Effect of gamma radiation on the stability of UV replicated composite mirrors

Rafael J. Zaldivar; Hyun I. Kim; Geena L. Ferrelli

doi:10.1117/1.OE.57.4.047102

10 April 2018 Effect of gamma radiation on the stability of UV replicated composite mirrors

Rafael J. Zaldivar, Hyun I. Kim, Geena L. Ferrelli

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Optical Engineering, Vol. 57, Issue 4, 047102 (April 2018). https://doi.org/10.1117/1.OE.57.4.047102

Abstract

Composite replicated mirrors are gaining increasing attention for space-based applications due to their lower density, tailorable mechanical properties, and rapid manufacturing times over state-of-the-art glass mirrors. Ultraviolet (UV)-cured mirrors provide a route by which high-quality mirrors can be manufactured at relatively low processing temperatures that minimize residual stresses. The successful utilization of these mirrors requires nanometer scale dimensional stability after both thermal cycling and hygrothermal exposure. We investigate the effect of gamma irradiation as a process to improve the stability of UV replicated mirrors. Gamma radiation exposure was shown to increase the cure state of these mirrors as evidenced by an increase in modulus, glass transition temperature, and the thermal degradation behavior with dosage. Gas chromatography–mass spectroscopy also showed evidence of consumption of the primary monomers and initiation of the photosensitive agent with gamma exposure. The gamma-exposed mirrors exhibited significant improvement in stability even after multiple thermal cycling in comparison with nonirradiated composite mirrors. Though improvements in the cure state contribute to the overall stability, the radiation dosage was also shown to reduce the film stress of the mirror by over 80% as evidenced using Stoney replicated specimens. This reduction in residual stress is encouraging considering the utilization of these structures for space applications. This paper shows that replicated composite mirrors are a viable alternative to conventional optical structures.

CC BY: © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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Rafael J. Zaldivar, Hyun I. Kim, and Geena L. Ferrelli "Effect of gamma radiation on the stability of UV replicated composite mirrors," Optical Engineering 57(4), 047102 (10 April 2018). https://doi.org/10.1117/1.OE.57.4.047102

Received: 31 October 2017; Accepted: 16 March 2018; Published: 10 April 2018

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