Modeling the spectral response for the soft X-ray imager onboard the ASTRO-H satellite

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• 作者：Shota Inoue^a ; ^b ; ^{shota@ess.sci.osaka-u.ac.jp" class="auth_mail" title="E-mail the corresponding author} ; Kiyoshi Hayashida^a ; ^b ; Shuhei Katada^a ; ^b ; Hiroshi Nakajima^a ; ^b ; Ryo Nagino^a ; ^b ; Naohisa Anabuki^a ; ^b ; Hiroshi Tsunemi^a ; ^b ; Takeshi Go Tsuru^c ; Takaaki Tanaka^c ; Hiroyuki Uchida^c ; Masayoshi Nobukawa^d ; Kumiko Kawabata Nobukawa^c ; Ryosaku Washino^c ; Koji Mori^e ; Eri Isoda^e ; Miho Sakata^e ; Takayoshi Kohmura^f ; Koki Tamasawa^f ; Shoma Tanno^g ; Yuma Yoshino^g ; Takahiro Konno^g ; Shutaro Ueda^h ; On behalf of ASTRO-H/SXI team
• 关键词：X-ray ; Charge-coupled device ; P-channel CCD ; ASTRO-H
• 刊名：Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
• 出版年：2016
• 出版时间：21 September 2016
• 年：2016
• 卷：831
• 期：Complete
• 页码：415-419
• 全文大小：1633 K

文摘

The ASTRO-H satellite is the 6th Japanese X-ray astronomical observatory to be launched in early 2016. The satellite carries four kinds of detectors, and one of them is an X-ray CCD camera, the soft X-ray imager (SXI), installed on the focal plane of an X-ray telescope. The SXI contains four CCD chips, each with an imaging area of class="mathmlsrc">title="View the MathML source" class="mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0168900216300900&_mathId=si0024.gif&_user=111111111&_pii=S0168900216300900&_rdoc=1&_issn=01689002&md5=b8eb7190f42d193ff4ab5f6b7e70fb37">class="imgLazyJSB inlineImage" height="10" width="75" alt="View the MathML source" style="margin-top: -5px; vertical-align: middle" title="View the MathML source" src="/sd/grey_pxl.gif" data-inlimgeid="1-s2.0-S0168900216300900-si0024.gif">class="mathContainer hidden">class="mathCode">$31\mathrm{mm}\times 31\mathrm{mm}$, arrayed in mosaic, covering the field-of-view of class="mathmlsrc">class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0168900216300900&_mathId=si0025.gif&_user=111111111&_pii=S0168900216300900&_rdoc=1&_issn=01689002&md5=11f25f75e59015852867582e6e9caca1" title="Click to view the MathML source">38^′×38^′class="mathContainer hidden">class="mathCode">, the widest ever flown in orbit. The CCDs are a P-channel back-illuminated (BI) type with a depletion layer thickness of class="mathmlsrc">title="View the MathML source" class="mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0168900216300900&_mathId=si0026.gif&_user=111111111&_pii=S0168900216300900&_rdoc=1&_issn=01689002&md5=14ca6b0cba9c4bfd7a0b95874a7f2a08">class="imgLazyJSB inlineImage" height="11" width="33" alt="View the MathML source" style="margin-top: -5px; vertical-align: middle" title="View the MathML source" src="/sd/grey_pxl.gif" data-inlimgeid="1-s2.0-S0168900216300900-si0026.gif">class="mathContainer hidden">class="mathCode">$200\mathrm{\mu }\mathrm{m}$. We operate the CCDs in a photon counting mode in which the position and energy of each photon are measured in the energy band of 0.4–12 keV. To evaluate the X-ray spectra obtained with the SXI, an accurate calibration of its response function is essential. For this purpose, we performed calibration experiments at Kyoto and Photon Factory of KEK, each with different X-ray sources with various X-ray energies. We fit the obtained spectra with 5 components; primary peak, secondary peak, constant tail, Si escape and Si fluorescence, and then model their energy dependence using physics-based or empirical formulae. Since this is the first adoption of P-channel BI-type CCDs on an X-ray astronomical satellite, we need to take special care on the constant tail component which is originated in partial charge collection. It is found that we need to assume a trapping layer at the incident surface of the CCD and implement it in the response model. In addition, the Si fluorescence component of the SXI response is significantly weak, compared with those of front-illuminated type CCDs.