The performance of the ATHENA X-ray Integral Field Unit

The X-ray Integral Field Unit (X-IFU) is a next generation microcalorimeter planned for launch onboard the Athena observatory. Operating a matrix of 3840 superconducting Transition Edge Sensors at 90 mK, it will provide unprecedented spectro-imaging capabilities (2.5 eV resolution, for a field of view of 5') in the soft X-ray band (0.2 up to 12 keV), enabling breakthrough science. The definition of the instrument evolved along the phase A study and we present here an overview of its predicted performances and their modeling, illustrating how the design of the X-IFU meets its top-level scientific requirements. This article notably covers the energy resolution, count-rate capability, quantum efficiency and non X-ray background levels, highlighting their main drivers

The Athena X-ray Integral Field Unit (X-IFU)

The X-ray Integral Field Unit (X-IFU) is the high resolution X-ray spectrometer of the ESA Athena X-ray observatory. Over a field of view of 5' equivalent diameter, it will deliver X-ray spectra from 0.2 to 12 keV with a spectral resolution of 2.5 eV up to 7 keV on similar to 5 '' pixels. The X-IFU is based on a large format array of super-conducting molybdenum-gold Transition Edge Sensors cooled at similar to 90 mK, each coupled with an absorber made of gold and bismuth with a pitch of 249 mu m. A cryogenic anti-coincidence detector located underneath the prime TES array enables the non X-ray background to be reduced. A bath temperature of similar to 50 mK is obtained by a series of mechanical coolers combining 15K Pulse Tubes, 4K and 2K Joule-Thomson coolers which pre-cool a sub Kelvin cooler made of a He-3 sorption cooler coupled with an Adiabatic Demagnetization Refrigerator. Frequency domain multiplexing enables to read out 40 pixels in one single channel. A photon interacting with an absorber leads to a current pulse, amplified by the readout electronics and whose shape is reconstructed on board to recover its energy with high accuracy. The defocusing capability offered by the Athena movable mirror assembly enables the X-IFU to observe the brightest X-ray sources of the sky (up to Crab-like intensities) by spreading the telescope point spread function over hundreds of pixels. Thus the X-IFU delivers low pile-up, high throughput (> 50%), and typically 10 eV spectral resolution at 1 Crab intensities, i.e. a factor of 10 or more better than Silicon based X-ray detectors. In this paper, the current X-IFU baseline is presented, together with an assessment of its anticipated performance in terms of spectral resolution, background, and count rate capability. The X-IFU baseline configuration will be subject to a preliminary requirement review that is scheduled at the end of 2018. The X-IFU will be provided by an international consortium led by France, the Netherlands and Italy, with further ESA member state contributions from Belgium, Czech Republic, Finland, Germany, Ireland, Poland, Spain, Switzerland and contributions from Japan and the United States.Peer reviewe

Corot, une mission bien remplie

International audienceThe CoRoT mission developped since 1993 was dedicated to the observation of ultra high precision measurements of the variations of stellar fluxed on long and continuous durations. His two major objectives were the detection of stellar oscillations and of extrasolar planets. A a pionnier mission, it had to invent several methods and to built the successive steps of the data treatment. They are rapidly described. The low cost 'CNES Petites Missions" programme imposed severe contraints on the instrument concept (Organisation and management, choice of the detectors, of the orbit, reduction of all parasite lights) which have been and will be guides for new generation projects. Some scientific highlights are then presented on both programmes, as for instance the use of the seismic tool as an indicator of the structure and evolution of the Galaxy, the first detection of a super-Earth, and the first precise characterisation of a brown dwarf . CoRoT has opened several avenues in instrumentation as well as science. It is shown how some aspects of this heritage have been used in the design and development of its two major heiress: CHEOPS to be launched in 2018 and the more ambitious PLATO, to be launched in 2025

Na2Fe3(SO4)4 là vật liệu cathode mới với điện thế cao dùng cho pin sodium-ion

Based on the density functional theory, we propose a promising cathode material, Na2Fe3(SO4)4, applicable for sodium-ion batteries. The crystal structure, stability, average voltage, and diffusion mechanism are carefully investigated to evaluate the electrochemical properties. The proposed material exhibits a high voltage of 4.0 V during the Na extraction. A small polaron is proved to be formed preferably at the first nearest Fe sites to Na vacancy and simultaneously accompanies the Na vacancy during its migration. Four elementary diffusion processes of the polaron–Na vacancy complexes, namely two parallel and two crossing processes, have been explored. The significant difference of activation energies between parallel and crossing processes suggests the substantial effect of the small polaron migration on the Na vacancy diffusion. We found that the parallel process along the [001] direction has the lowest activation energy of 808 meV, implying that the Na vacancy preferably diffuses in a zigzag pathway along the [001] direction.Chúng tôi đề xuất một vật liệu cathode mới Na2Fe3(SO4)4 có thể dùng cho pin sodium-ion dựa theo lý thuyết phiếm hàm mật độ. Cấu trúc tinh thể, tính bền, điện thế trung bình và cơ chế khuếch tán được khảo sát cẩn thận để đánh giá các tính chất điện hóa. Vật liệu đề xuất có thể đạt điện thế cao 4.0 V trong quá trình giải phóng ion Na. Chuẩn hạt polaron nhỏ ưu tiên hình thành tại vị trí Fe gần nhất với vị trí khuyết ion Na và chuyển động đồng thời với vị khuyết ion Na trong suốt quá trình chuyển động của nó. Bốn quá trình khuếch tán của tổ hợp vị trí khuyết ion Na và polaron được khảo sát gồm có 2 quá trình song song và 2 quá trình chéo. Sự khác biệt về năng lượng kích hoạt giữa các quá trình song song và chéo cho thấy hiệu ứng đáng kể của các polaron nhỏ đến quá trình khuếch tán của vị trí khuyết ion Na. Chúng tôi nhận thấy quá trình song song dọc theo hướng [001] có năng lượng kích hoạt thấp nhất là 808 meV, điều này gợi ý rằng vị trí khuyết ion Na ưu tiên khuếch tán theo một đường zigzag dọc theo hướng [001]

