Results of light quenching factor measurements of CaWO4 at mK temperatures for the dark matter experiments CRESST and EURECA

The CRESST and the future EURECA experiments aim at the direct detection of Cold Dark Matter (DM) with scintillating CaWO4 crystals operated as cryogenic detectors at mK temperatures. DM particles such as the highly motivated Weakly Interacting Massive Particles (WIMPs) are expected to coherently scatter off nuclei and the corresponding nuclear recoils can be measured by the induced heat (phonon channel) and the corresponding scintillation light. Light Quenching Factors (QFs) quantify the individual reduction of the relative light yield for O, Ca and W recoils compared to electron recoils. The QFs of CaWO4 are of utmost importance for the DM analysis as they allow a discrimination of backgrounds and - if a positive signal is observed - a WIMP mass-spectroscopy. Recently an extensive facility for the measurement of light QFs at mK temperatures via neutron scattering (time-of-flight) has been set up and successfully commissioned at the Maier-Leibnitz Laboratorium (MLL) in Garching. We present here first results for the QFs of CaWO4 crystals at low temperatures.