ASSESSMENT OF DOSE-COEFFICIENTS AS A PERFORMANCE PARAMETER FOR OPTICAL GLASSES IN A SPACE RADIATION ENVIRONMENT

摘要

Optical glass materials are damaged due to irradiation. The objective of this activity was to establish a suitable experimental and theoretical basis for the application of Dose-Coefficients as a performance parameter in the testing and qualification of optical glasses for use in a space radiation environment. We have measured the radiation induced wavefront aberrations in samples of the following commercial glasses: LaK9, LaK9G15, BK7, BK7G15, BK7G25 and Fused Silica. A differential experimental technique was used in order to detect the very small effects as predicted by the theory. The dose dependence of the refractive index changes that we have measured, is linear. This provides confirmation of the Dose-Coefficient approach. Based on our experimental data we show that radiation induced aberrations (such as defocussing) in a typical space optical system can be estimated to be significant for even a relatively low total dose of several hundred kRad. We also conclude that, contrary to the general expectation, radiation hardness based only on component spectral transmittances is insufficient to fully qualify radiation stability of high resolution optical systems.