研究者業績
基本情報
- 所属
- 国立研究開発法人宇宙航空研究開発機構 宇宙科学研究所 宇宙物理学研究系 准教授
- 学位
- 博士(理学)(2004年3月 東京大学)
- 研究者番号
- 60446599
- ORCID ID
https://orcid.org/0000-0003-0441-7404- J-GLOBAL ID
- 202001021434500706
- researchmap会員ID
- R000012970
研究キーワード
6経歴
2-
2022年3月 - 現在
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2006年7月 - 2022年2月
学歴
3-
2001年4月 - 2004年3月
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1999年4月 - 2001年3月
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1995年4月 - 1999年3月
受賞
2主要な論文
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Publications of the Astronomical Society of Japan 70(6) 2018年10月1日 査読有り責任著者We present the results from the Hitomi Soft Gamma-ray Detector (SGD) observation of the Crab nebula. The main part of SGD is a Compton camera, which in addition to being a spectrometer, is capable of measuring polarization of gamma-ray photons. The Crab nebula is one of the brightest X-ray / gamma-ray sources on the sky, and, the only source from which polarized X-ray photons have been detected. SGD observed the Crab nebula during the initial test observation phase of Hitomi. We performed the data analysis of the SGD observation, the SGD background estimation and the SGD Monte Carlo simulations, and, successfully detected polarized gamma-ray emission from the Crab nebula with only about 5 ks exposure time. The obtained polarization fraction of the phase-integrated Crab emission (sum of pulsar and nebula emissions) is (22.1 $\pm$ 10.6)% and, the polarization angle is 110.7$^o$ + 13.2 / $-$13.0$^o$ in the energy range of 60--160 keV (The errors correspond to the 1 sigma deviation). The confidence level of the polarization detection was 99.3%. The polarization angle measured by SGD is about one sigma deviation with the projected spin axis of the pulsar, 124.0$^o$ $\pm$0.1$^o$.
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Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 765 192-201 2015年9月2日 査読有り筆頭著者責任著者The Soft Gamma-ray Detector (SGD) is one of the instrument payloads onboard ASTRO-H, and will cover a wide energy band (60--600 keV) at a background level 10 times better than instruments currently in orbit. The SGD achieves low background by combining a Compton camera scheme with a narrow field-of-view active shield. The Compton camera in the SGD is realized as a hybrid semiconductor detector system which consists of silicon and cadmium telluride (CdTe) sensors. The design of the SGD Compton camera has been finalized and the final prototype, which has the same configuration as the flight model, has been fabricated for performance evaluation. The Compton camera has overall dimensions of 12 cm x 12 cm x 12 cm, consisting of 32 layers of Si pixel sensors and 8 layers of CdTe pixel sensors surrounded by 2 layers of CdTe pixel sensors. The detection efficiency of the Compton camera reaches about 15% and 3% for 100 keV and 511 keV gamma rays, respectively. The pixel pitch of the Si and CdTe sensors is 3.2 mm, and the signals from all 13312 pixels are processed by 208 ASICs developed for the SGD. Good energy resolution is afforded by semiconductor sensors and low noise ASICs, and the obtained energy resolutions with the prototype Si and CdTe pixel sensors are 1.0--2.0 keV (FWHM) at 60 keV and 1.6--2.5 keV (FWHM) at 122 keV, respectively. This results in good background rejection capability due to better constraints on Compton kinematics. Compton camera energy resolutions achieved with the final prototype are 6.3 keV (FWHM) at 356 keV and 10.5 keV (FWHM) at 662 keV, respectively, which satisfy the instrument requirements for the SGD Compton camera (better than 2%). Moreover, a low intrinsic background has been confirmed by the background measurement with the final prototype.
