ pairs at high pT, i.e. the so-called boosted regime, is characterized by two collimated jets which contain most of the particles originating from the top decays. We investigate a scenario with both top quarks decaying hadronically. We attempt a definition of "top jet", by considering the substructure of the selected "fat" jets resulting from the top decay and we study the contamination from QCD events (the background). Theoretical predictions of the differential cross sections as a function of the azimuthal difference between the two top jets, as well as pt distribution of the top jets is presented using the definition of “top jets”, on analogies at QCD dijet topologies.
CDCC calculations of total fusion cross sections for reactions of the weakly bound $^{6}$Li with targets $^{28}$Si, $^{59}$Co, $^{96}$Zr, $^{144}$Sm and $^{209}$Bi at energies around the Coulomb barrier are presented. In the cluster structure frame of $^{6}$Li$\rightarrow \alpha +d$, short-range absorption potentials are considered for the interactions between the $\alpha$ and -$d$ fragments with the targets. The effect of resonance states ($l=2, J^{\pi}=3^{+},2^{+},1^{+}$) and non-resonance states of $^{6}$Li on fusion is studied by i) omitting resonance states from the full discretized breakup space and ii) by considering only the resonance discretized space. A systematic analysis of the effect on fusion from resonance breakup couplings is carried out from light to heavy target masses.
The rare-earth nuclei have well-known collective properties. The theoretical description of these nuclei represents a challenge to nuclear models, due to the enormous dimensions of the valence space, making the problem unmanageable. This leads us to use symmetry-based models, where it is possible to calculate in a free-truncation environment. In this work we present results for the energy spectrum and the electromagnetic properties in even-even Yb isotopes using the pseudo-SU(3) shell model. The model considers a Nilsson Hamiltonian that additionally includes the quadrupole-quadrupole and pairing interactions, systematically parameterized. The results show that the model considered is a powerful theoretical tool, allowing us to describe the normal parity sector of deformed rare earth nuclei.
Full angular distributions for the elastic scattering of the $^9$Be + $^{80}$Se system were measured at eleven bombarding energies around the Coulomb barrier namely, 17,18, 19, 20, 21, 22, 23, 24, 25, 30 and 32.8 MeV, in order to investigate the influence of the breakup of the weakly bound $^9$Be projectile on the reaction mechanisms. The $^9$Be beams were delivered by the 20 UD tandem accelerator of the TANDAR Laboratory at Buenos Aires. The experimental data have been analyzed in the framework of the optical model using two different potentials: 1) a semi-microscopic double folding potential with normalization factors for the real and imaginary parts, $N_R$ and $N_I$ respectively, as free parameters, and 2) a phenomenological Wood-Saxon potential with six free parameters, namely the depth, radius parameter and diffusivity for the real part ($V$, $r_{0R}$ and $a_R$) and the similarly for the imaginary part ($W$, $r_{0I}$ and $a_I$). The coupling to the breakup channel, at energies close and below the Coulomb barrier, is reflected as an increase of the imaginary part of the potential as a function of the decreasing bombarding energies, while the real part decreases in strength. The correlation is explained by the dispersion relation, which connects the real and imaginary parts of the nuclear potential. The analysis of the the present experimental data shows that the energy dependence of the two parts of the optical potential indeed presents a behavior consistent with the so called Breakup Threshold Anomaly (BTA). The uncertainties in the study of the parameter´s dependence with energy are studied using the covariance-matrix method [2]. As a conclusion, we will show that the BTA is determined unambiguously, independently of the model chosen for the nuclear potential.
A local and gauge invariant version of QCD Lagrangian is introduced. The model includes Nambu- Jona-Lasinio (NJL) terms within its action in a surprisingly renormalizable form. This occurs thanks to the presence of action terms which at first sight, look as breaking power counting renormalizability. However, those terms also modify the quark propagators, to become more decreasing than the Dirac propagator at large momenta, indicating power counting renormalizability. The approach, can also be interpreted as generalized renormalization procedure for massless QCD. The free propagator, given by the substraction between a massive and a massless Dirac ones, in the Lee-Wick form, suggests that the theory also retains unitarity. The appearance of finite quark masses already in the tree approximation in the scheme is determined by the fact that the new action terms explicitly break chiral invariance. The approach looks as being able to implement the Fritzsch Democratic Symmetry breaking ideas about the quark mass hierarchy. Also, it seems that a link of the theory with the SM can follow after employing the Zimmermann’s couplings reduction scheme. The renormalized Feynman diagram expansion of the model is written here and the formula for the degree of divergence of the diagrams is derived. The primitive divergent graphs are identified and the two gloun legs ones are evaluated. The result shows the required gauge invariant transversal structure.
COMPASS is a modern fixed target experiment at a secondary beam of the Super Proton Synchrotron at CERN. The purpose of the experiment is the study of hadron structure and hadron spectroscopy with muon and hadron beams of high intensity. The COMPASS setup is a multipurpose universal spectrometer based on two analysing magnets and equipped with various tracking detectors, electromagnetic and hadron calorimeters, muon filters and Cherenkov detectors for particle identification. COMPASS has an intensive physics programme which includes the following topics: study of nucleon spin structure in semi-inclusive deep inelastic scattering and Drell-Yan process; measurement of the generalized parton distributions for the nucleon in reactions of deeply virtual Compton scattering and deeply virtual meson productions; search for new hadronic states and study of their production mechanisms; test of low-energy QCD models in Primakoff reactions. A physics programme for the period after 2020 is under discussion.
A method for determination of Cr, Fe, Co, Ni, Cu, Zn, Hg and Pb in waters by Energy Dispersive X Ray Fluorescence (EDXRF) was implemented, using a radioisotopic source of $^{238}$Pu. For previous concentration was employed a procedure including a coprecipitation step with ammonium pyrrolidinedithiocarbamate (APDC) as quelant agent, the separation of the phases by filtration, the measurement of filter by EDXRF and quantification by a thin layer absolute method. Sensitivity curves for K and L lines were obtained respectively.
The sensitivity for most elements was greater by an order of magnitude in the case of measurement with a source of $^{238}$Pu instead of $^{109}$Cd, which means a considerable decrease in measurement times. The influence of the concentration in the precipitation efficiency was evaluated for each element. In all cases the recoveries are close to 100%, for this reason it can be affirmed that the method of determination of the studied elements is quantitative.
Metrological parameters of the method such as trueness, precision, detection limit and uncertainty were calculated. A procedure to calculate the uncertainty of the method was elaborated; the most significant source of uncertainty for the thin layer EDXRF method is associated with the determination of instrumental sensitivities. The error associated with the determination, expressed as expanded uncertainty (in %), varied from 15.4% for low element concentrations (2.5-5 μg/L) to 5.4% for the higher concentration range (20-25 μg/L).
The great interest in rare earth elements (ETR) is due to the many and valuable applications that these elements have in the science and economy of many countries. On the other hand highly sensitive methods are generally required for the determination of these elements in many of the matrices of interest such as geological samples. An alternative is to apply chemical separation procedures, prior to analysis.
In the present work, model experiments were performed to study the ETR separation performance of Cr, Fe, Ni and some elements of the alkaline earth and platinum groups by cation exchange in HCl medium. The final determination in the eluates was carried out by Inductively Coupled Plasma Atomic Emission Spectrometry (EEA-ICP). The elaborated method was used in the ETR analysis in 100 geological samples supplied by the Institute of Geology and Paleontology of MINEM. In the latter case, the determination of ETR was performed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). An analysis of the obtained results is presented in the work
Peloids from some Cuban spas (San Diego, Elguea, Santa Lucía, Cajío and Colony) have been studied using Instrumental Neutron Activation Analysis (INAA). Concentrations of 30 major, minor and trace elements in the peloids are reported, including an important group of REE (La, Ce, Nd, Sm. Eu, Gd, Tb, Tm and Yb). No difference is observed for metal contents (including REE) determined for raw and maturated peloids from San Diego spa. Elemental concentrations are compared with other worldwide reported peloids. The iron-normalization using raw (non-matured) mud from San Diego spa as reference material shows that an anthropogenic metal input is present in the Elguea, Cajío and Colony spas. The measured REE contents are in the same order of magnitude as those reported for Earth’s upper crust average shales and muds as well as with worldwide reported peloids. However, the behavior of the normalized-to-chondrites REE shows different patterns for Cuban peloids matured with marine and fresh waters, respectively.
The FAZIA detector is a new fully digital array based on Silicon(300um)+Silicon(500um)+CsI(Tl)(10cm) telescopes. It is design to study heavy ions collisions in the Fermi energies range using a fully integrated digital electronics. Some details about the construction of this array and about the incredible performance in terms of isotopic separation will be given. Finally, some preliminary results about the isospin physics which can be studied with such powerful tool will be shown.
Time of flight neutron spectrometry requires for high detection efficiency. In this work we present a detector which is based on a neutron-gamma converter ($^{10}$B disk) followed by a gamma detector (BaF$_2$). The response function to convert time of flight spectrum to energy one was constructed. About four times higher efficiency, compared to an equal thickness $^{6}$Li-doped typically-used neutron detector is predicted. The well-known $^{7}$Li(p,n)$^{7}$Be reaction is used to compare the calculated detector response with the measured one. The low energy tail of the neutron spectrum is well reproduced.
LENOS (Legnaro NeutrOn Source) project at the LNL-INFN (Italy) is a neutron irradiation facility for nuclear astrophysics studies and data validation for energy and non-energy applications. It is based on a high current low energy RFQ. The facility, will use the 5MeV, 50 mA proton beam of RFQ under test at LNL to produce an unprecedent neutron flux, precisely shaped to a Maxwell-Boltzmann energy distribution. A new method has been proposed to obtain the desired neutron spectra at different stellar energies and a dedicated target, able to sustain a very high specific power, has been developed and tested. We will present the facility, the method used to shape the neutron beam, the results of the high power test of the microchannel water cooled target and the preliminary results of a measurement dedicated to the validation of the proposed method.
Beside the neutron facility based on RFQ, we have currently partially financed an higher neutron energy facility based on the new Cyclotron of 35-70MeV tuneable energy and up to 750uA current. The high energy facility is called NEPHIR and at the moment, is dedicated to the study of Single Event Effect (SEE) on electronic devices. The 70MeV proton beam will produce an atmospheric like neutron spectra up to 70 MeV using a novel technique and novel target: the neutron spectra is constructed by a weighted convolution of neutron spectra coming from different reactions. The target able to use two different materials and thus two different reactions, is a rotating target.
The opportunity to have the tenable energy between 35 and 70 MeV will offer also the opportunity to produce quasi-monochromatic neutron beam, whose applications span from fundamental physics to applied one (within the framework of SEE studies allow the search for threshold effects for instance). Finally, in the long term a pulsing system with about 2 ns time width is planned to allow a neutron Time of Flight facility. In this presentation, the novel method to produce atmospheric neutron spectra, the target design, the calculations for the production of quasi mono-energetic neutron beam with p,Li and p,Be reactions will be presented.
Spin-isospin excitations can be studied by beta decay and charge exchange reactions in mirror nuclei, shedding light on mirror symmetry, hence we can compare our results on the beta decay of proton-rich nuclei with the results of charge exchange experiments when appropriate targets for the mirror nuclei are available. Accordingly we have performed experiments at GSI and GANIL to study $T_z$ =-1 and $T_z$ =-2 nuclei respectively where it became clear that the study of heavier, more exotic systems, demands beam intensities available only at the RIKEN Nishina Center. In this work we present the first experimental observation of the beta-delayed protons in the decay of the $T_z$ =-2 ${}^{64}$Se.
We have performed an experiment using the fragmentation of a 345 MeV·A ${}^{78}$Kr beam with typical intensity of 200 particle nA on a Be target. The fragments were separated in flight using the BigRIPS separator and implanted in three double-sided Silicon strip detectors (DSSSD) named WASSSABi (60 mm × 40 mm × 1.2 mm, 60 horizontal and 40 vertical strips). The implantation setup was surrounded by the EUROBALL-RIKEN Cluster Array (EURICA). We perform time correlation between the ${}^{64}$Se implantations and beta signals within a single pixel defined as the crossing of one X and one Y strip. In addition, only the strips where the highest energy has been deposited are correlated. The DSSSD detectors were calibrated using an external electron conversion ${}^{207}$Bi source. Due to the fact that the proton emitted is in prompt coincidence with the beta particle, also partially absorbed in the DSSSD detector, shifts in the measured energies are expected. These energy shifts were estimated using the ${}^{57}$Zn and ${}^{61}$Ge beta-delayed proton spectra observed in the same experiment. The ${}^{57}$Zn and ${}^{61}$Ge proton energies were taken from literature. Three proton peaks were observed for ${}^{64}$Se, (1612(10), 2003(13), and 3249(22) keV) and the proton energy errors were estimated from the fit for each proton peak as well as the systematic shift with the proton energies reported in the literature.
The Legnaro National Laboratories have a long-standing tradition in gamma-ray spectroscopy. They hosted the most recent HPGe arrays, from GASP, one of the first Compton-shielded large HPGe array to AGATA, the first operational tracking array worldwide.
In this context, a new resident gamma-ray spectrometer GALILEO has been developed. After a 1-y long commissioning campaign, a physics campaign started. In such campaign, GALILEO has been combined with a light-charge particle and a neutron array, EUCLIDES and NEUTRON WALL, respectively, for the investigation of neutron-deficient nuclei. The experiments performed so far aimed mainly at studying the shape coexistence phenomenon in medium-mass and heavy nuclei, the octupole correlations in the Ba region and the isospin symmetry breaking effect in light nuclei. The first results will be reported.
An experimental campaign to study heavy-ion induced one- and two-nucleon transfer reactions has been performed at INFN-Laboratori Nazionali del Sud in Catania (Italy). In particular reactions induced by 18O and 20Ne beams at energies above the Coulomb barrier on different target isotopes have been explored with high resolution (both in energy and angle) and in a quite wide angular range including zero degrees. The aim of this study is two-fold. First of all, the experimental observations and the analysis of the reaction mechanism in two-nucleon transfer reactions in a quantum-mechanical description can give interesting information on the role of the pairing force in populating specific excited states and resonances, such as the so called Giant Pairing Vibration. Moreover, the study of multi-nucleon transfer cross-sections is a crucial aspect for recently proposed research projects involving the use of nuclear reactions of double charge exchange in relation with the physics of neutrinoless double beta decay. The multi-nucleon transfer mechanism could compete with the double meson exchange mechanism in double charge exchange reactions and their role must be understood in order to extract accurate information on the nuclear matrix elements of interest.
The LUCID-2 detector is the main online and offline luminosity provider of the ATLAS experiment. It provides over 100 different luminosity measurements from different algorithms for each of the 2808 LHC bunches. LUCID was entirely redesigned in preparation for LHC Run 2: both the detector and the electronics were upgraded in order to cope with the challenging conditions expected at the LHC center of mass energy of 13 TeV with only 25 ns bunch-spacing. While LUCID-1 used gas as a Cherenkov medium, the LUCID-2 detector is in a new unique way using the quartz windows of small photomultipliers as the Cherenkov medium. The main challenge for a luminometer is to keep the efficiency constant during years of data-taking. LUCID-2 is using an innovative calibration system based on radioactive 207 Bi sources deposited on the quartz window of the readout photomultipliers. This makes it possible to accurately monitor and control the gain of the photomultipliers so that the detector efficiency can be kept stable at a percent level. A description of the detector and its readout electronics will be given, as well as preliminary results on the ATLAS luminosity measurement and related systematic uncertainties.
Beta disintegration is studied in the presence of a magnetic field, which imposes a preferential direction on the emission of neutrinos. It is explored the possibility that this anisotropy in neutrino emission can account for observed Neutron (Quarks) Star velocities (kicks). The conditions under which the anisotropic emission of neutrinos (due to the magnetic field present in the system) causes a ``kick'' of the compact star are discussed. The matrix element for the beta decay process is computed from first principles taking into account the $W$ boson propagator in presence of a strong magnetic field. The neutrino emissivity is also computed.
The SoLid experiment intends to search for active-to-sterile anti-neutrino oscillation at very short baseline from the SCK$\bullet$CEN BR2 research reactor (Mol, Belgium). A novel detector approach to measure reactor anti-neutrinos was developed based on an innovative sandwich of composite polyvynil-toluene and $^{6}$LiF:ZnS scintillators. The system is highly segmented and read out by a network of wavelength shifting optical fibers and silicon photomultipliers (SiPMs). This detector will have few passive shielding, relying on its volume segmentation and robust neutron identification capabilities to reject the backgrounds components of the experiment and provide a precise measurement.
We will describe the principle of detection and the detector design. Results from the first full scale detector prototype (SM1) measurements will be presented. Particular focus will be made on the current status and the expected results of the SoLid experiment. The SoLid Phase I is planing to start data taking in fall 2017 and will be able to provide important results to clarify the so-called Reactor Antineutrino Anomaly.
Naturally occurring radioactive materials (NORM) are continuous and an unavoidable feature of life on Earth and are present in its crust since its origin. The irradiation of the human body from external terrestrial sources is mainly due to gamma rays coming from natural radionuclides, such as 40K and the elements of the series of 238U and 232Th. These primordial radionuclides present long half-lives, decaying to achieve stability, producing ionizing radiation. It is very important to study radionuclide distribution in soils to understand the radiological implications in relation to the exposure of the human body to ionizing radiation and the knowledge of which components are found in one specific geographic region. Natural background radiation studies are needed to establish reference levels, especially in areas where the risk of radioactive exposure may be higher, and this risk index can be worsened through the soil mineral extraction, generating Technologically Enhanced Naturally Occurring Radioactive Material (TENORM). On the other hand, the secondary effects of natural radiation are also of extreme importance, since the human being feeds on animals and plants, which determine the intake of natural radionuclides. In this work the distribution of natural radiation from Southeastern Brazilian beach sands using gamma-ray spectrometry was studied. In most of the samples studied the dose due to external exposure to gamma-rays, proceeding from natural terrestrial elements, are within the values 0.3 and 1.0 mSv/year, typical range indicated by the United Nations Scientific Committee on the Effects of Atomic Radiation. Gamma-ray technique was used to evaluate the transfer rate of these radionuclides from soil to the plants. Energy-Dispersive X-Ray Spectroscopy (EDS) microanalysis and X-Ray Fluorescence were used also to assist in the sample analysis. The study of natural radiation present in TENORM, plants and food was done. Various chemical processes have been applied in TENORM considering waste samples from extraction of phosphatic rocks, in order to make viable the extraction process and reducing the amount of radioactive waste
In part I of this analysis, the striking similarities of the declining oil production in the North Sea, Indonesia and Mexico were used to model the future maximum possible oil production per annum in all larger countries and regions of the planet from 2015 to 2050.
