Hans Kraus

Abstract:

The perspective of using CaMoO4 as a scintillation target in cryogenic rare event searches has provided strong motivation for the optimisation of this material. A single crystal of CaMoO4, exhibiting high optical quality, was produced and its scintillation light response to particle excitation and its decay time constant were investigated over the 7-300K temperature range. The scintillation at room temperature is strongly affected by thermal quenching. The main decay time constant is found to be 15.7 +/- 0.4 mu s at T= 300K; cooling to 7K increases the scintillation decay time constant to 380 +/- 20 mu s. The scintillation efficiency of the CaMoO4 crystal was evaluated by comparison with a reference CaWO4 crystal measured under the same conditions; we estimate the light output of CaMoO4 to be 55 +/- 20% that of CaWO4 at 294K and 95 +/- 30% at 7K. The study confirmed that calcium molybdate optimised for high light yield is a very attractive material for use in cryogenic phonon-scintillation detectors in rare event searches. (c) 2007 Elsevier B.V. All rights reserved.

Abstract:

CRESST I1 is a WIMP search experiment using cryogenic detectors to detect heat and scintillation signals in Caw04 crystals simultaneously. Competitive limits on the coherent WIMP-nucleon scattering cross section and other results from runs from the upgrade to CRESST I1 are shown. New features and upgrades installed on the CRESST I1 setup are described and the status of the experiment is presented.

Abstract:

We present results on WIMP dark matter interaction, obtained using cryogenic phonon-scintillation detectors. The targets are CaWO4 scintillating crystals with phonon sensors, while scintillation is detected with an associated cryogenic light detector. The combination of phonon and light signals leads to a strong suppression of nonnuclear recoil backgrounds. Results obtained before the upgrade of CRESST are presented and a status report on the upgrade itself is given.

Abstract:

EURECA (European Underground Rare Event Calorimeter Array) is a new project, searching for dark matter, with largely the present groups of the CRESST and EDELWEISS experiments and already a few new groups. The aim is to explore scalar cross sections in the 10(-9) - 10(-10) picobarn region with a target mass of up to one tonne. A major advantage of EURECA is our planned use of more that just one target material (multi target experiment for WIMP identification). In preparation for this large-scale experiment, R&D for EURECA is provided through the current phases of CRESST and EDELWEISS.

Abstract:

The CRESST experiment is designed to search for weakly interacting massive particle dark matter with cryogenic detectors. CRESST II will use up to 33 CaWO(4) crystals with a total mass of approximately 10 kg. These many detectors require a readout system based on 66-channel superconducting quantum interference devices (SQUIDs). In this article we report on the development of a modular superconducting connector for the 66-channel SQUID readout circuit. We show that the technique developed reliably produces superconducting contacts.