Imaging spectroscopy with Ta/Al DROIDs: performance for different geometries

Item does not contain fulltextIn this paper we present the preliminary results from experiments with Distributed Read Out Imaging Devices (DROIDs) in the optical and in the X-ray regime. For the optical results DROIDs of different lengths ranging from 200 to 700 ?m have been used with an STJ lay-up of Ta/Al/AlOx/Al/Ta with thicknesses of 100/30/1/30/100 nm. With this data the behavior with different absorber length has been investigated to determine an optimal absorber size for a DROID array to be used in the optical wavelength regime. The optimum absorber size has been found to be 30x400 um. The X-ray data has been obtained with a similar device structure but with 60 nm aluminium trapping layers to increase the trapping of quasiparticles in the STJs. In this paper we only present the data obtained with the standard DROID size of 400?m. With this device an extensive set of measurements have been performed which involves; a scan in photon energy ranging from 50eV to 1900 eV, a scan in temperature and a scan in bias voltage. We report here only results from the preliminary analysis of the data obtained with readout electronics comprising the normal preamplifier and subsequent shaping stage. For the final analyzes the pulses resulting from the STJs have been digitized and are ready to be analyzed. The pulses have been used to estimate the decay time of the STJs which appear to be very short. This is probably caused by the poor trapping of quasiparticles. Detailed results on this process will be presented however at a later date