Geant4 simulation of the residual background in the ATHENA Wide Field Imager from protons deflected by the Charged Particle Diverter

X-ray telescopes opened up a new window into the high-energy universe. However, the last generation of these telescopes encountered an unexpected problem: their optics focused not only X-rays but low-energy (so called soft) protons as well. These protons are very hard to model and can not be distinguished from X-rays. For example, 40\% of XMM-Newton observations is significantly contaminated by soft proton induced background flares. In order to minimize the background from such low-energy protons the Advanced Telescope for High ENergy Astrophysics (ATHENA) satellite introduced a novel concept, the so called Charged Particle Diverter (CPD). It is an array of magnets in a Hallbach design, which deflects protons below 76 keV before they would hit the Wide Field Imager (WFI) detector. In this work, we investigate the effect of scattering of the deflected protons with the CPD walls and the inner surfaces of the WFI detector assembly. Such scattered protons can loose energy, change direction and still hit the WFI. In order to adopt the most realistic instrument model, we imported the CAD model of both the CPD and the WFI focal plane assembly. Soft protons corresponding to $\approx$2.5 hours of exposure to the L1 solar wind are simulated in this work. The inhomogeneous magnetic field of the CPD is included in the simulation. We present a preliminary estimate of the WFI residual background induced by soft proton secondary scattering, in the case of the optical blocking filter present in the field of view. A first investigation of the volumes responsible for scattering the protons back into the field of view is reported.Comment: SPIE conference proceedin

Athena Charged Particle Diverter (CPD) scientific assessment: preliminary results on the WFI residual background

Soft protons deflected by the CPD can potentially be scattered at lower energy and still reach the detection plane. Proton scattering measurements with samples of the Athena CPD surface, WFI baffle, and other compositions with different levels of roughness are currently being finalized, together with the validation of proton scattering simulations, to study the impact of secondary proton scattering. Preliminary results indicate that protons are indeed scattered with the CPD surface, with a level of mean roughness > tens of nm, with an efficiency almost uniform in scattering angle and large energy losses (>90% at 100 keV). The presence of heavier elements increases the scattering efficiency, while the impact of the roughness is still under investigation. SRIM and Geant4 simulations modelling the surface roughness are currently ongoing, and preliminary SRIM simulations are in general consistent with the measured distributions, but discrepancies in the energy losses are still under study. Preliminary results on the WFI CPD simulation aimed to confirm its compliance with the residual background requirement and to estimate the impact of secondary proton scattering were obtained with a combined simulation of the Athena SPO and the proton interaction with the WFI optical filters and detection plane, assuming no roughness on the exposed surfaces. The statistical uncertainty of the present results, with few protons reaching the WFI, is not yet enough to perform a final CPD scientific assessment and characterization of the secondary proton scattering. We can however conclude with current SRIM simulations that the WFI residual background level), if the CPD is present, is well within the requirement of 5 ✕ 10-4 counts cm-2 s-1 keV-1 in the 2 - 7 keV energy range, with a maximum level of (3.4±2.0) ✕ 10-5 counts cm-2 s-1 keV-1 obtained with only the OBF filter. Most of the protons generating background counts scatter with the filter wheel structure as the last scattering interaction. Current results indicate that no corrective measures are required to minimise the secondary proton scattering or increase the CPD efficiency, but the adoption of vanes or coatings in the filter wheel structure could help reduce the secondary proton flux at the WFI

Enabling planetary science across light-years. Ariel Definition Study Report

Ariel, the Atmospheric Remote-sensing Infrared Exoplanet Large-survey, was adopted as the fourth medium-class mission in ESA's Cosmic Vision programme to be launched in 2029. During its 4-year mission, Ariel will study what exoplanets are made of, how they formed and how they evolve, by surveying a diverse sample of about 1000 extrasolar planets, simultaneously in visible and infrared wavelengths. It is the first mission dedicated to measuring the chemical composition and thermal structures of hundreds of transiting exoplanets, enabling planetary science far beyond the boundaries of the Solar System. The payload consists of an off-axis Cassegrain telescope (primary mirror 1100 mm x 730 mm ellipse) and two separate instruments (FGS and AIRS) covering simultaneously 0.5-7.8 micron spectral range. The satellite is best placed into an L2 orbit to maximise the thermal stability and the field of regard. The payload module is passively cooled via a series of V-Groove radiators; the detectors for the AIRS are the only items that require active cooling via an active Ne JT cooler. The Ariel payload is developed by a consortium of more than 50 institutes from 16 ESA countries, which include the UK, France, Italy, Belgium, Poland, Spain, Austria, Denmark, Ireland, Portugal, Czech Republic, Hungary, the Netherlands, Sweden, Norway, Estonia, and a NASA contribution

