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Mini review of research requirements for radioactive waste management including disposal
No full textInternational audienceThis brief overview of research needs related to radioactive waste management and disposal is intended to provide a framework for addressing some important research questions related to historical developments and some large industrial mega-projects for geological disposal of radioactive waste that are currently being developed. Considering that the level of industrial development varies considerably between countries, research in this field of knowledge has a strong international and long-term orientation, encompassing both basic and applied research, including optimisation
Production of Pb-203 from target manufacturing to chemical separation Tl/Pb
No full textInternational audienceLead 212 (t1/2 = 10.6 h) and lead 203 (t1/2 = 51.9 h), can be used as a theranostic pair of isotopes for theranostic applications in nuclear medicine. 212Pb is obtained by decay of 224Ra and is used for alpha targeted therapy whereas 203Pb is produced by proton irradiation of a thallium target and allows for single photon emission computed tomography (SPECT) thanks to its 279.2 keV (80.9%) photons. Current production of Pb-203 uses natTl bombarded by a proton beam. In this work, we consider alternative production routes using enriched 205Tl deuteron beams in order to limit the level of 201Pb (t1/2 = 9.33h) impurities. Starting from cross section measurements, we have defined optimal production parameters and yields. In parallel, we have developed a manufacturing process of the target by electroplating as well as a separation chemical process using a Pb resin provided by Triskem. This scheme will allow us to produce 203Pb in the near future
Polarization of and Hyperons along the Beam Direction in Pb-Pb Collisions at =5.02 TeV
No full textInternational audienceThe polarization of the Λ and Λ¯ hyperons along the beam (z) direction, Pz, has been measured in Pb-Pb collisions at sNN=5.02 TeV recorded with ALICE at the Large Hadron Collider (LHC). The main contribution to Pz comes from elliptic flow-induced vorticity and can be characterized by the second Fourier sine coefficient Pz,s2=⟨Pzsin(2φ-2Ψ2)⟩, where φ is the hyperon azimuthal emission angle and Ψ2 is the elliptic flow plane angle. We report the measurement of Pz,s2 for different collision centralities and in the 30%–50% centrality interval as a function of the hyperon transverse momentum and rapidity. The Pz,s2 is positive similarly as measured by the STAR Collaboration in Au-Au collisions at sNN=200 GeV, with somewhat smaller amplitude in the semicentral collisions. This is the first experimental evidence of a nonzero hyperon Pz in Pb-Pb collisions at the LHC. The comparison of the measured Pz,s2 with the hydrodynamic model calculations shows sensitivity to the competing contributions from thermal and the recently found shear-induced vorticity, as well as to whether the polarization is acquired at the quark-gluon plasma or the hadronic phase
Thermalization of non-Abelian gauge theories at next-to-leading order
No full textInternational audienceWe provide the first next-to-leading-order (NLO) weak-coupling description of the thermalization process of far-from-equilibrium systems in non-Abelian gauge theory. We study isotropic systems starting from either over- or underoccupied initial conditions and follow their time evolution toward thermal equilibrium by numerically solving the QCD effective kinetic theory at NLO accuracy. We find that the NLO corrections remain well under control for a wide range of couplings and that the overall effect of NLO corrections is to reduce the time needed to reach thermal equilibrium in the systems considered
nEXO: neutrinoless double beta decay search beyond 10 year half-life sensitivity
No full textInternational audienceThe nEXO neutrinoless double beta (0νββ) decay experiment is designed to use a time projection chamber and 5000 kg of isotopically enriched liquid xenon to search for the decay in Xe. Progress in the detector design, paired with higher fidelity in its simulation and an advanced data analysis, based on the one used for the final results of EXO-200, produce a sensitivity prediction that exceeds the half-life of 10 years. Specifically, improvements have been made in the understanding of production of scintillation photons and charge as well as of their transport and reconstruction in the detector. The more detailed knowledge of the detector construction has been paired with more assays for trace radioactivity in different materials. In particular, the use of custom electroformed copper is now incorporated in the design, leading to a substantial reduction in backgrounds from the intrinsic radioactivity of detector materials. Furthermore, a number of assumptions from previous sensitivity projections have gained further support from interim work validating the nEXO experiment concept. Together these improvements and updates suggest that the nEXO experiment will reach a half-life sensitivity of 1.35 × 10 yr at 90% confidence level in 10 years of data taking, covering the parameter space associated with the inverted neutrino mass ordering, along with a significant portion of the parameter space for the normal ordering scenario, for almost all nuclear matrix elements. The effects of backgrounds deviating from the nominal values used for the projections are also illustrated, concluding that the nEXO design is robust against a number of imperfections of the model
The force-force-correlator in hot QCD perturbatively and from the lattice