In part II, the oil export and oil consumption patterns, that were established in recent decades, are combined with the consequences of the forecast declines in regional oil production that were developed in part I of this analysis. The results are quantitative predictions of the maximum possible region-by-region oil consumption during the next 20 years.
The predictions indicate that several of the larger oil consuming and importing countries and regions will be confronted with the economic consequences of the onset of the world's final oil supply crisis as early as 2020. In particular, during the next few years a reduction of the average per capita oil consumption of about 5%/year is predicted for most OECD countries in Western Europe, and slightly smaller reductions, about 2-3%/year, is predicted for all other oil importing countries and regions. The consequences of the predicted oil supply crisis are thoroughly at odds with business-as-usual, never-ending-global-growth predictions of oil production and consumption.
Our study aimed to investigate road dust from relevant locations in Havana city and the associated health risks of potentially toxic elements (PTEs) to humans using X-ray fluorescence analysis. The Geoaccumulation Index, Enrichment Factor and Integral Pollution Index were used to describe pollution characteristics of roadside dust in urban areas associated with traffic and child activities (schools, parks, etc.) from Havana city central metropolitan area (Old Havana, Central Havana, San Miguel del Padrón and Regla municipalities and the Alamar district). Results indicate that industrial roadside dust is contaminated with Pb near high traffic, as well as power and gas station locations, and with Zn and Cu in areas were reconstruction works were performed. The Hazard Quotient (HQ) and Hazard Index (HI) values for all the exposure routes (ingestion, inhalation, and dermal contact) were below the international established limits, except for Pb, Zn and Cu in mentioned areas. The risk of contracting cancer from the studied metals was found to be in safe levels as the RI (carcinogenic risks) values were below the international established limits.
In order to potentiate the experiments with Brazil Radioactive Ion Beam (RIBRAS), new VME (Versa Module Euro Card) Data Acquisition (DAQ) modules characteristics to control, triggering and data acquisition will be described. The DAQ will define to include the Strip Array and Neutron Wall detectors with maximum readout efficiency, no dead time, data selection and event synchronization.
CAEN digitizer modules for VME provide features like zero suppressed readout and overflow suppression. Zero suppression, once enabled, prevents conversion of value which is lower than user defined threshold. Overflow suppression, once enabled, aborts the memorization of data which constitutes an ADC overflow.
Adding FPGAs (field programmable gate array) to data acquisition provides pre- and post-algorithmic processing on data. The hardware elements chosen should have features that make the modules easy to program and handle, while the FPGAs should be reprogrammable when required.
For simplification of the interaction between DAQ elements, provision of standalone working mode for each sub detectors, easy reconfiguration of active sub-detector and easy hardware replacement, the DAQ hardware units are functionally subdivided into hierarchy by logical level along the data stream.
During the last 6 year, the infrastructure related with Experimental Nuclear Physics at the Physics Institute, UNAM, has been benefited with an unprecedented injection of resources: four new beam lines were mounted at the CN-Accelerator Van der Graaff of 5.5 MV, which originally had just one. Moreover, a modern Tandetron AMS system of 1 MV was acquired in order to establish this kind of technique for the first time at Mexico. This AMS system is nowadays a National Laboratory called LEMA.
In one of the lines of the Van der Graaff Accelerator was built a permanent windowless Supersonic Gas target (SUGAR), which is been completed with a neutron wall composed of 16 scintillator crystals (MONDE). With this combination will be possible to measure coincidences between charge particles and neutrons and/or gammas.
To complete the AMS system, and additional beam line will be coupled to the accelerator in order to extract intense and pure stable beams at low energy. In addition, the current radioactive beams used for AMS purposes, will be able to be used with an acceptable intensity in order to develop experiments related with the scattering and resonances of $^{13,14}$C and $^{26}$Al, using light targets.
In this work are presented some of the characteristics of all these new systems: the first data related with the commissioning of the Supersonic Gas Target, where the $^{14}$N(d,$\alpha$)$^{12}$C was studied, achieving a good resolution for the alpha resonances and proving the good qualities of the entire system; besides, is described the first approximation for the measurements of cross sections for the $^{28}$Si(d,$\alpha$)$^{26}$Al and $^{25}$Mg(p,$\gamma$)$^{26}$Al reactions at low energies, where are used the two accelerators that were mentioned before, the CN-Accelerator to produce the reaction, and the AMS system to measure the concentration of $^{26}$Al produced after the irradiation. These $^{26}$Al concentrations are directly related with cross sections of a particular reaction energy, whose values are currently interesting for Astrophysics parameters.
This research is been partially supported by PAPIIT-DGAPA-UNAM-Project: IA101616.
Recently the installation of a Van de Graaff accelerator in the Campus Macul of the Universidad Tecnológica Metropolitana has promoted the formation of the Laboratorio de investigación aplicada con tecnologías atomicas y nucleares (LIATAN). One of the objectives of this scientific laboratory is the development of advanced research mainly in the field of material sciences and environmental sciences using atomic and nuclear technology. This facility is to be considered as a complex laboratory, consisting of facilities that once were operating in other institutions and that will enhance its operation through a project that our University leads.
An essential component of the LIATAN Laboratory is a Van de Graaff electrostatic accelerator. This equipment includes very complex research instruments which are unique in the country since allowing different kind of studies by using IBA techniques[1] such as characterization of surface material samples or to determine trace elements in aerosols samples. On the other hand, a linear electron accelerator will also be installed at the LIATAN laboratory. This accelerator was donated by the National Cancer Institute and it was mainly used for the treatment of tumor diseases and the study of other solid, liquid, gaseous samples. Both facilities are aimed to promote further applied atomic and nuclear research in our country. This talk will describe the main characteristics of the LIATAN facilities and future research prospects.
Acknowledgments: The authors recognize financial support from Dirección de investigación y desarrollo académico (DIDA) of Universidad Tecnológica Metropolitana.
I will present the low-energy light Radioactive Ion Beam (RIB) in-flight facility EXOTIC [1-4], operational at the INFN-Laboratori Nazionali di Legnaro (INFN-LNL) and the associated experimental set up [5] designed for nuclear physics and nuclear astrophysics experiments. I will present the outline of the experimental program carried out employing the produced RIBs and discuss few selected recent experiments. Finally, I will give the perspectives of the EXOTIC project.
Despite all the information we have accumulated during the past decades about the structure of $^{12}$C we have not resolved a number of detail, for example, the geometry of its second excited state at 7.65 MeV (0$^+$), the Hoyle-State, has not yet been solved. Recent results have showed a possible 2$^+$ resonance between 9-12 MeV that could be related with a collective rotational or vibrational excitation while a resonance at 13.3 MeV is a strong candidate for the corresponding 4$^+$ excitation. In particular, a most recent measurement in which a new high spin Jπ = 5$^-$ resonance at 22.4 MeV which matches with that predicted ground state rotational band of an oblate equilateral triangle with a D3h symmetry. Symmetry that was observed for the first time in nuclear physics. Through angular correlations it was possible to characterize the 22.4 state in terms of spin and parity.
The structure of A=9 nuclei are relevant in astrophysics and nuclear structure. The measurement of the low-lying excited states in 9B nucleus through the $^9$Be($^3$He,t)$^9$B reaction, with the K600 spectrometer in conjunction with a segmented silicon detector array was performed at iThemba LABS facility. Of particular interest was the investigation of the first ½$^+$ state in $^9$B in order to address discrepancies that currently exist between theoretical models in describing these nuclei.
Recently, an experimental campaign was performed at the LAFN (Open Laboratory of Nuclear Physics) of the University of São Paulo. Various angular distributions were obtained at energies around the Coulomb barrier for the $^7$Li + $^{120}$Sn and $^{10,11}$B + $^{120}$Sn reactions. Besides the elastic scattering, other reaction channels, such as projectile and target-like excitation, and transfer of nucleons, were observed. Details on the experiment, and a theoretical analysis performed within the coupled-channel formalism, will be presented.
We study the thermodynamical properties of a neutral vector boson gas in a constant magnetic field starting from the spectrum obtained by Proca formalism.
Bose Einstein Condensation (BEC) and magnetization are obtained, for the three and one dimensional cases, in the limit of low temperatures. In three dimensions the gas undergoes a phase transition to a usual BEC in which the critical temperature depends on the magnetic field. Therefore, the condensation is reached not only decreasing the temperature, but also by increasing the field. For the one dimensional gas a diffuse BEC appears. In both, one and three dimensions, the magnetization is a positive quantity and for densities under a critical value the gas can sustain its own magnetic field.
The anisotropic pressures are also considered. The pressure exerted along the field is always positive, but the perpendicular pressure might be negative and the system turns out to be susceptible to suffer, under certain conditions, a transversal magnetic collapse.
The above describe phenomenology is manifested for magnetic fields and densities in the order of those typical of compacts objects. In this regard, a brief discussion of astrophysical implications is presented.
Measurements of the azimuthal angle correlation between the two jets with the largest transverse momenta (pt) in inclusive 2-jet topologies, close to the back-to-back configuration, are presented for several regions of the leading jet transverse momentum. The features of the different models considered in the comparisons and their physical impact are discussed.
A novel imaging device is proposed based on the gamma-backscattering technique described in Refs. [1,2], developed at GSI (Darmstadt, Germany) and modified by the Nuclear Physics Group at National University in Bogotá, which has been successfully tested by observation of concealed objects behind metallic walls, inspection of metallic structures and localization of buried objects [3,4]. The camera comprises essentially a positron source, a backscattering detector and a position detector that determines the direction of correlated 511 keV gamma-rays used to inspect the object. The backscattered gamma-rays are detected with a Compton Camera, following a design presented in Ref. [5], which provides additional information on the position where the scattering process occurs. In order to evaluate the imaging capabilities of the new camera a simulation was developed using the GEANT4 [6] simulation toolkit. In this work, a description and characterization of the new device is presented. Simulated results suggest already methods to improve the position resolution of the camera, which has been applied to study defects presented in corroded metallic structures.
This work was supported in part by Universidad Nacional de Colombia DIB 13440 and Colciencias 110152128824.
The tertiary structure and interactions with intermediate filament proteins of the desmoplakin C-terminal, a cytolinker protein related to severe skin diseases and fatal cardiovascular failures, has been determined by the use of two complementary techniques: Nuclear Magnetic Resonance (NMR) and Small Angle X-Ray Scattering (SAXS). NMR spectroscopy provided the atomic structure detail and interactions dynamics information of the desmoplakin linker domain, while SAXS was used to solve the global shape and orientation of the B-linker-C desmoplakin multi-domain. By resolving the ambiguities of the orientations of the individual domains with SAXS it was possible to discriminate between similar structural conformations obtained by NMR. Through the use of these two techniques, we gauged the architecture of the desmoplakin plakin repeat domains B and C in a construct including the linker domain, with the latter offering a pair of basic residues that recognise acidic residues on helical intermediate filament proteins that enhances the desmoplakin binding activity with these proteins.
Studies on magnetic moments and life-times of exotic nuclei have unveil properties which have leaded to the deeper understanding of the nature and behavior of the nuclear potential. During last years, the alpha-transfer technique has been useful for the study of properties of nuclear species which cannot be created with the current radioactive beam facilities. One of these characteristics, the magnetic moment of short life-time spin-states, had always been a huge challenge because several difficulties such as the alignment of the nuclear spin along a quantum axis. The Transient Field technique allows the measurement of nuclear magnetic moments using the variations of the angular distribution of the emitted gamma-ray radiation, from the state of interest, with a resolution around mrad. In addition to the latter, the Doppler Shift Attenuation Method allows to establish the life-time of excited nuclear states. In this work the measurement of the 2$^+$ and 4$^+$ spin-states of the deficient-neutron $^{110}$Sn and the life-time of the $^{106}$Cd excited spin-sates will be presented, the experimental technique makes use of the alpha-transfer reaction in combination with Transient-field technique and DSAM.
Keywords: Alpha transfer, Transient Field, Coulomb excitation, DSMA, life-time, magnetic moments.
The spectroscopy of heavy nuclei near the $N$=152 and $N$=162 deformed shell gaps provides precious information to improve current predictions of long-lived super-heavy elements in the Island of Stability. Due to deformation, in fact, substates of spherical orbits in the island of stability can be found near the Fermi level in these lighter systems. At the JAEA-Tokai Tandem accelerator, the first in-beam $\gamma$-ray spectroscopy of $^{252}$Fm (Z=100, N=152) was attempted. $^{252}$Fm was produced via the multi-nucleon transfer reaction $^{249}$Cf($^{12}$C,$^9$Be) respectively at 75 and 77 MeV. The target radioactivity was nearly 150 kBq. The target chamber was surrounded by a new particle-gamma detection setup, comprising an array of Silicon detectors to detect and identify the light reaction ejectiles, and a mixed array of four Germanium and four LaBr$_3$(Ce) detectors, with an absolute photopeak efficiency of nearly 30% at 150 keV. $\gamma$-ray transitions from $^{252}$Fm were discriminated by the coincident detection of $^{9}$Be. The analysis revealed candidate peaks for $^{252}$Fm E2 transitions in ground-state rotational band. The implications of this measurement and future plans using a $^{254}$Es target will be presented.
The SoLid experiment aims to measure the anti-neutrino energy spectrum 6--9 m from the core of the BR2 nuclear reactor at SCK$\bullet$CEN in Mol, Belgium. The main goals are to provide a very sensitive search for short-baseline neutrino oscillations and to resolve the reactor neutrino anomaly. The proposed detector technology will be very useful for anti-neutrino detection in other settings as well, such as nuclear safeguard and non-proliferation monitoring of nuclear reactors.
The experiment uses a novel, highly segmented composite scintillator detector. The detector unit is based on 5 cm polyvinyl toluene scintillator cubes, thin neutron sensitive $^6$LiF:ZnS(Ag) sheets and a reflective Tyvek layer wrapping them for light tight. A first large scale detector prototype based on this technology was deployed at the BR2 reactor by the end of 2014. The main purpose was to study the capability of the detector design to discriminate background. Due to the low overburden and proximity to a nuclear reactor, efficient background reduction is crucial for a successful experiment.
This contribution will be presenting and discussing the advantages of the SoLid detector design for background reduction. The background components studied include atmospheric and spallation neutrons induced by cosmic rays and possible natural radioactivity contamination from the decay chains of $^{238}$U and $^{232}$Th. The results are based on the data taken with the prototype detector and its full chain GEANT4 based Monte Carlo simulations.
Nowadays one of the main problems of Physics is not to know the origin and nature of the acceleration of cosmic expansion during the present and future stages in the evolution of the Universe. The research carried out includes the study of a model based on the Higgs field non-minimally coupled to gravity. Cosmological implications of the Higgs field have been studied for some years, and they have taken more importance after the recent discovery of the Higgs Boson in 2012 at the Large Hadrons Collider in Geneva, Switzerland. Using the dynamical systems technique, we study the possibility that the cosmological Higgs field non-minimally coupled to gravity can lead to the current behavior of the universe. We consider a homogeneous and isotropic flat Friedmann-Robertson-Walker (FRW) metric. We prove that there are two possible late time attractors corresponding to stable de Sitter solutions. These two solutions correspond to late-time accelerated expansion.
Heavy quark $c\acute{c}$ has been studied in the non-relativistic framework using interquark potential models of the form of sum of power of the interquark distance. The form of potential is based on phenomenology facts. The proposed potential was solved numerically using a program written on C++. Mass spectra and the expectation value of the radius have been estimated for different quantum mechanical state for $c\acute{c}$ system. The results have been compared with other similar and recent works. The mass spectra obtained is in acceptable agreement with the experimental data for $c\acute{c}$.
Employing the Feynman diagrams technique, the GBW model for performing nucleon-dipole interaction and the Regge theory, a new approach for computing in a unique way (perturbative and non-perturbative), the vector meson production has been presented.
The interaction between the color dipole created by the virtual photon and the nucleon is carried out by the exchange of two virtual gluons, which connect the color dipole with the gluonic sea inside of the nucleon trough a three gluonic vertex. The model was
explored in the production of ρ0 ,ϕ and J⁄ψ.
The ionizing radiation absorbed by semiconductor devices can change their properties by modifying the electrical parameters that characterize them and, in the case of memories, processors, can modify the information contained in these devices. In this way, the development of electronic devices resistant to radiation and the qualification of devices confirming that they are more tolerant to the effects of ionizing radiation, require a qualified workforce with the specific knowledge of the physical mechanisms acting on the devices when exposed to the radiation. It is also necessary to know all internationally existing standards for the qualification of devices. Digital systems are often used in space applications to process data, implement control logic, or even store data from sensors. These systems are composed of electronic devices, such as transistors, microcontrollers and microprocessors, which are exposed to ionizing radiation. The use of Field-Programmable Gate Arrays (FGPAs) in aerospace & defense field has become a general consensus among Integrated Circuits (ICs) and embedded system designers. Radiation-hardened electronics used in this domain is regulated under important political and commercial treaties. In order to refrain from these undesired political and commercial barriers COTS FPGAs have been considered as a promising alternative to replace ICs. The development of instrumentation that makes it possible to design new electronic devices, based on new materials and new technologies, as well as knowing how to properly characterize a device, is extremely important for this research area to be self-sufficient in our country. This research project aims to study the effects of ionizing radiation from X-rays, alpha source, protons and heavy ions on electronic devices. The specific objective of the project is to operationalize a system for radiation testing and a methodology for the qualification of electronic devices and components when subjected to radiation doses induced by heavy ions, particles and X-rays. We intend to study the physical phenomena responsible for the effects of radiation and generate training in this strategic area.
