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29 July 2010 Current status of the pre-collimator development for the ASTRO-H x-ray telescopes
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Abstract
We present the current status of the pre-collimator for the stray-light reduction, mounted on the ASTRO-H X-Ray Telescopes (XRT). Since the ASTRO-H XRTs adopt the conical approximation of the Wolter-I type grazing incident optics, X-rays from a source located far from the telescope boresight create a ghost image in the detector field of view (FOV) as a stray light, and then reduce the signal-to-noise ratio even in the hard X-ray band. We thus plan to mount the pre-collimator, which is comprised of cylindrical blades aligned with each primary mirror, onto the XRTs to remove the stray light. While the pre-collimator for the Soft X-ray Telescopes is designed by the similar principle adopted for the Suzaku pre-collimator, that for the Hard X-ray Telescopes requires some trade-off studies to select an appropriate blade material. The HXT pre-collimator currently utilizes the aluminum blade with the 50 mm height and 150 μm thickness. We examined the observational effects by the hard X-ray (> 10 keV) stray light and the expected performance of the pre-collimator in some scientific cases, using a ray-tracing simulator. We found that the Galactic center may be mostly covered with the stray light from the well-known bright X-ray sources. In addition, the flux estimation of the extended X-ray emission such as the Cosmic X-ray Background is also found to have large (~ 30%) uncertainty due to the stray light from the outside of the XRT FOV. The pre-collimator improves the situations; the stray light covering the source-free region in the Galactic center can be reduced by half and the uncertainty of the flux determination for the diffuse source decreases down to < 10%.
© (2010) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Hideyuki Mori, Yoshito Haba, Takuya Miyazawa, Akihiro Furuzawa, Yuzuru Tawara, Hideyo Kunieda, Shigeo Yamauchi, Hisamitsu Awaki, Manabu Ishida, Yoshitomo Maeda, Aya Bamba, Ryo Iizuka, Takashi Okajima, and Richard Mushotzky "Current status of the pre-collimator development for the ASTRO-H x-ray telescopes", Proc. SPIE 7732, Space Telescopes and Instrumentation 2010: Ultraviolet to Gamma Ray, 77323E (29 July 2010); https://doi.org/10.1117/12.856803
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