論文 - 武田 彩希
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Takeda A., Mori K., Nishioka Y., Hida T., Yukumoto M., Kanemaru Y., Yonemura S., Mieda K., Tsuru T.G., Tanaka T., Kurachi I., Arai Y.
Journal of Instrumentation 15 ( 12 ) 2020年12月
担当区分：筆頭著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Journal of Instrumentation
This paper reports on the development of on-chip pattern processing in the event-driven silicon-on-insulator pixel detector for X-ray astronomy with background rejection purpose. X-ray charge-coupled device (CCD) detectors, well-established pixel detectors used in this field, has proven that classification of detected events considering their spatial pattern is effective for particle background rejection. Based on the current architecture of our device and from the CCD images obtained in space, we first established a design concept and algorithm of the pattern processor to be implemented. Then, we developed a new device, including a prototype pattern-processing circuit. Experiments using X-ray and beta-ray radioisotopes demonstrated that the pattern processor properly works as expected, and the particle background rejection is realized in an on-chip fashion. This function is useful, especially in a limited-resource system such as the CubeSat.
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Takeda A., Mori K., Nishioka Y., Fukuda K., Yukumoto M., Hida T., Tsuru T.G., Tanaka T., Uchida H., Hayashi H., Harada S., Okuno T., Kayama K., Arai Y., Kurachi I., Kohmura T., Hagino K., Negishi K., Oono K., Yarita K., Matsumura H., Kawahito S., Kagawa K., Yasutomi K., Shrestha S., Nakanishi S., Kamehama H.
Journal of Instrumentation 15 ( 11 ) 2020年11月
担当区分：筆頭著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Journal of Instrumentation
This paper reports the spectroscopic performance improvement of the silicon-oninsulator (SOI) pixel detector for X-ray astronomy, by introducing a double-SOI (D-SOI) structure. For applications inX-ray astronomical observatories, we have been developing a series of monolithic active pixel sensors, named as “XRPIXs,” based on SOI pixel technology. The D-SOI structure has an advantage that it can suppress a parasitic capacitance between the sensing node and the circuit layer, due to which the closed-loop gain cannot be increased in our conventional XRPIXs with a single-SOI (S-SOI) structure. Compared to the S-SOI XRPIX, the closed-loop gain is doubled in the D-SOI XRPIX. The readout noise is effectively lowered to 33% (16 e (rms)), and the energy resolution at 6.4 keV is improved by a factor of 1.7 (290 eV in FWHM). The suppression of the parasitic capacitance is also quantitatively evaluated based on the results of capacitance extraction simulation from the layout. This evaluation provides design guidelines for further reduction of the readout noise.
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Single event tolerance of x-ray silicon-on-insulator pixel sensors 査読あり
Hagino K., Hayashida M., Kohmura T., Doi T., Tsunomachi S., Kitajima M., Tsuru T.G., Uchida H., Kayama K., Mori K., Takeda A., Nishioka Y., Yukumoto M., Mieda K., Yonemura S., Ishida T., Tanaka T., Arai Y., Kurachi I., Kitamura H., Kawahito S., Yasutomi K.
Journal of Astronomical Telescopes, Instruments, and Systems 8 ( 4 ) 2022年10月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Journal of Astronomical Telescopes, Instruments, and Systems
We evaluate the single event tolerance of the x-ray silicon-on-insulator (SOI) pixel sensor named XRPIX, developed for the future x-ray astronomical satellite FORCE. In this work, we measure the cross-section of single event upset (SEU) of the shift register on XRPIX by irradiating heavy ion beams with linear energy transfer (LET) ranging from 0.022 to 68 MeV / (mg/cm2). From the SEU cross-section curve, the saturation cross-section and threshold LET are successfully obtained to be 3.4-0.9+2.9×10-10 cm2/bit and 7.3-3.5+1.9 MeV/(mg/cm2), respectively. Using these values, the SEU rate in orbit is estimated to be â‰2 0.1 event / year primarily due to the secondary particles induced by cosmic-ray protons. This SEU rate of the shift register on XRPIX is negligible in the FORCE orbit.
