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Monolithic amplifier and current biasing for SQUID readout-AwaXe_v4
No full textInternational audienceThe X-IFU is one of the two instruments of the ESA ATHENA mission, offering an unprecedented high spectral resolution. In the detection and readout chain of the X-IFU, the first warm stage is the WFEE subsystem. It mainly includes low-noise amplifiers and current sources to read out and bias cryogenic stages. Based on the development of four previous versions of the ASICs dedicated to the WFEE, a new version has been recently developed to transfer analogue functions to a thinner SiGe technology node of 130 nm. This paper updates the development of this new ASIC
Recherche de matière noire légère avec l’expérience DAMIC-M
No full textDAMIC-M (Dark Matter in CCDs at Modane) is a near-future experiment that aims at searching for low-mass dark matter particles through their interactions with silicon atoms in the bulk of charge-coupled devices(CCDs). Pioneer in this technique was the DAMIC experiment at SNOLAB. Its successor, DAMIC-M, will have a detector mass 17 times larger and will employ a novel CCD technology (skipper amplifiers) to achieve sub-electron readout noise. Strengthened by these characteristics, DAMIC-M will reach unmatched sensitivity to the dark matter candidates of the so-called hidden sector. A challenging requirement is to control the radiogenic background down to the level of a fraction of events perkeV per kg-day of target exposure. To meet this condition, Geant4 based simulations are being utilized to optimize the detector design, drive the material selection and handling, and test background rejection techniques. Furthermore, precise measurements were carried out with skipper CCDs to characterize the spectrum of Compton scattered electrons, which represent a dominant source of environmental background at low energy. This thesis focuses on the explored detector designs, the corresponding predicted background, and the strategies implemented for its mitigation and characterization.DAMIC-M (Dark Matter in CCDs at Modane) est une expérience en cours de développement qui aura pour objectif de détecter des particules de matière noire de faible masse grâce à l’interaction de ces dernières avec les atomes de silicium qui composent des capteurs photographiques CCDs. DAMIC à SNOLAB a été la première expérience à utiliser cette technologie pour la recherche de matière noire. Son successeur, DAMIC-M, aura une masse de détection 17 fois plus grande et utilisera une nouvelle technologie CCD (amplificateurs skipper) pour obtenir un bruit de lecture inférieur à un électron. Ces caractéristiques permettront à DAMIC-M d’atteindre une sensibilité inégalée aux candidats matière noire du «hidden sector» . Unetelle sensibilité requiert un excellent contrôle du bruit de fond radiogénique, il doit en effet être contraint au niveau d’une fraction d’évènement par keV par kg-jour d’exposition.Pour répondre à cette exigence, des simulations Geant4 sont utilisées pour optimiser la conception du détecteur, piloter la sélection et la manipulation des matériaux et tester les techniques de rejet du bruit de fond.De plus, afin de caractériser le spectre d’électrons diffusés par diffusion Compton, qui représentent une source dominante de bruit de fond à basse énergie, des mesures ont été réalisées avec des CCD skipper. Cette thèse se concentre sur les différentes configurations de détecteur testées, l’estimation du bruit de fond associé ainsi que sur les différentes stratégies mises en œuvre pour la caractérisation et l’atténuation de celui-ci
Impact of fresh fuel loading management in fuel cycle simulators: A functionality isolation test
No full textInternational audienceFuel cycle simulator development started many years ago by several research and engineering institutions or consulting firms for a wide range of applications. To improve confidence in the results, institutions may be tempted to increase the complexity of their software even if this complexity might not be necessary. On the other hand, some simulators may be used outside their range of validity when used in very specific applications. The FIT (Functionality Isolation Test) project is an international effort devoted to improve the confidence in the data produced by fuel cycle simulation tools. The scientific goal is to determine the optimum level of detail a fuel cycle simulator needs according to the type of study and the required confidence level. The project relies on a wide variety of fuel cycle simulators with a large range of complexity levels. The FIT project consists of isolating the impact of one targeted functionality on fuel cycle simulations. The impact of the functionality is assessed using a set of simple basic exercises specifically designed for this purpose, called ”functionality isolation.” The present work focuses on the impact on simulation results of using a fuel loading model (a relation that links the stock isotopic composition with the fresh fuel fabrication according to the reactor requirements) or a fixed fraction approach (the fresh fuel fissile fraction is fixed and does not depend on the stock isotopic composition). The paper first presents the FIT project. The exercise design is described and results show that using a fuel loading model approach has an important impact on fuel cycle outputs under certain conditions that are described. This result is reinforced by the fact that all fuel cycle simulators used in this exercise provide similar conclusions
Économie de l’énergie nucléaire 1: Analyse économique du cycle électronucléaire
No full textInternational audienceCet ouvrage expose les éléments économiques factuels, précis, complets et accessibles de l’énergie nucléaire afin de contribuer à un débat éclairé et dépassionné. Il présente, dans un premier temps, une analyse approfondie des politiques stratégiques relatives à l’énergie nucléaire en France et dans le monde. Puis, il traite de la formation des coûts de production de l’électricité nucléaire, que ce soit pour les réacteurs actuels ou du futur. Les aspects méthodologiques sont présentés de manière exhaustive et illustrés d’exemples et d’études de cas détaillés. Enfin, Économie de l’énergie nucléaire 1 propose une étude économique pertinente de la composante combustible de l’énergie nucléaire. Dans ce cadre, les aspects relatifs au marché de l’uranium sont présentés avant de décrire précisément les composantes techniques et économiques qui se trouvent en amont du cycle nucléaire. Coordonnateurs : Jacques Percebois "Professeur émérite à l’Université de Montpellier, Jacques Percebois est le fondateur du CREDEN et d’un master en économie de l’énergie. Auteur de plusieurs ouvrages sur l’énergie, il a été membre de plusieurs commissions nationales sur le nucléaire." Nicolas Thiollière "Nicolas Thiollière est physicien nucléaire, enseignant-chercheur à IMT Atlantique et rattaché au laboratoire de recherche fondamentale Subatech. Il est spécialiste de la modélisation des réacteurs et du cycle du combustible.
