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Transport properties and equation-of-state of hot and dense QGP matter near the critical endpoint in the phenomenological dynamical quasiparticle model
No full textInternational audienceWe extend the effective dynamical quasiparticle model (DQPM)—constructed for the description of nonperturbative QCD phenomena of the strongly interacting quark-gluon plasma (QGP)—to large baryon chemical potentials, μB, including a critical endpoint (CEP) and a first-order phase transition. The DQPM description of quarks and gluons is based on partonic propagators with complex self-energies where the real part of the self-energies is related to the quasiparticle mass and the imaginary part to a finite width of their spectral functions (i.e., the imaginary parts of the propagators). In DQPM the determination of complex self-energies for the partonic degrees of freedom at zero and finite μB has been performed by adjusting the entropy density to the lattice QCD data. The temperature-dependent effective coupling (squared) g2(T/Tc), as well as the effective masses and widths of the partons are based on this adjustments. The novel extended dynamical quasiparticle model, named “DQPM-CP,” makes it possible to describe thermodynamical and transport properties of quarks and gluons in a wide range of temperature, T, and baryon chemical potential, μB, and reproduces the equation of state of lattice QCD calculations in the crossover region of finite T,μB. We apply a scaling ansatz for the strong coupling constant near the CEP, located at (TCEP,μBCEP)=(0.100,0.960) GeV. We show the equation of state as well as the speed of sound for T>Tc and for a wide range of μB, which can be of interest for hydrodynamical simulations. Furthermore, we consider two settings for the strange quark chemical potentials, (I) μq=μu=μs=μB/3 and (II) μs=0,μu=μd=μB/3. The isentropic trajectories of the quark-gluon plasma matter are compared for these two cases. The phase diagram of DQPM-CP is close to PNJL calculations. The leading order pQCD transport coefficients of both approaches differ. This elucidates that the knowledge of the phase diagram alone is not sufficient to describe the dynamical evolution of strongly interacting matter
Predicting iodine solubility at high pressure in borosilicate nuclear waste glasses using optical basicity: an experimental study
No full textInternational audienceConstraining the systematic evolution of iodine solubility in borosilicate glasses is required for the formulation of adequate glass matrices able to immobilize 129I representing a major troublesome radioisotopes produced by nuclear anthropic activities. We investigated experimentally the change in iodine solubility in a large series of borosilicate glasses synthesized under high-pressure conditions (1.5 GPa) and at 1350 °C. The nature of network modifying cation (Na, K, Rb, Ca, Ba and Sr) and the concentration of B2O3 (~ 10 mol.%) have been tested. The XPS measurements showed that iodine speciation in glasses is mostly represented by iodide (I−) for a range of iodine solubility from 0.3 to 3.1 mol.% as determined by SEM EDS and LA-ICP-MS analyses. The iodine solubility is enhanced in glasses with lower B2O3 content and with a higher concentration in network modifying cation. Regardless of the cation nature: alkali or alkaline-earth; increasing the cation size appears to induce a decrease in iodine solubility. We used the optical basicity (ΛGlass) and iono-covalent parameter (ICPGlass) to express the large variety of investigated glass compositions; both relating to the electron donor capability of the glass. We show that iodine solubility is positively correlated with ΛGlass and accordingly negatively correlated with ICPGlass. It implies that more iodine will be dissolved in glass compositions having a stronger electron-donating capability. Evidence of the relationship between iodine solubility and oxygen network is shown by the iodine solubility positive trend with equilibrium constant of the oxygen speciation. Future work should take these parameters into consideration for modeling iodine solubility in borosilicate glasses providing additional information are collected such as the boron, aluminum and silicon speciation in glasses
Midrapidity cluster formation in heavy-ion collisions