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A broadband X-ray imaging spectroscopy in the 2030s: the FORCE mission 査読あり 国際共著
Koji MORI, Ayaki TAKEDA
Proceedings of SPIE - The International Society for Optical Engineering 121812 1218122 2022年7月
記述言語：英語 掲載種別：研究論文（国際会議プロシーディングス）
DOI： 10.1117/12.2628772
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Kitajima M., Hagino K., Kohmura T., Hayashida M., Oono K., Negishi K., Yarita K., Doi T., Tsunomachi S., Tsuru T.G., Uchida H., Kayama K., Kodama R., Tanaka T., Mori K., Takeda A., Nishioka Y., Yukumoto M., Mieda K., Yonemura S., Ishida T., Arai Y., Kurachi I.
Journal of Astronomical Telescopes, Instruments, and Systems 8 ( 2 ) 2022年4月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Journal of Astronomical Telescopes, Instruments, and Systems
We have been developing the monolithic active pixel detector XRPIX onboard the future x-ray astronomical satellite FORCE. XRPIX is composed of complementary metal-oxide-semiconductor pixel circuits, SiO2 insulator, and Si sensor by utilizing the silicon-on-insulator (SOI) technology. When the semiconductor detector is operated in orbit, it suffers from radiation damage due to x-rays emitted from celestial objects as well as cosmic rays. From previous studies, positive charges trapped in the SiO2 insulator are known to cause degradation of the detector performance. To improve the radiation hardness, we developed XRPIX equipped with a double-SOI (D-SOI) structure, introducing an additional silicon layer in the SiO2 insulator. This structure is aimed at compensating for the effect of the trapped positive charges. Although the radiation hardness of the D-SOI detectors to cosmic rays has been evaluated, the radiation effect due to x-ray irradiation has not been evaluated. Thus, we then conduct an x-ray irradiation experiment using an x-ray generator with a total dose of 10 krad at the SiO2 insulator, equivalent to 7 years in orbit. As a result of this experiment, the energy resolution in full-width half maximum for the 5.9 keV x-ray degrades by 17.8 % ± 2.8 % and the dark current increases by 89 % ± 13 %. We also investigate the physical mechanism of the increase in the dark current due to x-ray irradiation using technology computer-Aided design simulation. It is found that the increase in the dark current can be explained by the increase in the interface state density at the Si / SiO2 interface.
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Detection of Recoil Electron Tracks using an SOI Pixel Sensor for an Advanced Compton Camera
Kagaya M., Katagiri H., Kato R., Tojo N., Takeda A., Shimazoe K., Tsuru T.G., Tanaka T., Uenomachi M., Zhang L.
2021 IEEE Nuclear Science Symposium and Medical Imaging Conference Record, NSS/MIC 2021 and 28th International Symposium on Room-Temperature Semiconductor Detectors, RTSD 2021年11月
記述言語：英語 掲載種別：研究論文（国際会議プロシーディングス） 出版者・発行元：2021 IEEE Nuclear Science Symposium and Medical Imaging Conference Record, NSS/MIC 2021 and 28th International Symposium on Room-Temperature Semiconductor Detectors, RTSD 2022
Sub-MeV line gamma-ray observations are important probes to elucidate various high-energy phenomena in astrophysics. An advanced Compton imaging technique is useful for detecting gamma rays in these bands. This camera can estimate an arrival direction of a gamma-ray event by event, thus, this camera can eliminate accidental events and false spots, which appear in a reconstructed image using a classical Compton camera. Furthermore, a semiconductor detector is essential for observing line gamma rays. In this study, we developed a prototype Compton camera using a silicon-on-insulator (SOI) pixel sensor. Using the prototype, we performed to detect recoil-electron tracks and estimated a recoil direction using a recoil-electron track. We succeeded in detecting electron tracks released from 511-keV gamma rays and estimating recoil directions. Furthermore, we reconstructed the arrival direction of a gamma ray and demonstrated to identify the source position by back-projection method. The angular resolution of an advanced Compton camera described two parameters, which is angular resolution measure (ARM) and scatter plane deviation (SPD). We obtained these tentative value from the reconstructed image. ARM and SPD are approximately 10° and 80-100°, respectively. For future plan, we will evaluate the quantitative detailed performances of the prototype under the various conditions.