The objective of the experiment is to measure NORM (Naturally Occurring Radioactive Material) in natural samples and calculate their concentrations. For this purpose, experiments detecting the radiation of several gamma-ray calibration sources located at different positions around an HPGe detector were conducted. The efficiency calibration curve for each position was obtained, a piece of information useful to determine the concentration of radionuclides within an extended source. To perform the validation of the results an IAEA reference standard (40K) was placed in different geometries within the volume of a lead shield together with the HPGE detector and the efficiency correction was considered to determine the concentration of radioactive material. The measurement of the 40K concentration was compared with the activity concentration values reported in the calibration certificate of the reference standard. The usefulness of this work is to measure NORM in natural samples to calculate their activity concentration without using the comparison with a reference standard.
On the basis of the atomic displacement energy ($T_d$) calculated using the Density Functional Theory with Tight Binding Approximation (DFTB), the cross sections of electron-induced atomic displacement were obtained as a function of the order of the fullerene. Three types of defects commonly induced by radiation (mono-vacancy, di-vacancy and Stone-Wales) were also analyzed, determining their formation energies and the structural changes they produce in the molecule. The results are consistent with the model for the transformation of polyhedral structures to spherical nano-onions under electron irradiation, proposed by Ugarte in 1995.
Every day, the population is exposed to various types of radiation sources. In particular, the radon is the most common radiation present in a gas form. Radon belongs to the radioactive series of uranium and in its decay emits alpha particles of 5.49 MeV. To detect these alpha particles, an effective method very commun is to use Solid State Nuclear Track Detectors (SSNTD). This work propose a comparative study of track diameters using three kinds of CR-39 SSNTDs concerning the chemical etching time. The measurements have been performed exposing the sample plastic detectors to an 241Am radiation source during about 6.5 hours and chemical etched using well known solutions [2-4]. Two different temperatures have been used in this process (70 and 80 $^{\circ}$C) and different ranges of time. The diameter of the tracks has been obtained and followed between one chemical etching and other by taking digitalized images with calibration scale of 50μm and using the ImageJ code [5]. The track density have been calculated and the comparative results will be presented.
References
[1] S. Bing, Nucl. Tracks Radiat. Meas. 22, (1993) 451.
[2] J. N. Corrêa and et al., Rad. Phys. and Chem. 104, (2014) 104.
[3] F H Manocchi and et al., J. Radiol. Prot. 34, (2014) 339.
[4] S. Guedes and et al., Radiation Measurements 31, (1999) 287.
[5] Programme ImageJ: http://imagej.nih.gov/ij/index.html.
Semiconductor devices are susceptible to ionization radiation and this kind of event can change their behaviour and electrical properties, causing since a simple current peak on output of the circuit to a logical inversion, each event have your own root cause that can variable from an absorbed radiation dose to a different source of radiation. To deal with these problems is necessary understand the mechanisms behind of each event and use this knowledge to build circuits and semiconductor devices more robust to the radiation. The spatial program and military applications use electronic systems composed of microcontrollers, memories and other parties that can be exposed to radioactive environments in their normally use, a way to handle an unexpected behaviour are needed to avoid accidents. Electronic devices simulation is one of the methods to study the effects of ionizing radiation effects in semiconductor systems. The capability of isolate regions of the device under tests and control the simulation environment bring the possibility of observing the component of an event and understand the mechanisms behind of the event. This research project aims were create a 3D struct to simulate a commercial P-MOSFET (3N163), the effects of a Total Ionization Dose of X-Ray was widely studied and the effects of heavy ions emission is the object of studies in this work to observe the SEE event. The main purpose of the simulations is understanding the results collected to extract the main data and study secondary results that don’t was captured in the field experiment.
The age of sediment layers in regions near to the coast in Pinar del Rio province are determined using the quartz photoluminescence method. In some locations the studied layer could be associated with altimetry measurements allowing future analysis of recent tectonic movements. The method for sample collection, preparation and measurement are described. The results analysis indicates variations in the age of formation of these geological structures.
The natural dose rate is one of the physical magnitudes calculated during the process of age determination of geological sediments with the luminescence technique. The dose rate is calculated on the basis of the radioactive content presented in the sediments. Because of the low content of these radioactive isotopes a low background system should be used. In the present work the low background gamma spectrometric system used in the luminescence dating laboratory at CEADEN is described. The construction of a reference material with a similar composition to common sediments is also described. Finally, the radioactive content of quartz rich sediment from Pinar del Rio province and the respective natural dose rate are presented.
The gamma spectrometry is the most popular technique for the determination and quantification of the radioactive nuclei present in a radioactive source. In order to obtain the quantification of the radioactive material it is necessary to determine the efficiency of the detector for the energies of the gamma photons emitted from the source.
In the present work we present the theoretical development and the first tests of a new method to calibrate the efficiency of a gamma radiation detector for point sources.
The method consists in the determination of the detector efficiency using a mono-energetic gamma source (such determination must be realized experimentally), which we will be named the reference energy. Using a mono-energetic source is the easiest way to do this. Then from this value we can extrapolate the efficiency to the complete energy range using the physics of first principles of gamma radiation detection theory. Therefore the proposed method corresponds to a semi-empirical method.
In the first work we show the application and the study for the validation of the method using one reference energy (661,65 keV). In this second work we will apply the method using three references energies along the gamma energy range of interest, due to that in the first work the agree between the obtained values by the proposed method and the expected values were worse while the energies were farther of the reference energy.
The reference energies will be: 59,54 keV, 661,65 keV and 1460,65 keV, which are associated to the $^{241}$Am, $^{137}$Cs and $^{40}$K respectively. The second part of the method, the extrapolation from the reference energies to the gamma range, will be done over the energies emitted by $^{152}$Eu. All simulations will be done using FLUKA code.
We expect to improve the results obtained by the extrapolation from one energy reference to the complete energy range, with this new proposal considering a set of reference energies and a local extrapolation from these.
In previous researches, it has been identified the presence of tetragonal and rhombohedral crystalline phases in ferroelectric ceramic samples of PbZr$_{0.53}$Ti$_{0.47}$O$_3$ doped with La (1%) (PLZT) irradiated with $^{60}$Co gamma rays, showing their corresponding XRD patterns not conclusive evidences of phase transformations between both phases assisted by gamma irradiation.
The present work concerns with the evaluation of the gamma radiation damage of the irradiated PLZT samples, taking into the account the depleted atom displacement threshold energies due to the presence of point defects in the studied ceramic samples, as has been reported in [1].
It has been crystallographic evaluated, also, XRD reflexions of the non-irradiated PLZT samples, as well as of the irradiated ones by using new research tools of extrinsic and intrinsic nature [2], which are introduced in the present work, according their dependence or not of the choice of a particular crystalline vector basis.
In particular, in the case of the extrinsic methods, it has been established for cubic, tetragonal, orthorhombic and rhombohedral crystalline structures, an important property of the mean square value of the inverse of the interplanar distances taken over those reflexions owing the same value of the sum of square of their Miller Indexes. It results that the former one is proportional to the value of the sum the square Miller Indexes.
On the other hand, new intrinsic evaluation methods were introduced, like the density of reflexion lines and the differences between successive values of the inverse of the interplanar distances.
It results, that all studied PLZT samples ( non- gamma irradiated and irradiated ones) comprise two crystalline phases (with tetragonal and rhombohedral structures), where the application of the intrinsic and extrinsic developed methods showed drastic qualitative and quantitative difference among the non-irradiated simple on regard to the irradiated one. The irradiated PLZT XRD patterns showed the presence of two phases with tetragonal and rhombohedral crystalline structures close to the corresponding single-phase reference systems, which are tending to a pseudo – cubic symmetry.
For luminescence dating to be an accurate absolute dating technique it is very important that we are able to deliver absolutely known radiation doses in the laboratory. This is normally done using a beta source calibrated against an absolutely known reference source or by using a reference luminescence material that has been irradiated in a radiation calibration facility. Here we describe in detail the preparation and luminescence characteristics of a new quartz reference material of the luminescence dating laboratory at CEADEN. A selected sample of quartz extracted from a query in Pinar del Rio province has been treated to extract high pure quartz grains with diameters ranging from 180 to 250 µm. The resulting material was further treated to sensitize and stabilize the luminescence signal prior being irradiated to 5.0±0.3 Gy at the secondary calibration gamma source (related to BIPM) at the CPHR. With this material the dose rate of beta source of the automated luminescence reader LF02 has been calculated to be 0.034±0.002 Gy/s.
For decades, the great economic benefit that represents the use of radiotracers has been recognized by the international industry, however, this technique is still underutilized. The main cause is the lack of timely availability of required radiotracer. Previous studies show the possibility of labeling sediments (with a high content of aluminosilicates) with $^{99m}$Tc. This paper aims to develop a methodology for labeling silica sand with $^{99m}$Tc for using as solid radiotracer. Labeling the pretreated silica sand and untreated using varying concentrations of stannous fluoride and chloride as reducing agents and different times labeling was performed. The influence of different parameters of the pretreatment of sand in labeling yields obtained was evaluated and the effectiveness of the methods used to reduce $^{99m}$TcO$_4^-$ (R$_{red\%}$ > 87%) by ascending paper chromatography was proved. Changes in the composition of the silica sand after its pretreatment is able to observe from SEM-EDS techniques. It was possible to establish a methodology for obtaining solid $^{99m}$Tc labeled radiotracers in support of silica sand with an estimated preparation time of 4 hours a R$_{ret\%}$ equal to 74% (or a methodology for obtaining solid radiotracers labeling with $^{99m}$Tc in support of silica sand with an estimated preparation time and a R$_{ret\%}$ equal to 74%).
The simulation of the spectroscopy systems using MC codes is a common practice in these days. The most popular softwares to do this are MCNP and Geant4 codes. In this work we present the simulation of a gamma spectroscopy system based on a coaxial HPGe detector using FLUKA code. The geometrical characterization of the detector was done from manufacturer information and using the spatial FEP efficiency distribution of the detector for 661.65 keV. The last one was used to determine the dimensions of the inner cavity of the detector, which are not informed by the manufacturer. Due to the differences between the real and simulated response functions, we suppose that these are proportional.
The aims of this work is double. On the one hand, to characterize the detector without the necessity to apply a radiography or any other technique that is not directly associated to a nuclear physics laboratory. And, on the other hand, to validate the simulation of a coaxial HPGe detector using FLUKA code.
2-hydroxyethyl methacrylate/Acrylamide hydrogels were prepared by simultaneous radiation induced cross-linking copolymerization of acrylamide (AAm), 2-hydroxyethyl methacrylate (HEMA) and water mixtures at a radiation dose of 10 kGy. Hydrogesl were characterized by infrared spectroscopy. Dynamic and equilibrium swelling of hydrogels in water and in buffer solutions were investigated. They were sensitive to pH and temperature. Swelling was non–Fickean and increased with increasing the acrylamide content. Temperature dependence of the equilibrium water uptake of copolymers exhibited a discontinuity around 35ºC resulting from the weakening of the hydrogen bonds between the hydroxyl groups of HEMA and the amide groups of AAm . The thermodynamic and network parameters derived from swelling and mechanical measurements are compared and discussed. They exhibit a strong dependence on the AAM content in the hydrogel. The doxorubicin release was governed by copolymer composition, the absorbed dose and their self solubility in water media.
Biomaterials have received a considerable attention over the last 30 years as a means of treating diseases and easing suffering. These materials have found applications in approximately 8000 different kinds of medical devices; even though biomaterials have had a pronounced impact in medical treatment, a need still exists to be able to design and develop better polymer, ceramic, and metal systems. Nowadays, the emergence of micro- and nanoscale science and engineering has provided new avenues for engineering materials with macromolecular and even down to molecular-scale precision, leading to diagnostic and therapeutic technologies that will revolutionize the way health care is administered. Mainly, micro and nanosystems from polymers, such as nanogels, have achieved a great attention in biomedical applications due to they have lots of advantages over conventional systems since they enhance the delivery, extend the bioactivity of the drug, show minimal side effects, demonstrate high-performance characteristics and are more economical.
Several of techniques have been described for the synthesis of nanomaterials from polymers. However, the use of ionizing radiation (γ, e-), to obtain polymeric micro and nanogels are characterized by the possibility of obtaining products with a high degree of purity, which ones are a technological novelty mainly in biomaterial manufacture and therefore in biomedical applications.
The irradiation dose influence on nanogels synthesis by gamma radiation in diluted PVP solutions at a dose ranging from 3 - 22 kGy was performed in this paper. The experiments were performed in absence of oxygen using aqueous PVP solution (0.05 – 0.3 %). Crosslinking reactions were carried out at 25 °C in a gamma irradiation chamber with a $^{60}$Co source (ISOGAMMA LLCo). The Scanning Electron Microscopy (SEM), Attenuate Total Reflection Spectroscopy (ATR), Dynamic Light Scattering (DLS), and Viscosimetry were used as characterization techniques.
Keywords: polymeric nanogels, gamma irradiation, biomaterial.
The intrinsic spatial efficiency method is a general and absolute method to determine the efficiency of any extended source. This was experimentally demonstrated and validated only for cylindrical sources and the gamma photons emitted by $^{137}$Cs (661,65 keV).
Also, we carried out a research to tested the method for different shapes and sizes. Due to the difficulty that the preparation of sources with any shape represents, the simplest way to do this is by the simulation of the spectroscopy system and the source. We simulated the spectroscopy system and the sources using the FLUKA code. The shapes of the sources were: rings, discs, cylindrical shells, spheres and spherical shells. In such work we only considered gamma photons with an energy of 661.65 keV.
In this work we present a test of the intrinsic spatial efficiency method for sources with the shapes already mentioned and for energies different to 661.65 keV. The gamma energies considered in this new work will be: 59.54 keV ($^{241}$Am), 351.93 keV ($^{214}$Pb), 911.19 keV ($^{228}$Ac), and 1460.65 keV ($^{40}$K).
Until this moment we have applied the method by simulation for ring sources emitting 1460.65 keV gamma photons, and located coaxially on different positions along the axial axes.
The preliminary results shown an excellent agree between the absolute efficiencies determined by the standard relative method (statistical count) and the intrinsic spatial efficiency method. The relative bias in all cases are lesser than 1.1%.
Electric Field Gradients (EFG) at Zn and O sites in disordered $^{57}$Fe doped ZnO matrixes arising from $^{57}$Mn irradiated ZnO samples with wurtzite crystal structure were simulated through DFT atomistic calculations methods. The ZnO disordered crystal defective structures were simulated by means of overdimensioned unit cells (supercell) containing Zn vacancies at different concentrations with a $^{57}$Fe atom per supercell. Previous DFT electron density calculation results in these defective crystalline structures reported in [1] were applied.
Electric Point Charge Model (PCM) was also applied to calculate EFG at Zn and O sites in the same $^{57}$Fe doped ZnO supercells as before, where Steinheimer antishielding factors γ͚ values were taken from previously reported ones. A new methodology based on algebraic invariants, as I and D named, of the EFG resulting secular equations for both, DFT and PCM EFG data, were introduced and applied. It was proved that the second degree invariant I is proportional to the electrical quadrupole splitting at $^{57}$Fe sites.
It results that a general agreement among Zn and O DFT- and PCM- EFG invariant data statistical distributions was observed, though the best results were achieved at the supercell with higher dimension (3x3x2) and the lowest vacancy concentration, where a good linear correlations among DFT and PCM I and D data were proved and the resulting effective γ͚ values are very close to the previously reported ones. It was concluded that PCM approach might be applied as an initial numerical assessment for EFG data for high dimensioned supercells.
In OSL dating of sediments the application of the single aliquot regenerative (SAR) protocol requires the calibration of each aliquot by giving them a known dose using an internal beta source with a dose rate ranging from 100 to 30 mGy/s. In the case of old samples that have received in natural conditions doses higher than 70 Gy the time employed to equate this dose may be significant. One distinctive feature implemented in the LF02 automated luminescence reader is the possibility of external irradiating the samples without manipulating them. The goal of this process is to reduce the total irradiation time by simultaneously irradiating all the aliquots in a gamma cell facility. The aim of the present work is to establish the conditions and the dose rate of the external irradiation process when using the gamma irradiation facility at CEADEN.
Present work deals with the scientific problems and the “states of arts” on regard the knowledge of the physical and structural behaviors of composite materials based on superconducting YBa$_2$Cu$_3$O$_7$ (YBCO) and carbon nanostructured compounds (wires and onnions), as well as, their electron and gamma radiation response, which are nominated as YBCO-Nano/C.
Based in the application of radiation transport simulation codes relying on the Monte Carlo Methods, and the Monte Carlo assisted Classical Method (MCCM) an assessment of the radiation damage in terms of displacements per atom (dpa) rate spatial distributions, as well as, of the energy deposition distribution in the composite YBCO-Nano/C is presented.
A simple structural model of the composite YBCO-Nano/C is introduced and justified, where a comparison among the behaviors its different physical properties with the irradiation treatment is discussed.
Under progressive and intensive radiation damage conditions atom displacement threshold energy, $T_d$, calculations through Molecular Dynamic Methods must take into the account, in addition to the framework of single recoil atom excitation in an ideal crystalline lattice, multiple excitations and real crystal structures with point defects, in order to reach a better approach to situations emerging from severe and intensive radiation damage impacts on irradiated materials.
At the present work, atom displacement threshold energies evaluations are performed by application of Molecular Dynamics, MD, calculation tools under the assumption that the BaTiO$_3$ tetragonal crystalline structure possesses vacancies. In this context, a 2x2x2 over-dimensioned tetragonal BaTiO$_3$ unit cell was considered containing several primitive ones and owing vacancies on Ba, Ti and O atomic positions under the requirements of electrical charge balance.
On this basis and following a previous report [1,2] on an ideal BaTiO$_3$ tetragonal structure, the present report concern with Ba, Ti and O MD $T_d$ calculation, where the corresponding primary knock-on atom (PKA) defect formation probability functions dependence on the initial excitation energies were calculated at principal crystal directions, and compared with previous one calculated at an ideal BaTiO$_3$ ideal tetrahedral crystal structure.
