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 demonstrating feasibility of producing polyimide films suitable for use as x-ray filter substrates specifically optimized for cryogenic applications. 5000Å thick polyimide films were processed using different cure cycles, and burst pressure (tensile strength) analyses were performed at 293, 77, and 4 Kelvin (K). Test data showed that polyimide films are inherently stronger at cryogenic temperatures than at room temperature (20.5% at 4K). Through cure modification, film strength was increased an additional 9% at 4K over that of the standard cure clearly showing the feasibility of film optimization.