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Proton radiation hardness of x-ray SOI pixel sensors with pinned depleted diode structure
Hayashida M., Hagino K., Kohmura T., Kitajima M., Yarita K., Oono K., Negishi K., Tsuru T.G., Tanaka T., Uchida H., Kayama K., Kodama R., Mori K., Takeda A., Nishioka Y., Hida T., Yukumoto M., Arai Y., Kurachi I., Kitamura H., Kawahito S., Yasutomi K.
Journal of Astronomical Telescopes, Instruments, and Systems 7 ( 3 ) 2021年7月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Journal of Astronomical Telescopes, Instruments, and Systems
X-ray silicon-on-insulator (SOI) pixel sensors, "XRPIX,"are being developed for the next-generation x-ray astronomical satellite, "FORCE."The XRPIX is fabricated with the SOI technology, which makes it possible to integrate a high-resistivity Si sensor and a low-resistivity Si complementary metal oxide semiconductor (CMOS) circuit. The CMOS circuit in each pixel is equipped with a trigger function, allowing us to read out outputs only from the pixels with x-ray signals at the timing of x-ray detection. This function thus realizes high throughput and high time resolution, which enables to employ anti-coincidence technique for background rejection. A new series of XRPIX named XRPIX6E developed with a pinned depleted diode (PDD) structure improves spectral performance by suppressing the interference between the sensor and circuit layers. When semiconductor x-ray sensors are used in space, their spectral performance is generally degraded owing to the radiation damage caused by high-energy protons. Therefore, before using an XRPIX in space, it is necessary to evaluate the extent of degradation of its spectral performance by radiation damage. Thus, we performed a proton irradiation experiment for XRPIX6E for the first time at Heavy Ion Medical Accelerator in Chiba in the National Institute of Radiological Sciences. We irradiated XRPIX6E with high-energy protons with a total dose of up to 40 krad, equivalent to 400 years of irradiation in orbit. The 40-krad irradiation degraded the energy resolution of XRPIX6E by 25 ± 3 %, yielding an energy resolution of 260.1 ± 5.6 eV at the full-width half maximum for 5.9 keV X-rays. However, the value satisfies the requirement for FORCE, 300 eV at 6 keV, even after the irradiation. It was also found that the PDD XRPIX has enhanced radiation hardness compared to previous XRPIX devices. In addition, we investigated the degradation of the energy resolution; it was shown that the degradation would be due to increasing energy-independent components, e.g., readout noise.
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Low-energy X-ray performance of SOI pixel sensors for astronomy, “XRPIX” 査読あり
Kodama R., Tsuru T.G., Tanaka T., Uchida H., Kayama K., Amano Y., Takeda A., Mori K., Nishioka Y., Yukumoto M., Hida T., Arai Y., Kurachi I., Kohmura T., Hagino K., Hayashida M., Kitajima M., Kawahito S., Yasutomi K., Kamehama H.
