Polyimide foils as backing supports for optical filters

Optical filters for X-ray telescopes require thin, mechanically and thermally stable, self-supporting backings. Polyimide foils, 25 cm in diameter, having such characteristics and with areal density of 25-140 μg/cm2, have been produced applying a modified method of foil preparation by in situ polymerisation. The modified method and results of mechanical properties tests of the foils are described.