No full textInternational audienceHigh-energy particles traversing a medium experience modified dispersion. In the Quark-Gluon Plasma, such dispersion affects jet propagation and transport properties and should be determined better. Above ~ 2T we expect strongly coupled infrared behavior and perturbative ultraviolet behavior, allowing a perturbative matching to an effective theory called EQCD, which can be studied non-perturbatively. We study the relevant non-local operator in EQCD at next-to-leading order which allows for a complete EQCD-to-lattice match and prepares the groundwork for a matching between EQCD and full QCD. Our results in EQCD show remarkable agreement between perturbation theory and the lattice in the expected regime
Material radiopurity control in the XENONnT experiment
No full textInternational audienceThe selection of low-radioactive construction materials is of the utmost importance for rare-event searches and thus critical to the XENONnT experiment. Results of an extensive radioassay program are reported, in which material samples have been screened with gamma-ray spectroscopy, mass spectrometry, and Rn emanation measurements. Furthermore, the cleanliness procedures applied to remove or mitigate surface contamination of detector materials are described. Screening results, used as inputs for a XENONnT Monte Carlo simulation, predict a reduction of materials background (17%) with respect to its predecessor XENON1T. Through radon emanation measurements, the expected Rn activity concentration in XENONnT is determined to be 4.2 () \upmu Bq/kg, a factor three lower with respect to XENON1T. This radon concentration will be further suppressed by means of the novel radon distillation system
Performance of novel VUV-sensitive Silicon Photo-Multipliers for nEXO
No full textInternational audienceLiquid xenon time projection chambers are promising detectors to search for neutrinoless double beta decay (0), due to their response uniformity, monolithic sensitive volume, scalability to large target masses, and suitability for extremely low background operations. The nEXO collaboration has designed a tonne-scale time projection chamber that aims to search for 0 of \ce{^{136}Xe} with projected half-life sensitivity of ~yr. To reach this sensitivity, the design goal for nEXO is 1% energy resolution at the decay -value (~keV). Reaching this resolution requires the efficient collection of both the ionization and scintillation produced in the detector. The nEXO design employs Silicon Photo-Multipliers (SiPMs) to detect the vacuum ultra-violet, 175 nm scintillation light of liquid xenon. This paper reports on the characterization of the newest vacuum ultra-violet sensitive Fondazione Bruno Kessler VUVHD3 SiPMs specifically designed for nEXO, as well as new measurements on new test samples of previously characterised Hamamatsu VUV4 Multi Pixel Photon Counters (MPPCs). Various SiPM and MPPC parameters, such as dark noise, gain, direct crosstalk, correlated avalanches and photon detection efficiency were measured as a function of the applied over voltage and wavelength at liquid xenon temperature (163~K). The results from this study are used to provide updated estimates of the achievable energy resolution at the decay -value for the nEXO design
Room Temperature ASIC for Cryogenic TES/SQUID Control and Readout
No full textInternational audienceThis paper updates the development of a warm front-end electronics (WFEE) dedicated to cryogenic sensors readout. It belongs to the X-ray integral field unit instrument of ESA's future space observatory: ATHENA. This instrument integrates cryogenic elements such as 3168 transition edge sensors as detectors, multiplexed into 96 channels using time-division multiplexing (TDM). One TDM channel will be read out by two stages of superconducting quantum interference device (SQUID), followed by a WFEE and finally, a digital readout system, both two last stages operating at about 300 K. In the WFEE, 96 TDM channels will be distributed in 48 application-specific integrated circuits (ASIC). Each channel includes one low-noise amplifier to amplify the multiplexed signal and 5 configurable current sources to bias the SQUIDs and TES in the cryogenic stages. Additionally, two channels within the same ASIC share a serial bus "RS485/(IC)-C-2" to configure the current sources (current SlowDACs) and housekeeping elements that monitor the temperature, current and voltage of the ASIC. The ASIC presented in this paper, "AwaXe_v3" (AwaXe: Athena Warm Asic for the X-ifu Electronics), is developed for the WFEE using an AMS 350 nm SiGe BiCMOS technology. It is the first prototype of the WFEE integrating two complete TDM channels. Representative measurement results that characterise the main components of the WFEE will be discussed in this paper as an update on the use of ASIC for the TES/SQUID readout
What do we need to deliver “online” adapted radiotherapy treatment plans?
No full textNational audienceDuring the joint SFRO/SFPM session of the 2019 congress, a state of the art of adaptive radiotherapy announced a strong impact in our clinical practice, in particular with the availability of treatment devices coupled to an MRI system. Three years later, it seems relevant to take stock of adaptive radiotherapy in practice, and especially the “online” strategy because it is indeed more and more accessible with recent hardware and software developments, such as coupled accelerators to a three-dimensional imaging device and algorithms based on artificial intelligence. However, the deployment of this promising strategy is complex because it contracts the usual time scale and upsets the usual organizations. So what do we need to deliver adapted treatment plans with an “online” strategy