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Spatial Stability of Kr83m calibration events in XENONnT experiment
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In-medium effects on hidden strangeness production in heavy-ion collisions
No full textInternational audienceWe study ϕ meson production in heavy-ion collisions from subthreshold energies of 1.23 A GeV up to RHIC energies within the microscopic Parton-Hadron-String Dynamics (PHSD) transport approach where novel production channels for ϕ mesons based on a coupled channel T-matrix approach are implemented along with the collisional broadening of the ϕ meson spectral width in medium. Since ϕ meson production is closely related to the production of kaons and antikaons, antikaon properties are described via the self-consistent coupled-channel unitarized scheme within a SU(3) chiral Lagrangian (G-matrix) which incorporates explicitly the s− and p− waves of the kaon-nucleon interaction, while the in-medium modifications of kaons are accounted for via a kaon-nuclear potential, which is assumed to be proportional to the local baryon density
Uranium speciation and transport behavior in the wetland of the former extraction mine of Rophin (France)
No full textInternational audienceIntroductionIn the vicinity ofold uranium mines, wetlands prove to be specific zones with significant amountsof accumulated U. At the center ofthe ancient mining district of Lachaux in France (45.994°N,3.596°E), the site of Rophin (within the ZATU: Uranium Working Zone = Long Term SocioEcological Research Tool ofCNRS) is characterized by awetland areawith high U concentrationsup to 3.6 g.kg-1. In this context, the main challenge is to describe the behavior ofU and relevantdecay products in the wetland using a predictive model that combines chemical speciation andtransport.MethodsThe overall adopted scientific approach is to propose a mechanistic description ofthe mobility ofthese elements, from the molecular scale (speciation) to in situ behavior (lability), by couplingfield and laboratory experiments with modelling. Batch desorption and column experiments werecarried out with in situ soil samples to assess the mobile fraction part of U and its distributioncoefficients (Kd). Labile behavior of U was examined directly on site by using the DGT/DETtechniques while U speciation was investigated by the combination ofseveral techniques (SEM,XAS). From laboratory data, predictive modelling (smart-Kd model) was implemented under sitespecific conditions.ResultsObservations by SEM, XANES and EXAFS confirmed the U transportin particulate form duringthe mining activities and the establishment of reducing conditions over time, implying thepresence of both U(IV) and U(VI). Labile quantity and Kd values of U were confirmed to behomogeneous at the scale of the Rophin wetland and consistent with in situ labile behaviordeduced from the DGT/DET approach, considering a kinetically controlled interaction.ConclusionsThanks to the combination of different techniques, a better understanding of what happened inthe wetland over 70 years can be achieved. All these data should now allow us to define the keyparameters to be integrated in the reactive part ofthe transport model ofthe Rophin sit
Dynamique des fluctuations dans les collisions d’ions lourds
No full textL’univers a un jour été composé d’une soupe de matière appelé le plasma de quark et de gluons. Aujourd’hui on observe des états liés de quark et de gluons, les hadrons. L’étude de la transition de phase entre ces deux états de la matière nucléaire est primordiale dans la compréhension de l’univers actuel. Il est désormais possible de reproduire des conditions similaires à celles de l’univers primordial dans les collisions d’ions lourds relativiste et ainsi d’étudier la transition expérimentalement. Les fluctuations des nombres net de baryon, charge électrique et d’étrangeté sont des observables de choix dans cette approche, en particulier pour la recherche d’un éventuel point critique (CP). Les collisions d’ions lourds sont des expériences dynamiques, l’équilibre thermodynamique n’est peut-être pas atteint pendant la collision, rendant les études dynamiques indispensables. Dans cette thèse, on étudie l’impact de la dynamique des collisions d’ions lourds sur l’évolution diffusive des fluctuations de densités des charges conservées. On démontre la grande sensibilité des signaux provenant du point aux coefficients de diffusion ainsi qu’à la température de freeze-out révélant ainsi un grand impact de la dynamique. Une première approche de diffusion couplée avec des coefficient de diffusion réalistes montre que le signal peut survivre longtemps dans le phase hadronique.L’univers a un jour été composé d’une soupe de matière appelé le plasma de quark et de gluons. Aujourd’hui on observe des états liés de quark et de gluons, les hadrons. L’étude de la transition de phase entre ces deux états de la matière nucléaire est primordiale dans la compréhension de l’univers actuel. Il est désormais possible de reproduire des conditions similaires à celles de l’univers primordial dans les collisions d’ions lourds relativiste et ainsi d’étudier la transition expérimentalement. Les fluctuations des nombres net de baryon, charge électrique et d’étrangeté sont des observables de choix dans cette approche, en particulier pour la recherche d’un éventuel point critique (CP). Les collisions d’ions lourds sont des expériences dynamiques, l’équilibre thermodynamique n’est peut-être pas atteint pendant la collision, rendant les études dynamiques indispensables. Dans cette thèse, on étudie l’impact de la dynamique des collisions d’ions lourds sur l’évolution diffusive des fluctuations de densités des charges conservées. On démontre la grande sensibilité des signaux provenant du point aux coefficients de diffusion ainsi qu’à la température de freeze-out révélant ainsi un grand impact de la dynamique. Une première approche de diffusion couplée avec des coefficient de diffusion réalistes montre que le signal peut survivre longtemps dans le phase hadronique