Recherche de signatures spectrales de cations aromatiques dans l'absorption diffuse interstellaire (confrontation spectroscopie de laboratoire, observations astronomiques)

Les Hydrocarbures Aromatiques Polycycliques (PAHs) sont maintenant reconnus comme un constituant important de la phase gazeuse du milieu interstellaire. Cette famille de molécules et en particulier leurs dérives ioniques semble être l'un des candidats les plus prometteurs pour l'identification des Bandes Diffuses Interstellaires (DIBs). Ces bandes d'absorption sont observées dans le visible sur des spectres d'étoiles masquées par des nuages. L'identification de PAHs comme molécules responsables de ces bandes ne peut se faire que par comparaison directe avec des spectres de PAHs obtenus dans des conditions se rapprochant le plus possible de celles du milieu interstellaire. Ces conditions de basse température et d'absence de collisions ont été reconstituées en laboratoire grâce à la technique du jet supersonique. Un complexe de van der Waals PAH-Ar est alors ionise par ionisation résonnante à deux photons. L'absorption par cet ion d'un photon laser visible accordable provoque le départ de l'atome d'argon, et la détection de cette dissociation au spectromètre de masse permet, l'obtention du spectre du cation PAR. Grâce a cette technique, les spectres du phénylacétylène(+)-Ar et de l'acénaphthène(+)-Ar ont pu être enregistrés. Le profil spectral des bandes est large et lorentzien, indiquant une dynamique intramoléculaire dominée par des mécanismes de conversion interne ultrarapide. Deux campagnes d'observations au Télescope Bernard Lyot du Pic du Midi ont permis la recherche systématique de ces bandes larges grâce à un protocole d'observation et à un traitement des données spécifiques. Des limites supérieures d'abondance on été déterminées pour cinq cations PAHs. Les zones d'absorption interstellaire repérées dans nos spectres sont de largeur variable et certaines sont vraisemblablement le résultat d'une combinaison de l'absorption de plusieurs espèces. D'après nos mesures entre 525 et 840 nm, l'absorption interstellaire diffuse représente 87 % de l'absorption interstellaire.Polycyclic Aromatic Hydrocarbons (PAHs) are now recognized as an important constituent of the interstellar medium gaseous phase. This family of molecules and in particular their ionic derivatives seems to be one of the most promising candidates for identification of the Diffuse Interstellar Bands (DIBs). These absorption bands are observed in the visible spectral range in the spectra of stars partially masked by gas cloud. The possible identification of PAHs as molecules responsible for these bands must be done through direct comparison with PAHs spectra recorded in conditions as close as possible to those of the interstellar medium. These low temperature and collision-free conditions can be recreated in the laboratory with supersonic beams. A van der Waals complex PAH-Ar is then ionized by resonant two-photon ionization. The ion absorption of a tunable visible laser photon causes the argon departure, and the detection of this dissociation by a mass spectrometer allows the recording of the PAH cation spectrum. Using this technique, the spectra of phenylacetylene(+)-Ar and of acenaphthene(+)-Ar could be obtained. The spectral profile is wide and lorentzian, showing an intramolecular dynamics dominated by ultrafast internal conversion. Two observation campaigns with the Télescope Bernard Lyot at the Pic du Midi allowed us to perform a systematic search for this broad bands, thanks to specific observational protocole and data processing. Upper-limits of abundance were determined for five PAH cations. Interstellar absorption zones identified in our spectra are of variable width and some of them are very likely the result of a combination due to several species. According to our measurements between 525 and 840 nm, the diffuse interstellar absorption represents 87 % of the interstellar absorption in front of BD +404220 star.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

A well-preserved Michelsberg Culture domed oven from Kortrijk, Belgium

In 2015, a domed oven from the late fifth millennium cal BC was excavated near Kortrijk, northern Belgium. In terms of its size, tripartite structure, stone flooring and well-preserved domed combustion chamber, the oven is unique in Neolithic Western Europe, although mostly smaller, less well-preserved parallels are known in northern France. Such features are thought to have appeared in Western Europe in the Early to Middle Neolithic periods (post-Linearbandkeramik Culture). Their appearance and possible use for drying cereals may be related to a change from individual (household) to communal processing of cereals, and/or indicate adaptation to a wetter climate by newly settled agro-pastoralist communities

Blue highly fluorescent boron difluoride complexes based on phthalazine-pyridine.