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 986 2021年1月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
We have been developing a new type of X-ray pixel sensors, “XRPIX”, allowing us to perform imaging spectroscopy in the wide energy band of 1–20keV for the future Japanese X-ray satellite “FORCE”. The XRPIX devices are fabricated with complementary metal-oxide-semiconductor silicon-on-insulator technology, and have the “Event-Driven readout mode”, in which only a hit event is read out by using hit information from a trigger output function equipped with each pixel. This paper reports on the low-energy X-ray performance of the “XRPIX6E” device with a Pinned Depleted Diode (PDD) structure. The PDD structure especially reduces the readout noise, and hence is expected to largely improve the quantum efficiencies for low-energy X-rays. While F-K X-rays at 0.68keV and Al-K X-rays at 1.5keV are successfully detected in the “Frame readout mode”, in which all pixels are read out serially without using the trigger output function, the device is able to detect Al-K X-rays, but not F-K X-rays in the Event-Driven readout mode. Non-uniformity is observed in the counts maps of Al-K X-rays in the Event-Driven readout mode, which is due to region-to-region variation of the pedestal voltages at the input to the comparator circuit. The lowest available threshold energy is 1.1keV for a small region in the device where the non-uniformity is minimized. The noise of the charge sensitive amplifier at the sense node and the noise related to the trigger output function are ∼18e− (rms) and ∼13e− (rms), respectively.
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Development of the detector simulation framework for the Wideband Hybrid X-ray Imager onboard FORCE 査読あり
Suzuki H., Tamba T., Odaka H., Bamba A., Hagino K., Takeda A., Mori K., Hida T., Yukumoto M., Nishioka Y., Tsuru T.G.
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 979 2020年11月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
© 2020 Elsevier B.V. FORCE is a Japan–US space-based astronomy mission for an X-ray imaging spectroscopy in an energy range of 1–80 keV. The Wideband Hybrid X-ray Imager (WHXI), which is the main focal plane detector, will use a hybrid semiconductor imager stack composed of silicon and cadmium telluride (CdTe). The silicon imager will be a certain type of the silicon-on-insulator (SOI) pixel sensor, named the X-ray pixel (XRPIX) series. Since the sensor has a small pixel size (30–36 μm) and a thick sensitive region (300–500 μm), understanding the detector response is not trivial and is important in order to optimize the camera design and to evaluate the scientific capabilities. We have developed a framework to simulate observations of celestial sources with semiconductor sensors. Our simulation framework was tested and validated by comparing our simulation results to laboratory measurements using the XRPIX 6H sensor. The simulator well reproduced the measurement results with reasonable physical parameters of the sensor including an electric field structure, a Coulomb repulsion effect on the carrier diffusion, and arrangement of the degraded regions. This framework is also applicable to future XRPIX updates including the one which will be part of the WHXI, as well as various types of semiconductor sensors.
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Radiation damage effects on double-SOI pixel sensors for X-ray astronomy 査読あり
Hagino K., Yarita K., Negishi K., Oono K., Hayashida M., Kitajima M., Kohmura T., Tsuru T.G., Tanaka T., Uchida H., Kayama K., Amano Y., Kodama R., Takeda A., Mori K., Nishioka Y., Yukumoto M., Hida T., Arai Y., Kurachi I., Hamano T., Kitamura H.
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 978 2020年10月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
© 2020 Elsevier B.V. The X-ray SOI pixel sensor onboard the FORCE satellite will be placed in the low earth orbit and will consequently suffer from the radiation effects mainly caused by geomagnetically trapped cosmic-ray protons. Based on previous studies on the effects of radiation on SOI pixel sensors, the positive charges trapped in the oxide layer significantly affect the performance of the sensor. To improve the radiation hardness of the SOI pixel sensors, we introduced a double-SOI (D-SOI) structure containing an additional middle Si layer in the oxide layer. The negative potential applied on the middle Si layer compensates for the radiation effects, due to the trapped positive charges. Although the radiation hardness of the D-SOI pixel sensors for applications in high-energy accelerators has been evaluated, radiation effects for astronomical application in the D-SOI sensors has not been evaluated thus far. To evaluate the radiation effects of the D-SOI sensor, we perform an irradiation experiment using a 6-MeV proton beam with a total dose of ∼5krad, corresponding to a few tens of years of in-orbit operation. This experiment indicates an improvement in the radiation hardness of the X-ray D-SOI devices. On using an irradiation of 5 krad on the D-SOI device, the energy resolution in the full-width half maximum for the 5.9-keV X-ray increases by 7±2%, and the chip output gain decreases by 0.35±0.09%. The physical mechanism of the gain degradation is also investigated; it is found that the gain degradation is caused by an increase in the parasitic capacitance due to the enlarged buried n-well.
