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Do Ultra-Thin Polymer X-Ray Windows Leak Water Vapor?

Published online by Cambridge University Press:  02 July 2020

A. Nielson  and
J. Thorne
A. Nielson
Affiliation:
MOXTEK Inc., Orem, UT84058
J. Thorne
Affiliation:
Department of Chemistry, Brigham Young University, Provo, UT84602
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Extract

Ultra-thin polymer x-ray windows have been developed for energy dispersive spectroscopy (EDS) that enable analysis of the elements lighter in mass than sodium while protecting the detector from light and gases. Windowless detectors produce the ultimate in detector sensitivity, however that sensitivity is lost when ice and other contaminants form on the detector. Polymer windows have had a problem with icing in the past, however modern ultra-thin polymer windows contain metalized layers to prevent the diffusion of water. Nevertheless, over the course of time it has been observed that some detectors with polymer windows that are kept continually cool with liquid nitrogen form a thin layer of ice that attenuates light element sensitivity. The source of this water has been hypothesized to be a gradual leak of water vapor through the polymer x-ray window. This hypothesis has been questioned on the basis that the windows were helium leak tight to 1 x 10−9 mbar L/sec and helium is a smaller molecule than water.

Type
Mas Celebrates: Fifty Years of Electron Probe Microanalysis
Information
Microscopy and Microanalysis , Volume 5 , Issue S2: Proceedings: Microscopy & Microanalysis '99, Microscopy Society of America 57th Annual Meeting, Microbeam Analysis Society 33rd Annual Meeting, Portland, Oregon August 1-5, 1999 , August 1999 , pp. 588 - 589
Copyright
Copyright © Microscopy Society of America

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