No full textInternational audienceWe study the production of clusters and hypernuclei at midrapidity employing the Parton-Hadron-Quantum-Molecular-Dynamics (PHQMD) approach, a microscopic n-body transport model based on the QMD propagation of the baryonic degrees of freedom with density dependent 2-body potential interactions. In PHQMD the cluster formation occurs dynamically, caused by the interactions. The clusters are recognized by the Minimum Spanning Tree (MST) algorithm. We present the PHQMD results for cluster and hypernuclei formation in comparison with the available experimental data at relativistic energies. PHQMD allows to study the time evolution of formed clusters and the origin of their production, which helps to understand how such weakly bound objects are formed and survive in the rather dense and hot environment created in heavy-ion collisions. It offers therefore an explanation of the 'ice in the fire' puzzle. To investigate whether this explanation of the 'ice in the fire' puzzle applies only to the MST results we study also the deuterons production by coalescence. We embed MST and coalescence in the PHQMD and UrQMD transport approaches in order to obtain model independent results. We find that both clustering procedures give very similar results for the deuteron observables in the UrQMD as well as in the PHQMD environment. This confirms that our solution for the 'ice in the fire' puzzle is common to MST and coalescence and independent of the transport approach
Personnalisation du calcul de la dose absorbée pour les radiothérapies
No full textMémoire présenté en vue de l'obtention de l'habilitation à diriger des recherche
Mise en service du MFT et préparation d’analyses de données Run 3 dans l’expérience ALICE (LHC, CERN)
No full textThe ALICE detector is designed to study the Quark-Gluon Plasma (QGP), a state in which strongly interacting partonic matter is deconfined in a hot and dense medium. The measurement of quarkonium, an important probe of QGP, is possible with ALICE in two regions: at midrapidity, through their dielectron decays, and at forward rapidity, through their dimuon decays with the muon spectrometer. In order to expand the physics program at the forward rapidity region, the Muon Forward Tracker (MFT) was installed in ALICE during the long shutdown, a period in which upgrades take place to prepare for the nextdata taking period. The work of this thesis focuses first on software developments for MFT commissioning tool and the official detector control system. Then, algorithm development was done for the track matching between the muon spectrometer and the MFT based on machine learning. Once the matching is performed and global muon tracks are extracted, the calculation of the point of closest approach between the muon tracks was required for the separation of prompt and non-prompt J/ψ contributions. Thus, the secondary vertexing algorithm was also developed. Finally, quality assessments for Run 3 simulations were done to prepare for the upcoming data taking.Le détecteur ALICE est conçu pour étudier le Plasma de Quarks et de Gluons(PQG), un état dans lequel la matière hadronique se trouve déconfinée dans un milieu chaud et dense. La mesure de quarkonium, une sonde importante du PQG, est possible avec ALICE dans deux régions de rapidités : la rapidité centrale, par leurs désintégrations di-électroniques, et la rapidité en avant, par leurs désintégrations dimuons avec le spectromètre à muons. Afin d’élargir le programme de physique dans la région de rapidité vers l’avant, le Muon Forward Tracker (MFT) a été installé dans ALICE durant la période d’amélioration du LHC, précédant le Run 3 (période de prise de données actuelle). Le travail de cette thèse se concentre d’abord sur les développements d’un outil de commissioning du MFT ainsi que le système de contrôle officiel du détecteur. Dans un deuxième temps, un algorithme reposant sur des techniques de machine learning a été développé pour l’association des traces entre spectromètre à muons et le MFT. Après l’association de ces traces, et donc la possibilité d’extraction des traces globales de muons, le calcul du point de distance minimale entre ces dernières est requis afin de pouvoir séparer les contributions prompt et non-prompt de particules telles que le J/ψ. Donc, l’outil nécessaire a été également développé. Enfin, des évaluations de simulations Run 3 ont été menées afin de préparer la prise de données
Early taphonomy of benthic foraminifera in Storfjorden ‘sea‐ice factory’: the agglutinated/calcareous ratio as a proxy for brine persistence