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New pixel detector concept DuTiP for Belle II upgrade and the ILC with an SOI technology 査読あり
Ishikawa A., Arai Y., Baudot J., Haba J., Kachel M., Kurachi I., Li T., Ono S., Takayanagi T., Takeda A., Tsuboyama T., Yamada M.
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 978 2020年10月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
© 2020 Elsevier B.V. Belle II detector upgrade is being discussed aiming to collect five times larger integrated luminosity of 250 ab−1. The beam background level is expected five times higher than current design, thus a new pixel vertex detector with faster readout should be developed. We have invented a new pixel detector concept DuTiP for the Belle II upgrade which can be also used for the International Linear Collider (ILC) with small modifications. To realize the DuTiP concept, an SOI technology is chosen as a baseline with a pixel size of 35μm×35μm. The DuTiP concept and its application to a monolithic pixel detector in an SOI technology are explained.
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Proton radiation hardness of x-ray SOI pixel detectors with pinned depleted diode structure 査読あり
Hayashida M., Kohmura T., Hagino K., Oono K., Negishi K., Yarita K., Kitajima M., Tsuru T.G., Tanaka T., Uchida H., Kayama K., Kodama R., Mori K., Takeda A., Nishioka Y., Hida T., Yukumoto M., Arai Y., Kurachi I., Hamano T., Kitamura H., Kawahito S., Yasutomi K.
Proceedings of SPIE - The International Society for Optical Engineering 11454 2020年7月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Proceedings of SPIE - The International Society for Optical Engineering
We are developing an X-ray SOI pixel detector "XRPIX"for the next generation X-ray astronomical satellite "FORCE". XRPIX is the detector using SOI (Silicon-On-Insulator) technology which makes it possible to integrate a high-resistivity Si sensor part and a low-resistivity Si CMOS circuit part. The CMOS circuit is equipped with the trigger function, which can read out only the output signal of the pixel where the X-ray is incident. This function realizes high throughput and high time resolution, enabling the background rejection with anticoincidence technique. A new series of XRPIX named XRPIX6E, we developed, with a Pinned Depleted Diode (PDD) structure improves the spectral performance by suppressing the interference between the sensor layer and the circuit layer. When semiconductor X-ray detectors are used in space, it is known that their spectral performance is degraded due to radiation damage caused by high-energy protons. Therefore, before using XRPIX in space, it is necessary to evaluate how much the spectral performance will be degraded by radiation damage. Then we performed proton irradiation experiment for XRPIX6E for the first time at HIMAC in National Institute of Radiological Sciences. We irradiated XRPIX with high-energy protons up to a total dose of 40 krad, equivalent to 400 years irradiation in orbit. As a result, the energy resolution in full width half maximum at the 5:9 keV degrades by 25 ± 3%, however, is better than the required performance of FORCE, 300 eV at 6 keV. It was also found that the PDD structure XRPIX has better radiation hardness than the previous XRPIX series. In addition, We investigated about the degradation of the energy resolution; it was found that the degradation would be due to increasing energy independent components, for example, readout noise.
DOI： 10.1117/12.2562392
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Simulation study on SOI based electron tracking Compton camera using deep learning method 査読あり
Shimazoe K., Toyoda K., Uenomachi M., Yoshihara Y., Takahashi H., Takeda A.