Measurement of prompt -meson production and azimuthal anisotropy in Pb–Pb collisions at =5.02TeV
No full textInternational audienceThe production yield and angular anisotropy of prompt Ds+ mesons were measured as a function of transverse momentum (pT) in Pb–Pb collisions at a centre-of-mass energy per nucleon pair sNN=5.02TeV collected with the ALICE detector at the LHC. Ds+ mesons and their charge conjugates were reconstructed at midrapidity (|y|<0.5) from their hadronic decay channel Ds+→ϕπ+, with ϕ→K−K+, in the pT intervals 2<pT<50GeV/c and 2<pT<36GeV/c for the 0–10% and 30–50% centrality intervals. For pT>10GeV/c, the measured Ds+-meson nuclear modification factor RAA is consistent with the one of non-strange D mesons within uncertainties, while at lower pT a hint for a Ds+-meson RAA larger than that of non-strange D mesons is seen. The enhanced production of Ds+ relative to non-strange D mesons is also studied by comparing the pT-dependent Ds+/D0 production yield ratios in Pb–Pb and in pp collisions. The ratio measured in Pb–Pb collisions is found to be on average higher than that in pp collisions in the interval 2<pT<8GeV/c with a significance of 2.3σ and 2.4σ for the 0–10% and 30–50% centrality intervals. The azimuthal anisotropy coefficient v2 of prompt Ds+ mesons was measured in Pb–Pb collisions in the 30–50% centrality interval and is found to be compatible with that of non-strange D mesons. The main features of the measured RAA, Ds+/D0 ratio, and v2 as a function of pT are described by theoretical calculations of charm-quark transport in a hydrodynamically expanding quark–gluon plasma including hadronisation via charm-quark recombination with light quarks from the medium. The pT-integrated production yield of Ds+ mesons is compatible with the prediction of the statistical hadronisation model
Prompt D, D, and D production in Pb–Pb collisions at = 5.02 TeV
No full textInternational audienceThe production of prompt D, D, and D mesons was measured at midrapidity (|y| < 0.5) in Pb–Pb collisions at the centre-of-mass energy per nucleon–nucleon pair = 5.02 TeV with the ALICE detector at the LHC. The D mesons were reconstructed via their hadronic decay channels and their production yields were measured in central (0–10%) and semicentral (30–50%) collisions. The measurement was performed up to a transverse momentum (p) of 36 or 50 GeV/c depending on the D meson species and the centrality interval. For the first time in Pb–Pb collisions at the LHC, the yield of D mesons was measured down to p = 0, which allowed a model-independent determination of the p-integrated yield per unit of rapidity (dN/dy). A maximum suppression by a factor 5 and 2.5 was observed with the nuclear modification factor (R) of prompt D mesons at p = 6–8 GeV/c for the 0–10% and 30–50% centrality classes, respectively. The D-meson RAA is compared with that of charged pions, charged hadrons, and J/ψ mesons as well as with theoretical predictions. The analysis of the agreement between the measured R, elliptic (v) and triangular (v) flow, and the model predictions allowed us to constrain the charm spatial diffusion coefficient D. Furthermore the comparison of R and v with different implementations of the same models provides an important insight into the role of radiative energy loss as well as charm quark recombination in the hadronisation mechanisms.[graphic not available: see fulltext
Solar Kaluza-Klein axion search with NEWS-G
No full textInternational audienceKaluza-Klein axions appear in theories with extra dimensions as higher mass, significantly shorter lifetime, excitations of the Peccei-Quinn axion. When produced in the Sun, they would remain gravitationally trapped in the solar system, and their decay to a pair of photons could provide an explanation of the solar corona heating problem. A low-density detector would discriminate such a signal from the background, by identifying the separation of the interaction point of the two photons. The NEWS-G collaboration uses large volume spherical proportional counters, gas-filled metallic spheres with a spherical anode in their centre. After observation of a single axionlike event in a 42 day long run with the SEDINE detector, a 90% C.L. upper limit of gaγγ<8.99×10-13 GeV−1 is set on the axion-photon coupling for the benchmark of a Kaluza-Klein axion density on Earth of na=4.07×1013 m−3 and two extra dimensions of size R=1 eV−1
