Development of the UV/ion shields for the Advanced X-ray Astrophysics Facility high-resolution camera (AXAF HRC)

The Advanced X-ray Astrophysics Facility (AXAF) is a major NASA spaceobservatory (launch 1998). One of its two focal plane detectors is theHigh Resolution Camera (HRC) assembly consisting of two microchannelplate (MCP) based detectors. Key components of the two HRC detectorsare UV/Ion shields consisting of metalized sub-micron plasticmembranes, designed to prevent UV light and low energy chargedparticles from reaching the detectors' sensitive surfaces. We discussthe design issues and present results of recent measurements and tests.Soft X-ray/UV transmission measurements have been conducted at theSpace Science Laboratory (SSL), University of California at Berkeley,and at the Osservatorio Astronomico di Palermo G.S. Vaiana, Italy, onsample films of different plastic materials under study, namely Lexan,Polyimide, Parylene-C, and VYNS. Acoustic tests of baseline designUV/Ion shields' samples have been conducted at the Marshall SpaceFlight Center (MSFC). Computer simulations have been conducted toestimate the HRC count rate due to diffuse UV background and Hotstars.