Soft x-ray windows for position-sensitive proportional counters

Methods have been developed to make ultrathin low-leak x-ray entrance windows which can withstand atmospheric pressures. The first prototypes have been 6 mm or 20 mm diameter windows with film thicknesses 0.5 micrometers - 2.5 micrometers of polyimide and 40 nm - 100 nm of aluminum. Also 0.5 micrometers - 1 micrometers thick beryllium windows with diameter of 6 mm have been fabricated. The goal is to fabricate 140 mm and 70 mm diameter windows for Danish-Finnish position sensitive proportional counters to be flown on the Soviet SPECTRUM-ROENTGEN-GAMMA satellite.