P. Christ

EURECA — the European future of cryogenic dark matter searches

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 pico-barn 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.

Interpretation of Light-Quenching Factor Measurements

We observe that the pattern of the quenching factor for scintillation light from various ions, recently studied in CaWO4 in connection with dark matter detectors, can be understood as a saturation phenomenon in which the light output is simply proportional to track length, independent of the ion and its energy. This observation is in accord with the high dE/dx limit of Birks’ law. It suggests a simple model for the intrinsic resolution of light detectors for low energy ions, which we briefly discuss.

High detection sensitivity achieved with cryogenic detectors in combination with matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry.

Cryogenic detectors directly measure the impact energy of any impinging particle independent of its velocity. Thus, a very high, mass-independent, detection efficiency is expected from their application in time-of-flight mass spectrometry. The cryogenic detector applied here is based on a superconducting phase-transition thermometer and was implemented in a dual reflector time-of-flight mass spectrometer (N-geometry). A dilution series, using standard sample preparation procedures, shows that the detection limit for insulin (Mr: 5734) can be decreased by several orders of magnitude, down to 0.5 amol on the MALDI target. Detection limits for rhM-CSF β (Mr: 49,032) and for polyclonal IgG (Mr: ca 150,000) in the high femtomole and low picomole range, respectively, were established.

Fast cryodetector and SQUID read-out for mass spectrometry

We report a cryogenic detector with a superconducting phase transition thermometer and SQUID read-out for time of flight (TOF) mass spectrometry of biomolecules. Cryogenic detectors combine 100% detection efficiency independent of the mass of the molecule, an excellent energy resolution and a low threshold. Implementation of the cryogenic detectors into TOF mass spectrometers is expected to improve the efficiency of the detection of large biomolecules. To reach a high time resolution, we have developed two new read-outs based on a double stage SQUID and a cooled amplifier.

Results and status of the CRESST experiment

CRESST (Cryogenic Rare Event Search with Superconducting Thermometers) employs cryogenic detectors for the direct search for weakly interacting massive dark matter particles (WIMPs). In the second phase of the experiment scintillating calcium tungstate crystals are used to discriminate background by means of different light yield for background and WIMP signals. After first results with this novel technique have been obtained, the experimental setup is being upgraded for further background reduction and larger target mass. The results and present status of the experiment will be presented.