Measurement of the soft X-ray response of P-channel back-illuminated CCD

P-channel charge-coupled devices (CCDs) made from N-type silicon wafers were originally developed for ground-based optical and near-infrared telescopes. The thick depletion layer of these CCDs provides the significant advantage of high quantum efficiency (QE) for hard X-rays. On the other hand, high...

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Published in:	Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment Vol. 704; pp. 140 - 146
Main Authors:	Ueda, Shutaro, Hayashida, Kiyoshi, Nakajima, Hiroshi, Anabuki, Naohisa, Tsunemi, Hiroshi, Kan, Hiroaki, Kohmura, Takayoshi, Ikeda, Shoma, Kaneko, Kenta, Watanabe, Tatsuo, Mori, Koji, Nobukawa, Masayoshi, Murakami, Hiroshi, Sakata, Kazuya, Todoroki, Shotaro, Yagihashi, Nobuyoshi, Mizuno, Eiki, Muramatsu, Masaharu, Suzuki, Hisanori, Takagi, Shin'ichiro
Format:	Journal Article
Language:	English
Published:	Elsevier B.V 01-03-2013
Subjects:	ASTRO-H Charge coupled devices Depletion Detectors Low energy P-channel BI CCD Prototypes Soft X-ray response Soft x-rays Surface layer X-ray CCD X-rays X-ray CCD Soft X-ray response P-channel BI CCD ASTRO-H
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Summary:	P-channel charge-coupled devices (CCDs) made from N-type silicon wafers were originally developed for ground-based optical and near-infrared telescopes. The thick depletion layer of these CCDs provides the significant advantage of high quantum efficiency (QE) for hard X-rays. On the other hand, high QE for soft X-rays is obtained with back-illuminated (BI) and fully depleted CCDs in which only a thin dead layer exists on the surface of incidence. Thus, P-channel BI CCDs can be applicable as superior wide band X-ray detectors. We have developed such a device specifically for the Soft X-ray Imager (SXI) on board the X-ray astronomy satellite ASTRO-H, scheduled to be launched in 2014. We previously reported that the depletion layers of our CCDs, a prototype of SXI-CCDs, have a thickness of more than 200μm. In this paper, we report a novel soft X-ray response of P-channel BI CCDs. First, we irradiate fluorescent X-rays of O, F, Na, Al, Si and K to the SXI prototype. This experiment reveals that our CCD has a significant low-energy tail structure in the soft X-ray response. Since the intensity of the low-energy tail is larger for lower X-ray energies, the tail is originated on the CCD surface layer. Then, we fabricate a new type of CCDs by applying an alternative treatment to its surface layer. The soft X-ray response of the CCD is measured by irradiation of monochromatic X-rays from 0.25keV to 1.8keV in a synchrotron facility, KEK-PF. The intensity of the low-energy tail for 0.5keV incident X-ray is one order of magnitude smaller than that for the previous CCD. The same treatment will be applied to the surface layer of the SXI flight model.
Bibliography:	ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23
ISSN:	0168-9002 1872-9576
DOI:	10.1016/j.nima.2012.11.187