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IEEE Transactions on Nuclear Science 56(3) 777-782 2008年11月4日 査読有り筆頭著者責任著者We developed CdTe double-sided strip detectors (DSDs or cross strip detectors) and evaluated their spectral and imaging performance for hard X-rays and gamma-rays. Though the double-sided strip configuration is suitable for imagers with a fine position resolution and a large detection area, CdTe diode DSDs with indium (In) anodes have yet to be realized due to the difficulty posed by the segmented In anodes. CdTe diode devices with aluminum (Al) anodes were recently established, followed by a CdTe device in which the Al anodes could be segmented into strips. We developed CdTe double-sided strip devices having Pt cathode strips and Al anode strips, and assembled prototype CdTe DSDs. These prototypes have a strip pitch of 400 micrometer. Signals from the strips are processed with analog ASICs (application specific integrated circuits). We have successfully performed gamma-ray imaging spectroscopy with a position resolution of 400 micrometer. Energy resolution of 1.8 keV (FWHM: full width at half maximum) was obtained at 59.54 keV. Moreover, the possibility of improved spectral performance by utilizing the energy information of both side strips was demonstrated. We designed and fabricated a new analog ASIC, VA32TA6, for the readout of semiconductor detectors, which is also suitable for DSDs. A new feature of the ASIC is its internal ADC function. We confirmed this function and good noise performance that reaches an equivalent noise charge of 110 e- under the condition of 3-4 pF input capacitance.
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Astrophysical Journal 651(1 I) 421-437 2006年7月3日 査読有り筆頭著者責任著者We present results from quantitative modeling and spectral analysis of the high mass X-ray binary Vela X-1 obtained with the Chandra HETGS. The spectra exhibit emission lines from H-like and He-like ions driven by photoionization, as well as fluorescent emission lines from several elements in lower charge states. In order to interpret and make full use of the high-quality data, we have developed a simulator, which calculates the ionization and thermal structure of a stellar wind photoionized by an X-ray source, and performs Monte Carlo simulations of X-ray photons propagating through the wind. The emergent spectra are then computed as a function of the viewing angle accurately accounting for photon transport in three dimensions including dynamics. From comparisons of the observed spectra with the simulation results, we are able to find the ionization structure and the geometrical distribution of material in Vela X-1 that can reproduce the observed spectral line intensities and continuum shapes at different orbital phases remarkably well. It is found that a large fraction of X-ray emission lines from highly ionized ions are formed in the region between the neutron star and the companion star. We also find that the fluorescent X-ray lines must be produced in at least three distinct regions --(1)the extended stellar wind, (2)reflection off the stellar photosphere, and (3)in a distribution of dense material partially covering and possibly trailing the neutron star, which may be associated with an accretion wake. Finally, from detailed analysis of the emission lines, we demonstrate that the stellar wind is affected by X-ray photoionization.
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IEEE Transactions on Nuclear Science 52(5 III) 2045-2051 2005年10月 査読有り筆頭著者責任著者We are developing a Compton camera based on Si and CdTe semiconductor imaging devices with high energy resolution. In this paper, results from the most recent prototype are reported. The Compton camera consists of six layered double-sided Si Strip detectors and CdTe pixel detectors, which are read out with low noise analog ASICs, VA32TAs. We obtained Compton reconstructed images and spectra of line gamma-rays from 122 keV to 662 keV. The energy resolution is 9.1 keV and 14 keV at 356 keV and 511 keV, respectively. © 2005 IEEE.
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Astrophysical Journal 597(1 II) 2003年9月12日 査読有り筆頭著者責任著者We report the detection of a fully-resolved, Compton-scattered emission line in the X-ray spectrum of the massive binary GX 301-2 obtained with the High Energy Transmission Grating Spectrometer onboard the Chandra X-ray Observatory. The iron K-alpha fluorescence line complex observed in this system consists of an intense narrow component centered at an energy of E = 6.40 keV and a redward shoulder that extends down to ~6.24 keV, which corresponds to an energy shift of a Compton back-scattered iron K-alpha photon. From detailed Monte Carlo simulations and comparisons with the observed spectra, we are able to directly constrain the physical properties of the scattering medium, including the electron temperature and column density, as well as an estimate for the metal abundance.