The purpose of this work was to investigate fission modes in the fission of heavy actinides. The experiments have been carried out at the U400 cyclotron at the FLNR JINR (Dubna, Russia) using the double-arm time-of-flight spectrometer CORSET. To investigate the role of closed proton and neutron shells in fission of $^{248}$Cf, $^{254}$Fm and $^{260}$No nuclei at an excitation energy of 40-45 MeV the mass and energy distributions of fission fragments in the reactions $^{16}$O+$^{232}$Th, $^{16}$O+$^{238}$U, $^{22}$Ne + $^{232}$Th and $^{22}$Ne + $^{238}$U have been measured. For the compound nucleus $^{260}$No$^*$ formed in the reaction $^{22}$Ne + $^{238}$U an increase of fragment yields in the superasymmetric mass region of 52/208 u, that corresponds to the formation of pair of two double magic nuclei $^{48}$Ca and $^{208}$Pb, were observed. Moreover, for $^{260}$No$^*$ compound nucleus at the initial excitation energy of 41 MeV the bimodal fission was observed. In this case at the symmetric mass split the both fission fragments was close to the double magic $^{132}$Sn. For the compound nuclei $^{248}$Cf and $^{254}$Fm* formed in the reactions $^{16}$O+$^{232}$Th, $^{16}$O+$^{238}$U and $^{22}$Ne + $^{232}$Th an increase of fragment yields in the mass region 70/180 u that corresponds to the nuclei $^{70}$Ni was observed. It present an interesting case because the initial excitation energy of compound nuclei was around 40-45 MeV whereas typically shell structure starts to break at around 20-30 MeV.
The Monte Carlo Simulation of Atom Displacement, MCSAD, algorithm and code have been developed and applied in solid materials for the assessment of electron and gamma radiation damage. In the code, single primary knock-on atom (PKA), processes are taken into account in regard to atom displacement (AD) occurrences, which give a well-suited description of radiation damage effects on relative low particle fluency irradiation environments. In addition, target matrix main properties on regard with electron and gamma quanta transport are assumed to remain constant during the radiation transport, it means that, and consequently, material related atom displacement threshold energies and density consequently do not change at different calculation history trails, which supposes a weak radiation damage effects on the target properties. However, under high brightness and fluency irradiation environments, the foregoing MCSAD algorithm and code assumptions are not adequate for describing progressive and intensive radiation damage effects on a given target matrix.
The estimation of spectrosopic properties of neutron-deficient nuclei in the A=100 tin mass region is needed for the understanding of the rp-process path and the experimental exploration of the nuclear landscape. In order to evaluate some spectroscopic properties of the Gamow-Teller $\beta^+$ decay of neutron deficient tin isotopes of A=100, we have performed shell model calculations by means of Oxbash nuclear structure code. The jj45pn valence space used consists of nine proton and neutron orbitals. The calculations included few valence hole-proton and particle-neutron in $\pi$g$_{9/2}$ and $\nu$g$_{7/2}$ orbitals respectively, in $^{100}$Sn doubly magic core. Effective interaction deduced from CD-Bonn one is introduced taking into account the nuclear monopole effect in this mass region. The results are then compared with the available experimental data.
Keywords: Nuclear Structure, $^{100}$Sn core, Monopole Effect, Oxbash Nuclear structure code, $\beta^+$ decay, neutron deficient tin isotopes.
Nowadays, much attention has been given to the problem of obtaining accurate numerical solutions of fixed source discrete ordinates problems. In this work, we described and tested four different numerical methods to solve one-group unidimensional discrete ordinates problems. First, we derived the Diamond Difference (DD) method, next it´s implemented the Linear Discontinuous (LD) and Spectral Green Function (SGF) methods and finally, we obtained the hybrid Linear-Discontinuous Spectro-Nodal (LD-SN) method for discrete ordinates problems. These methods are based on the use of the standard balance equations, which holds in each spatial cell and for each discrete ordinates direction, and consider four different auxiliary equations for the cell-average angular flux. Numerical results of benchmarks are given to illustrate and compare the methods’ accuracy. SGF demonstrated be the best method with no spatial truncation errors, follow by LD-SN, LD and DD, respectively. The LD-SN results proved be better than SGF in computational storage and numerical calculation per direction and per iteration.
Keywords: fixed source problems, discrete ordinates, hybrid linear-discontinuous spectro-nodal
The production of heavy clusters in nuclear reactions is a mechanism that until now is not well understood despite its importance and its wide variety of applications: radiation protection, space and engineering design, medical physics, the design of accelerators and others. According to the Exciton Cascade Model (CEM), there are three possible ways of producing high energy heavy clusters. The first mechanism is through the coalescence of the nucleons produced in the Intra-Nuclear Cascade (INC), the second way is through the pre-equilibrium model, and the last one is the so-called Fermi break-up.
In this work, a new theoretical approach is developed based on the INC model, which allows explaining the formation of light clusters through a first principles coalescence criterion that does not depend directly on experimental parameters and, at the same, can reproduce the experimental data. It is considered a semi-classical Wigner’s distribution function in phase space. The calculations have been assessed for the production of deuterons in p-197Au collisions in an energetic range of 2 – 10 GeV and the results obtained for the deuteron emission probabilities, and the total cross section is shown and compared with the experimental data.
An extension to the Monte Carlo assisted Classical Method (MCCM) methodology was developed and implemented. The extension allows to calculate the atom displacement per atom (dpa) profiles considering threshold displacement energies which are spatially inhomogeneous. Calculation of the dpa profiles was performed using both, the standard methodology and extended one for gammas of 1.25, 3, 7 and 12 MeV energies for the BaTiO$_3$ ceramic. Significant differences for the oxygen sublattice in all the energy range were found, being these ones the highest ones. In general, the dpa profiles calculated at the same sample deep and energy with the standard MCCM are between one or two orders higher than the ones calculated through the extension.
The production of neutron-rich heavy elements takes place via the rapid neutron capture process (r-process). To favour neutron captures over beta decays the astrophysical environment should be explosive like the one found in the core-collapse supernovae. In this work, we focus on the High Entropy Winds (HEW) in Type II supernovae which are one of the more promising sites for the r-process. After the neutron capture rates decrease, due to drop in the neutron density, the remaining nuclides can be highly unstable. After considerable time, these nuclei will decay to stability. The final abundances of elements will depend, besides of neutron capture, on other processes such as beta decay, alpha decay, photo dissociation, alpha capture and beta-delayed neutron emission. The present work evaluates the contribution that these processes have to the final abundances of certain nuclides and studies the dependence of that contribution in the presence of each one of the other processes. For our nucleosynthesis calculations, we used rJava 2.0, software that is able to simulate the physical environment of HEW as well as other r-process sites as the ejecta of neutron star mergers and the ejecta of quarknova.
In this work, the cross sections of the nuclear reactions $^{13}$C(n, γ)$^{14}$C and $^{14}$N(n, p)$^{14}$C are experimentally measured using the accelerators mass spectrometry (AMS) technique. To carry out this experiment we use the thermal neutron flux produced by the TRIGA Mark III nuclear reactor located at the National Institute of Nuclear Research (ININ) in Mexico. The concentration of $^{14}$C with respect to that of $^{12}$C in materials before and after neutron irradiation was determined in the Laboratory of Accelerators Mass Spectrometry (LEMA) of the Institute of Physics of the National Autonomous University of Mexico (UNAM). From the measurements of the relative $^{14}$C/$^{12}$C concentration it was possible to determine the corresponding cross sections. This work establishes an experimental protocol for the measurement of cross sections of neutron induced nuclear reactions at thermal energies. The results obtained for the $^{14}$N(n, p)$^{14}$C reaction are in good agreement with the values previously reported by other authors. On the other hand, for the $^{13}$C(n, γ)$^{14}$C reaction, the obtained values differ from those previously reported, which impels us to continue studying this reaction.
In this work, we have realized some spectroscopic calculations in the frame work of the nuclear shell model, in order to estimate the Gamow-teller (GT) $\beta^+$ decay of A=98 proton rich isobars in $^{100}$Sn mass region near rp-process path. The calculations are carried out by means of Oxbash nuclear structure code, taking into account the monopole effect in the studied mass region. The obtained results are then compared to the available experimental data.
Understanding the mechanism of energy loss of charged particles in matter is very important in atomic and nuclear physics given its application in fields such as material and surface science or radiation damage studies. In the last few years, there has been a renewed interest in increasing the accuracy of energy loss and straggling experimental values in order to determine some key parameters included in the theory of stopping power. However, there is still a lack of data about the straggling and the stopping power even for light ions.
In this work we present new data on the stopping power of Hf and Pd for protons and alphas particles in the energy range between 0.3 and 2.5 MeV. These measurements were carried out by using a 2.5 MV Van de Graaff accelerator of the Laboratory of Accelerators and Radiation Technologies (LATR) in C2TN/IST (Lisbon, Portugal). Transmission methodology was used to determine the stopping power cross sections by measuring the energy loss of protons and alphas passing through very thin foils made of Hf and Pd. So far, a good agreement has been found between the obtained results and values reported in literature (SRIM-2013, ICRU49). Additionally, modified Bethe–Bloch theory is being used to extract Pd mean excitation/ionization energy (I) and Barkas effect parameter (b) from the available experimental data.
Acknowledgments: The authors recognize financial support through “Proyecto de Iniciación en I+D y Creación, VRAC código L1-17, Universidad Tecnológica Metropolitana”. The authors gratefully acknowledge the invaluable technical support from F. Baptista (C2TN/IST).
In recent years, the investigation of spallation reactions have caught the attention of scientific community due to their application in the transmutation of nuclear waste by using the Accelerator Driven System (ADS) reactors. Due to the experimental difficulties that nuclear reactions researches face; the study of spallation reaction by using simulation codes is more suitable for generating more complete database for different energy ranges. This work aims to study spallation reactions induced by protons at intermediate energies 0.5 - 2 GeV on non-fissionable nuclei by using the Monte Carlo code: CRISP (Collaboration Rio-Ilhéus-São Paulo). The target nuclei studied were: $^{27}$Al, $^{91}$Zr, $^{184}$W, $^{197}$Au and $^{208}$Pb, focusing on the last one. Multiplicity of light particles obtained with CRISP was compared with the available experimental data and other Monte Carlo codes involved in the study of spallation reactions, resulting on a quite satisfactory agreement.
The study of nuclei out of the line of stability has been one of the main fields of research in low energy nuclear physics [1]. Light exotic nuclei such as 6He, 11Be, 11Li, 8B and others are produced in laboratory [2-4] and present new interesting phenomena such as the Borromean structure and the neutron and proton halos [5]. Nuclei like 7Be [6] and 8Li are not so exotic, however, may have much interest in both, nuclear structure and in nuclear astrophysics aspects [7]. The synthesis of heavy elements in stars, has to overcome the mass gaps A=5 and A=8 for which there are no stable elements. For A=8 there are two bound nuclides, 8Li and 8B, which are mirror nuclei, and have half-lifes of arround 800 ms. The presence of these nuclei in stars could affect the nucleosynthesis of heavy elements up to 12C. In addition, nuclear data about nuclei A=8 is very scarce. This work propose measurements of 8Li elastic scattering on several targets: 9Be, 27Al, 58Ni, and 120Sn at laboratory energies from 16 to 32 MeV. Elastic scattering angular distributions at these energies will provide information about the nuclear potential. The interplay between Coulomb and nuclear effects can be investigated, as a function of the target mass. In addition, measurements with the light target 9Be may provide important spectroscopic information of the proton transfer reaction 9Be(8Li,9Be). The measurements will be performed at University of Sao Paulo, using the 8Li beam produced by the RIBRAS (Radioactive Ion Beams in Brasil) facility [8].
Very High Temperature Reactor (VHTR) designs of Generation IV, offer promising performance characteristics; they can provide sustainable energy, improved proliferation resistance, inherent safety, and high temperature heat supply. The 10MW High Temperature Reactor-Test Module (HTR-10) is a pebble bed reactor (PBR). To achieve the commercialization of these reactors in the nuclear industry, it is necessary to take into account very important factors such as safety, because the investigation of their thermo-hydraulic characteristics is a key tool for the design and safe operation of VHTR. Currently the use of codes of Computational Fluid Dynamics (CFD) for the deterministic safety analysis of nuclear reactors have been increased, because it is a tool able to describe in detail the thermal-hydraulic phenomena occurring in the cooling system of the reactor core. In this paper from CFD models (porous and / or realistic) is described with good accuracy the thermal-hydraulic behavior of the reactor core HTR-10 at steady state and the results are compared with a benchmark. The maximum temperature values in the porous medium model were reached at the reactor core outlet, specifically in the central zone. Therefore, the realistic simulation was performed in that region, in order to verify the behavior of the maximum temperature reached by the fuel, which do not exceed the allowable limit for this type of nuclear fuel. The results obtained are consistent with the results presented by other authors using other techniques and simulation models.
An experimental protocol to study the total cross section for the $^{13}$C(d, p)$^{14}$C nuclear reaction via AMS is being developed for energies in the center-of-mass frame between 100 and 533 keV. We started a series of experiments in which two aluminium cathodes filled with natural-graphite (98.9$\%$ 12C, 1.1$\%$ 13C) were irradiated at a deuterium energy of 4 MeV at the 6.0 MeV Tandem Van de Graaff Accelerator of the Instituto Nacional de Investigaciones Nucleares (ININ) in Mexico. The number of incident particles was determined using RBS techniques. The relative concentrations of $^{14}$C/$^{12}$C were analyzed using AMS at the Laboratorio Nacional de Espectrometría de Masas con Aceleradores (LEMA) of the Universidad Nacional Autónoma de México (UNAM). The relevance of the $^{13}$C(d, p)$^{14}$C reaction in the study of compound nucleus formation as well as in some astrophysics scenarios, and the importance of the development of the AMS technique to measure cross sections of nuclear reactions of astrophysical interest in Mexico are also discussed.
Plenary Sessions on Wednesday-Friday mornings (25 min + 5 min)
SPES (Selective Production of Exotic Species) is the INFN project for a Nuclear Physics facility with Radioactive Ion Beams (RIBs). It is in advanced construction in Legnaro, with several technological innovations and challenges foreseen, comprehensive of new achievements and improvements.
SPES will provide mostly neutron-rich exotic beams derived by the fission fragments (1013 fiss/s) produced in the interaction of an intense proton beam (200 microA) on a direct UCx target. Several other targets will be developed to provide users a large beam selection. The expected SPES beam intensities, their quality and, eventually, their maximum energies (up to 11 MeV/A for A=130) will permit to perform forefront research in nuclear structure and nuclear dynamics, studying a region of the nuclear chart far from stability. This goal will be reached by coordinating the developments on the accelerator complex and those of up to date experimental set ups.
The schedule of the project is organized so to give low energy beams (1+ species at 40 keV) at the beginning of 2019, while post accelerated beams up to the maximum energies (around 10-11 MeV/n) are foreseen in 2021, after the installation of the newly developed RFQ new injection system for the ALPI post accelerator.
The technical design and the installation phases will be described, followed by the description of some challenging arguments in the Nuclear Physics program to be performed at the Legnaro National Laboratory.
An significant part of the upgrade of the Dubna Radiactive Ion Beams facility is the replacement of the ACCULINNA fragment separator with a new high acceptance device - the ACCULINNA-2. The project of a new in-flight facility for low energy 30-60 AMeV primary beams with 3 ≤ Z ≤ 36 has been started in 2011. The new device is destined to add considerably to the studies of drip-line nuclei performed with the use of variety of direct reactions known to be distinctive to the 15 – 50 AMeV exotic secondary RIBs. An overview of the design, construction and commissioning studies of the ACCULINNA-2 device will be presented.
Secondary beam profiles as well as production rates were measured for 15N (49.7 AMeV) primary beam and Be (2 mm) target. Example dE-ToF identification spectra and calculated beam purity for 6He 31.5 AMeV and 12Be 39.4 AMeV as a main components of secondary beams will be demonstrated. Measured isotope yields agrees with LISE++ simulations. Future upgrades of ACCULINNA 2 setup (zero degree spectrometer, RF-kicker) and prospects of new experiments achievable in next years are presented.
The “Radioactive Ion Beams in Brasil” (RIBRAS) facility is the first device in the Southern Hemisphere to produce unstable secondary beams. It is in operation since 2004 and it consists of two super-conducting solenoids of maximum magnetic field B = 6.5T, coupled to the 8UD-Pelletron tandem Accelerator installed at the University of São Paulo Physics Institute. The radioactive ions produced by in-flight transfer reactions of stable projectiles, are selected and focalized by the solenoids into a scattering chamber. Low energy (3-5 MeV/u) radioactive beams
of $^6$He, $^8$Li, $^{7,10}$Be, $^{8,12}$B are produced currently and used to study elastic, inelastic, and transfer reactions on a variety of light, medium mass and heavy secondary targets. The 2n halo $^6$He and the 1p halo $^8$B are particularly interesting to study the role of the halo on the elastic and total reaction cross sections.
Since 2012 RIBRAS can produce purified beams, using both solenoids with a degrader between them. The use of purified beams opens new possibilities, as the resonance scattering studies using inverse kinematics, examples are the (p,p), (p,d), and (p,α) reactions using an $^8$Li beam hitting thick CH 2 targets to measure their excitation functions. The spectroscopy of the highly excited states of $^9$Be were studied in this way.
Fusion reactions are also possible with purified beams, we are programming to measure the fusion cross section by activation and off-line gamma-spectroscopy, and also by on-line particle-gamma coincidence. The interest is to study the influence of the 2n-halo structure of $^6$He on the fusion process. Our Cuban colleague Ivan Padron who spent a year in Sao Paulo put a large (2mx2m) position sensitive neutron detector, also called neutron wall, in operating conditions.
It can be used to measure break-up processes of neutron rich radioactive beams hitting a secondary target.
The installation of RIBRAS has opened many new possibilities to our Pelletron laboratory even approaching the frontiers of nuclear physics, demonstrated by the large number of publications and participations in international conferences.
Plenary Sessions on Wednesday-Friday mornings (25 min + 5 min)
Overarching questions such how and where are the heavy elements synthesized, and what is the mechanism of stellar explosions, like supernovae, have been the subject of study of nuclear astrophysics for the last decades. These puzzles are closely connected to the behavior of matter under extreme density and temperature conditions. Our current understanding relies on simulations, micro-physics input, observations and the connections among them. In this talk, I shall discuss the influence that the nuclear physics input, e.g. weak processes and the nuclear matter Equation of State, has on the above mentioned astrophysical phenomena.
