Nouveau spectro-imageur CdTe à très haute résolution spatiale et spectrale pour l'astronomie X et gamma

The thesis work presented in the manuscript corresponds to the first development phase of the MC2 project, an ambitious R & D effort to realize a new type of CdTe-based imaging spectrometer for future hard X- and gamma-rays astronomy missions. The objective is to achieve a 300 micron-pitch pixelated detector plane hybrided with a very low noise front-end electronics for a total pixel density multiplied by 4 compared to the most advanced system recently available in the laboratory (Caliste HD module). Moreover, thanks to the joint development of reading circuits adapted to the interconnection of pixelated detectors with low capacitance and low leakage current, spectroscopic performances of such system are assumed to approach inherent limitations of the CdTe detector, specifically for the lowest energies. My work was organized in parallel and complementary areas: evaluation of current systems, feedback and identification of issues associated with the development of highly-resolved detection planes, implementation and complete characterization of a new two-dimensional ASIC specifically developed for this application, and modelling and study of the associated sensor to optimize the design of the detector pattern. Finally, a first hybrid prototype was completed and first experimental tests thereby conducted.Le travail de thèse présenté dans le manuscrit s'inscrit dans le cadre de la première phase de développement du projet MC2, un effort de R&D ambitieux visant à mettre sur pied un nouveau type de spectro-imageur en CdTe pour de futures missions d'astronomie X-dur et gamma. L'objectif est de réaliser un plan de détection pixelisé au pas de 300 microns couplé à une électronique frontale hautes performances, pour une densité de pixels multipliée par 4 par rapport au système le plus avancé récemment achevé au laboratoire (instrument Caliste HD). Par ailleurs, grâce à la réalisation conjointe de circuits de lecture adaptés à l'interconnexion de détecteurs pixelisés de faible capacité électrique et de faible courant de fuite, la réponse en spectrométrie de tels systèmes se rapproche des limites intrinsèques du détecteur. Mon travail s'est organisé selon des axes parallèles et complémentaires : évaluation des systèmes actuels, retour d'expérience et mise en évidence des problématiques associées à la réalisation de spectro-imageurs de pas encore plus réduits, mise en oeuvre et caractérisation complète d'une électronique frontale 2D spécifiquement développée pour cette application, puis modélisation et étude du capteur associé afin d'optimiser le design de ce dernier. Enfin, un tout premier prototype d'hybride complet a été réalisé et les premiers tests expérimentaux menés

The SE-CpFM Detector for the Crystal-Assisted Extraction at CERN-SPS

International audienceThe UA9 experiment at CERN-SPS investigates the manipulation of high energy hadron beams using bent silicon crystals since 2009. Monitoring and characterization of channeled beams in the high energy accelerators environment ideally requires in-vacuum and radiation hard detectors. For this purpose the Cherenkov detector for proton Flux Measurement (CpFM) was designed and developed. It features a fused silica bar in the beam pipe vacuum which intercepts charged particles and generates Cherenkov light. In this contribution the SE-CpFM (Slow Extraction CpFM) detector is described in detail. It has been installed in early 2016 in the TT20 extraction line of SPS to study the feasibility of the crystal-assisted extraction from the SPS. Before the installation the detector has been fully characterized in 2015, during the UA9 data taking in the H8-SPS extraction line with 180 GeV pions. The single particle detection efficiency and the photoelectron yield per proton have been estimated and are shown in this contribution

The Cherenkov Detector for Proton Flux Measurement (CpFM) in the UA9 Experiment

International audienceThe UA9 experiment at the CERN SPS investigates the possibility to use bent crystals to steer particles in high energy accelerators. In this framework the CpFM have been developed to measure the beam particle flux in different experimental situations. Thin movable fused-silica bars installed in the SPS primary vacuum and intercepting the incoming particles are used to radiate Cherenkov light. The light signal is collected outside the beam pipe through a quartz optical window by radiation hard PMTs. The PMT signal is readout by the WaveCatcher acquisition board, which provides count rate as well as waveform information over a configurable time window. A bundle of optical fibers can be used to transport the light signal far from the beam pipe, allowing to reduce the radiation dose to the PMT. A first version of the CpFM has been successfully commissioned during the data taking runs of the UA9 Experiment in 2015, while a second version has been installed in the TT20 extraction line of the SPS in 2016. In this contribution the design choices will be presented and the final version of the detector will be described in detail

Low Energy Characterization of Caliste HD, a Fine Pitch CdTe-Based Imaging Spectrometer