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IEEE Transactions on Nuclear Science 48(4 I) 950-959 2001年7月20日 査読有りCadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe) have been regarded as promising semiconductor materials for hard X-ray and Gamma-ray detection. The high atomic number of the materials (Z_{Cd} =48, Z_{Te} =52) gives a high quantum efficiency in comparison with Si. The large band-gap energy (Eg ~ 1.5 eV) allows us to operate the detector at room temperature. However, a considerable amount of charge loss in these detectors produces a reduced energy resolution. This problem arises due to the low mobility and short lifetime of holes. Recently, significant improvements have been achieved to improve the spectral properties based on the advances in the production of crystals and in the design of electrodes. In this overview talk, we summarize (1) advantages and disadvantages of CdTe and CdZnTe semiconductor detectors and (2) technique for improving energy resolution and photopeak efficiencies. Applications of these imaging detectors in future hard X-ray and Gamma-ray astronomy missions are briefly discussed.
MISC
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Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023) 2023年8月18日
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Space Telescopes and Instrumentation 2022: Ultraviolet to Gamma Ray 2022年8月31日
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Space Telescopes and Instrumentation 2022: Ultraviolet to Gamma Ray 2022年8月31日
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Space Telescopes and Instrumentation 2022: Ultraviolet to Gamma Ray 2022年8月31日
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Journal of Astronomical Telescopes, Instruments, and Systems 7(03) 2021年7月1日
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Space Telescopes and Instrumentation 2020: Ultraviolet to Gamma Ray 2020年12月13日
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電気学会研究会資料. ECT = The papers of technical meeting on electronic circuits, IEE Japan / 電子回路研究会 [編] 2020(55-58) 1-4 2020年9月17日
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Proceedings of SPIE - The International Society for Optical Engineering 11444 2020年© 2020 SPIE The X-Ray Imaging and Spectroscopy Mission (XRISM) is the successor to the 2016 Hitomi mission that ended prematurely. Like Hitomi, the primary science goals are to examine astrophysical problems with precise high-resolution X-ray spectroscopy. XRISM promises to discover new horizons in X-ray astronomy. XRISM carries a 6 x 6 pixelized X-ray micro-calorimeter on the focal plane of an X-ray mirror assembly and a co-aligned X-ray CCD camera that covers the same energy band over a large field of view. XRISM utilizes Hitomi heritage, but all designs were reviewed. The attitude and orbit control system were improved in hardware and software. The number of star sensors were increased from two to three to improve coverage and robustness in onboard attitude determination and to obtain a wider field of view sun sensor. The fault detection, isolation, and reconfiguration (FDIR) system was carefully examined and reconfigured. Together with a planned increase of ground support stations, the survivability of the spacecraft is significantly improved.
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Proceedings of SPIE - The International Society for Optical Engineering 11444 2020年© 2020 SPIE The X-Ray Imaging and Spectroscopy Mission, XRISM, is currently scheduled to launch in 2022 with the objective of building on the brief, but significant, successes of the ASTRO-H (Hitomi) mission in solving outstanding astrophysical questions using high resolution X-ray spectroscopy. The XRISM Science Operations Team (SOT) consists of the JAXA-led Science Operations Center (SOC) and NASA-led Science Data Center (SDC), which work together to optimize the scientific output from the Resolve high-resolution spectrometer and the Xtend wide-field imager through planning and scheduling of observations, processing and distribution of data, development and distribution of software tools and the calibration database (CaldB), support of ground and in-flight calibration, and support of XRISM users in their scientific investigations of the energetic universe. Here, we summarize the roles and responsibilities of the SDC and its current status and future plans. The Resolve instrument poses particular challenges due to its unprecedented combination of high spectral resolution and throughput, broad spectral coverage, and relatively small field-of-view and large pixel-size. We highlight those challenges and how they are being met.
