Measurement of the transmission of the UV/ion shields for the AXAF High-Resolution Camera

摘要

The Advanced X-ray Astrophysics Facility (AXAF) is scheduled for launch in summer/fall 1998. One of its two focal plane instruments is the high resolution camera (HRC). The HRC consists of two detectors; an imaging detector (HRC-I) and a detector (HRC-S) for the spectroscopic read-out of the low energy transmission grating (LETG). Both detectors are comprised of a chevron pair of microchannel plates with a crossed grid charge detector (CGCD) and a UV/ion shield (UVIS). Each UVIS is mounted as a free standing window in front of the MCPs. The HRC-I UVIS is 10 cm multiplied by 10 cm and consists of 5000 angstrom polyimide, one side of which is coated with 700 angstrom aluminum. The other side is coated with 200 angstroms of carbon. The HRC-S UVIS consists of three 3 cm multiplied by 10 cm segments. The thickness of the polyimide film (2000 - 2500 angstrom) and of the aluminum coating (300 - 2000 angstrom) of each segment has been varied to optimize the shield's performance with the LETG. In this paper, x-ray transmission models are presented. Results of laboratory x-ray transmission measurements of the flight HRC-I UVIS at various energies in the range of 0.1 to 1.5 keV, as well as results of x-ray transmission measurements of a flight UVIS-I witness sample, are discussed. Results of UV transmission measurements of a flight UVIS-I witness sample also are presented.