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Green beam lines, a challenging concept
No full textDue to increasing environmental and economic constraints, optimization of ion beam transport and equipment design becomes essential. The future should be equipped with planet-friendly facilities, that is, solutions that reduce environmental impact and improve economic competitiveness. The tendency to increase the intensity of the current and the power of the beams obliges us and brings us to new challenges. Installations tend to have larger dimensions with increased areas, volumes, weights and costs. A new ion beam transport prototype was developed and used as a test bed to identify key issues to reduce beam losses and preserve transverse phase-space distributions with large acceptance conditions
Étonnants infinis
No full textInternational audienceL’immensité de notre Univers ne cesse d’intriguer et de stimuler les imaginations.Pour mieux appréhender l’infiniment grand et l’histoire de l’Univers depuis ses tout premiers instants, il faut se tourner vers un autre infini, l’infiniment petit, et ses quarks, leptons et bosons, à la base du modèle standard de la physique des particules. En les étudiant, on cherche à percer le secret de l’organisation de la matière à la plus petite échelle. Sans l’infiniment petit, on ne peut décrire ni le Big Bang, ni le comportement des grandes structures stellaires, ni la naissance de la matière. Et sans ces deux infinis ensemble, on ne peut bâtir les modèles théoriques expliquant la matière noire, l’énergie noire ou fonder la gravitation quantique.Les physiques des infinis sont des physiques hors normes qui se racontent à grand renfort de superlatifs. Elles nécessitent des installations internationales de très grande envergure, et nous entraînent dans des voyages aux confins de la perception où l’on flirte avec la vitesse de la lumière et jongle avec les limites des propriétés de la matière.En trente courts chapitres abondamment illustrés, cet ouvrage rend compte de ce que l’on sait déjà comme de ce que l’on cherche encore
The use of stable lead isotopes for the identification of the sources and transport processes leading to the release of radioactive contaminants downstream of former uranium mine sites
No full textInternational audienceRadioactive-enriched material produced during past uranium mining activities,such as tailings and mine drainage water, potentially releases radioactive contaminants into the surrounding soils and sediments.Activities of U and its decay products could be therefore significantly higher than those of the local geochemical background. Moreover, weathering and erosion of the local bedrock could also lead to a high level of uranium up to 4000 mg.kg-1[1]. Thus, highlighting the potential sources and mechanisms driving radioactive elements dissemination in the vicinity of former U mines is a key element for the decision-making process, the effective management and remediation of contaminated sediments and soils. This research aims to identify the sources of radioactive contaminants and their transport mechanism by using stable Pb isotopes and radioactive disequilibrium of the 238U-decay series. The study area is a wetland located downstream of U mine tailings, Rophin (France), considered a uranium territory workshop (ZATU). The exploited uranium mineral is parsonsite Pb2(UO2)(PO4)2, rich incommon Pb [2].High U concentration up to 3147 mg.kg-1(34 mg.kg-1in local bedrock) was observed in a soil core extracted in the wetland. The results of stable Pb isotopic analysis indicate that U accumulation is linked with a whitish clay soil layer below the organic topsoil layer. The 206Pb/207Pb ratio of this layer reveals a radiogenic signature ~1.73 (local background ~1.20), which means it probably originates from previous mining activities. The alignments of Pb isotope ratio data in three isotope diagrams highlight the mining impact on the soils. Many studies have evaluated the percentage of mining contamination by Pb binary isotope mixing models [3]. We remark here the high content of common Pb in parsonsite could lead to an underestimation of mining impacts. So, the evaluation needs more cautious in this context. Moreover, our results show the mobility of U in the soil core. However, more studies are needed in order to better understand the processes governing the mobility of U and its decay products and to shed new light on their codispersion or not with the radiogenic lead of the U-or
General balance functions of identified charged hadron pairs of (π,K,p) in Pb–Pb collisions at <math altimg="si1.svg"><msub><mrow><msqrt><mrow><mi>s</mi></mrow></msqrt></mrow><mrow><msub><mrow/><mrow><mi mathvariant="normal">NN</mi></mrow></msub></mrow></msub><mo linebreak="goodbreak" linebreakstyle="after">=</mo></math> 2.76 TeV
No full textInternational audienceFirst measurements of balance functions (BFs) of all combinations of identified charged hadron (π,K,p) pairs in Pb–Pb collisions at sNN=2.76 TeV recorded by the ALICE detector are presented. The BF measurements are carried out as two-dimensional differential correlators versus the relative rapidity (Δy) and azimuthal angle (Δφ) of hadron pairs, and studied as a function of collision centrality. The Δφ dependence of BFs is expected to be sensitive to the light quark diffusivity in the quark–gluon plasma. While the BF azimuthal widths of all pairs substantially decrease from peripheral to central collisions, the longitudinal widths exhibit mixed behaviors: BFs of ππ and cross-species pairs narrow significantly in more central collisions, whereas those of KK and pp are found to be independent of collision centrality. This dichotomy is qualitatively consistent with the presence of strong radial flow effects and the existence of two stages of quark production in relativistic heavy-ion collisions. Finally, the first measurements of the collision centrality evolution of BF integrals are presented, with the observation that charge balancing fractions are nearly independent of collision centrality in Pb–Pb collisions. Overall, the results presented provide new and challenging constraints for theoretical models of hadron production and transport in relativistic heavy-ion collisions
Combined sensitivity of JUNO and KM3NeT/ORCA to the neutrino mass ordering
