Environmental Testing of High Tc Superconductive Thermal Isolators for Space-Borne Cryogenic Detector Systems

Abstract

ABSTRACTNASA's requirements for space-based cryogenic detector systems include the long-term storage of the liquid helium cryogen necessary for the optimized performance of far-infrared (IR) detectors. Significant heat loads on the liquid helium dewars exist due to the numerous electrical connections to the detectors, accounting for approximately 20 percent of the total heat load for some systems. High temperature superconductor lead assemblies are under development to replace the existing manganin wires connecting instruments at 80 K to the detector array at 4.2 K. These superconductive elements provide adequate current transport properties, while decreasing the thermal load on the liquid helium dewar. As a result, mission lifetimes can be extended by 10 percent or more.Thick films of the superconductive material on low thermal conductivity substrates (e.g. yttria stabilized zirconia and fused silica) have been proposed to replace the existing lead assemblies. This work describes some of the design constraints on such a device as well as preliminary analyses of the effects of vibration, gamma irradiation, and long term exposure to high vacuum and liquid nitrogen encountered in operating such a device in space.