International audienceThree new boron difluoride complexes based on phthalazine–pyridine, denoted (6), (7) and (8), have been synthesized and their photophysical and electrochemical properties have been studied. Solutions of these new BF 2-complexes exhibit an intense blue fluorescence under UV light at low concentrations. Fluorescence quantum yields (QYs) have been determined by photoluminescence (PL) spectroscopy and decay times (t) by semi-empirical methods. QYs of (6), (7) and (8) vary from 25% to 79%. HOMO and LUMO energy levels have been estimated by cyclic voltammetry and PL spectroscopy. The HOMO and LUMO energy levels, at BÀ5.3 eV and BÀ2.3 eV, respectively, make these new complexes interesting candidates as blue emitters in OLED applications

Defining the human sperm microtubulome: an integrated genomics approach

International audienc

Athena charged particle diverter simulations: effects of micro-roughness on proton scattering using Geant4

The last generation of X-ray focusing telescopes operating outside the Earth's radiation belt discovered that optics were able to focus not only astrophysical X-ray photons, but also low-energy heliophysical protons entering the Field of View (FOV). This "soft proton" contamination affects around 40\% of the observation time of XMM-Newton. The ATHENA Charged Particle Diverter (CPD) was designed to use magnetic fields to move these soft protons away from the FOV of the detectors, separating the background-contributing ions in the focused beam from the photons of interest. These magnetically deflected protons can hit other parts of the payload and scatter back to the focal plane instruments. Evaluating the impact of this secondary scattering with accurate simulations is essential for the CPD scientific assessment. However, while Geant4 simulations of grazing soft proton scattering on X-ray mirrors have been recently validated, the scattering on the unpolished surfaces of the payload (e.g. the baffle or the diverter itself) is still to be verified with experimental results. Moreover, the roughness structure can affect the energy and angle of the scattered protons, with a scattering efficiency depending on the specific target volume. Using Atomic Force Microscopy to take nanometer-scale surface roughness measurements from different materials and coating samples, we use Geant4 together with the CADMesh library to shoot protons at these very detailed surface roughness models to understand the effects of different material surface roughnesses, coatings, and compositions on proton energy deposition and scattering angles. We compare and validate the simulation results with laboratory experiments, and propose a framework for future proton scattering experiments.Comment: 12 pages, 6 figures, 2 tables, SPIE conference proceedin

Multi-hit early life adversity affects gut microbiota, brain and behavior in a sex-dependent manner

The accumulation of adverse events in utero and during childhood differentially increases the vulnerability to psychiatric diseases in men and women. Gut microbiota is highly sensitive to the early environment and has been recently hypothesized to affect brain development. However, the impact of early-life adversity on gut microbiota, notably with regards to sex differences, remains to be explored. We examined the effects of multifactorial early-life adversity on behavior and microbiota composition in C3H/HeN mice of both sexes exposed to a combination of maternal immune activation (lipopolysaccharide injection on embryonic day 17, 120 µg/kg, i.p.), maternal separation (3hr per day from postnatal day (PND)2 to PND14) and maternal unpredictable chronic mild stress. At adulthood, offspring exposed to multi-hit early adversity showed sex-specific behavioral phenotypes with males exhibiting deficits in social behavior and females showing increased anxiety in the elevated plus maze and increased compulsive behavior in the marble burying test. Early adversity also differentially regulated gene expression in the medial prefrontal cortex (mPFC) according to sex. Interestingly, several genes such as Arc, Btg2, Fosb, Egr4 or Klf2 were oppositely regulated by early adversity in males versus females. Finally, 16S-based microbiota profiling revealed sex-dependent gut dysbiosis. In males, abundance of taxa belonging to Lachnospiraceae and Porphyromonadaceae families or other unclassified Firmicutes, but also Bacteroides, Lactobacillus and Alloprevotella genera was regulated by early adversity. In females, the effects of early adversity were limited and mainly restricted to Lactobacillus and Mucispirillum genera. Our work reveals marked sex differences in a multifactorial model of early-life adversity, both on emotional behaviors and gut microbiota, suggesting that sex should systematically be considered in preclinical studies both in neurogastroenterology and psychiatric research