No full text24 pages, 9 figuresInternational audienceThis article presents the potential of a combined analysis of the JUNO and KM3NeT/ORCA experiments to determine the neutrino mass ordering. This combination is particularly interesting as it significantly boosts the potential of either detector, beyond simply adding their neutrino mass ordering sensitivities, by removing a degeneracy in the determination of between the two experiments when assuming the wrong ordering. The study is based on the latest projected performances for JUNO, and on simulation tools using a full Monte Carlo approach to the KM3NeT/ORCA response with a careful assessment of its energy systematics. From this analysis, a determination of the neutrino mass ordering is expected after 6 years of joint data taking for any value of the oscillation parameters. This sensitivity would be achieved after only 2 years of joint data taking assuming the current global best-fit values for those parameters for normal ordering
Proton beam dosimetry at ultra‐high dose rates (FLASH): Evaluation of GAFchromic™ (EBT3, EBT‐XD) and OrthoChromic (OC‐1) film performances
No full textInternational audiencePurpose: The ARRONAX cyclotron facility offers the possibility to deliver proton beams from low to ultra-high dose rates (UHDR). As a good control of the dosimetry is a prerequisite of UHDR experimentations, we evaluated in different conditions the usability and the dose rate dependency of several radiochromic films commonly used for dosimetry in radiotherapy. Methods: We compared the dose rate dependency of three types of radiochromic films: GAFchromic™ EBT3 and GAFchromic™ EBT-XD (Ashland Inc., Wayne, NJ, USA), and OrthoChromic OC-1 (OrthoChrome Inc., Hillsborough, NJ, USA), after proton irradiations at various mean dose rates (0.25, 40, 1500, and 7500 Gy/s) and for 10 doses (2–130 Gy). We also evaluated the dose rate dependency of each film considering beam structures, from single pulse to multiple pulses with various frequencies. Results: EBT3 and EBT-XD films showed differences of response between conventional (0.25 Gy/s) and UHDR (7500 Gy/s) conditions, above 10 Gy. On the contrary, OC-1 films did not present overall difference of response for doses except below 3 Gy. We observed an increase of the netOD with the mean dose rate for EBT3 and EBT-XD films. OC-1 films did not show any impact of the mean dose rate up to 7500 Gy/s, above 3 Gy. No difference was found based on the beam structure, for all three types of films. Conclusions: EBT3 and EBT-XD radiochromic films should be used with caution for the dosimetry of UHDR proton beams over 10 Gy. Their overresponse, which increases with mean dose rate and dose, could lead to non-negligible overestimations of the absolute dose. OC-1 films are dose rate independent up to 7500 Gy/s in proton beams. Films response is not impacted by the beam structure. A broader investigation of the usability of OC-1 films in UHDR conditions should be conducted at intermediate and higher mean dose rates and other beam energies. © 2022 American Association of Physicists in Medicin
Monte Carlo Studies of the MPD Detector Performance for the Measurement of Hypertritons in Heavy-Ion Collisions at NICA Energies
No full textInternational audienceHeavy-ion collisions at NICA energies provide a unique opportunity for the study of the production of hypernuclei in dense baryonic matter. In this paper, the details of the reconstruction procedure for hypertritons with the MPD detector in Bi + Bi collisions at NICA energies are presented
Simultaneous scintillation light and charge readout of a pure argon filled Spherical Proportional Counter
No full textInternational audienceThe possible use of a Spherical Proportional Counter for the search of neutrinoless double beta decay is investigated in the R2D2 R&D project. Dual charge and scintillation light readout may improve the detector performance. Tests were carried out with pure argon at 1.1 bar using a 6 × 6 mm2 silicon photomultiplier. Scintillation light was used for the first time to trigger in a spherical proportional counter. The measured drift time is in excellent agreement with the expectations from simulations. Furthermore the light signal emitted during the avalanche development exhibits features that could be exploited for event characterization
GPU-based optical simulation of the DARWIN detector
No full textInternational audienceUnderstanding propagation of scintillation light is critical for maximizing the discovery potential of next-generation liquid xenon detectors that use dual-phase time projection chamber technology. This work describes a detailed optical simulation of the DARWIN detector implemented using Chroma, a GPU-based photon tracking framework. To evaluate the framework and to explore ways of maximizing efficiency and minimizing the time of light collection, we simulate several variations of the conventional detector design. Results of these selected studies are presented. More generally, we conclude that the approach used in this work allows one to investigate alternative designs faster and in more detail than using conventional Geant4 optical simulations, making it an attractive tool to guide the development of the ultimate liquid xenon observatory
Uranium retention in a Callovo-Oxfordian clay rock formation: From laboratory-based models to in natura conditions
No full textInternational audienceFor the performance assessment of radioactive waste disposal, it is critical to predict the mobility of radionuclides in the geological barrier that hosts it. A key challenge consists of assessing the transferability of current knowledge on the retention properties deduced from model systems to in natura situations. The case of the redox-sensitive element uranium in the Callovo-Oxfordian clay formation (COx) is presented herein. Extensive experimental work was carried out with respect to parameters affecting uranium speciation (pH, PCO2, [Ca] and redox potential) with illite, COx clay fraction and raw COx claystone. The “bottom-up” approach implemented, with illite and montmorillonite as reactive phases, quantitatively explains the adsorption results of U(VI) and U(IV) on COx. While retention is high for U(IV) (Rd∼104 L kg−1), it remains very low for U(VI) (Rd∼4 L kg−1) due to the formation of soluble ternary Ca(Mg)–U(VI)-carbonate complexes. The applicability of the sorption model was then assessed by comparing predictive analyses with data characterizing the behavior of naturally-occurring U ( 70 L kg−1. (Elsevier