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9 March 2019 Simulations of film stress effects on mirror segments for the Lynx X-ray Observatory concept
Brandon D. Chalifoux, Youwei Yao, Ralf K. Heilmann, Mark L. Schattenburg
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Journal of Astronomical Telescopes, Instruments, and Systems, Vol. 5, Issue 2, 021004 (March 2019). https://doi.org/10.1117/1.JATIS.5.2.021004
Abstract
The Lynx X-ray Observatory concept, under study for the 2020 NASA Decadal Survey, will require a telescope with ∼2  m2 of effective area and a point-spread function (PSF) with ∼0.5-arc sec half-power diameter (HPD) to meet its science goals. This requires extremely accurate thin grazing-incidence mirrors with a reflective x-ray coating. A mirror coating, such as 15-nm-thick iridium, can exhibit stress exceeding 1 GPa, significantly deforming segmented mirrors and blurring the PSF. The film stress and thickness are neither perfectly repeatable nor uniform. We use finite element analysis and ray tracing to quantify the effects of integrated stress inaccuracy, nonrepeatability, nonuniformity, and postmounting stress changes on segmented mirrors. We find that if Lynx uses segmented mirrors, it will likely require extremely small film stress (∼10  MPa) and nonuniformity (<1  %  ). We show that realigning mirrors and matching complementary mirror pairs can reduce the HPD from uniform film stress by a factor of 2.3  ×   and 5  ×  , respectively. Doubling mirror thickness produces much less than the 4  ×   HPD reduction that would be expected from a flat mirror. The x-ray astronomy community has developed numerous methods of reducing the PSF blurring from film stress, and Lynx may require several of these in combination to achieve 0.5 arc sec HPD using segmented mirrors.
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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Brandon D. Chalifoux, Youwei Yao, Ralf K. Heilmann, and Mark L. Schattenburg "Simulations of film stress effects on mirror segments for the Lynx X-ray Observatory concept," Journal of Astronomical Telescopes, Instruments, and Systems 5(2), 021004 (9 March 2019). https://doi.org/10.1117/1.JATIS.5.2.021004
Received: 1 November 2018; Accepted: 13 February 2019; Published: 9 March 2019
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Cited by 9 scholarly publications and 1 patent.
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KEYWORDS
Mirrors
Ray tracing
Point spread functions
X-rays
Silicon films
Coating
Silicon
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