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Proceedings Paper

Development of precision Wolter mirrors for solar x-ray observations
Author(s): Taro Sakao; Satoshi Matsuyama; Takumi Goto; Jumpei Yamada; Shuhei Yasuda; Kazuto Yamauchi; Yoshiki Kohmura; Ayumi Kime; Akira Miyake; Tadakazu Maezawa; Hirokazu Hashizume; Yoshinori Suematsu; Noriyuki Narukage; Shin-nosuke Ishikawa
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Paper Abstract

High resolution imagery of the Sun's X-ray corona provides an essential clue in understanding dynamics and heating processes of plasma particles there. However, X-ray imagery of the Sun with sub-arcsecond resolution has so far never been conducted due to severe technical difficulty in fabricating precision Wolter mirrors. For future X-ray observations of the solar corona, we are attempting to realize precision Wolter mirrors with sub-arcsecond resolution by adopting advanced surface polish and metrology methods to sector mirrors which consist of a portion of an entire annulus, by direct polishing onto the mirror substrate. Based on the knowledge obtained through fabrication of the first (in 2013) and second (in 2014) engineering Wolter mirrors and subsequent evaluations on their X-ray focusing performance, the third engineering mirror was made in 2015−2016. The primary target of improvement over the second mirror was to suppress figure error amplitude especially for spatial frequencies around 1 mm-1 and to suppress the large astigmatism that was present in the second mirror, by introducing improved deterministic polish and smoothing on the precision mirror surfaces (32.5 mm × 10 mm in area for both parabola and hyperbola segments), as well as by careful characterization of the systematic error in the figure measurement system for the precision polish. Measurements on the focusing performance of thus-fabricated third Wolter mirror at SPring-8 synchrotron facility with 8 keV X-rays demonstrated that the mirror attained sub-arcsecond focusing performance with its HPD (half-power diameter) size reaching as small as ~0.2 arcsec for meridional focusing while ~0.1 arcsec for sagittal focusing. The meridional focusing achieved nearly diffraction limited performance (~0.12 arcsec FWHM for the PSF core). We also confirmed that the large astigmatism noted in the second mirror was correctly removed in the third mirror with the correction of the above-mentioned systematic error.

Paper Details

Date Published: 23 August 2017
PDF: 11 pages
Proc. SPIE 10386, Advances in X-Ray/EUV Optics and Components XII, 103860E (23 August 2017); doi: 10.1117/12.2273507
Show Author Affiliations
Taro Sakao, Institute of Space and Astronautical Science (Japan)
The Graduate Univ. for Advanced Studies (Japan)
Satoshi Matsuyama, Osaka Univ. (Japan)
Takumi Goto, Osaka Univ. (Japan)
Jumpei Yamada, Osaka Univ. (Japan)
Shuhei Yasuda, Osaka Univ. (Japan)
Kazuto Yamauchi, Osaka Univ. (Japan)
Yoshiki Kohmura, SPring-8, RIKEN (Japan)
Ayumi Kime, Japan Aerospace Exploration Agency (Japan)
Akira Miyake, Canon Inc. (Japan)
Tadakazu Maezawa, Natsume Optical Corp. (Japan)
Hirokazu Hashizume, Natsume Optical Corp. (Japan)
Yoshinori Suematsu, National Astronomical Observatory of Japan (Japan)
Noriyuki Narukage, National Astronomical Observatory of Japan (Japan)
Shin-nosuke Ishikawa, Institute of Space and Astronautical Science (Japan)

Published in SPIE Proceedings Vol. 10386:
Advances in X-Ray/EUV Optics and Components XII
Christian Morawe; Ali M. Khounsary; Shunji Goto, Editor(s)

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