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T: Fachverband Teilchenphysik

T 62: Suche nach dunkler Materie III

T 62.6: Vortrag

Dienstag, 1. März 2016, 18:05–18:20, VMP9 SR 28

Production of CaWO₄ crystals for direct dark matter search with CRESST — •Andrea Münster for the CRESST collaboration — Physik-Department and Excellence Cluster Universe, Technische Universität München, D-85748 Garching, Germany

The direct dark matter search experiment CRESST (Cryogenic Rare Event Search with Superconducting Thermometers) uses scintillating CaWO₄ single crystals as targets for possible recoils of dark matter particles. Since several years these CaWO₄ crystals are produced directly at the Technische Universität München (TUM) including the CaWO₄ powder production from the raw materials CaCO₃ and WO₃, the CaWO₄ crystal growth via the Czochralski method as well as the after-growth treatment of the crystals. In the recently finished CRESST-II Phase 2 (2013-2015), 4 TUM-grown crystals were installed in the main cryostat for the first time. Showing one of the best radiopurities of all installed crystals combined with an excellent detector performance the analysis of the crystal TUM40 resulted in the best sensitivity for low-mass dark matter particles in 2014. For the upcoming CRESST-III phase 2 we aim for a further improvement in radiopurity by a factor of 100. First results of a chemical purification of the raw materials as well as future plans to reduce the intrinsic background via recrystallization will be presented. This research was supported by the DFG cluster of excellence “Origin and Structure of the Universe”, by the Helmholtz Alliance for Astroparticle Physics, by the Maier-Leibnitz-Laboratorium (Garching) and by the BMBF.