Scientific investigations in the cultural heritage and objects of art are routinely performed in Europe and the United States a few decades ago, in Brazil we are currently increasingly using atomic and nuclear methods for this purpose. Since 2003 the Group of Applied Physics with accelerators of the Institute of Physics of the University of São Paulo has worked with various methodologies for characterization and analysis of cultural objects. The analysis methods include processes of imaging and techniques for elemental and compositional characterization. These methods used together allow the better understanding of the materials and techniques used in the creative process and manufacturing of the objects. In the processes of analysis are used as imaging techniques: Photos with visible light, reflectography Infrared, fluorescence radiation with ultraviolet light, images with tangential light and digitized radiography; that are used to examine and document the artistic and cultural heritage objects. In the determinations of the characteristic materials of the objects present in the collections, we used analyzes for determining the existing elements and chemical compounds in the surface layers of these. The techniques involve ion beam analysis such as Particle Induced X-Ray Emission, Rutherford Backscattering and currently Ion Luminescence. Extending further the possibility of analysis, it has been used the techniques of X-ray Fluorescence and Raman spectroscopy with portable equipment that can be used in museums themselves. The results of these analyzes are providing valuable information about the manufacturing process and provide new information of the objects and all this has allowed a new collaboration with different São Paulo museums such as Pinacoteca, Museum of Contemporary Art (MAC-USP), Paulista Museum, Museum of Archaeology and Ethnology (MAE-USP) and the Institute of Brazilian Studies (IEB-USP). Several works and studies are being carried out systematically in these institutions in different artworks in the museum’s collections such as easel paintings, ceramic objects, papers, photos, etc. The information obtained are allowing the formation of a database about materials, pigments and manufacturing techniques of various artists. Particularly in the study of easel paintings the characterization of pigments in parallel with the imaging techniques has allowed to reveal the artist's creative process and has determined the palette used by the artist in one particular work. The purpose of this systematic study is to produce useful information to historians, curators, conservators and restorers for the expansion of knowledge in art history, but also in determining and defining the technical conditions and preservation of the cultural heritage material. The group of applied physics to the study of the historical and artistic heritage objects (NAP-FAEPAH) was formed in the University of São Paulo with collaboration of the different museums and institutions, and several works are been performed and will be presented and discussed.
For the fisrt time, a Saliba's painting was investigated by means analytical technique, MA-XRF (Macro- X-Ray Fluorescence). The LANDIS-X, a novel mobile scanner, allowed to obtain elemental distribution of the pigments allowing better elucidating palette and painting technique.
Spherically symmetric solutions are presented of the equations of motion for a scalar field interacting with gravity (EKG equations) in the Colombeau-Egorov’s sense. The scalar fields are confined within the interior region and the exterior fields are purely gravitational and coinciding with the Schwarzschild ones. The solution resembles the so called ”gravastars” which had been discussed in the literature. These solutions of the EKG equations open a possibility for the existence of static boson stars. The argumentation is based in defining a one parameter ϵ dependent family of radial dependencies of the metric and the scalar field, being infinitely differentiable. Afterwards, it is argued that in the limit ϵ-> 0, the EKG equations are satisfied in the sense of the generalized functions. The solutions exhibit properties which qualitatively support their physical meaning. For example close to the boundary at the interior, the scalar field energy density pile up towards to the limit surface. On the other hand, also close to the separation surface, but on the outside, the known ”non-hair” theorem, clearly indicates that any scalar field perturbation also tends to be attracted to the boundary. The work also suggests the possibility for obtaining a regular gravastar, after using the found singular configuration as a first step in an iterative solution of the quantum EKG equations.
We use Hartle's formalism to study the effects of rotation in the structure of magnetized white dwarfs within the framework of general relativity. The inner matter is described by means of an equation of state for electrons under the action of a constant magnetic field, which breaks the SO(3) symmetry and introduces a splitting of the pressure into one parallel and other perpendicular to the magnetic field. Solutions correspond to typical densities of white dwarfs and values of magnetic field below 10$^{13}$G, considering perpendicular and parallel pressures independently, as if associated to two different equations of state.
Rotation effects obtained accounts for an increase of the maximum mass for both, magnetized and non-magnetized stable configurations, up to about 1.5 M$_⊙$. Further effects studied include the deformation of the stars, which become oblate spheroids and the solutions for other quantities of interest, such as the moment of inertia, quadrupolar momentum and eccentricity. In all cases, rotation effects are dominant with respect to those of the magnetic field.
Attenuation of hadrons with open or hidden heavy flavor, produced in relativistic heavy ion collisions, is described within the color-dipole approach. A charmonium propagating through a dense matter can be broken-up by either Debye screening of the binding potential (melting), or due to color-exchange interactions with the surrounding medium (absorption). These two effects are found to have similar magnitudes and both vanish at high transverse momenta of the charmonium.
Although hadrons with open heavy flavor, charm and beauty, have been predicted to have a high survival probability, they were found to be strongly suppressed by final state interactions with the created dense medium. While vacuum radiation of high-$p_T$ heavy quarks ceases at a short time scale, production of a heavy flavored hadrons in a dense medium is considerably delayed due to prompt breakup in the medium. This causes a strong suppression of the heavy quark yield in a good accord with available data.
Carbon nanostructures, obtained by underwater arc discharge of graphite electrodes, were studied by X-Ray Photoelectron Spectroscopy (XPS). It was observed that the spectra of the samples taken from the floating part of the synthesis products, composed basically by Carbon nano-onions (CNO), present differences with those obtained from the precipitate , which contains a mixture of CNOs and multi-walled Carbon Nanotubes (MWCNT). These differences are related with the presence of atoms of carbon located in orbitals with different degree of hybridization (sp$^2$-sp$^3$), which in turn is related to the diverse grade of curvature of the planes of carbon in the nanostructures present in the samples.
The obtained results indicate that XPS can be an important element in the characterization of the products obtained by the above-mentioned method of synthesis.
We demonstrated in previous investigations that the internal structure of paintings can be visualized with conventional radiography in transmission mode when paintings have the proper stratigraphy. Unfortunately, there are many paintings that do not result in useful images. This problem can be solved by using radiography in emission mode. With this technique, the painting is irradiated with high energetic X-rays originating from an X-ray tube operating at 100 keV – 320 keV while inside the painting low energetic signals such as photoelectrons or characteristic photons are being generated. These signals escape from the top 10 µm of the painting and are able to illuminate the imaging plate. However, this technique has also some disadvantages. One of them is that it is not able to visualize underlying paintings. In this study, we explored the possibility to enhance the information depth by increasing the energy of the photon source from 100 keV up to 1.3325 MeV (i.e., Co60 source). At the same time, we also studied the impact of the energy on the contrast between pigments and on the lateral resolution. For this, we used mathematical simulation of particle transport in matter to understand the relation between input particle (particle type such as photon, electron or positron and the energy of the particle), the material being irradiated (element from which it is composed, thickness) and the output signal (generated particle types, energy, dispersion). Finally, we will show that it is possible to image paintings using a Co60 source.
During the last two decades, the Nuclear Physics Group of National University (GFNUN) has been leading nuclear basic research, generating innovation edge based on its own basic research, training researchers, public servers and society, and building technological transfer. The nuclear Colombian context presents a weakness on strategical nuclear programs and politics based on technical knowledge, low technical formation of decision makers and regulatory supervisors, and low coordination and not assumed responsibility between different governmental dependencies [1]. Colombia is a developing country which economy is highly depending on extractives activities, commodities, agro-industry and tourism. GFNUN is leading three main techniques not only to be applied in the local context but also worldwide which are an innovative methodology to evaluate radioactive materials, and nuclear techniques for corrosion detection and explosives detection for security and defense, and humanitarian demining purposes.
An interesting point as example of the technological evolution is the fact that ate sixth year of developing the demining detection technique, GFNUN found a derived application based on. This is corrosion diagnosis with gamma retrodispersion and explosives detection for security and defense. Now, the corrosion detection technology and explosives detection are starting their third and first year of development, respectively, and the results are promissory but specialized strategies for the technological transfer to the market, potential investors, and a trustworthy royalties system for the researchers are needed; specially in a developing economy context.
Experimental angular distributions for the $^{7}$Li + $^{120}$Sn elastic and inelastic (projectile and target excitations) scattering, and for the neutron stripping reaction, have been obtained at $E_{{\rm LAB}}=$ 20, 22, 24 and 26 MeV, covering an energy range around the Coulomb barrier ($V_{B}^{{\rm(LAB)}}\approx21.4$ MeV). Coupled channel and coupled reaction channel calculations were performed and both describe satisfactorily the experimental data sets. The $\frac{1}{2}^{-}$ state $^{7}$Li inelastic excitation (using a rotational model), as well as the projectile coupling to the continuum ($\alpha$ plus a tritium particle) play a fundamental role on the proper description of elastic, inelastic and transfer channels. Couplings to the one-neutron stripping channel do not significantly affect the theoretical elastic scattering angular distributions. The spectroscopic amplitudes of the transfer channel were obtained through a shell model calculation. The theoretical angular distributions for the one-neutron stripping reaction agreed with the experimental data.
Nuclear reactions induced by neutron-rich radioactive beams have opened new possibilities for studying nuclei far from stability line [1]. The increase of the reaction cross-sections for neutron rich nuclei compared to the stable nuclei can be attributed to their larger nuclear radii. In order to observe this effect a systematic investigation of total reaction cross sections from elastic scattering measurements using the $^9$Be target and tightly bound, weakly bound and exotic projectiles have been performed [2]. In particular, the $^6$He+$^9$Be exotic system shows large values of the reaction cross section compared to reactions induced by stable weakly bound projectiles [1,2]. For this light system, the Coulomb interaction is smaller than nuclear interaction. Thus, the Coulomb breakup of the projectile is expected to have less influence. Another study was carried out to verify the dependence of the observed enhancement as a function of the target mass. The analysis was extended to the $^6$He scattering on light, medium and heavy mass targets. The results showed a weak, but considerable, enhancement in the total reaction cross section for $^6$He+$^9$Be system in comparison to $^6$He scattered on heavy targets [2]. From the total reaction cross sections values, the $^6$He nuclear interaction radius are extracted using a new method employing a simple geometric relation [3]. A comparison with the radius of the $^6$He obtained at higher energies is presented.
Heavy ion nuclear reaction studies are an important tool to observe and disentangle different and competing mechanisms, which may arise in the different energy regimes. In particular, at relatively low bombarding energy the comparison between pre-equilibrium and thermal emission of light charged particles from hot nuclei is interesting. Indeed, nuclear structure of the interacting partners and reaction dynamics may be strongly correlated, especially at energies close to the Coulomb barrier, and it emerges when some nucleons or clusters of nucleons are emitted or captured [1].
In particular, a major attention has been devoted, in the last years, to the possible observation of cluster structure effects in the competing nuclear reaction mechanisms [2], especially when fast processes are involved.
At this purpose, the four reactions $^{16}$O+$^{30}$Si at 111 MeV, $^{16}$O+$^{30}$Si at 128 MeV, $^{18}$O+$^{28}$Si at 126 MeV and $^{19}$F+$^{27}$Al at 133 MeV have been measured, to study the onset of pre-equilibrium in an energy range where, for central collisions, complete fusion is expected to be the favorite mode. Experimental data were collected, using the GARFIELD+RCo array, fully equipped with digital electronics [3], at Legnaro National Laboratories.
Following the identification of particles and the energy calibration procedures, the complete analysis has been performed on an event-by-event basis. Experimental data are compared to some theoretical predictions: in particular, both dynamical models based on either Stochastic Mean Field (Twingo [5]) or Anti-symmetrized Molecular Dynamics (AMD [4]) and/or fully statistical model (Gemini++ [6]) have been considered. Events generated through these codes are filtered through a software replica of the setup, in order to take into consideration any possible distortions of the distributions due to the finite size of the apparatus.
Differences between the experimental data and the predicted data, which are based on very different physical assumptions, can evidence possible entrance channel effects, which may be due to the cluster nature of the colliding partners.
After a general introduction on the experimental campaign, this contribution will focus on the preliminary results obtained so far.
The chromium - compensated gallium arsenide is attaining a relevant position between the materials devoted to the development and fabrication of radiation detectors. This material shows high resistance to the radiation damage, high effective Z, relative low production cost, possibility to grow large area films, etc. Some results from the study of Timepix hybrid detectors based on GaAs:Cr by using the Monte Carlo modeling of radiation transport are presented in this contribution. The MCNPX, GEANT4, SRIM and MCCM code systems were used for this purpose. In-depth profiles of the energy deposited by the incident radiation within the sensor active volume are included. Similarly the shapes and dimensions of the charge carriers clouds generated by different energy incident photons, in different geometrical conditions, are also obtained and presented. The ranges of two different energy $^{22}$Ne ions in GaAs:Cr material and the contributions from each energy loss channel were also determined in the U-400M cyclotron. In addition, the effective displacement cross-sections and the number of displacement per atom produced for each atomic specie are presented when the device is irradiated with electrons and photons at different energies.
Giant-dipole- resonance photoneutrons (GRN) are produced by LINAC 2300 CX operating in the range of 15 MV. During radiotherapy treatment unwanted neutron dose is delivered to patients. To establish the thermal and epithermal photo-neutrons field during radiotherapy treatments Nuclear Track Methodology (NTM). The well tested polyallyldiclogola carbonate (PADC type CR-39 TM on that a thin boron film is deposite to convert neutrons in charged paticles by 10 B(n,α) reaction are employed. The passive device register with efficiency charged particles as a damaged volume these are visible after chemical etching (6N, NaOH, 70 o C) under light transmission microscope (10 x 40).
Tracks of the order of micrometers are visible and their diameters are measure to determine track densities and histogram bars. These provide information on the neutron intensity and energy groups.
Enhancement effects are observed on absorbed dose due to both scattered photo-neutrons and (γ,n) reactions and a relatively good response is observed for mixed radiation field. To solve the difficulty in measuring the photoneutron spectra that is produced from the head of the LINAC due to very intense gamma irradiation, can be used this metodology for stablish the energies of neutrons
and is corroborated by MCNPX the neutron spectra, establishing the additional dose that is attributed to the neutron component.
In this work we calculated two kinetic parameters of the RECH-$1$ research nuclear reactor: the effective delayed neutrons fraction, $\beta_{eff}$, and the mean neutron generation time $\Lambda$ using the Monte Carlo codes MCNP6 [1] and Serpent 2 [2] and the neutron cross section library ENDFV.VII.$1$.
To calculate $\beta_{eff}$ we used the method proposed by Meulekamp and van der Marck[3]. In this method the effective delayed neutron fraction is estimated as
$$ \beta_{eff} \sim 1 - \frac{k_p}{k}, $$ where $k_p$ is the prompt effective neutron multiplication factor and $k$ is the total effective neutron multiplication factor. To calculate the effective neutron generation time we used the pulsed neutron source method[4]. In this technique a burst of neutrons is injected in a subcritical system and then the decay of the neutron population is observed as a function of time. After the system thermalization and decay of higher flux modes, the fundamental-mode decay constant, $\alpha_0$ can be measured using the point kinetic approximation. The relation between $\alpha_0$ and the reactivity, $\rho$, is obtained from the point kinetics equations: $$ \alpha_0 = \frac{\rho - \beta_{eff}}{\Lambda}. $$
These calculations will be contrasted with reactor operation experimental campaign results during next year.
The Generation IV Very High Temperature Reactor (VHTR) is envisioned as an outstanding prototype among the six nuclear systems propose in the Generation IV. The characteristics that highlights this reactor are focused in the low electricity generation costs, short construction periods, in proliferation resistance and physical protection. Nevertheless, it presents essential challenges to be deployed as a sustainable energy taking into consideration the high temperatures (1000°C in normal operation and up to 1800°C in accidents conditions) and burnup degrees (150–200 GWd/TonU) achievable in these reactors. One of these key challenges is the nuclear safety which mainly relies on the quality and integrity of the coated fuel particles (TRISO). In this investigation will be studied the thermomechanical behavior of the TRISO fuel in function of the variation of different parameters taking into consideration the deep burnup degrees planned to be reached in the VHTR. The studies performed in this investigation included the evaluation of key parameters in the TRISO such as: release of fission gases and CO, gas pressure, temperature distributions, kernel migration, maximum stress values, and failure probabilities. In order to achieve this goal will be used coupled computational modeling using analytical methods and Monte Carlo and CFD codes such as MCNPX version 2.6e and Ansys version 14.
Nowadays, the experiments related to the High Energy Physics and others fields demand the use of detectors with greater radiation resistance, and the novel material GaAs:Cr had demonstrated excellent radiation hardness compared with other semiconductors. On the basis of the evidences obtained in the JINR experiment with the use of 22 MeV electrons beam generated by the LINAC-800 accelerator, an analysis of the electron radiation effects on GaAs:Cr and Si detectors is presented. The measured I-V characteristics showed a dark current increase with dose, and an asymmetry between the two branches of the behaviors for all detectors. Analyzing the MIP spectra and CCE dose dependence measurements a deterioration process of the detectors collection capacity with the dose increase was found, although the behaviors are somewhat different according to the detector type. The detailed explanation of these effects from the microscopic point of view appears in the text, and are generally linked to the generation of atomic displacement, vacancies and other radiation defects, modifying the energy levels structure of the target material. These changes affect the lifetime and concentration of the charge carriers, and other characteristics of the target material.
In this work the characterization of a multichannel analyzer conceived in the CEADEN and developed on the basis of an FPGA, is presented. The system consists of 2048 channels; 32 000 counts per channel at most; 4.5ns of sampling time and a dead time of 16ns. A differential non-linearity (DNL) of +3.62 ± 1.56 and a non-integral linearity (INL) of +0.29 ± 0.05, in addition with the increase of the counting rate the channel of the centroid of the peak moves 64 channels as an average towards the left Of the spectrum, while the FWHM of the peaks remains practically constant between 7 and 8 channels. The spectra obtained for radiation sources are in correspondence with the characteristics of each source. In summary these features ensure that this multi-channel analyzer can be used in nuclear spectrometry.