Journal of Instrumentation 15 ( 2 ) 2020年2月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Journal of Instrumentation
© 2020 IOP Publishing Ltd and Sissa Medialab. Compton imaging is a promising method of sub MeV to a few MeV gamma-rays and expected to use in various application field, such as medical imaging, environmental monitoring and astrophysics. Several types of Compton camera has beed developed using different materials. One of the drawbacks in conventional Compton imaging is relatively low signal to background ratio caused by its projected Compton cones. Recoil electron tracking is one straight-forward way to improve the signal-to-background ratio, however, it is only realized in gaseous detectors. The realization of electron tracking in solid detectors is under investigation because of its short track in scatter materials. We demonstrated the capability of electron tracking in silicon-on-insulator (SOI) pixel detector with 30 μm pixels size. The extraction of ejected direction of recoil electrons in Compton scattering is an important problem. In this work, we investigated the use of deep learning for estimating the angle in plane and depth using Geant 4 Monte Carlo simulation. The effect of pixel size to the estimation accuracy and SPD is characterized for the application of actual silicon-on-insulator based SOI detectors. The imaging capability is also characterized using predicted recoil electron direction.
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Belle II 検出器アップグレードに向けたピクセル崩壊点検出器の要求性能の研究およびSOI技術を用いた設計
幅 淳二, 新井 康夫, 石川 明正, 小野 峻, 倉知 郁生, 武田 彩希, 高柳 武浩, 坪山 透, 山田 美帆
日本物理学会講演概要集 75.1 ( 0 ) 79 - 79 2020年
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軟X線/硬X線の広帯域を高感度観測する次世代衛星 FORCE：サイエンスとミッション提案の現状
中澤 知洋, 森 浩二, 鶴 剛, 上田 佳宏, 石田 学, 松本 浩典, 粟木 久光, 村上 弘志, 寺田 幸功, 久保田 あや, 馬場 彩, 小高 裕和, 谷津 陽一, 幸村 孝由, 萩野 浩一, 小林 翔悟, 内山 泰伸, 北山 哲, 高橋 忠幸, 渡辺 伸, 飯塚 亮, 山口 弘悦, 大橋 隆哉, 中嶋 大, 古澤 彰浩, 田中 孝明, 内田 裕之, 野田 博文, 常深 博, 伊藤 真之, 信川 正順, 信川 久実子, 太田 直美, 寺島 雄一, 深沢 泰司, 水野 恒史, 高橋 弘充, 大野 雅功, 武田 彩希, 岡島 崇, 他FORCE WG
日本物理学会講演概要集 75.1 523 - 523 2020年
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Development of integration-type silicon-on-insulator monolithic pixel detectors using a float zone silicon 査読あり
Mitsui S., Arai Y., Miyoshi T., and Takeda A.
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 2019年11月
記述言語：英語 掲載種別：研究論文（学術雑誌）
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Sub-pixel response of double-SOI pixel sensors for X-ray astronomy 査読あり
Hagino K., Negishi K., Oono K., Yarita K., Kohmura T., Tsuru T., Tanaka T., Harada S., Kayama K., Matsumura H., Mori K., Takeda A., Nishioka Y., Yukumoto M., Fukuda K., Hida T., Arai Y., Kurachi I., and Kishimoto S.
Journal of Instrumentation 2019年10月
記述言語：英語 掲載種別：研究論文（学術雑誌）
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Measurement of Charge Cloud Size in X-Ray SOI Pixel Sensors 査読あり
Hagino K., Oono K., Negishi K., Yarita K., Kohmura T., Tsuru T., Tanaka T., Uchida H., Harada S., Okuno T., Kayama K., Amano Y., Matsumura H., Mori K., Takeda A., Nishioka Y., Fukuda K., Hida T., Yukumoto M., Arai Y., Kurachi I., Miyoshi T., Kishimoto S.