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Proceedings of SPIE - The International Society for Optical Engineering 11444 2020年© 2020 SPIE The XRISM is the X-ray astronomical mission led by JAXA/NASA/ESA with international participation, plan to be launched in 2022 (Japanese fiscal year), to quickly recover the high-resolution X-ray spectroscopy of astrophysical objects using the micro-calorimeter array after the failure of Hitomi. To enhance the scientific outputs of the mission, the Science Operations Team (SOT) is structured independently from the instrument teams and the mission operation team (MOT). The responsibilities of the SOT are summarized into four categories: 1) Guest observer program and data distributions, 2) Distribution of the analyses software and calibration database, 3) Guest observer supporting activities, and 4) the performance verification and optimization (PVO) activities. Before constructing the Operations Concept of the XRISM mission, the lessons on the Science Operations learned from the past Japanese X-ray missions (ASCA, Suzaku, and Hitomi) are reviewed, and 16 kinds of lessons are identified by the above categories: lessons on the importance of avoiding nonpublic (“animal”) tools, coding quality of public tools both on the engineering viewpoint and the calibration accuracy, tight communications with instrument teams and operations team, well-defined task division between scientists and engineers etc. Among these lessons, a) importance of the early preparations of the operations from the ground stage, b) construction of the independent team for the Science Operations from the instrument developments, and c) operations with well-defined duties by appointed members are recognized as the key lessons for XRISM. Then, i) the task division between the Mission and Science Operations and ii) the subgroup structure within the XRISM team are defined in detail as the XRISM Operations Concept. Then, following the Operations Concept, the detail plan of the Science Operations is designed as follows. The Science Operations tasks are shared among Japan, US, and Europe operated by three centers, the Science Operations Center (SOC) at JAXA, the Science Data Center (SDC) at NASA, and European Space Astronomy Centre (ESAC) at ESA. The SOT is defined as a combination of the SOC and SDC; the SOC is designed to perform tasks close to the spacecraft operations, such as spacecraft planning of science targets, quick-look health checks, pre-pipeline data processing, etc., and the SDC covers the tasks on the data calibration processing (pipeline processing), maintenance of the analysis tools etc. The data-archive and users-support activities are planned to be covered both by the SOC and SDC. Finally, the details of the Science Operations tasks and the tools for the Science Operations are also described in this paper. This information would be helpful for a construction of Science Operations of future X-ray missions.
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Proceedings of SPIE - The International Society for Optical Engineering 10699 2018年© 2018 SPIE. The ASTRO-H mission was designed and developed through an international collaboration of JAXA, NASA, ESA, and the CSA. It was successfully launched on February 17, 2016, and then named Hitomi. During the in-orbit verification phase, the on-board observational instruments functioned as expected. The intricate coolant and refrigeration systems for soft X-ray spectrometer (SXS, a quantum micro-calorimeter) and soft X-ray imager (SXI, an X-ray CCD) also functioned as expected. However, on March 26, 2016, operations were prematurely terminated by a series of abnormal events and mishaps triggered by the attitude control system. These errors led to a fatal event: the loss of the solar panels on the Hitomi mission. The X-ray Astronomy Recovery Mission (or, XARM) is proposed to regain the key scientific advances anticipated by the international collaboration behind Hitomi. XARM will recover this science in the shortest time possible by focusing on one of the main science goals of Hitomi,"Resolving astrophysical problems by precise high-resolution X-ray spectroscopy".1 This decision was reached after evaluating the performance of the instruments aboard Hitomi and the mission's initial scientific results, and considering the landscape of planned international X-ray astrophysics missions in 2020's and 2030's. Hitomi opened the door to high-resolution spectroscopy in the X-ray universe. It revealed a number of discrepancies between new observational results and prior theoretical predictions. Yet, the resolution pioneered by Hitomi is also the key to answering these and other fundamental questions. The high spectral resolution realized by XARM will not offer mere refinements; rather, it will enable qualitative leaps in astrophysics and plasma physics. XARM has therefore been given a broad scientific charge: "Revealing material circulation and energy transfer in cosmic plasmas and elucidating evolution of cosmic structures and objects". To fulfill this charge, four categories of science objectives that were defined for Hitomi will also be pursued by XARM; these include (1) Structure formation of the Universe and evolution of clusters of galaxies; (2) Circulation history of baryonic matters in the Universe; (3) Transport and circulation of energy in the Universe; (4) New science with unprecedented high resolution X-ray spectroscopy. In order to achieve these scientific objectives, XARM will carry a 6 × 6 pixelized X-ray micro-calorimeter on the focal plane of an X-ray mirror assembly, and an aligned X-ray CCD camera covering the same energy band and a wider field of view. This paper introduces the science objectives, mission concept, and observing plan of XARM.
