Hans Kraus

Abstract:

Using heat pulses, we studied the elastic scattering of THz phonons in sapphire and calcium tungstate, two materials of interest as absorbers in composite detectors of particles and photons. For sapphire, we modelled the power dependences of specularly reflected and bulk scattered phonons, whilst for calcium tungstate the transmitted diffusive signal was measured. In both materials, the measured rate was consistent with Rayleigh scattering by isotopes, of oxygen in Al2O3 and of tungsten in CaWO4. In addition, strongly non-linear effects were observed in CaWO4. (C) 2002 Elsevier Science B.V. All rights reserved.

Abstract:

Cryogenic detectors are detectors based upon detection mechanisms which require low temperatures in the sub-kelvin range, such as superconductivity. This article introduces the two main representatives of cryogenic detectors, superconducting tunnel junctions and low-temperature calorimeters with superconducting thermometers. The operating principles, signal generation and noise sources are discussed in each case. These detectors are already applied to experiments in particle-astrophysics and in optical astronomy. They are considered as the next generation instrumentation in certain areas of astrophysics, material analysis and high-resolution spectroscopy. Since 1996, they are also considered for applications in time-of-flight spectrometry of heavy bio-molecules. Successful applications of both detectors types in this area are briefly reviewed. © 2002 Elsevier Science B.V. All rights reserved.

Abstract:

The low transition temperature of tungsten should allow fabrication of X-ray detectors combining high-energy resolution and enlarged absorber area (similar to1 mm(2)). We present first results obtained for lead and gold absorbers read out by tungsten superconducting phase transition thermometers (W-SPT) using a variety of detector geometries.

Abstract:

The upgrade of the CRESST experiment to a 10 kg target of phonon/light detectors necessitates the installation of 66 readout channels in the CRESST cryostat. We report on the status of this upgrade and discuss the issues related to the installation of the correspondingly high number of SQUIDs and wires in an ultra-low temperature environment.