Replaceable Be and Al windows for X-ray beam lines

Abstract

Construction details and results of ongoing performance tests are presented for two ultra-high vacuum compatible, free-convection cooled window assemblies in which the window disk is easily replaceable. In the Be window assembly, an 0.25 mm thick Be disk, 38 mm in diameter is sealed into a stainless steel adapter flange using 0.5 mm diameter pure Al wire. The assembly is leak-10 3 tight to better than 1 x 10 atm cm /sec before and after multiple bakeouts to 250° C. However, an unexplained temperature-dependent He leak, with a maximum magnitude in the low 10 atm cm /sec range at 250° C, appears during bakeout. Possible causes for this leak are discussed. In the Al window assembly, a 25 /im thick Al disc, 60 mm in diameter acts as the sealing medium as well as the window material over a 10 mm by 50 mm opening. This assembly remains leak tight to better than 1 x 10 atm cm /sec throughout multiple bakeouts to 150° C and has been successfully tested in white and monochromatic beam lines at the NSLS x-ray ring.