Improving the Quality of CaWO4 Target Crystals for CRESST

Abstract The Cryogenic Rare Event Search with Superconducting Thermometers (CRESST) experiment aims at the direct detection of dark matter particles via their elastic scattering off nuclei in a scintillating CaWO $$_4$$ 4 target crystal. crystal is operated together light detector mK temperature and read out by Transition Edge Sensor. For many years, crystals have successfully been produced in-house Technical University Munich (TUM) focus on high radiopurity which crucial to reduce background originating from radioactive contamination. In order further improve crystals, an extensive chemical purification raw materials synthesised powder has performed. addition, gradient simulation growth process subsequently optimisation furnace goal intrinsic stress was carried out. We present results radiopurity. A grown purified material installed current CRESST set-up. equipped instrumented holder used measure alpha decay rate preliminary analysis showing significantly reduced natural chains.