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Proceedings Paper

Reflectivity and polarization sensitivity of a bent crystal with DLC deposition
Author(s): Ryo Iizuka; Shingo Kusunoki; Atsushi Tokuno; Yohko Tsuboi; Seiya Takeda; Satoshi Yamamuro; Kazuyoshi Misumi; Hiroki Akasaka; Naoto Ohtake; Masanori Saito
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Paper Abstract

We report a development of a bent crystal for use of X-ray polarimeter. A Si(100) crystal sheet was deposited with DLC (Diamond-Like Carbon) and bent by the difference in the internal stress between the DLC and Si. An angular reflectivity of the crystal was measured at 8 keV (Cu-Kα). The center of the reflection peak appeared at the Bragg angle expected for the (400) plane of Si(100). With the bending of the crystal, the angular width of the peak is broadened. A sample indicated the angular width of 2 degree, which is equivalent to the energy width of 0.5 keV. The modulation factor was measured to be more than 0.9 for 8 keV energy emission. If the energy of the X-ray emission is at Fe-K lines (~7 keV), which are very important for X-ray astronomy, the Bragg angle becomes more close to 45 degree. It means that higher sensitivity for the polarization would be expected for these lines. The sensitivity in wide energy band with the high modulation factor indicates that the bent crystal can be a new tool for the X-ray polarimeter. A preliminary design of the polarimetric optics composed by the Si(100) crystal and a small-size detector (e.g. X-ray CCD camera) is proposed. For celestial objects with large spatial extent with large emitting energy band, our optics could collect X-rays much more efficiently than existing optics with high signal to noise ratio. Any kind of crystals can be bent with our method, and then a combination of different crystals will further improve the performance of the polarimetric optics.

Paper Details

Date Published: 29 July 2010
PDF: 11 pages
Proc. SPIE 7732, Space Telescopes and Instrumentation 2010: Ultraviolet to Gamma Ray, 77324R (29 July 2010); doi: 10.1117/12.857965
Show Author Affiliations
Ryo Iizuka, Chuo Univ. (Japan)
Shingo Kusunoki, Chuo Univ. (Japan)
Atsushi Tokuno, Chuo Univ. (Japan)
Yohko Tsuboi, Chuo Univ. (Japan)
Seiya Takeda, Chuo Univ. (Japan)
Satoshi Yamamuro, Chuo Univ. (Japan)
Kazuyoshi Misumi, Chuo Univ. (Japan)
Hiroki Akasaka, Nagaoka Univ. of Technology (Japan)
Naoto Ohtake, Tokyo Institute of Technology (Japan)
Masanori Saito, Tokyo Institute of Technology (Japan)

Published in SPIE Proceedings Vol. 7732:
Space Telescopes and Instrumentation 2010: Ultraviolet to Gamma Ray
Monique Arnaud; Stephen S. Murray; Tadayuki Takahashi, Editor(s)

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