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Proceedings Paper

Development of bent crystal for imaging polarimetry
Author(s): Kota Okada; Takashi Awaya; Yohko Tsuboi; Ryo Iizuka; Naoto Ohtake
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Paper Abstract

We are developing a Bragg crystal polarimeter which has high modulation factor. The point we aim is to bend the crystal; by using bent crystal, we can reflect X-ray emission with broadened energy width, focus it on a small detector, which increases S/N ratio, and obtain imaging capability. We bent Si (100) crystal sheets by depositing Diamond-Like Carbon (DLC) on the backside of reflection surface. They are bent by the residual stress between the DLC and crystal. We can control the curvature by changing the DLC thickness. The angular reflectivity was measured with the line emission at 8.04 keV (Cu-Kα). We confirmed that the angular width is broadened to 1 degree, which is equivalent to the energy width of 0.5 keV. The integrated reflectivity becomes larger, as the curvature radius of crystal becomes small. The modulation factor of bent Si is 0.74, which is higher than that of the flat Si of 0.51. Having the wide energy band with the high modulation factor, the bent Si crystal can be a new tool for the X-ray polarimeter. We have also made the bent Ge(111) crystal and measured the same performances. The modulation factor of both the flat and the bent Ge were 0.99 , when using the 8.04 keV (Cu-Kα) beam, as we expected. This means that by choosing crystals, we can make efficient observations with aimed energy band. We report the status of our development.

Paper Details

Date Published: 17 September 2012
PDF: 7 pages
Proc. SPIE 8443, Space Telescopes and Instrumentation 2012: Ultraviolet to Gamma Ray, 84434L (17 September 2012); doi: 10.1117/12.926053
Show Author Affiliations
Kota Okada, Chuo Univ. (Japan)
Takashi Awaya, Chuo Univ. (Japan)
Yohko Tsuboi, Chuo Univ. (Japan)
Ryo Iizuka, Chuo Univ. (Japan)
Naoto Ohtake, Tokyo Institute of Technology (Japan)

Published in SPIE Proceedings Vol. 8443:
Space Telescopes and Instrumentation 2012: Ultraviolet to Gamma Ray
Tadayuki Takahashi; Stephen S. Murray; Jan-Willem A. den Herder, Editor(s)

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