Nowadays, the use of Aqueous Homogeneous Reactors (AHR) for the production of medical isotopes, mainly 99Mo, is potentially advantageous because of their low cost, small critical mass, inherent passive safety, and simplified fuel handling, processing and purification characteristics. However, it faces some challenges to be successfully deployed for the production of medical isotopes. This paper summarized the computational modeling efforts carried out by our research group in order to solve some of the identified challenges. The studies carried out included the neutronic and thermal-hydraulic modeling of 75 kWth AHR based on the LEU configuration of the ARGUS reactor. In addition are presented and discussed benchmarking exercises that included neutronic and thermal-hydraulic results of two solution reactors, the SUPO and ARGUS reactors. The computational platform utilized for the neutronic and thermal-hydraulics studies included the utilization of the MCNPX version 2.6e and ANSYS CFX 14 computational codes and two computational clusters in Cuba and Brazil, the InSTEC-IRL cluster and UFPE-DEN-GER cluster. The neutronic studies included the determination of parameters such as critical height, 99Mo and others medical isotopes production. Thermal-hydraulics studies were focused on demonstrating that sufficient cooling capacity exists to prevent fuel overheating. Our group studies and the results obtained contribute to demonstrate the feasibility of using AHR for the production of medical isotopes, however additional studies are necessary to confirm these results and contribute to development and demonstration of their technical, safety, and economic viability.
The service provided by the Gamma Cameras (GC) in the nuclear medicine departments fails because of their breakdown, generally due to the associated electronics and not to the physical detection components. For this reason, it was decided to develop an electronic system that allows the recovery and optimization of disused GC, starting with the design of the preamplifier for each photomultiplier tube (PMT). The circuit was designed and simulated and the list of components necessary for the construction of the preamplifier was generated, as well as the printed circuit board was designed for its assembly. By simulating the preamplifier this worked in linear mode. This determines that the amplitude of the output signal is proportional to the amount of charge delivered by the detector. This card allows an automatic adjustment of the signals of the PMTs as do the modern GC. Besides, the circuit was designed and simulated for 37 and 75 PMTs, and the printed circuit board was designed for both cases.
The advanced GaAs:Cr material for radiation detection is in the scope of many scientific and technological institutions in the world, as consequences of its proved superior properties and economic advantages. Experiments made at the JINR Dzhelepov Laboratory of Nuclear Problems for the energy calibration of a hybrid GaAs:Cr-based Timepix detector with alpha particles reaffirm that this device is able to register this particle in energy range from 3140 keV to 7687 keV. The mathematical simulation was used to calculate the transmitted energy, making possible the experimental calibration with the use of Mylar as absorbent. By calibrating the detector with characteristic X rays of some target materials and using a two steps fitting procedure was determined the relationship between the photon energies and the registered by the detector TOT counts. The energy calibration with alpha particles was performed according to linear function y = 362.08 + 2.41 x, with R$^2$ = 0.99, and verified with the measurement of the $^{218}$Po line of radon in air.
This paper describes the development of an instrument for Radiological Monitoring and Gamma Alarm (GAMAL01). It monitors the burst of radiation produced during a radioactive accident and triggers an alarm for evacuation in case the radiation exceeds an established threshold. The instrument consists of two sections, analog and digital.
Key words: Geiger Müller counters, data acquisition systems, gamma radiation, radiological protection, dosimetry.
Positron emission tomography (PET) is one of the most important diagnostic tools in medicine, allowing three-dimensional imaging of functional processes in the body. It is based on a detection of two gamma rays with an energy of 511 keV originating from the point of annihilation of the positron emitted by a radio-labeled agent. By measuring the difference of the arrival times of both annihilation photons it is possible to localize the tracer inside the body. The gamma rays are normally detected by a scintillation detector, which timing accuracy is limited by a photomultiplier and a scintillator. By replacing a photo sensor with a micro channel plate PMT (MCP-PMT) and a scintillator with Cherenkov radiator, it is possible to localize the interaction position to the cm level. In a pioneering experimental study with Cherenkov detectors using $PbF_2$ crystals and microchannel plate photomultiplier tubes MCP-PMT a time resolution better than 100 ps was achieved. In this work a DRS4 digital ring sampler chip was used to read out single photons output signals from two different MCP-PMTs (Hamamatsu R3809 and Burle 85001) with a sampling rate of 5$\times$10$^9$ samples/s. The digitized waveforms were analyzed and a comparison between the two detectors timing response was made. The best time resolutions achieved were 161 and 224 ps FWHM for the Hamamatsu and Burle MCP-PMT respectively.
High resistivity gallium arsenide compensated by chromium has demonstrated a good suitability as a sensor material for hybrid pixel detectors used in X-ray imaging systems with photon energies up to 60 keV. The material is available with thickness up to 1 mm and thanks to its Z number and fully active volume of the sensor high absorption efficiency in this energy region is provided. Although GaAs:Cr-based detectors are mostly designed for X-ray applications, it can be used for charged particle tracks registration, that will be shown.
In this work the results of the GaAs:Cr-based Timepix detectors tests with various particles sources are reported. The energy and spatial resolution, mu-tau distribution over sensor area have been determined. By means of scanning the detector with pencil photon beam generated by synchrotron facility, the geometrical mapping of pixel sensitivity is obtained as well as the energy resolution of a single pixel. The long-term stability of the detector has been evaluated based on the measurements performed over one year. It’s well known that the main performance limitation of thick GaAs:Cr-based detectors is caused by readout electronic with relatively small pixels due to the charge sharing effect. But by optimizing the bias voltage it was possible to achieve an FWHM of 2.5 keV at 25 keV in a single photon counting mode. Also the radiation hardness of GaAs:Cr sensors was investigated by means of irradiation with 20 MeV electrons and some results will be presented.
In recent years, CT has proven itself as a method of nondestructive research in biology, geology, industry, and other fields. However, until recently, the detectors used in CT recorded only the intensity of the radiation, losing information about the energy. The method of dual-energy CT partially corrects this deficiency. With the advent of hybrid matrix detectors with the single photon counting, it became possible to take into account the energy of radiation by comparison with one or more energy thresholds. The ability to use high-Z semiconductors as a sensor makes it possible to increase the efficiency of the detector. This work is devoted to the development of a method of spectral CT with a Timepix detector and a GaAs: Cr sensor. The possibility of material decomposition based on the dependence of the linear attenuation coefficient on energy is demonstrated.
Among the most modern ionizing radiation detectors, the hybrid based on GaAs:Cr Timepix stands out as one of the most competitive due to its characteristics, such as its high Z and its strong resistance to radiational damage. In addition to their use in high energy physics research, they have been effectively employed in the medical visualization, spatial technologies, geological prospecting, among others advanced fields. The target of this work is a 900 μm GaAs:Cr detector with Timepix read-out technology. Some detector characteristics for three experimental conditions were measured and studied using the X-rays generated by a synchrotron and by an X-ray tube provided with different materials for obtaining the corresponding fluorescence photons. A composite function was used to decompose the differential spectra in to the most important involved contributions. As an additional tool in the investigation, the mathematical modeling of the movement within the detector active volume of the generated by radiation charge carriers was used. The results of the charge-sharing studies showed a noticeable prevalence in the detector of this phenomenon, changing its contribution according to the experiment characteristics. The detector was calibrated for all the planned experiments and the energy resolution of the system was calculated. From the analysis of all obtained results and their comparison with the previously reported in literature data, it was confirmed that the detector has a marked charge-sharing effect between neighboring pixels, seeing its performance more affected as the energy of the incident photons growths.
The High Performance Light Water Reactor is one of the most promising concepts of the Fourth-Generation reactors. Uranium mono nitride (UN) and Uranium mono carbide (UC) as nuclear fuel alternative for the HPLWR, offer the advantage of high thermal conductivity as compared to UO$_2$. The use of coating can solve the problems of the reactive nature for UN and UC which arise when these fuels are used in light water thermal reactors. In this paper, a thermal-hydraulic study of the HPLWR fuel assembly, for UO$_2$, UN and UC, using Computational Fluid Dynamics (CFD) codes was carried out. The use of UN coated with ZrC layers and UC coated with TiN layers and the changes of the fuel thermal conductivity with the porosity were also studied. The radial and axial temperature distributions in the fuels were obtained for all the cases. The maximum temperature values obtained using UN and UC, (coated and uncoated), were lower than those obtained with UO$_2$. The fuel porosity changes have little influence on the fuel maximum temperature using UN and UC, while using UO$_2$ the maximum temperature increases in 511 K with a 0.2 % porosity increase.
Fusion reaction play a critical role in stellar evolution and nucleosynthesis [1]. However, the important fusion reaction still carry large uncertainties at Gamow region due to the low cross sections and, the limited theoretical understanding on the mechanisms related to the fluctuations that occur in the cross section [2]. Recently, we investigated $^{12}$C+$^{12}$C system, by making use of the so-called multi-channel folding model [3]. Our formulation, the nucleon-nucleon interaction can be described from the DDM3Y density-dependent potential [4] and it allows the inclusion of elastic and inelastic channels and the fusion cross section. Therefore, from the coupled-channel system, elastic and fusion cross-sections are simultaneously calculated. The explicit inclusion of inelastic channels, the imaginary part of the optical potential are only an absorption contribution of short range [5]. The $^{12}$C+$^{12}$C results show that the inclusion of inelastic channels and the presence of the Hoyle state improvement the agreement with experimental data [3]. Our model has been applied to the $^{16}$O+$^{16}$O and $^{12}$C+$^{16}$O systems, but the inclusion of the inelastic channels did not show a strong contribution in the determination of the astrophysical factor in the region of astrophysical interest.
In the last decades, a renewed attention to clustering in nuclei has emerged due to the study of weakly bound nuclei at the drip lines [1]. Clusters in nuclear systems can be related to their dynamical formation or their structural presence (pre-formation) in nuclei. While for light nuclei several links between cluster emission and its connection with nuclear structure and dynamics have been pointed out [1,2], this is less obvious when moving towards heavier systems, where the determination of pre-formed clusters within nuclear matter is more complicated and there is still a lack of experimental evidences of such structure effects. An interesting way to investigate the structural properties of medium mass systems is to study, in central collisions, the competition between evaporation and pre-equilibrium light particles emission as a function of entrance channel parameters [2].
An experimental campaign has started at the Legnaro National Laboratories using the GARFIELD + RCo multi-detector system [3] with the aim of confirming alpha clusterization in nuclei by comparing pre-equilibrium emission in terms of energy spectra and multiplicities, for different entrance channel parameters like beam velocity, mass asymmetry and structure of the reacting partners.
In particular, the two systems $^{16}$O + $^{65}$Cu and $^{19}$F + $^{62}$Ni, leading to the same compound system $^{81}$Rb*, have been studied at the same beam velocity (16 AMeV). Angular distributions and the light charged particles emission spectra in coincidence with evaporation residues have been measured up to very forward angles.
The experimental data have been first compared with the predictions of the Moscow Pre-equilibrium Model (MPM) [4] and then with the statistical model GEMINI++ [5]. A comparison with the dynamical models SMF [6] and AMD [7] has also been done. Recent results of the data analysis will be presented. The analysis is still in progress.
Air quality models are an important tool to assess the responsibility for existing air pollution levels through the evaluation of source-receptor relationships. Back trajectories have frequently been used to identify potential source areas of air pollutants and to clarify their respective contribution at receptor sites.
CALMET/CALPUFF modelling system is well known, and several validation tests were performed until now. This system has a Back Trajectory Analysis Module that creates plots of back trajectories corresponding to user specified air quality events and locations. Each path is initiated for a particular location and starting time. Then the path of some air parcel that impacts that location at that time is mapped back in time to identify potential transport patterns and source regions associated with some air quality event.
In this work, the Back Trajectory Analysis Module of CALMET/CALPUFF system is apply in order to assess the well location of a hypothetical radiological monitoring network around the location of the major potential source of radioactive pollutants to guarantee the detection of a possible accidental spill. In this case study Havana Airport was considered the source. Eight radiological monitoring stations were placed 20km from the source arranged according eight directions (N, NE, E, SE, S, SW, W, NW). The study was conducted during a typical dry season.
As result was obtained that detection is unlikely in two stations (N and S) due to the distance between source and receptor. The remoteness of the source causes three stations (NE, E and SE) to remain blind during the complete season. Only three stations (NW, W and SW) probably will detect radioactivity during the season selected.
The nearness of the radiological monitoring station to the potential source of radioactive pollutants should be taken in account considered to guarantee the detection of a possible accidental spill regardless of the period studied.
Building on the success of the large nuclear plants, SMRs offer the potential to expand the use of clean, reliable nuclear energy to a broad range of customers and energy applications. In this work, a model to describe the neutronics parameters of a SMR core that can produce up to 530 MW of thermal power was developed. Using this model, several configurations of fuel enrichment to obtain the most homogeneous distributions of the power inside the fuel assemblies during all the core lifetime were studied. Temperature reactivity coefficients and mass variation of the principal isotopes for the optimized core were calculated. Finally, thermal hydraulics studies of the highest temperature section in the core was performed to obtain the temperature distributions in the fuel, in the moderator and the radial temperature distribution inside the hottest pin of the fuel assembly was obtained.
Tri-structural Isotropic (TRISO) based fuel with SiC matrix can be used in Light Water Reactors (LWRs) for enhancing its safety features in extreme situations. Besides the simplification of the design, the utilization of TRISO fuel particles in PWR technology enhances its integrity by confining the radioactive fission products within fuel itself during the reactor operation. In this work, the preliminary conceptual design of a small PWR core using TRISO fuel was carried out. The neutronic simulation of the core is carry out using MCNPX program version 2.6e. This reactor produces 25MW of thermal power and with approximately 4 years of effective full power years. A multifactorial statistical study about the influence of three parameters in the effective multiplication coefficient value was carried out; particles size, fuel enrichment and packing fraction. The core was optimized in order to obtain in the first load the necessary excess of reactivity to reach the cycle duration. The power distributions in the first load and at the end of the cycle were obtained, with a total maximum power peaking factor of 2.55. The integral effectiveness of the absorber rods and the energetic spectrum in the most important cycle states were calculated.
Slags are final by-products involved in the iron and steelmaking process. The general tendency in the foundry workshops in Cuba is to consider slag as a waste material and deposit it in the yards of the workshops or in municipal landfills affecting the environment. Its composition and characteristics depend and vary widely according to the raw material used, the technology employed and the cooling rate once extracted from the furnace. The chemical and mineralogical characterization of slag generated in cupola furnace in the ``9 de Abril" smelter of Sagua la Grande has been performed using techniques such as: EDX, XRD and FTIR.
The objective of this work was to evaluate the exposure levels to PM10 to which workers are exposed during the working day. Sampling was carried out in two workplace areas of a factory located in Santa Clara city: the iron casting workshop and the unmolding workshop. The factory utilizes as raw materials: iron scrap, ferroalloys, coke, and materials from the own process as pig iron and return sand, which are important sources of the pollutants present in particulate matter. The concentrations of PM10 on the air were determined by gravimetric analysis. The samples were analyzed by Energy Dispersive X-ray Fluorescence (EDXRF) and Ionic Chromatography (IC) for determining the elemental composition and some ions of interest. X-ray Diffraction (XRD) analysis was applied to selected samples in order to identify possible phases of compounds commonly found in this type of industries. The results were compared with the reported in the Cuban Standard NC872:2011 that regulates the harmful substances in the air of the working zone and evaluates the occupational exposure.
One of the nuclear techniques that are being investigated by different groups in the field of explosives detection and demining is the thermal Neutron Backscattering Technique (NBT). NBT is based on the fact that the buried target is Hydrogen-rich and therefore if it is in a media with different Hydrogen content and it is exposed to a fast neutron source, the number of backscattered thermal neutrons produced by the moderation process will give us a signal from which we can infer the presence of the Hydrogen-rich target. NBT is used to locate buried Hydrogen-rich objects using a fast neutron source and two $^3$He neutron detectors. Special problems need to be understood as well as is necessary to study the advantages, disadvantages and limits of the technique in the Colombian case. One of the most important issues that have to be investigated is the soil moisture. The backscattered neutrons intensity was related with the soil water content for farming soil, with and without Hydorgen-rich objects in soil. The experimental results are presented with the purpose of comparing the soil water content as measured by NBT and the gravimetric method. NBT intensity signal changes for both object and soil water content, and the best performance in the data analysis.
In this work, several oil samples from different Brazilian basins were investigated using Energy Dispersive X-Ray Fluorescence spectroscopy technique (ED-XRF) aiming to obtain qualitative information about their chemical composition [1,2]. The budget of analyzed samples was composed of twelve oil samples from five distinct oil fields belonging to the Campos Basin of the Esp ́ırito Santo and to the Santos Basin, Brazil. The samples were trickled on a thick Kym foil (99.9%) with 2 cm of diameter. The ED-XRF measurements were carried out using a portable device (Amptek XR-100SDD model) [3,4] and the spectra analysis were performed using the WinQxas software. Besides, to enhance the detection of some elements at lower concentrations, Tungsten and Aluminum filters were placed at the exit of the X-ray tube. The preliminary results indicate the presence of S, Cl, K chemical elements and with the use of Al and W filters, identification of Br and Sr at lower concentrations in four oil samples from the Marlim, Pampo and Jubarte fields of the Campos Basin could be also achieved. In addition, the obtained data so far raise the question how these different chemical elements are correlated with the different oil basis especially for those elements present at low concentrations.
References
[1] D.A. Skoog, D.M. West, F.J. Holler, Fundamentals of Analytical Chemistry. New York: Saunders College Publishing, 2006.
[2] P. Tasch, F. Damiani, T ́ecnicas de an ́alise e caracteriza ̧c ̃ao de materiais: XRF - X-Rays Fluorescence Spectroscopy. Campinas: Unicamp, 2000.
[3] Amptek - http://amptek.com/, acessed in april 2017.
[4] C.B. Zamboni, S. Metairon, L. Kovacs, D.V. Macedo, M.A. Rizzutto., Journ. Radioanal. Nucl. Chem. 307 1641, 2015.
The present work presents a procedure designed for the improvement of the Quality Management System (QMS) implemented in the laboratories of Chemical Analysis and Materials of the CEADEN according to NC ISO / IEC 17025: 2006 in order to allow a stability in time of their status as accredited laboratories. In these laboratories, nuclear and complementary techniques are used in research and scientific and technical services related to the environment, food safety, nuclear safety and security of other technological facilities, among others.
Following a diagnosis of the QMS and identification of the main deficiencies of the last accreditation period, an improvement procedure based on the Plan-Do-Check-Act cycle (PDVA) is applied, which is a methodological tool that can be applied to other testing laboratories of this type that have the status of accredited or that claim to obtain it. Different techniques and tools are used such as expert method, cause - effect diagram, interrelations diagram, interviews, brainstorming, among others.
