dc.contributor.author Brossard, Alexis en dc.date.accessioned 2020-03-03T16:28:41Z dc.date.available 2020-03-03T16:28:41Z dc.identifier.uri http://hdl.handle.net/1974/27649 dc.description.abstract The NEWS-G collaboration uses Spherical Proportional Counters to search for Weakly Interacting Massive Particles (WIMP). The first detector developed for this goal is a 60 cm diameter sphere installed at the Laboratoire Souterrain de Modane in France. In 2015, the collaboration took a run with neon as the target material for an exposure of 9.7 $\mathrm{kg\cdot days}$. This run allowed new limits to be set on the spin-independent WIMP-nucleon cross-sections with $\mathrm{90\%}$ confidence upper limit of $\mathrm{\sigma_{SI} < 4.4 \times 10^{-37} cm^{2}}$ for a $\mathrm{0.5\, GeV/c^{2}}$ WIMP. The study of the background events observed during this run shows that it is dominated by the presence of the $\mathrm{^{210}Pb}$ decay chain in the different materials composing the detector, its shielding, and on the inner surface of the sphere. The experiences acquired during the utilization of SEDINE and the analysis of its data allowed a procedure to be developed to avoid radioactive contaminations and minimize the background of the experiment. The background of the next detector was estimated by a stringent selection of the materials, the measurements of their radioactive contaminations and the simulation of the different components. The development of new sensors allows a better homogeneity of the detector response and good data acquisition in large detector. The new detector is a 140 cm diameter sphere, to be installed at SNOLAB in Canada in 2020. Its performance will be also enhanced by the development of methods of signal characterisation and calibration. en dc.language.iso eng en dc.relation.ispartofseries Canadian theses en dc.rights Queen's University's Thesis/Dissertation Non-Exclusive License for Deposit to QSpace and Library and Archives Canada en dc.rights ProQuest PhD and Master's Theses International Dissemination Agreement en dc.rights Intellectual Property Guidelines at Queen's University en dc.rights Copying and Preserving Your Thesis en dc.rights This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner. en dc.rights CC0 1.0 Universal en dc.rights.uri http://creativecommons.org/publicdomain/zero/1.0/ dc.subject Dark Matter en dc.subject Spherical Proportional Counter en dc.subject Gas Detector en dc.subject Radioactive Background en dc.title Optimization of spherical proportional counter backgrounds and response for low mass dark matter search en dc.type thesis en dc.description.degree PhD en dc.contributor.supervisor Gerbier, Gilles en dc.contributor.supervisor Giomataris, Ioannis en dc.contributor.department Physics, Engineering Physics and Astronomy en dc.degree.grantor Queen's University at Kingston en
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