International audienceCaliste HD is a recently developed micro-camera designed for X and gamma-ray astronomy, based on a 1×1 cm$^2$ CdTe Schottky pixelated detector. Its entire surface is composed of 256 pixels, disposed on a 16 × 16 pixel array. This spectrometer is buttable on its 4 sides and can be used to create a large focal plane. It is also designed for space environment. Its IDeF-X front-end electronics has low power consumption, excellent noise performance and a wide dynamic range, from 2 keV to 1 MeV. Moreover, electronic noise performances of this device were optimized to set the low level energy threshold lower than 2 keV.This paper focuses on the Caliste HD performance near the low energy limit. For this purpose, we have exposed the CalisteHD module to a mono-energetic X-ray beam, and set energies between 2 and 12 keV. We measured accurately the detectionefficiency in this energy range and found it to be ranging from 39% to 75% for energies from 2.2 keV to 11.6 keV, consideringonly particles detected in the single-event photopeak and ignoring events impinging between two adjacent pixels. Thisefficiency detection profile thereby highlights crucial effects of the Pt electrode opacity on Caliste HD low energy response, andsuggests the presence of absorption zones at the interface between CdTe crystal and platinum. Respective thickness of eachlayer were estimated by simulation and confirmed by RBS ($Rutherford\ Backscattering\ Spectroscopy$).Besides, using a mono-energetic beam allows fine energy resolution measurement, which was found to be ranging from560 to 760 eV FWHM between 2 and 12 keV. In addition, the linearity of this spectrometer and the issue of charge sharingbetween adjacent pixels were studied. This study revealed that spectroscopic performances remain excellent for such boundaryoperating conditions

Observation of channeling in bent crystals at the CERN LHC

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Impact on disease mortality of clinical, biological, and virological characteristics at hospital admission and overtime in COVID‐19 patients

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Paediatric COVID-19 mortality: a database analysis of the impact of health resource disparity

Background The impact of the COVID-19 pandemic on paediatric populations varied between high-income countries (HICs) versus low-income to middle-income countries (LMICs). We sought to investigate differences in paediatric clinical outcomes and identify factors contributing to disparity between countries.Methods The International Severe Acute Respiratory and Emerging Infections Consortium (ISARIC) COVID-19 database was queried to include children under 19 years of age admitted to hospital from January 2020 to April 2021 with suspected or confirmed COVID-19 diagnosis. Univariate and multivariable analysis of contributing factors for mortality were assessed by country group (HICs vs LMICs) as defined by the World Bank criteria.Results A total of 12 860 children (3819 from 21 HICs and 9041 from 15 LMICs) participated in this study. Of these, 8961 were laboratory-confirmed and 3899 suspected COVID-19 cases. About 52% of LMICs children were black, and more than 40% were infants and adolescent. Overall in-hospital mortality rate (95% CI) was 3.3% [=(3.0% to 3.6%), higher in LMICs than HICs (4.0% (3.6% to 4.4%) and 1.7% (1.3% to 2.1%), respectively). There were significant differences between country income groups in intervention profile, with higher use of antibiotics, antivirals, corticosteroids, prone positioning, high flow nasal cannula, non-invasive and invasive mechanical ventilation in HICs. Out of the 439 mechanically ventilated children, mortality occurred in 106 (24.1%) subjects, which was higher in LMICs than HICs (89 (43.6%) vs 17 (7.2%) respectively). Pre-existing infectious comorbidities (tuberculosis and HIV) and some complications (bacterial pneumonia, acute respiratory distress syndrome and myocarditis) were significantly higher in LMICs compared with HICs. On multivariable analysis, LMIC as country income group was associated with increased risk of mortality (adjusted HR 4.73 (3.16 to 7.10)).Conclusion Mortality and morbidities were higher in LMICs than HICs, and it may be attributable to differences in patient demographics, complications and access to supportive and treatment modalities

Rare predicted loss-of-function variants of type I IFN immunity genes are associated with life-threatening COVID-19

BackgroundWe previously reported that impaired type I IFN activity, due to inborn errors of TLR3- and TLR7-dependent type I interferon (IFN) immunity or to autoantibodies against type I IFN, account for 15-20% of cases of life-threatening COVID-19 in unvaccinated patients. Therefore, the determinants of life-threatening COVID-19 remain to be identified in similar to 80% of cases.MethodsWe report here a genome-wide rare variant burden association analysis in 3269 unvaccinated patients with life-threatening COVID-19, and 1373 unvaccinated SARS-CoV-2-infected individuals without pneumonia. Among the 928 patients tested for autoantibodies against type I IFN, a quarter (234) were positive and were excluded.ResultsNo gene reached genome-wide significance. Under a recessive model, the most significant gene with at-risk variants was TLR7, with an OR of 27.68 (95%CI 1.5-528.7, P=1.1x10(-4)) for biochemically loss-of-function (bLOF) variants. We replicated the enrichment in rare predicted LOF (pLOF) variants at 13 influenza susceptibility loci involved in TLR3-dependent type I IFN immunity (OR=3.70[95%CI 1.3-8.2], P=2.1x10(-4)). This enrichment was further strengthened by (1) adding the recently reported TYK2 and TLR7 COVID-19 loci, particularly under a recessive model (OR=19.65[95%CI 2.1-2635.4], P=3.4x10(-3)), and (2) considering as pLOF branchpoint variants with potentially strong impacts on splicing among the 15 loci (OR=4.40[9%CI 2.3-8.4], P=7.7x10(-8)). Finally, the patients with pLOF/bLOF variants at these 15 loci were significantly younger (mean age [SD]=43.3 [20.3] years) than the other patients (56.0 [17.3] years; P=1.68x10(-5)).ConclusionsRare variants of TLR3- and TLR7-dependent type I IFN immunity genes can underlie life-threatening COVID-19, particularly with recessive inheritance, in patients under 60 years old