1 January 1991 Pulsed electron-beam testing of optical surfaces
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Abstract
Rapid pulsed low energy electron bean irradiation of optical surfaces has proved to be a cost effective technique to test for radiation hardness and/or optical film adhesion. A rapid pulse (60 ns 130 ns) of electrons generates strong thermomechanical shock waves in the target surface to a depth of several micrometers. Spire''s pulsed electron beam sources (SPIPULSETh 300 and SPIPULSE 5000) are contaminantfree up to a fluence of 1. 0 cal/cm2 so that precise artifactfree optical scatter (e. g. bidirectional reflectance distribution function (BRDF)) measurements can be made before and after irradiation. Fluence reproducibility from shot to shot is 5 thus allowing direct comparisons of radiation responses of different samples or different irradiation sites to be made. Pulsed ebeams have been successfully applied to conductive and nonconductive optical surfaces such as metal and SiC mirrors optical baffles and ceramic optical coatings. A simple model is presented to demonstrate that radiationinduced conductivity (RIC) occurs during intense electron bombardment of any material. For alumina a time constant for the discharge of any residual charge build up that might occur during electron bombardment is estimated to be 30 picoseconds. For the ebeam radiation pulse lengths and fluence levels considered here alumina behaves as a conductive material. Several experimental examples are given including measurements of ebeam induced material blowoff for alumina. 1 .
© (1991) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Brian W. Murray, Edward A. Johnson, "Pulsed electron-beam testing of optical surfaces", Proc. SPIE 1330, Optical Surfaces Resistant to Severe Environments, (1 January 1991); doi: 10.1117/12.47511; https://doi.org/10.1117/12.47511
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