How Efficient Are Monte Carlo Calculations Together With the Q-System to Determine Radioactive Transport Limits? Case Study on Medical Radionuclides
No full textInternational audienceThe development of the so-called theranostics approach, in which imaging information are used to define a personalized therapeutic strategy, is driving the increasing use of radionuclides in nuclear medicine. They are artificially produced either in nuclear reactors, charged particle accelerators, or using radionuclide generators. Each method leads to radioisotopes with different characteristics and then clinical utility. In the first two cases they are extracted from stable or radioactive target bombarded with a particle beam. After extraction/purification of the target, the radionuclides, either implanted on solid or in liquid form, needs to be transported to a centralized production site, a radiopharmacy or an hospital. The transport of needed radioactive material must obey strict rules. For a radionuclide, a limit in activity that it is possible to transport has been established for each type of allowed packages. For type A package these limits are called A1 (for special form sources, i.e., certified perfectly sealed and encapsulated sources) and A2 (for non-special form sources). However, these limits can be easily reached if the activity to transport is high or if the radionuclide of interest is a “non–conventional” one. Indeed, for many radionuclides, there are no available/tabulated A1 and A2 and, in these cases, a very conservative set of values is imposed. This is in particular the case for some of the non-conventional radionuclide of interest in medicine (as for example Tb-149 or Tb-161). The non-tabulated values, and in general the A1/A2 limit, can be evaluated following the so-called Q-system and using Monte Carlo calculations. In the present work, we have used the MCNPX Monte Carlo code to evaluate dose rate values in different exposure scenarios. This has allowed us to determine A1/A2 coefficients for several non-conventional radionuclides of interest for medical applications. The developed technique can be extended easily to other radionuclides and can be adapted in case of changes in regulatory rules
The KM3NeT multi-PMT optical module
No full textInternational audienceThe optical module of the KM3NeT neutrino telescope is an innovative multi-faceted large area photodetection module. It contains 31 three-inch photomultiplier tubes in a single 0.44 m diameter pressure-resistant glass sphere. The module is a sensory device also comprising calibration instruments and electronics for power, readout and data acquisition. It is capped with a breakout-box with electronics for connection to an electro-optical cable for power and long-distance communication to the onshore control station. The design of the module was qualified for the first time in the deep sea in 2013. Since then, the technology has been further improved to meet requirements of scalability, cost-effectiveness and high reliability. The module features a sub-nanosecond timing accuracy and a dynamic range allowing the measurement of a single photon up to a cascade of thousands of photons, suited for the measurement of the Cherenkov radiation induced in water by secondary particles from interactions of neutrinos with energies in the range of GeV to PeV. A distributed production model has been implemented for the delivery of more than 6000 modules in the coming few years with an average production rate of more than 100 modules per month. In this paper a review is presented of the design of the multi-PMT KM3NeT optical module with a proven effective background suppression and signal recognition and sensitivity to the incoming direction of photons
CORI research on cement-organics-radionuclides-interactions within the collaborative EURAD project
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The DAMIC-M Experiment: Status and First Results
No full textInternational audienceThe DAMIC-M (DArk Matter In CCDs at Modane) experiment employs thick, fully depleted silicon charged-coupled devices (CCDs) to search for dark matter particles with a target exposure of 1 kg-year. A novel skipper readout implemented in the CCDs provides single electron resolution through multiple non-destructive measurements of the individual pixel charge, pushing the detection threshold to the eV-scale. DAMIC-M will advance by several orders of magnitude the exploration of the dark matter particle hypothesis, in particular of candidates pertaining to the so-called "hidden sector." A prototype, the Low Background Chamber (LBC), with 20g of low background Skipper CCDs, has been recently installed at Laboratoire Souterrain de Modane and is currently taking data. We will report the status of the DAMIC-M experiment and first results obtained with LBC commissioning data
Characterization of the background spectrum in DAMIC at SNOLAB
No full textInternational audienceWe construct the first comprehensive radioactive background model for a dark matter search with charge-coupled devices (CCDs). We leverage the well-characterized depth and energy resolution of the DAMIC at SNOLAB detector and a detailed geant4-based particle-transport simulation to model both bulk and surface backgrounds from natural radioactivity down to 50 eVee. We fit to the energy and depth distributions of the observed ionization events to differentiate and constrain possible background sources, for example, bulk H3 from silicon cosmogenic activation and surface Pb210 from radon plate-out. We observe the bulk background rate of the DAMIC at SNOLAB CCDs to be as low as 3.1±0.6 counts kg-1 day-1 keVee−1, making it the most sensitive silicon dark matter detector. Finally, we discuss the properties of a statistically significant excess of events over the background model with energies below 200 eVee