15 October 1997 Gas permeability through thin-foil x-ray filters
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Abstract
We have measured the permeation rates of helium and water through thin-foil UV-blocking filters used in the ASTRO-E/x- ray spectrometer (XRS) instrument. In the XRS program, there is a concern that outgassed contaminants such as water could permeate through the outermost filter which will be at room temperature and freeze on the inner filters which will be at cryogenic temperatures. The filters tested consisted of approximately 1000 angstroms Al on approximately 1000 angstroms of either Lexan or polyimide. Measurements were made using a vacuum apparatus consisting essentially of two small chambers separated by the filter under test. A helium leak detector was used to measure helium permeation rates, and a residual gas analyzer (RGA) was used to detect water. Results discussed include permeation rate as a function of pressure difference across a filter, the ratio of helium permeation rate over water permeation rate, and the effect of the aluminum layer thickness on permeation.
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June L. Tveekrem, June L. Tveekrem, Ritva A. M. Keski-Kuha, Ritva A. M. Keski-Kuha, Andrew T. Webb, Andrew T. Webb, } "Gas permeability through thin-foil x-ray filters", Proc. SPIE 3114, EUV, X-Ray, and Gamma-Ray Instrumentation for Astronomy VIII, (15 October 1997); doi: 10.1117/12.278900; https://doi.org/10.1117/12.278900
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