The successful NuSTAR telescope was fabricated with thin glass mirrors formed into conic shapes by thermal slumping of thin glass sheets onto high precision mandrels. While mirrors generated by this process have very good figure, the best mirrors to date have a resolution limited to ~7 arc sec, due primarily to mid-range scale spatial frequency errors. These mid-range errors are believed to be due to clumping and particulates in the anti-stick coatings used to prevent sticking between mandrel and mirrors. We have developed a new slumping process which avoids sticking and surface-induced mid-range error by floating hot glass substrates between a pair of porous air bearing mandrels through which compressed nitrogen is forced. We report on the design and testing of an improved air bearing slumping tool and show results of short and long slumping cycles.
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Mark L. Schattenburg ; Brandon Chalifoux ; Michael D. DeTienne ; Ralf K. Heilmann and Heng Zuo
Progress report on air bearing slumping of thin glass mirrors for x-ray telescopes
", Proc. SPIE 9603, Optics for EUV, X-Ray, and Gamma-Ray Astronomy VII, 96030R (September 4, 2015); doi:10.1117/12.2189970; http://dx.doi.org/10.1117/12.2189970