IEEE Transactions on Nuclear Science 66 ( 7 ) 1897 - 1905 2019年7月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：IEEE Transactions on Nuclear Science
© 1963-2012 IEEE. We report on a measurement of the size of charge clouds produced by X-ray photons in X-ray Silicon-on-insulator (SOI) pixel sensor named XRPIX. We carry out a beam scanning experiment of XRPIX using a monochromatic X-ray beam at 5.0 keV collimated to 10 μm with a 4-μmφ pinhole and obtain the spatial distribution of single-pixel events at a subpixel scale. The standard deviation of charge clouds of 5.0-keV X-ray is estimated to be σcloud=4.30± 0.07μm. Compared to the detector response simulation, the estimated charge cloud size is well explained by a combination of photoelectron range, thermal diffusion, and Coulomb repulsion. Moreover, by analyzing the fraction of multi-pixel events in various energies, we find that the energy dependence of the charge cloud size is also consistent with the simulation.
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Kayama K., Tsuru T., Tanaka T., Uchida H., Harada S., Okuno T., Amano Y., Hiraga J., Yoshida M., Kamata Y., Sakuma S., Yuhi D., Urabe Y., Tsunemi H., Matsumura H., Kawahito S., Kagawa K., Yasutomi K., Shrestha S., Nakanishi S., Kamehama H., Arai Y., Kurachi I., Takeda A., Mori K., Nishioka Y., Fukuda K., Hida T., Yukumoto M., Kohmura T., Hagino K., Oono K., Negishi K., Yarita K.
Journal of Instrumentation 14 ( 6 ) 2019年6月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Journal of Instrumentation
© 2019 IOP Publishing Ltd and Sissa Medialab. We have been developing a monolithic active pixel sensor, "XRPIX", for the Japan led future X-ray astronomy mission "FORCE" observing the X-ray sky in the energy band of 1-80 keV with angular resolution of better than 15′′. XRPIX is an upper part of a stack of two sensors of an imager system onboard FORCE, and covers the X-ray energy band lower than 20 keV . The XRPIX device consists of a fully depleted high-resistivity silicon sensor layer for X-ray detection, a low resistivity silicon layer for CMOS readout circuit, and a buried oxide layer in between, which is fabricated with 0.2 μm CMOS silicon-on-insulator (SOI) technology. Each pixel has a trigger circuit with which we can achieve a 10 μs time resolution, a few orders of magnitude higher than that with X-ray astronomy CCDs. We recently introduced a new type of a device structure, a pinned depleted diode (PDD), in the XRPIX device, and succeeded in improving the spectral performance, especially in a readout mode using the trigger function. In this paper, we apply a mesh experiment to the XRPIX devices for the first time in order to study the spectral response of the PDD device at the subpixel resolution. We confirmed that the PDD structure solves the significant degradation of the charge collection efficiency at the pixel boundaries and in the region under the pixel circuits, which is found in the single SOI structure, the conventional type of the device structure. On the other hand, the spectral line profiles are skewed with low energy tails and the line peaks slightly shift near the pixel boundaries, which contribute to a degradation of the energy resolution.
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Evaluation of Kyoto's event-driven X-ray astronomical SOI pixel sensor with a large imaging area 査読あり
Hayashi H., Tsuru T., Tanaka T., Uchida H., Matsumura H., Tachibana K., Harada S., Takeda A., Mori K., Nishioka Y., Takebayashi N., Yokoyama S., Fukuda K., Arai Y., Kurachi I., Kawahito S., Kagawa K., Yasutomi K., Shrestha S., Nakanishi S., Kamehama H., Kohmura T., Hagino K., Negishi K., Oono K., Yarita K.
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 924 400 - 403 2019年4月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
© 2018 We have been developing monolithic active pixel sensors, named “XRPIX” based on the silicon-on-insulator (SOI) pixel technology for future X-ray astronomy satellites. XRPIX has the function of event trigger and hit address outputs. This function allows us to read out analog signals only of hit pixels on trigger timing, which is referred to as the event-driven readout mode. Recently, we processed “XRPIX5b” with the largest imaging area of 21.9 mm × 13.8 mm in the XRPIX series. X-ray spectra are successfully obtained from all the pixels, and the readout noise is 46 e − (rms) in the frame readout mode. The gain variation was measured to be 1.2% (FWHM) among the pixels. We successfully obtain the X-ray image in the event-driven readout mode.