IR filters for high responsivity cryogenic detectors

Modern cryogenic detectors, such as Superconducting Tunnel Junctions and Tr ansition Edge Sensors, provide single photon counting performance, medium t o high energy resolution, high count rates and good photon collection effic iency over a wide wavelength range. In order to avoid background limited pe rformance, it is necessary to shield the detectors from any thermal IR radi ation originating from the surrounding warm surfaces. In this paper we anal yse the contribution of the thermal radiation to the detector performance a nd describe the IR filters used in the S-Cam camera and in other experiment al configurations. Future detectors may require very severe attenuation of the IR flux (lambda > 1 mu m). Solutions to this problem are proposed and t heir validity demonstrated with experimental results. (C) 2000 Elsevier Sci ence B.V. All rights reserved.