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Optimisation du pouvoir de résolution et du rejet du fond radioactif de détecteurs ionisation-chaleur équipés de couches minces thermométriques pour la détection directe de WIMPs.

Abstract : The EDELWEISS experiment aims at the direct detection of WIMPs as possible candidates for dark matter. It uses heat-and-ionization detectors that can discriminate these particles from the radioactive background. To date, this method is limited by events with incomplete charge collection that occur just beneath the detectors electrodes. In order to identify and reject these undesirable events, we have developed detectors equipped with thin films used both as thermometers – and hence sensitive to the transient athermal regime – and as electrodes for the charge collection. This thesis focuses on the optimization of such thin films regarding surface events rejection and on the modelling of the physical processes enabling this identification. The optimization must both maximize the fiducial volume and conserve an energy resolution such that the recoil energy threshold is of the order of 30 keV. Our work explores four generations of detectors each of which corresponds to successive evolutions in their conception. In all cases, the electrode-thermometer is an amorphous Anderson insulator NbSi thin film polarized by two interleaved comb-shaped niobium electrodes. In spite of constant progress in the successive detectors performances, the latest generation does not display the performances required for the EDELWEISS II experiment. Our work has shown the difficulty of the transient thermal signal modelling due to the complex contribution of the charge collection. This works has lead to new ideas regarding the detectors configuration, so that the athermal regime can be optimized to enhance both the rejection capability and the resolution.
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https://tel.archives-ouvertes.fr/tel-00401690
Contributor : Youri Dolgorouky <>
Submitted on : Monday, July 6, 2009 - 4:15:32 PM
Last modification on : Wednesday, September 16, 2020 - 4:06:12 PM
Long-term archiving on: : Wednesday, March 29, 2017 - 5:06:18 PM

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  • HAL Id : tel-00401690, version 2

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Youri Dolgorouky. Optimisation du pouvoir de résolution et du rejet du fond radioactif de détecteurs ionisation-chaleur équipés de couches minces thermométriques pour la détection directe de WIMPs.. Physique [physics]. Université Paris Sud - Paris XI, 2008. Français. ⟨tel-00401690v2⟩

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