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放射線 = Ionizing radiation 43(3) 103-106 2017年12月
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日本物理学会講演概要集 72 508-508 2017年<p>NGHXTあらため、FORCE衛星は1-80 keVの広帯域X線を高感度で撮像分光し、まだ見ぬ隠されたブラックホールや超新星残骸のフィラメントでの粒子加速の探査を目指している。2016年に変更した計画の内容、検出器および望遠鏡の開発状況、およびサイエンス検討の進捗を報告する。</p>
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第17回宇宙科学シンポジウム 講演集 = Proceedings of the 17th Space Science Symposium 2017年1月第17回宇宙科学シンポジウム (2017年1月5日-6日. 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)相模原キャンパス), 相模原市, 神奈川県著者人数: 56名ほか (JAXA staff: Ishida, Manabu ; Kokubun, Motohide ; Watanabe, Shin ; Iizuka, Ryo ; Ohta, Masayuki ; Sato, Rie ; Takahashi, Tadayuki ; Hagino, Koichi ; Harayama, Atsushi ; Maeda, Yoshitomo)資料番号: SA6000060046レポート番号: P-004
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日本物理学会講演概要集 71 372-372 2016年<p>2016年2月に打ち上げられた「ひとみ(ASTRO-H)」衛星搭載の硬X線及び軟ガンマ線検出器における徹底したバックグラウンド除去を担うBGOアクティブシールドについて、およそ2週間の衛星軌道上運用において計72ユニット全てのシールド系を問題なく動作させることに成功した。バックグラウンド除去機能や突発天体観測機能などの全ての機能も想定通り動作しており、本講演で衛星軌道上において実証された性能について報告する。</p>
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日本物理学会講演概要集 71 374-374 2016年<p>軟ガンマ線検出器(Soft Gamma-ray Detector、SGD)は、コンプトン運動学と反同時係数法を組み合わせることで、徹底的な低バックグラウンド化による高感度観測を目的とした検出器である。SGDで正確なスペクトル測定を実現するためには、搭載している集積回路のトリガー性能を評価し、ガンマ線検出効率のエネルギー依存性を較正する必要がある。本講演では、SGDの試験データを用い、トリガー性能を評価した結果について報告する。</p>
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日本物理学会講演概要集 71 370-370 2016年<p>本年2月17日に打ち上げられ3月26日に通信途絶したX線天文衛星「ひとみ」には、5-80 keVを2分角で撮像分光する硬X線撮像検出器(HXI)が搭載されていた。打ち上げ後、伸展式光学ベンチの展開を経て、3月8日よりHXI検出器の立ち上げを始めた。3月14日は2台のHXIが立ち上がり、観測を開始した。軌道上での性能は、エネルギー分解能を含め地上試験と一致し、無事に立ち上げに成功した。天体の撮像とスペクトルも取得できている。軌道上のバックグラウンドも40 keV以下ではほぼ期待通りの性能を発揮した。この結果について報告する。</p>
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日本物理学会講演概要集 71 371-371 2016年<p>2016年2月17日に打ち上げられたX線衛星「ひとみ」(ASTRO-H)に搭載された軟ガンマ線検出器(Soft Gamma-ray Detector:SGD)の軌道動作実績について報告する。SGDは、3月15日より順次、センサーの立ち上げを行い、通信途絶となった3月26日まで、機能的には正常に動作させることができた。一部の天体からのガンマ線信号の取得に成功し、高感度ガンマ線観測を行う上で重要となる軌道上バックグランドのデータを得た。SGDで初めて実現したSi/CdTe半導体コンプトンカメラで得られたこれらのデータについて、報告を行う。</p>
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日本物理学会講演概要集 71 373-373 2016年<p>2016年2月に打ち上げられたX線天文衛星「ひとみ(ASTRO-H)」に搭載された軟ガンマ線検出器(SGD)の主検出器はコンプトンカメラである。これまでに、実験による性能評価の一方で、シミュレーションによる検出器応答の作成が行われた。検出器の応答は、バックグラウンドや入射光子の偏光の影響を受ける。2015年11月に行われたSPring-8偏光ビーム試験の結果を含めて、本講演ではSGDコンプトンカメラの検出器応答について報告する。</p>
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Proceedings of SPIE - The International Society for Optical Engineering 9905 2016年© 2016 SPIE. The Large Observatory For x-ray Timing (LOFT) is a mission concept which was proposed to ESA as M3 and M4 candidate in the framework of the Cosmic Vision 2015-2025 program. Thanks to the unprecedented combination of effective area and spectral resolution of its main instrument and the uniquely large field of view of its wide field monitor, LOFT will be able to study the behaviour of matter in extreme conditions such as the strong gravitational field in the innermost regions close to black holes and neutron stars and the supra-nuclear densities in the interiors of neutron stars. The science payload is based on a Large Area Detector (LAD, >8m2 effective area, 2-30 keV, 240 eV spectral resolution, 1 degree collimated field of view) and a Wide Field Monitor (WFM, 2-50 keV, 4 steradian field of view, 1 arcmin source location accuracy, 300 eV spectral resolution). The WFM is equipped with an on-board system for bright events (e.g., GRB) localization. The trigger time and position of these events are broadcast to the ground within 30 s from discovery. In this paper we present the current technical and programmatic status of the mission.
