Analyse des images PLIF-Al à haute cadence pour l'étude de la combustion de goutte d'aluminium en flammes de propergol solide

International audienceThe combustion of aluminum particles is a key factor for solid-propellant propulsion in terms of performance and stability. An automatic detection of droplets in Al-PLIF image was developed. The "Maximally Stable Extremal Regions" detection method is evaluated on two image sets previously obtained at 1.0 and 1.5 MPa. The method shows good detection performances compared to a set of Ground Truth images for both pressure levels. When applied to 3000-image series, more than 35000 objects were detected on LIF images. This is very promising for future statistical analysis of Al combustion based on Al-PLIF diagnostic.La combustion des particules d'aluminium est un facteur crucial pour la propulsion solide en termes de performance et de stabilité. Cette présentation expose nos travaux actuels sur la détection automatisée de gouttelettes sur les images acquises par fluorescence laser (LIF) de l'aluminium atomique. La méthode de détection MSER (Maximally Stable Extremal Regions) est testée sur deux séries d'images obtenues pour des combustions de propergols aluminisés à 1.0 et 1.5 MPa.De bonnes performances de détection sont obtenues comparées aux images "Vérité Terrain". Plus de 35000 objets sont détectés sur les images LIF. Ces premiers résultats de détection automatisé sont encourageants pour une prochaine analyse statistique des diagnostics LIF de la combustion des gouttes d'aluminium

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements