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26 October 2007 Ground bakeout experiment of the optical blocking filter (OBF) for the Suzaku XIS
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The X-ray Imaging Spectrometers (XIS) on-board Suzaku is an X-ray CCD camera system that has features of low backgroud, good energy resolution, and high quantum efficiency (QE) at 0.2-12 keV band. However, an unexpected degradation of the QE at low energies (<1 keV) has emerged since November 2005. Some contaminants are considered to be adsorbed on the Optical Blocking Filter (OBF) for each sensor and cause the degradation. A suspected contamination source is rubber used in the shock absorber of the satellite gyro. For the recovery of the QE, we now design to remove the contaminants by increasing the OBF temperature. Before the on-board bakeout is performed, we need to confirm on the ground that it does not cause a serious damage to the OBF. In order to reproduce the on-board contamination, we adsorbed the contaminant of ~160 μg cm-2 from the rubber on a spare OBF and a Thermoelectric Quartz Crystal Microbalance simultaneously, which are cooled down to -40°C. Although enexpected wrinkles appeared on the OBF surface during the adsorption and they remained through the subsequent bakeout, we could not find any tears on it. In addition, we estimated the desorption rate at -15°C to be ~5 μg cm-2 per day. In our presentation, we also discuss the expected effect by the on-board bakeout based on these results.
© (2007) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Hideyuki Mori, Takeshi Go Tsuru, Hironori Matsumoto, Hideki Uchiyama, Midori Ozawa, Yohjiro Takikawa, Masayoshi Nobukawa, Katsuji Koyama, Ken'ichi Torii, Noriaki Tawa, Shunji Kitamoto, Keisuke Sudoh, and Takayoshi Kohmura "Ground bakeout experiment of the optical blocking filter (OBF) for the Suzaku XIS", Proc. SPIE 6686, UV, X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XV, 66860O (26 October 2007);

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