Mr. Tohya Yamagami Profile

Tohya Yamagami

at Kanto Gakuin Univ.

SPIE Involvement:

Author

Publications (2)

SPIE Journal Paper | 28 December 2023 Open Access

Development of the focal-plane CMOS detector for the GEO-X mission

Hiroshi Nakajima, Shotaro Nakamura, Kouichi Hagino, Ayumi Kiuchi, Takuya Matsumoto, Tohya Yamagami, Tomokage Yoneyama, Junko Hiraga, Yuichiro Ezoe, Masaki Numazawa, Kumi Ishikawa, Hisashi Kitamura

JATIS, Vol. 10, Issue 01, 016001, (December 2023) https://doi.org/10.1117/12.10.1117/1.JATIS.10.1.016001

KEYWORDS: X-rays, CMOS sensors, Sensors, Detector development, Dark current, Ultraviolet detectors, Ultraviolet radiation, Pulse signals, Magnetosphere, X-ray imaging

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Proceedings Article | 31 August 2022 Presentation + Paper

Development of the focal-plane CMOS detector for the GEO-X mission

Hiroshi Nakajima, Shotaro Nakamura, Koichi Hagino, Ayumi Kiuchi, Takuya Matsumoto, Tohya Yamagami, Tomokage Yoneyama, Junko Hiraga, Yuichiro Ezoe, Kumi Ishikawa

Proceedings Volume 12181, 121812C (2022) https://doi.org/10.1117/12.2628788

KEYWORDS: Sensors, X-rays, CMOS sensors, X-ray imaging, Spectroscopy, Magnetosphere, Detector development, X-ray detectors

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We are developing an x-ray CMOS detector for the GEO-X (GEOspace x-ray imager) mission that will perform soft x-ray (≤2 keV) imaging spectroscopy of Earth’s magnetosphere using a micro satellite. The mission instrument consists of a MEMS x-ray mirror and a focal plane detector. For the latter, we need a sensor with fine positional resolution and moderate energy resolution in the energy band of 0.3 to 2 keV. Because we observe the day-side structure of the earth’s magnetosphere, visible-light background must be decreased by shortening the integration time for readout. To satisfy the above requirements, a high-speed x-ray CMOS sensor is being evaluated as a primary candidate for the detector. We adopt back-side illuminated sensors that have been originally developed for visible-light or UV imaging. The sensors have different specification in terms of the thickness of epitaxial wafer and specific resistance. Irradiating sensors with monochromatic x-rays from ⁵⁵Fe, we obtained the energy resolution of 205 and 227 eV (FWHM) depending on the sensor type for single pixel events at 6 keV by cooling down the sensor to −15°C. On the other hand, we found that the pulse height of the events whose charges spread over multiple pixels are significantly lower than that of single pixel events in some chips. Then we selected the chips that shows better charge collection efficiency as flight candidate. Radiation tolerance of the sensor, especially in terms of total dose effect, is investigated with 100 MeV proton. The amount of dose ranges up to 100 krad depending on position in the sensor. In spite of the excessive dose compared with 10 krad/yr in the expected highly elliptical orbit, Mn Kα and Kβ are well resolved. The amount of degradation of energy resolution is less than 50 eV up to 10 krad, which ensures that we will be able to track and calibrate the change of the line width in orbit We also utilize multi-color x-rays to investigate spectroscopic performance in the energy band of 0.5 to 7 keV. Multiple lines below 1 keV are resolved and energy resolutions are evaluated as well as linearity performance.

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