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Proceedings of SPIE - The International Society for Optical Engineering 9905 2016年© 2016 SPIE. The Soft Gamma-ray Detector (SGD) is one of science instruments onboard ASTRO-H (Hitomi) and features a wide energy band of 60{600 keV with low backgrounds. SGD is an instrument with a novel concept of "Narrow field-of-view" Compton camera where Compton kinematics is utilized to reject backgrounds which are inconsistent with the field-of-view defined by the active shield. After several years of developments, the flight hardware was fabricated and subjected to subsystem tests and satellite system tests. After a successful ASTRO-H (Hitomi) launch on February 17, 2016 and a critical phase operation of satellite and SGD in-orbit commissioning, the SGD operation was moved to the nominal observation mode on March 24, 2016. The Compton cameras and BGO-APD shields of SGD worked properly as designed. On March 25, 2016, the Crab nebula observation was performed, and, the observation data was successfully obtained.
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Proceedings of SPIE - The International Society for Optical Engineering 9905 2016年© 2016 SPIE. Hitomi X-ray observatory launched in 17 February 2016 had a hard X-ray imaging spectroscopy system made of two hard X-ray imagers (HXIs) coupled with two hard X-ray telescopes (HXTs). With 12 m focal length, they provide fine (2′ half-power diameter; HPD) imaging spectroscopy at 5 to 80 keV. The HXI main imagers are made of 4 layers of Si and a CdTe semiconductor double-sided strip detectors, stacked to enhance detection efficiency as well as to enable photon interaction-depth sensing. Active shield made of 9 BGO scintillators surrounds the imager to provide with low background. Following the deployment of the Extensible Optical Bench (EOB) on 28 February, the HXI was gradually turned on. Two imagers successfully started observation on 14 March, and was operational till the incident lead to Hitomo loss, on 26 March. All detector channels, 1280 ch of imager and 11 channel of active shields and others each, worked well and showed performance consistent with those seen on ground. From the first light observation of G21.5-0.9 and the following Crab observations, 5-80 keV energy coverage and good detection efficiency were confirmed. With blank sky observations, we checked our background level. In some geomagnetic region, strong background continuum, presumably caused by trapped electron with energy ∼100 keV, is seen. But by cutting the high-background time-intervals, the background became significantly lower, typically with 1-3 × 10-4 counts s-1 keV-1 cm-2 (here cm2 is shown with detector geometrical area). Above 30 keV, line and continuum emission originating from activation of CdTe was significantly seen, though the level of 1-4 × 10-4 counts s-1 keV-1 cm-2 is still comparable to those seen in NuSTAR. By comparing the effective area and background rate, preliminary analysis shows that the HXI had a statistical sensitivity similar to NuSTAR for point sources, and more than twice better for largely extended sources.
