Hans Kraus

Abstract:

The inorganic scintillator is an important element of a new type of cryogenic phonon scintillation detectors (CPSD) developed for single particle detection. These detectors exhibiting superior energy resolution and ability to identify the type of interaction event are considered as a next generation instrumentation in the search for extremely rare events. The paper presents the latest results of our study on cryogenic scintillators thought for CPSD application in the search for dark matter. It gives a description of the concept of direct dark matter detection and the operation principles of GPSD. The paper envisages major materials requirements and summarises the results of the studies of luminescence and scintillation properties of tungstates (CaWO 4 and ZnWO4), molybdates (CaMoO4, MgMoO 4, and CdMoO4) and Ti-doped Al2O3 over a wide temperature range (9-300 K).

Abstract:

In the CRESST-II experiment, scintillating CaWO4 crystals are used as absorbers for direct WIMP (weakly interacting massive particles) detection. Nuclear recoils can be discriminated against electron recoils by measuring phonons and scintillation light simultaneously. The absorber crystal and the silicon light detector are read out by tungsten superconducting phase transition thermometers (W-SPTs). Results on the sensitivity of the phonon and the light channel, radiopurity, the scintillation properties of CaWO4 and on the WIMP sensitivity are presented.

Abstract:

For the first time the natural alpha decay of W-180 has been unambiguously detected in a (gamma, beta and neutron)-free background spectrum. This has been obtained by simultaneously measuring phonon and light signals with CRESST 11 cryogenic detectors. Results on the radio purity of the detectors and on the measured half-life of W-180 are presented.

Abstract:

The mass number dependence of the WIMP-nucleus scattering offers a method for identifying a true WIMP signal over a neutron background. In this paper we present a study on using a combination of ZnWO4 and CaWO4 absorbers to exploit this materials signature for WIMP detection. We show that already modest exposure in the region of 5 kg years should allow the detection of WIMP interaction for cross sections smaller than current experimental sensitivities. The combination of these two tungstates could form the basis of the first multi-target detector capable of WIMP identification through materials signature.

Abstract:

We present first competitive results on WIMP dark matter using the phonon-light-detection technique. A particularly strong limit for WIMPs with coherent scattering results from selecting a region of the phonon-light plane corresponding to tungsten recoils. The observed count rate in the neutron band is compatible with the rate expected from neutron background. CRESST is presently being upgraded with a 66 channel SQUID readout system, a neutron shield and a muon veto system. This results in a significant improvement in sensitivity.