No full textInternational audienceThe recurrent latent-heat polynya characterizing Storfjorden (Svalbard, Norway) triggers seasonal formation of thin first-year sea ice. This leads to the production of dense, salty, and corrosive brines that cascade towards the sea floor and mix with shelf waters. The bottom topography of the fjord is responsible for the retention of these dense waters in two central deep basins throughout the year. Recent studies show that living benthic foraminifera in Storfjorden are particularly affected by the persistence of brines on the sea floor, with a strong dominance of agglutinated (A) species and high degrees of dissolution of calcareous(C) faunas. Therefore, the A/C ratio, calculated on living faunas, was proposed as a proxy for brine persistence. In the present study we analyse the fossil faunas, found below the taphonomically active zone, to investigate the residual signal of the A/C proxy after the intense early taphonomic processes and challenge its applicability in sedimentary archives. Our results show that despite the generally high taphonomic loss inside the fjord, a high proportion of agglutinated species is still visible in fossil faunas at the stations experiencing regular and/or persistent presence of brine-enriched shelf waters. These results support the application of the A/C ratio in historical records to reconstruct the persistence of brines and indirectly the first-year sea ice formation in Storfjorden. This can be further applied to other Arctic fjords with similar settings and characterized by the production of brines during the winter–early spring season
Blind Benchmark Exercise for Spent Nuclear Fuel Decay Heat
No full textInternational audienceThe decay heat rate of five spent nuclear fuel assemblies of the pressurized water reactor type were measured by calorimetry at the interim storage for spent nuclear fuel in Sweden. Calculations of the decay heat rate of the five assemblies were performed by 20 organizations using different codes and nuclear data libraries resulting in 31 results for each assembly, spanning most of the current state-of-the-art practice. The calculations were based on a selected subset of information, such as reactor operating history and fuel assembly properties. The relative difference between the measured and average calculated decay heat rate ranged from 0.6% to 3.3% for the five assemblies. The standard deviation of these relative differences ranged from 1.9% to 2.4%
Influence of plutonium oxidation state on the formation of molecular hydrogen, nitrous acid and nitrous oxide from alpha radiolysis of nitric acid solution
No full textInternational audienceThe study of the formation of radiolytic products, such as molecular hydrogen and nitrous acid, is of primary importance in the reprocessing of spent nuclear fuel and the storage of aqueous solutions containing radioactive materials. The radiolytic yields of molecular hydrogen, nitrous acid and nitrous oxide from alpha radiolysis of nitric acid solutions containing plutonium have been experimentally investigated. The results have shown that the yields of radiolytic products depends on the nitric acid concentration as well as the oxidation state of plutonium. However, the influence of plutonium oxidation state on radiolytic yields is less notable as the nitric acid concentration increases. Molecular hydrogen production decreases with increasing nitric acid concentration while nitrous acid and nitrous oxide productions increase. While radiolytic yields from plutonium(IV) nitric acid solutions have been previously investigated, this study provides radiolytic yields from alpha radiolysis of plutonium(III) and plutonium(VI) nitric acid solutions for molecular hydrogen, nitrous acid and nitrous oxide. These information provide insight into the role played by plutonium redox behaviour on the formation of radiolytic products
Impact of initial states on the vapor hydration of iodine-bearing borosilicate glass
No full textInternational audienceUnder the context of long-term geological disposal of nuclear waste glass, the present work investigates the effectof initial states on the glass chemical durability in the vapor phase and during subsequent leaching. Glass withdifferent finishing steps of polishing and thermal annealing were prepared, vapor-hydrated, and aqueous-altered.Multiple characterizations of mechanical properties and structural modifications were performed to understandthe reduction of vapor hydration rates with annealed glasses. Discussions on the degradation of mechanicalproperties provide insights to understanding the variations of glass chemical durability, which shows a feasibleapproach to link mechanical and chemical studies together. By looking into the release of boron in the vaporphase, similarities between glass vapor hydration and glass aqueous alteration at residual rate are noticed, whichallow the proposition of mechanisms of boron release. Characterizations of the hydrated-then-altered glass revealthe transport-limiting property of the vapor hydrated layer
