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Walther-Meißner-Institut (WMI), Bayerische Akademie der Wissenschaften
Chair for Technical Physics (E23), Technische Universität München

Physics World; Focus on big Science


October 01, 2013

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October 2013

Through a crystal darkly -- Crystal Growth for Direct Dark Matter Search

In their hunt for dark matter, a group of physicists from the TUM and the Walther Meissner-Institute, have set up a special facility to grow and process scintillating single-crystals of calcium tungstate. The choice of CaWO4, as a detector material has several reasons: it can be grown in a satisfactorily radiopure way – the intrinsic radioactivity of about 2×10-3 Bq/kg, some 1,000,000 times lower than the levels of radioactivity in the human body – but also consists of 3 different nuclei which makes it a multi-element material for nuclear recoils of the dark matter particles known as WIMPs (Weakly Interacting Massive Particles) which are searched for within the CRESST and the future EURECA experiments in deep underground facilities located in Italy (and France). While the CRESST experiment in Italy requires only a modest 30 kg of CaWO4, the EURECA experiment calls for up to half a ton of CaWO4 crystals. So far, CRESST II and EURECA collaboration members Andreas Erb of the Bavarian Academy of Science and Jean-Côme Lanfranchi of the Technical University of Munich in Garching, Germany, had, as of July last year, produced some 40 crystals at their facility in Garching and also made a number of crystals weighing at least a kilogram (three times the weight of the presently used crystals), the largest being a whopping 1.8 kg.

Andreas Erb and Jean-Côme Lanfranchi, Cryst. Eng. Comm. 15, 2301
Physics World; Focus on big Science: Through a crystal darkly