Observation of a multiplicity dependence in the -differential charm baryon-to-meson ratios in proton-proton collisions at TeV
No full textInternational audienceThe production of prompt D0, Ds+, and Λc+ hadrons, and their ratios, Ds+/D0 and Λc+/D0, are measured in proton–proton collisions at s=13 TeV at midrapidity (|y|<0.5) with the ALICE detector at the LHC. The measurements are performed as a function of the charm-hadron transverse momentum (pT) in intervals of charged-particle multiplicity, measured with two multiplicity estimators covering different pseudorapidity regions. While the strange to non-strange Ds+/D0 ratio indicates no significant multiplicity dependence, the baryon-to-meson pT-differential Λc+/D0 ratio shows a multiplicity-dependent enhancement, with a significance of 5.3σ for 1<pT<12 GeV/c, comparing the highest multiplicity interval with respect to the lowest one. The measurements are compared with a theoretical model that explains the multiplicity dependence by a canonical treatment of quantum charges in the statistical hadronisation approach, and with predictions from event generators that implement colour reconnection mechanisms beyond the leading colour approximation to model the hadronisation process. The Λc+/D0 ratios as a function of pT present a similar shape and magnitude as the Λ/KS0 ratios in comparable multiplicity intervals, suggesting a potential common mechanism for light- and charm-hadron formation, with analogous multiplicity dependence. The pT-integrated ratios, extrapolated down to pT=0, do not show a significant dependence on multiplicity within the uncertainties
Deuteron production in ultrarelativistic heavy-ion collisions: A comparison of the coalescence and the minimum spanning tree procedure
No full textInternational audienceThe formation of deuterons in heavy-ion collisions at relativistic energies is investigated by employing two recently advanced models—the minimum spanning tree (MST) method and the coalescence model—by embedding them in the parton-hadron quantum molecular dynamics (PHQMD) and the ultrarelativistic quantum molecular dynamics (UrQMD) transport approaches. While the coalescence mechanism combines nucleons into deuterons at the kinetic freeze-out hypersurface, the MST identifies the clusters during the different stages of time evolution. We find that both clustering procedures give very similar results for the deuteron observables in the UrQMD as well as in the PHQMD environment. Moreover, the results agree well with the experimental data on deuteron production in Pb+Pb collisions at sNN=8.8 GeV (selected for the comparison of the methods and models in this study). A detailed investigation shows that the coordinate space distribution of the produced deuterons differs from that of the free nucleons and other hadrons. Thus, deuterons are not destroyed by additional rescattering
Charm-quark fragmentation fractions and production cross section at midrapidity in pp collisions at the LHC
No full textInternational audienceRecent pT-integrated cross-section measurements of the ground-state charm mesons and baryons, D0, D+, Ds+, Λc+, and Ξc0, are used to evaluate the charm fragmentation fractions and production cross section per unit of rapidity at midrapidity (|y|<0.5), in pp collisions at s=5.02 TeV at the LHC. The latter is dσcc¯/dy||y|<0.5=1165±44(stat)-101+134(syst) μb. These measurements were obtained for the first time in hadronic collisions at the LHC, including the charm baryon states, recently measured by ALICE at midrapidity. The charm fragmentation fractions differ significantly from the values measured in e+e- and ep collisions, providing evidence of the dependence of the parton-to-hadron fragmentation fractions on the collision system, indicating that the assumption of their universality is not supported by the measured cross sections. An increase of a factor of about 3.3 for the fragmentation fraction for the Λc+ with a significance of 5σ between the values obtained in pp collisions and those obtained in e+e- (ep) collisions is reported. The fragmentation fraction for the Ξc0 was obtained for the first time in any collision system. The measured fragmentation fractions were used to update the cc¯ cross sections per unit of rapidity at |y|<0.5 at s=2.76 and 7 TeV, which are about 40% higher than the previously published results. The data were compared with perturbative-QCD calculations and lie at the upper edge of the theoretical bands