A Web-Based Dynamic Nomogram to Predict the Risk of Methicillin-Resistant Staphylococcal Infection in Patients with Pneumonia

The aim of this study was to create a dynamic web-based tool to predict the risks of methicillin-resistant Staphylococcus spp. (MRS) infection in patients with pneumonia. We conducted an observational study of patients with pneumonia at Cho Ray Hospital from March 2021 to March 2023. The Bayesian model averaging method and stepwise selection were applied to identify different sets of independent predictors. The final model was internally validated using the bootstrap method. We used receiver operator characteristic (ROC) curve, calibration, and decision curve analyses to assess the nomogram model’s predictive performance. Based on the American Thoracic Society, British Thoracic Society recommendations, and our data, we developed a model with significant risk factors, including tracheostomies or endotracheal tubes, skin infections, pleural effusions, and pneumatoceles, and used 0.3 as the optimal cut-off point. ROC curve analysis indicated an area under the curve of 0.7 (0.63–0.77) in the dataset and 0.71 (0.64–0.78) in 1000 bootstrap samples, with sensitivities of 92.39% and 91.11%, respectively. Calibration analysis demonstrated good agreement between the observed and predicted probability curves. When the threshold is above 0.3, we recommend empiric antibiotic therapy for MRS. The web-based dynamic interface also makes our model easier to use

Experimental Characterization of Atmospheric Radiation Environment with Stratospheric Balloon

International audienceWe report a stratospheric flight with a CNES balloon for which we developed a silicon detector in order to obtain data on the atmospheric radiation environment. The number of detected protons is shown to be directly correlated with the altitude. Simulations with the MC-ORACLE code, which uses pre-calculated fluxes with QARM, are in good agreement with our experimental results

ATHENA X-IFU thermal filters development status toward the end of the instrument phase-A

The X-ray Integral Field Unit (X-IFU) is one of the two instruments of the Athena astrophysics space mission approved by ESA in the Cosmic Vision 2015-2025 Science Programme. The X-IFU consists of a large array of transition edge sensor micro-calorimeters that will operate at 100 mK inside a sophisticated cryostat. A set of thin filters, highly transparent to X-rays, will be mounted on the opening windows of the cryostat thermal shields in order to attenuate the IR radiative load, to attenuate radio frequency electromagnetic interferences, and to protect the detector from contamination. Thermal filters are critical items in the proper operation of the X-IFU detector in space. They need to be strong enough to survive the launch stresses but very thin to be highly transparent to X-rays. They essentially define the detector quantum efficiency at low energies and are fundamental to make the photon shot noise a negligible contribution to the energy resolution budget. In this paper, we review the main results of modeling and characterization tests of the thermal filters performed during the phase A study to identify the suitable materials, optimize the design, and demonstrate that the chosen technology can reach the proper readiness before mission adoption

The Athena X-ray Integral Field Unit (X-IFU)

The X-ray Integral Field Unit (X-IFU) on board the Advanced Telescope for High-ENergy Astrophysics (Athena) will provide spatially resolved high-resolution X-ray spectroscopy from 0.2 to 12 keV, with 5 arc second pixels over a field of view of 5 arc minute equivalent diameter and a spectral resolution of 2.5 eV up to 7 keV. In this paper, we first review the core scientific objectives of Athena, driving the main performance parameters of the X-IFU, namely the spectral resolution, the field of view, the effective area, the count rate capabilities, the instrumental background. We also illustrate the breakthrough potential of the X-IFU for some observatory science goals. Then we briefly describe the X-IFU design as defined at the time of the mission consolidation review concluded in May 2016, and report on its predicted performance. Finally, we discuss some options to improve the instrument performance while not increasing its complexity and resource demands (e.g. count rate capability, spectral resolution). The X-IFU will be provided by an international consortium led by France, The Netherlands and Italy, with further ESA member state contributions from Belgium, Finland, Germany, Poland, Spain, Switzerland and two international partners from the United States and Japan