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Proceedings Paper

Cryogenic distortion at 4.4 K of a 50-cm-diameter spherical beryllium mirror fabricated to reduce cryogenic distortion and hysteresis
Author(s): Gordon C. Augason; Dana S. Clarke; David D. Norris; Roger A. Paquin; John M. Kincade
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Paper Abstract

A 50 cm diameter, beryllium mirror was fabricated and cryogenically tested as a joint project between NASA-Ames Research Center and Jet Propulsion Laboratory. The purpose of this project was to determine the cryogenic distortion and hysteresis of a large, state-of-the-art beryllium mirror when cooled to liquid helium temperatures. The mirror blank was HIPed from I-70 special beryllium and machined to a plano-concave sphere with a 200 cm radius of curvature. The blank was annealed, acid etched, and thermally cycled may times during machining, figuring, and polishing to reduce stress. The mirror was tested twice to liquid helium temperature using the Ames Research Center Cryogenic Test Facility. No hysteresis or temporal instability was measured in the two tests. The cryogenic distortion was 0.5 p-v. This distortion is comparable to fused silica and is the lowest for any beryllium mirror tested by this facility.

Paper Details

Date Published: 23 October 1995
PDF: 11 pages
Proc. SPIE 2543, Silicon Carbide Materials for Optics and Precision Structures, (23 October 1995); doi: 10.1117/12.225299
Show Author Affiliations
Gordon C. Augason, Orion TechnoScience Inc. (United States)
Dana S. Clarke, Orion TechnoScience Inc. (United States)
David D. Norris, Jet Propulsion Lab. (United States)
Roger A. Paquin, Advanced Materials Consultant (United States)
John M. Kincade, Tinsley Labs., Inc. (United States)


Published in SPIE Proceedings Vol. 2543:
Silicon Carbide Materials for Optics and Precision Structures
Mark A. Ealey, Editor(s)

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