Radioactivity levels in peloids from some Cuban spas (San Diego, Elguea, Santa Lucía and Cajío) have been studied. The radionuclide concentration (in Bq.kg-1 dry weight) varied as follows: $^{226}$Ra = 6 – 1800, $^{137}$Cs = <2 – 5, $^{232}$Th = 6 – 38 and $^{40}$K = 47 – 365, being comparable to concentrations reported for therapeutic peloids used worldwide. Considering the short exposition times associated with the usual therapeutic practices in Cuban spas, the estimated annual equivalent dose in $^{226}$Ra-enriched peloids is well below the accepted equivalent dose values for the skin of peloids-based treatment users. Therefore, radioactivity levels present in peloids from the studied Cuban spas do not represent an impediment for its use with therapeutic purposes.
The regional offset correction ΔR of Marine Reservoir Effect (MRE), crucial for correcting $^{14}$C ages calibration for marine influenced samples, was determined for Cuban Northwest coast. Fifteen different locations were studied by $^{14}$C dating of pre-bomb known-age marine shells specimens of bivalves and gastropods from the Felipe Poey Museum collection. The distribution of results indicates ΔR values from -46 ± 38 to 140 ± 52 $^{14}$C yr and a possible pattern related to the position along the coast and ocean dynamics. We present both mean values for each region and a general ΔR of 28 ± 13 $^{14}$C yr for the northwestern coast of Cuba.
The application of the method of radioactive indicators in research and development of drugs is of great importance for the pharmaceutical industry. Many non-clinical and clinical trials rely on the radiolabelling of the molecules being tested as potential drugs. In the present investigation, a preliminary computational model was developed to obtain the possible structures of the CIGB-300 peptide without radiolabelling and radiolabelling. The radiolabelling with $^{99m}$Tc of the antitumor peptide CIGB-300 in its cyclic and non-cyclic forms was studied considering the influence of the peptide mass in the reaction, as well as the influence of the amount of the reducing system. The stability of the radiolabeling was evaluated by mean of cysteine and DTPA challenged and in dilution of serum albumin and fresh human serum. Subsequently, pharmacokinetic evaluation of radiolabeled peptide was performed to verify its tumor uptake in an experimental model in mice and to observe its tissues distribution. Sampling schedule follows a spars data design and the obtained information was processed using the Monolix Suit. Population and individual pharmacokinetic parameters were obtained after selecting the best-fit model. The study was supplemented with scintigraphic images. The results indicate that with only 100 μg of the non-cyclic peptide 98% of radiochemical purity is obtained and is stable, with adequate tumor uptake in the experimental model.
Concentrations of various chemical elements in street dusts from Camagüey city were studied by X-ray fluorescence analysis. The mean Cr, Co, Ni, Cu, Zn and Pb contents (in mg.kg$^{-1}$ dry weight) in the urban dust samples were compared with mean concentrations in other cities around the world. Spatial distribution maps indicated the same behaviour for Cr–Ni and Pb–Zn–Cu, whereas the spatial distribution of Co differs from the other heavy metals. The metal-to-iron normalization using Cuban average metal soil contents as background showed that street dusts from Camagüey city are moderately or significantly enriched with Zn-Pb in those areas associated with heavy traffic density and metallurgic plant location. However, the calculation of the potential ecological risk index shows that metal content do not represent a risk for the city´s population.
As part of the instrumentation development program of the luminescence dating laboratory at CEADEN a package of open-source software supporting the luminescence measuring process is carried out. The package released under the name of Sequence-Toolkit is routinely used to create and analyze the results of the measuring sequences introduced to the automated luminescence reader LF02. Here we describe the upgrade and the new features introduced in the new version of this package. The modifications are based on the recommendations arising after two years of exploitation of the initial version specially those concerning the speed of the data manipulation and also related to the migration to the new versions of Python and QT programming software.
Rhenium bis-arenes can be obtained by heating the corresponding potassium perrhenate (KReO$_4$) salt with an arene as a solvent and in the presence of aluminum chloride (AlCl$_3$) and zinc. Variations of this method, originally proposed by Fischer and Hafner, demonstrated that, in some cases, the reaction occurs without using Zn as a reductive agent, but also, that the presence of the Lewis acid is essential. The aim of this work is to study the interactions of AlCl$_3$ with benzene, as well as the reactivity of the system formed afterwards, in order to understand its role in the reaction pathway. Calculations at DFT/M06-2X and MP2 levels using 6-311G(2df,2pd) depicted that the association between AlCl$_3$ and benzene leads to the formation of a charge transfer adduct where the AlCl$_3$ is placed over one of the carbons of benzene. The charge is transfered from the aromatic $\pi$ system to the Al atom. The analysis of this complex through local reactivity descriptors allowed locating the areas of the benzene's $\pi$ system more susceptible to react with the Rhenium via electrophilic attack. Meta and orto positions are particularly reactive to that class of attack. Therefore, the initial association with rhenium should occur in these sites. Thus, results show that the formation of the AlCl$_3$-benzene adduct could be an important intermediate in the formation of [Re($\eta^6$-benzene)$_2$]$^+$ complex.
The losartan and its fluoro n-ethoxy-methyl-triazole losartan derivatives (FEM, n=0-3) were studied as potential candidates of $^{18}$F-labeled radiopharmaceuticals. Each derivate is obtained by the reaction of a terminal alkyne with a substituted azide in presence of Cu(I) catalyst. The stability and association energy of four FEM to the AT1 receptor was evaluated. The Density Functional Theory with the base 6-31G(2d, 2p) was used to evaluate radiotracers stability. In order to determine the functional that provides the best description of FEM, the experimental X-ray diffraction structure of losartan potassium was compared with calculated using different functionals, been the M06-2X the most suitable. The vibrational frequencies of the FEM structures and the bond dissociation energy (BDE) were also calculated. In both, vacuum and water calculations, the stability of compounds decreased following the order: FTEMT(n = 3)>FDEMTL(n = 2)>FMTL (n = 0) > FEMTL(n = 1). When water as implicit solvent was considered in the model, the difference of BDE was only 6kJ/mol. The electron density analysis of atoms in molecules was performed in order to characterize the intramolecular interactions in each FEM derivative. There was an increase of van der Waals type interactions with the increase of the length of the chain, being the FDEMTL the only one with two hydrogen bonds. Molecular Docking study was performed to evaluate the interactions of the four FEM with the receptor. All evaluated derivatives have similar interaction energy with the receptor than losartan. The FMTL derivative can be considered the best candidate as radiotracer.
The objective of the present study was to evaluate the distribution and accumulation of some heavy metals in surface sediments from the Mamposton reservoir (Mayabeque province, Cuba) and its main tributaries (Ganuza and Mamposton rivers and Pedroso dam). Furthermore, it was of great interest to assess their potential risk with regard to human health. Concentrations of Fe, Ni, Cu, Zn and Pb were determined by X-ray Fluorescence Analysis in samples collected in dry and rainy seasons. The results show a significant difference in metal contents in each season. Determined values corresponding to the contamination factor and modified degree of contamination indicate a very low to high degree of contamination effects for the studied sediments. The comparison with sediment quality guidelines reveals that the average concentration of Cu, Zn and Pb in Ganuza river sediments is higher than the established Threshold Effect Levels (TEL) [1]. On the other hand, the Ni content exceeds the established Probable Effect Levels (PEL) [1] in almost every studied location. Based on PEL-Q calculations [2] for Ni, Cu, Zn and Pb, the samples classify as sediments with a medium-low level of contamination in all the studied stations, except for one in the Ganuza River, which classifies as medium-high level of contamination.
Refs:
1. Long ER, MacDonald DD. Human Ecological Risk Assessment. 1998; 4:1019–1039.
2. McCready S, Birch GF, Long ER. Environment International, 2006; 32(4):455-465.
Plenary Sessions on Wednesday-Friday mornings (25 min + 5 min)
Five years ago, particle physicists announced the discovery of the Higgs boson, the last missing ingredient in the Standard Model.
Since then, the enormous wealth of data collected by the ATLAS experiment has allowed us to zoom in on the properties of this fundamental scalar that is linked to electroweak symmetry breaking, a fundamental ingredient in the model that describes the elementary particles. I will present the latest results on its properties like the mass, width, observation of different decay channels and coupling(structure) and discuss their implications in the context of the Standard Model. Because of the special role of the Higgs boson, the precision measurements can be used to look for physics beyond the Standard Model that are expected to show up at the TeV energies the LHC can probe, by looking for inconsistencies between the predicted and observed properties. I will discuss our strategy, the impact current limits have on these models and describe what new Higgs boson decay channels and properties we hope to be able to observe in the current LHC run(s).
The ALICE experiment at CERN investigates the properties of strongly interacting matter at high temperatures. This talk highlights some of the recent results from the collaboration,presenting key constraints on properties of the QCD matter. A brief description of the ALICE upgrade program is also given.
In the Run-2 of the Large Hadron Collider, CMS is recording an impressive amount of proton-proton collision data at a center of mass energy of 13 TeV. In this talk, we highlight the CMS status in 2017 and some of the latest physics results.
Plenary Sessions on Wednesday-Friday mornings (25 min + 5 min)
The Mu2e Experiment at Fermilab will search for coherent, neutrino-less conversion of negative muons into electrons in the field of an Aluminum nucleus. The dynamics of such charged lepton flavour violating (CLFV) process is well modelled by a two-body decay, resulting in a mono-energetic electron with an energy slightly below the muon rest mass.
If no events are observed in three years of running, Mu2e will set an upper limit on the ratio between the conversion and the capture rates \convrate of $\leq 6\ \times\ 10^{-17}$ (@ 90$\%$ C.L.). This will improve the current limit of four order of magnitudes with respect to the previous best experiment.
Mu2e complements and extends the current search for $\mu \to e \gamma$ decay at MEG as well as the direct searches for new physics at the LHC. This CLFV process probes new physics at a scale inaccessible to direct searches at either present or planned high energy colliders. Observation of a signal will be a clear evidence for new physics beyond the Standard Model.
To search for the muon conversion process, a very intense pulsed beam of negative muons ($\sim 10^{10} \mu/$ sec) is stopped on an Aluminum target inside a very long solenoid where the detector is also located. The Mu2e detector is composed of a straw tube tracker and a CsI crystals electromagnetic calorimeter. An external veto for cosmic rays is surrounding the detector solenoid. In 2016, Mu2e has passed the final approval stage from DOE and has started its construction phase. Data collection is planned for the end of 2021.
An overview of the physics motivations for Mu2e, the current status of the experiment and the required performances and design details of the calorimeter are presented.
The results of the Q-weak experiment at the Thomas Jefferson National Accelerator Facility are presented. The experiment performed the most precise measurement of the parity-violating electron-proton scattering asymmetry at low momentum transfer, resulting in the first direct determination of the weak charge of the proton (a weak force analog to the electric charge for the electromagnetic force) and the most precise value of the weak mixing (Weinberg) angle, for the first time measured in a semi-leptonic reaction. Since the weak mixing angle is precisely predicted by the Standard model, these results provide new constraints on classes of physics beyond the Standard Model and are complementary to direct searches in the high energy measurements. The requirements of this precise measurement posed technical challenges resulting in the design of a custom apparatus consisting of a triple collimator system, a resistive copper-coil toroidal magnet and eight fused silica Cherenkov detectors, the world’s highest power liquid hydrogen target, precision control of helicity-correlated beam properties and beam polarimetry. The detector array absorbed a scattered electron rate of about 7 GHz read out in integrating mode by custom-built modules. Dedicated low-current measurements were undertaken to determine the momentum transfer using sets of drift chambers before and after the toroidal magnet. The technical aspect of the Q-weak experiment will also be presented.
GRIFFIN [1], the Gamma-Ray Infrastructure For Fundamental Investigations of Nuclei is the new decay spectroscopy array located at TRIUMF, Canada’s National Laboratory for Nuclear and Particle Physics. GRIFFIN consists of 16 large-volume hyper-pure germanium clover detectors assisted by a custom-built digital data acquisition system, providing 10% efficiency for detecting gamma-rays at 1.3 MeV. A suite of ancillary detector systems can be coupled to GRIFFIN for comprehensive decay spectroscopy experiments with radioactive beams delivered by the TRIUMF-ISAC facility: SCEPTAR [2], an array of plastic scintillators for beta-particle tagging, and PACES [2], an array of five lithium-drifted cooled silicon detectors for high-resolution internal conversion-electron spectroscopy, eight lanthanum bromide scintillators for fast gamma-ray timing measurements [2], and a neutron detector array for the detection of beta-delayed neutron-emitting nuclei called DESCANT, [3]. This versatile experimental set-up allows for the identification of weak branching ratios and firm spin and parity assignments of excited states thorough angular correlation measurements.
Results obtained with the GRIFFIN spectrometer near and far from stability using beta decay of beams of 128−130Cd [4], 46,47K [5,6], 32Na [7], and 118,132In [8,9] will be presented along with a discussion of future opportunities, including the addition of the Compton and background suppression shields in 2018.
The GRIFFIN spectrometer is funded by the Canada Foundation for Innovation, TRIUMF, and the University of Guelph with matching contributions from the British Columbia Knowledge and Development Fund and the Ontario Ministry of Research and Industry. TRIUMF receives federal funding via a contribution agreement through the National Research Council of Canada. This research is supported by the Natural Sciences and Engineering Research Council of Canada.
Lima, the capital of Peru, and Callao, an urban region, form on of the largest urban centers in South America, with a total population of 10,9 million as of 2017. Three rivers supply water to the capital, however, water for municipal use is mainly taken from the Rimac and Chillon River. The estimated water availability is 148 m$^3$/person/year, well below the limit of 1000 m$^3$/person/year Falkermark establishes as of extreme scarcity. Therefore, it is of great importance the identification of water sources for the future.
An experimental study was conducted to analyze Lima´s groundwater origin. Water levels in a well located in Miraflores, near the Pacific Ocean, were observed between 2003 and 2009. A maximum water level was registered three years after the occurrence of a peak in a hydrologic station in Chosica, located approximately 35 km away. Therefore, it was estimated that the residence time, this is the time passing after water infiltrates the ground during a rainfall event, until it reaches the Miraflores well, is three years. Water samples extracted this well were analyzed. The estimated residence time is in agreement with the 3H contents which also indicate that the residence time is three years. In addition, The results obtained in the Miraflores well are also in agreement with the permeability of the valley, which is in the order of 1x10$^{-3}$ m/s. The permeability in the alluvial fan, on which Lima is located, is in the order of and 10$^{-4}$ m/s. The storage coefficient is 5% in the valley and 0.2% in the coastal area (INGEMMET, 1988).
In other hand, the relative abundance of 2H and 18O in wells in the Lima aquifer are in agreement with the hypothesis that the aquifer is recharged with water from rainfall events that occur in the highlands at an average elevation of 3000 m.
These results are useful to improve management of water resources for the 10.9 million inhabitants of the coastal city of Lima, whose water supply depends mainly of water flows of the Rimac river and water wells in the Lima aquifer. Optimization of water use is crucial in the present times characterized by climate change. In 2017, for example, due to a critical year of extreme floods, water supply from the Rimac River was interrupted and Lima had to use only water wells for municipal use.
Keywords: Coastal aquifer, Lima, water residence time.
Reference
INGEMMET. 1988. Estudio Geodinámico de la Cuenca del Río Rímac. (Boletín Nº 8b Serie C). Instituto Geológico Minero y Metalúrgico: Lima; 263.
Gamma-ray Compton backscattering has proven to be of interest for technical applications, one example being an imaging device [1] able of getting the shape of objects behind material obstacles. A big deal of work has been performed in order to characterize the process, which, given the huge mathematical difficulties of an intrinsically random, non-lineal process, numerical simulation is preferred [2]. However, since having an analytical approximation is a powerful prediction and evaluation tool, the analytical path deserves also exploration. An attempt to understand the difference in capacity to backscatter photons by different materials, and for the same material, for different thicknesses and densities produced an analytical expression for the single-backscattered intensity [3].
Obtaining a collective expression for higher scattering orders is a dauting task. A rather ambitious method in that direction uses transport theory to obtain both intensity and spectral shape of the scattered radiation [4]. This method, although offering completeness in the solution is rather difficult to implement in practical cases and simplified approaches might be needed. One example in that direction is the mixed analytical-numerical algorithm in Ref. [5]. Following this approach of incremental theoretical improvement we present a method and several theoretical and numerical results for only-double Compton scattering. These results may prove useful in practice since according to numerical simulations double Compton backscattering events may be responsible in some materials for more than $30\%$ of the total number of multiple scattering events whereas both together, single and double scattering, add up to more than $60\%$ of the total backscattered intensity.
This work presents the results obtained during the hydrochemical and isotopic characterization of the waters of the Mampostón - Jaruco basin in the province of Mayabeque, Cuba. Two sampling campaigns were carried out in different wells drilled in the area, carrying out the collection of hydrochemical data in the field, the analysis of macrocomponents and physico-chemical parameters in the laboratory, isotopic analysis ($^2$H and $^{18}$O) and the evaluation of the quality of the analytical data. The interpretation of the results showed that the waters are generally classified as calcium bicarbonate with very similar characteristics between them, suggesting a single origin (recharge). Possible recharge mechanisms involving surface sources in the region were identified.
Nucleosynthetic processes in supernovae and X-ray bursts often involve unstable ions and reactions that are difficult to produce at the relevant energies in rare beam facilities. Recent progress in astronomical observations and the chemical evolution of the Galaxy need to be accompanied with similar progress in understanding the relevant properties of rare isotopes through nuclear physics experiments. I will review the important role that rare isotopes play in understanding stellar explosions, show some examples of recent nuclear physics measurements and give a (very abbreviated) outlook of future nuclear astrophysics studies.
