Polyimide x-ray filter substrates optimized for cryogenic temperatures

New generation x-ray instruments for spacecraft such as ASTRO-E and CONSTELLATION-X have very specialized requirements, notably operation at cryogenic temperatures. Luxel Corporation, under a NASA Phase I SBIR contract, undertook the demonstration of feasibility of producing polyimide films suitable for use as x-ray filter substrates specifically optimized for cryogenic applications. 5000 angstrom thick polyimide films were processed using different cure cycles, and burst pressure analyses were performed at 293, 77, and 4 Kelvin. Test data showed that polyimide films are inherently stronger at cryogenic temperatures than at room temperature. Through cure modification, film strength was increased an additional 9 percent at 4K over that of the standard cure clearly showing the feasibility of film optimization.