19 August 1996 New fabrication processes for dimensionally stable beryllium mirrors
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Stability of beryllium mirrors is said to be unpredictable. Three recent mirrors demonstrate excellent stability. JPL produced a plano-concave, 0.5 m solid test mirror that was machined from a HIP'ed billet of special I-70 Be powder, polished bare and tested to 4K. It was thermally stable and had no hysteresis. The JPL ITTT 0.85 m primary mirror used similar material and processes, but with more stress relied treatments. Tests of this bare-polished, very lightweight single arch hyperboloidal mirror to 5K showed similar excellent results. The ESO VLT chopping secondary is a 1.12 m, machined lightweight, nickel plated, convex paraboloid. Similar fabrication processes are being used but with higher strength I-220 Be. In-processes testing indicates a stable mirror. The results show beryllium to be a stable and predictable mirror material.
© (1996) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Roger A. Paquin, Daniel R. Coulter, David D. Norris, Gordon C. Augason, Mark T. Stier, Marc Cayrel, Thomas B. Parsonage, "New fabrication processes for dimensionally stable beryllium mirrors", Proc. SPIE 2775, Specification, Production, and Testing of Optical Components and Systems, (19 August 1996); doi: 10.1117/12.246778; https://doi.org/10.1117/12.246778

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