The international ISOL facility ALTO, located at Orsay in France, provides stable ion beams based on a 15 MV tandem accelerator and neutron-rich radioactive ion beams from the interaction of a γ-flux induced by a 50 MeV 10 µA electron beam in a uranium carbide target. New setups are under preparation to extend the fundamental properties measured at ALTO of ground and excited states of exotic nuclei. As for example, high-precision mass measurements for an accurate determination of the nuclear binding energy. To perform those measurements two devices will be hosted at ALTO: a radiofrequency quadrupole to cool and bunch the continuous radioactive beam and the double penning trap mass spectrometer MLLTRAP, commissioned off-line at the Maier-Leibnitz Laboratory (MLL) in Munich, Germany. The unique ion production at the ALTO facility allows mass measurements in a neutron rich area of major interest around 132Sn. In this context, it is proposed to use neutron-rich silver isotopes (Z = 47, A > 121) to explore the possible weakening of the shell gap for Z < 50 and its impact on the A = 130 r-process elemental abundances. The already well measured masses (A < 121) in the silver isotopic chain will be used for the on-line commissioning. In addition, the development started at MLL on a novel detector-trap for in-trap decay spectroscopy will be carried out at ALTO. It will provide background free spectra via direct in-situ spectroscopy of stored ions. The status and timeline of the novel setup will be presented.
NUMEN proposes cross sections measurements of Heavy-Ion double charge exchange reactions as an innovative tool to access the nuclear matrix elements, entering the expression of the life time of Neutrinoless double beta decay (0νββ). If detected, such a process would give direct evidence to the Majorana-nature of neutrinos, opening a window to physics beyond the standard model.
A key aspect of the project is the use at INFN-Laboratori Nazionali del Sud (LNS) of the Superconducting Cyclotron (CS) for the acceleration of the required high resolution and low emittance heavy-ion beams and of MAGNEX large acceptance magnetic spectrometer for the detection of the ejectiles.
However, a main limitation on the beam current delivered by the accelerator and the maximum rate accepted by the MAGNEX focal plane detector must be sensibly overcome in order to systematically provide accurate numbers to the neutrino physics community in all the studied cases. The upgrade of the LNS facilities, in this view, is part of this project.
First experimental results, obtained at the INFN-Laboratori Nazionali del Sud in Catania using MAGNEX magnetic spectrometer, for the $^{40}$Ca($^{18}$O,$^{18}$Ne)$^{40}$Ar reaction at 270 MeV are shown. The data give encouraging indication on the capability to access quantitative information towards the determination of the Nuclear Matrix Elements for 0νββ decay. Preliminary results, in particular of the reaction $^{116}$Cd($^{20}$Ne,$^{20}$O)$^{116}$Sn at 15 MeV/u, performed at INFN LNS, are reported.
COFFEE-BREAK at ROOM “Bens Arrate”
Concerning thermal neutron induced fission of uranium 233, using a Monte Carlo simulation, we show how prompt neutron emission from fragments distorts the distribution of charge as a function of final mass and kinetic energy compared with the primary distribution. Since fission discovery, the yield of primary charge (Z), mass (A) and kinetic energy (E), has been one of the objectives of measurements of fragments [1]. However, only the yield of final fragment charge (z), mass (m) and kinetic energy (e), after prompt neutron emission, defined as Y(z,m,e), is accessible in low energy fission [1, 2]. In our Monte Carlo simulation, for each m, we calculate, the average of charge as a function of e. As input for the simulation, we assume that: i) the prompt neutron number (n) decreases linearly with kinetic energy (E), it’s equal to the neutron multiplicity (ν) when E is equal to the corresponding average, and it falls to zero at the corresponding maximal value (E_max) [3] and ii) the average of primary fragment charge is proportional to the primary fragment mass (A) and to the charge/mass ratio of fissioning nucleus (92/234). As output of the simulation, we obtain the distribution of final fragment mass (m=A-n), kinetic energy (e=E (1- n/A)) and charge (z=Z). As a result, for a fixed final mass in the region m = 80 - 100, prompt neutron emission produces a negative slope in the curve of average charge as a funtion of e. This result is in agreement with experimental data obtained by Quade et al [1]. Surprisingly, in the region of heavy fragment, contrary to what happens in the mass region m = 80 - 100, the curve of average charge as a funtion of e has a positive slope. In order to compare this results in that heavy mass region, data from experiments with new technologies is expected [2].
With the aim of studying the evolution of nuclear shells in the region of neutron-rich Sn isotopes, the MagicTin project (EU-MSCA 661777) will exploit the capabilities of the ACTAR TPC detector for measuring direct reactions in the Z≥50, A≥132 mass region.
In preparation for these experimental campaigns, to be done at the forthcoming radioactive ion beam facilities like SPES, HIE-ISOLDE or SPIRAL2, several preparatory steps are needed. Indeed, the detection of heavy-ion (Z≥50) induced reactions using an active target represents a challenge itself.
After providing an overview about the use of Active Targets in experiments with Radioactive Ion beams, I will focus on the status of the MagicTin project and its future perspectives.
The present work deals with the numerical simulation of gamma and electron radiation damage processes under high brightness and radiation particle fluency on regard to two new radiation induced atom displacement processes, which concern with both, the Monte Carlo Method based numerical simulation of the occurrence of atom displacement process as a result of gamma and electron interactions and transport in a solid matrix and the atom displacement threshold energies calculations based on Molecular Dynamic methodologies.
The two new radiation damage processes here considered in the framework of high brightness and particle fluency irradiation conditions are: 1) The radiation induced atom displacement processes due to a single primary knockout atom excitation in a defective target crystal matrix increasing its defect concentrations (vacancies, interstitials and Frenkel pairs) as a result of a severe and progressive material radiation damage and 2) The occurrence of atom displacements related to multiple primary knockout atom excitations for the same or different atomic species in an perfect target crystal matrix due to subsequent electron elastic atomic scattering in the same atomic neighborhood during a crystal lattice relaxation time.
In the present work a review of numeral simulation attempts of these two new radiation damage processes are presented, starting from the former developed algorithms and codes for Monte Carlo simulation of atom displacements induced by electron and gamma in irradiated materials and, in addition, the Molecular Dynamics calculations atom displacement threshold energies for defective crystalline materials as well as for the cases of multiple primary knockout atomic excitations.
Plenary Sessions on Wednesday-Friday mornings (25 min + 5 min)
Double beta decay (DBD) is a nuclear process with the longest lifetime measured until present, which study presents a great interest. Indeed, its possible neutrinoless double beta (0νββ) decay mode is a beyond Standard Model (BSM) process whose discovery would clarify if the lepton number is conserved, decide on the neutrinos character (are they Dirac or Majorana particles?) and give a hint on the scale of their absolute masses [1]. Theoretically, the study of 0νββ decay involves the accurate computation of the nuclear matrix elements (NME) and phase space factors (PSF), two key quantities entering the lifetimes of this process. In my talk I will make first a short review on the actual challenges to calculate the NME and PSF for DBD [2]-[4]. Then, I will show how from the study of 0νββ decay one can constrain BSM parameters related to the neutrino mass and Lorentz violation in weak decays.
References
1. Vergados, J.D., Ejiri, H., and Simkovic, F, Rep. Prog. Phys., 72, 106201 (2012).
2. M. Horoi and S. Stoica, Phys. Rev. C 81, 024321 (2010).
3. S. Stoica and M. Mirea, Phys. Rev. C 88, 037303 (2013).
4. A. Neacsu and S. Stoica, J. Phys.G 41, 015201 (2014).
5. S. Stoica and A. Neacsu, AHEP2014, 2014, article ID 745082.
6. S.Stoica, INPC2016, 12-16 September, 2016, Adelaide (oral presentation).
7. S. Stoica, MEDEX’17, May 29 – June 2, 2017, Prague (invit. lecture).
I will report on a quantitative study of the sub-Coulomb fusion of astrophysically important heavy-ion collisions, such as $^{16}$O + $^{16}$O and $^{12}$C + $^{12}$C. It is carried out using wave-packet dynamics. The low-energy collision is described in the rotating center-of-mass frame within a nuclear molecular picture [1]. A collective Hamiltonian drives the time propagation of the wave-packet through the collective potential-energy landscape that is calculated with a realistic two-center shell model [2-4]. Among other preliminary results, the theoretical sub-Coulomb fusion resonances for $^{12}$C + $^{12}$C seem to correspond well with observations. The method appears to be useful for expanding the cross-section predictions towards stellar energies.
Nuclear structure far from stability plays a crucial role in the processes that lead to the formation of the elements. In the specific case of the proton drip-line, its location constrains the path of nucleosynthesis in explosive astrophysical scenarios such as in supernovae and X-ray bursters.
In such scenarios, the density and temperature are so high, that rapid proton capture can occur, and unstable nuclei will be generated up to and beyond the proton drip-line. The path for these reactions depends on the level structure and existence of resonances in proton rich nuclei.
In order to achieve a theoretical understanding of the rapid proton capture (rp) process, the separation energies of proton drip-line nuclei are needed as input in the network calculations.
Direct experiments with unstable nuclei are still challenging, creating an obstacle to our understanding of their structure. However, the observation of proton emission and its theoretical interpretation has made possible to access the nuclear structure properties in the neutron deficient region of the nuclear chart, for nuclei with charges between 50 and 81[1,2]. It has also provided an indirect way to determine separation energies.
Proton radioactivity from nuclei with Z<50 is also of particular interest to estimate the time scale of the (rp) capture path, controlled by the properties of the waiting points isotopes, like for example the nucleus 72Kr, whose properties have not yet been constrained by direct measurements. The knowledge of the proton separation energies, and half-lives of the neighbour nuclei, would allow to establish the most probable path through 72Kr. This can be achieved
analysing the decay properties of Rb isotopes, recently produced at Riken [3].
It is the purpose of this talk to discuss recent developments in the field, and deduce constraints to the astrophysical processes.
Plenary Sessions on Wednesday-Friday mornings (25 min + 5 min)
Measurements in nuclear β decay played a crucial role in the development of the (V-A) theory of weak interactions, which is embedded in the standard electroweak model (SM). Experiments in β decay offer today a sensitive tool to search for physics beyond the SM, complementary to direct searches performed at high energies.
It has recently been observed that, in searches for new interactions and under very general assumptions, the determination of the so-called “Fierz interference term” in nuclear and neutron decays can potentially compete with searches at the LHC provided the sensitivity reaches a level below 10$^{−3}$ . This is because the Fierz term depends linearly on the exotic couplings whereas the cross sections for the production of new bosons depend quadratically. In nuclear and neutron decays the most direct and sensitive property to extract the Fierz term is the shape of the β energy spectrum.
This contribution presents recent precision measurements of β energy spectra in $^{6}$He and $^{20}$F decays performed at the National Superconducting Cyclotron Laboratory. A new technique that eliminates the very critical instrumental effect of back-scattering of electrons on detectors has been explored. The technique is being tested through the determination of the weak-magnetism contribution which can be accurately predicted in well selected transitions using the principle of Conservation of the Vector Current.
The accurate measurement of the baryon density by WMAP renders Big Bang Nucleosynthesis (BBN) a parameter free theory with only inputs from measurements of the relevant (12 canonical) nuclear reactions. BBN predicts with high accuracy the measured abundance of deuterium, helion and helium relative to hydrogen, but it over-predicts the abundance of 7Li relative to hydrogen by a factor of approximately three and more than three sigma difference from the observed value. This discrepancy was observed early on (more than thirty years ago) and is known as the “Primordial 7Li Problem”. Several attempts to reconcile this discrepancy by destroying 7Be with deuterons and helions or a conjectured d + 7Be resonance were ruled out as solutions of the 7Li problem. But the interaction of 7Be with neutrons that are also prevailing during the epoch of BBN, was not directly measured thus far in the BBN window. Also a hitherto unknown n + 7Be narrow resonance in 8Be at energies relevant for the BBN window was not yet ruled out. A worldwide effort for measuring the interaction of neutrons with 7Be is currently underway. We will discuss a measurement in the new neutron facility at the Soreq Applied Research Accelerator Facility (SARAF)
in Israel, that covers the “BBN energy window” with T = 0.5 - 0.8 GK and kT = 43 - 72 keV. We measured a significantly small upper limit on the 7Be(n,a) reaction and the first measurement of the 7Be(n,g1)8Be*(3.03 MeV) reaction (Ea = 1.5 MeV). Our measurement allow us to re-evaluate the so designated “7Be(n,a) reaction rate” first derived by Wagoner in 1969 and still used in BBN calculations. Our evaluated new rate demonstrates that the last possible avenue (of the n + 7Be interaction) for a standard nuclear physics solution of the 7Li problem does not solve the problem. We conclude on lack of standard nuclear physics solution to the “Primordial 7Li problem”.
The EMC effect is the observation that the structure of nucleons in nuclear medium is modified from that in free space. Over 1000 papers were written about the effect, but no explanation is commonly accepted. A linear correlation has recently been observed between the slopes of the EMC universal curve for 0.3 < x$_B$ < 0.7 in deep-inelastic (DIS) lepton scattering, d[F$_2$(A)/F$_2$(d)]/dx$_B$ and a$_2$(A/d), the per-nucleon inclusive quasi-elastic electron scattering cross-section ratios from SRC in nucleus A to that from deuterium for 1.4 < x$_B$ < 2. This correlation is surprising because of the vastly different energy and distance scales of EMC and short-range nucleon-nucleon correlations (SRC).
A recent explanation of this correlation is that the modification of F$_2$(A), the nucleon structure-function in the nuclear medium, depends on the virtuality of the nucleons, which is high for short-range correlated nucleons such that the EMC effect, to a large extent, is related to DIS from highly virtual, short-range correlated nucleon.
We study this hypothesis by detecting EMC events “tagged” by high-momentum (k$_p$ > k$_F$) protons recoiling backward to the momentum transfer, $q$, which have been shown to be spectators from scattering off their short-range correlated partners.
We shall present and discuss results of inclusive SRC, a$_2$(A/d), and “normal” EMC F$_2$(A)/F$_2$(d), as well as semi-exclusive SRC (“tagged” SRC), and semi-inclusive DIS (“tagged” EMC),
{$\sigma$[A(e,e’p$_{recoil}$)X]/A}/{$\sigma$[d(e,e’p$_{recoil}$)X/2]} for their respective X$_B$ ranges.
Transition strengths in the Ni isotopes between N=40 and N=50 have been recently subject of extensive experimental and theoretical investigations, aiming to understand whether the tensor forces act to reduce the Z=28 shell closure as the neutron g9/2 orbit is filled towards 78Ni.
The effect of the Z=28 shell gap quenching and its evolution from 68Ni towards 78Ni would be reflected as an enhancement in the quadrupole transition stregths, compared with the seniority scheme predictions for the neutron g9/2 subshell. In 70Ni, the large B(E2) value for the first 2+ excited state obtained by Coulomb excitation was interpreted as an evidence of a large neutron-induced polarization of the proton core. This interpretation was reinforced with a later inelastic proton scattering experiment on 74Ni, in which a large deformation parameter was found, pointing to an enhanced quadrupole collectivity.
In the last year however, a much lower B(E2) value was deduced for 74Ni in a Coulomb excitation experiment. In that work, both experimental and shell-model calculations using the residual LNPS interaction, restores the normal core polarization picture in the neutron rich Ni isotopic chain and suggests that the B(E2) strength predominantly corresponds to neutron excitation.
The known experimental transition strengths by Coulomb excitation are constrained to 70Ni and 74Ni so far.
We report on preliminary results from the Coulomb excitation of 72Ni performed at the Radioactive Isotope Beam Factory at RIKEN, Japan. The BigRIPS fragment separator was used to select and purify a secondary beam of 72Ni at 183 MeV/u. Coulomb excitation of 72Ni was produced by impinging the beam on a 950 mg/cm2 Au target. In order to identify the reaction products after the target, the ZeroDegree spectrometer was used, while the gamma-rays were detected with the 186 NaI(TI) detector array DALI2.
The present experimental study on $^{77}$Cu has been carried out at Radioactive Ion Beam Factory of the RIKEN Nishina Center. It will complement the previous study of $^{77}$Cu via beta decay of $^{77}$Ni where the low-lying states in $^{77}$Cu were identified as particle-core excitations through the comparison to the large scale Monte Carlo Shell Model calculations (E. Sahin et al. Phys.Rev.Lett. 118, 242502 (2017)). An almost unique way to characterize the states predicted as collective in the calculations is to measure the transition probabilities, i.e. B(E2) strengths. Hence the following Coulomb excitation experiment was performed to study the collective properties of low-lying states in $^{77}$Cu. The characterization of such states and in particular the mixing of both collective and single-particle configurations will provide significant information on the shell structure close to $^{78}$Ni. A Coulomb excitation measurement of the states due to the proton-core excitations in the case of $^{77}$Cu nucleus will also provide an estimation of the collectivity of the 2$^+$ state in th even-even $^{76}$Ni "core".
Exotic secondary beam particles were produced by induced fission of the $^{238}$U beam on a 3 mm thick $^{9}$Be target. The uranium beam was accelerated to an energy of 345 MeV/nuclen with an average beam intensity of 20 pnA. Fission products were selected and transported by the BigRIPS fragment separator. Coulomb excitation of the fragments was performed on a 900 mg/cm$^2$ thick $^{197}$Au target, mounted in front of the Zero Degree Spectrometer. The DALI2 NaI array was used to detect de-excitation gamma ray measured in coincidence with beam-like particles identified in the Zero Degree Spectrometer (ZDS). The experimental techniques and results will be discussed in the present contribution.
Recently, a new high-energy (up to 70 MeV) and high-intensity cyclotron has been installed at the INFN-LNL National Laboratories of Legnaro (Padova, Italy). This facility will be soon put in operation and one of its research goals will focus on the production of radioisotopes for medicine and, in particular, theranostics, in the context of the INFN LARAMED initiative.
As research group, we are presently involved in the measurements and modeling of proton-induced nuclear reactions for the production of theranostic isotopes such as 67Cu and 47Sc. A series of measurements have been already performed thanks to a collaboration with the Arronax facility (Nantes, France) and are reported in this very same Symposium by G. Pupillo, L. Mou, et al.
Here we review the theoretical reaction models in a study performed with various codes with the aim to guide, interpret, and support the experiments in the proton-induced reaction measurements. The understanding of reaction cross sections at low-intermediate energies is crucial in this context and requires the knowledge of nuclear models available in different codes, analytical or MonteCarlo, such as EMPIRE, TALYS, FLUKA and others.
The use of nuclear reaction codes is very important to interpret the measurement of production cross-sections and to complete the measurements with estimates of production of contaminants and/or stable isotopes that are difficult to measure, particularly if the measurements have to rely heavily on radiochemical techniques. We will present a general study of different model calculations to simulate isotope production useful in measurements of proton-induced production reactions of the two theranostic radio-isotopes 67Cu and 47Sc.