Hans Kraus

Abstract:

We report on the development of an imaging cryogenic X-ray spectrometer based upon X-ray absorption in sapphire and readout by two tungsten superconducting phase transition thermometers (SPTs). We achieve one-dimensional imaging over an absorber length of 10 mm with a position resolution of approximate to 200 mu m. (C) 2000 Elsevier Science B.V. All rights reserved.

Abstract:

A theoretical model to describe the spectral response of SIS tunnel junctions under irradiation in the presence of diffusion and edge losses of non-equilibrium quasiparticles has been developed. The model takes into account the back-tunnelling effect, in the general case of asymmetrical rates of tunnelling, gamma(12) not equal gamma(21). It provides a quantitative estimate of parameters like the edge reflectivity, the diffusion length and the diffusion coefficient, which are important parameters for a diagnostic of STJ-detectors. The predictions of the theory are compared with an experimental spectrum obtained from a Nb-based STJ. (C) 2000 Elsevier Science B.V. All rights reserved.

Abstract:

We have developed a fast current readout system for STJ detectors with a fast current preamplifier by direct signal observation. The preamplifier has frequency bandwidth of 110 MHz with stable voltage bias operation. By the various experiments using a Ta STJ and Nb STJ, it is confirmed that the readout system is effective for the evaluation of STJs, research of the mechanism for signal production process and the X-ray detection with high counting rate. (C) 2000 Elsevier Science B.V. All rights reserved.

Abstract:

The CRESST experiment in its first phase is using sapphire detectors with tungsten phase transition thermometers to search for dark matter WIMPs. At present Four 262 g detectors are performing first measurements under low background conditions. Detector performance as well as preliminary results from the background runs are presented. A second phase of CRESST using CaWO4 and simultaneous measurement of phonons and scintillation light is in preparation. (C) 2000 Elsevier Science B.V. All rights reserved.

Abstract:

The CRESST experiment in its first phase is using sapphire detectors with tungsten phase transition thermometers to search for dark matter WIMPs. At present four 262 g detectors are performing first measurements under low background conditions. Detector performance as well as preliminary results from the background runs are presented. A second phase of CRESST using CaWO4 and simultaneous measurement of phonons and scintillation light is in preparation.