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Proceedings of SPIE - The International Society for Optical Engineering 9905 2016年© 2016 SPIE. The Focusing Optics X-ray Solar Imager (FOXSI) is, in its initial form, a sounding rocket experiment designed to apply the technique of focusing hard X-ray (HXR) optics to the study of fundamental questions about the high-energy Sun. Solar HXRs arise via bremsstrahlung from energetic electrons and hot plasma produced in solar flares and thus are one of the most direct diagnostics of are-accelerated electrons and the impulsive heating of the solar corona. Previous missions have always been limited in sensitivity and dynamic range by the use of indirect (Fourier) imaging due to the lack of availability of direct focusing optics, but technological advances now make direct focusing accessible in the HXR regime (as evidenced by the NuSTAR spacecraft and several suborbital missions). The FOXSI rocket experiment develops and optimizes HXR focusing telescopes for the unique scientific requirements of the Sun. To date, FOXSI has completed two successful flights on 2012 November 02 and 2014 December 11 and is funded for a third flight. This paper gives a brief overview of the experiment, which is sensitive to solar HXRs in the 4-20 keV range, describes its first two flights, and gives a preview of plans for FOXSI-3.
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Proceedings of SPIE - The International Society for Optical Engineering 9968 2016年© SPIE 2016. We studied a surface effect of Double-sided Si Strip Detectors (DSSDs) in order to apply it for imaging spectroscopy of X-ray photons down to 5 keV for the first time. The Japanese cosmic X-ray satellite Hitomi, launched in February 2016, is equipped with the Hard X-ray Imager (HXI), which employs the DSSDs in 5-80 keV. In such a low energy band, the surface effect is non-negligible. When interstrip regions of p-side are irradiated, the DSSD sometimes show signals with negative pulse heights, presumably caused by positive surface charges between Si and SiO2 layers.1{5 The effect modifies the X-ray response of the HXI towards its low-energy end, below ∼ 10 keV. By irradiating the DSSD with uncollimated mono-energetic X-rays of different energies, we measured the fraction of the negative events to be 2% at 26.4 keV and 30% at 6.0 keV. Using an 8 keV colli- mated X-ray beam, we directly verified that the negative events originated from the interstrip gaps on the p-side where the SiO2 layers exist. The measured energy- and position- dependences can be modeled by assuming that the negative events are produced in approximately 25 μm deep and 120 μm wide interstrip regions. When the bias voltage are halved (from 350 V to 180 V), fraction of the negative events increased by a factor of ∼ 1:7, qualitatively consistent with this picture.
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IPAC 2016 - Proceedings of the 7th International Particle Accelerator Conference 2719-2721 2016年Copyright © 2016 CC-BY-3.0 and by the respective authors. Mitsubishi heavy Industries, Ltd. (MHI) released the ASTROCAM 7000HS, a radioactive substance visualization camera. The ASTROCAM 7000HS incorporates the technologies for the gamma-ray detector used for the ASTRO-H satellite, which MHI has been developing under entrustment from and together with scientists at the Institute of Space and Astronautical Science (ISAS) at the Japan Aerospace Exploration Agency (JAXA), and the design was modified for use on land to commercialize the product [1]. MHI and Mitsubishi Heavy Industries Mechatronics Systems, Ltd. (MHI-MS) performed on-site residual radiation measurements at the 50 GeV Main Ring (MR) of the Japan Proton Accelerator Research Complex (J-PARC) under collaboration with the High Energy Accelerator Research Organization (KEK) and the Japan Atomic Energy Agency (JAEA) and succeeded visualization of radiation hot spots of the accelerator components. The outline of the ASTROCAM 7000HS, the measurement principle and the first measurement results at the JPARC MR are described.
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Proceedings of SPIE - The International Society for Optical Engineering 9905 2016年© 2016 SPIE. We have developed a compact hard X-ray imaging system composed of a cadmium telluride double-sided strip detector (CdTe-DSD) and a coded mask. We investigate the imaging performance using two different coded masks with different sizes and patterns. In our system, a CdTe-DSD of pitch 250μm is used in conjunction with a coded mask is placed 70-100 mm above the detector to form a compact imaging system. We obtained an angular resolution of up to 11.8 arc min, as measured from gamma-ray lines of point-like radioactive isotope sources. This is consistent with that expected from the geometry. The energy resolution is 1.7 keV (FWHM) at 60 keV and the energy range of imaging is from 5 keV to 122 keV. These results agree very well with Monte Carlo simulations of the detector.
講演・口頭発表等
93共同研究・競争的資金等の研究課題
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