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 太陽系科学研究系 助教
- 学位
- 修士(理学)(東京大学)博士(理学)(東京大学)
- J-GLOBAL ID
- 201901006861784502
- researchmap会員ID
- B000359529
研究分野
1経歴
5-
2010年4月 - 現在
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2007年9月 - 2010年3月
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2007年4月 - 2007年8月
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2006年4月 - 2007年3月
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2003年4月 - 2006年3月
学歴
3-
2003年4月 - 2006年3月
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2001年4月 - 2003年3月
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- 2001年3月
委員歴
1-
2008年 - 2010年
論文
86-
Journal of Geophysical Research: Space Physics 2024年11月
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Journal of Geophysical Research: Space Physics 129(11) 2024年10月28日Abstract Near‐equatorial measurements of energetic electron fluxes, in combination with numerical simulation, are widely used for monitoring of the radiation belt dynamics. However, the long orbital periods of near‐equatorial spacecraft constrain the cadence of observations to once per several hours or greater, that is, much longer than the mesoscale injections and rapid local acceleration and losses of energetic electrons of interest. An alternative approach for radiation belt monitoring is to use measurements of low‐altitude spacecraft, which cover, once per hour or faster, the latitudinal range of the entire radiation belt within a few minutes. Such an approach requires, however, a procedure for mapping the flux from low equatorial pitch angles (near the loss cone) as measured at low altitude, to high equatorial pitch angles (far from the loss cone), as necessitated by equatorial flux models. Here we do this using the high energy resolution ELFIN measurements of energetic electrons. Combining those with GPS measurements we develop a model for the electron anisotropy coefficient, , that describes electron flux dependence on equatorial pitch‐angle, , . We then validate this model by comparing its equatorial predictions from ELFIN with in‐situ near‐equatorial measurements from Arase (ERG) in the outer radiation belt.
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Journal of Geophysical Research: Space Physics 129(6) 2024年5月31日Abstract We made observations of magnetic field variations in association with pulsating auroras with the magneto‐impedance sensor magnetometer (MIM) carried by the Loss through Auroral Microburst Pulsations (LAMP) sounding rocket that was launched at 11:27:30 UT on 5 March 2022 from Poker Flat Research Range, Alaska. At an altitude of 200–250 km, MIM detected clear enhancements of the magnetic field by 15–25 nT in both the northward and westward components. From simultaneous observations with the ground all‐sky camera, we found that the footprint of LAMP at the 100 km altitude was located near the center of a pulsating auroral patch. The auroral patch had a dimension of ∼90 km in latitude and ∼25 km in longitude, and its major axis was inclined toward northwest. These observations were compared with results of a simple model calculation, in which local electron precipitation into the thin‐layer ionosphere causes an elliptical auroral patch. The conductivity within the patch is enhanced in the background electric field and as a result, the magnetic field variations are induced around the auroral patch. The model calculation results can explain the MIM observations if the electric field points toward southeast and one of the model parameters is adjusted. We conclude that the pulsating auroral patch in this event was associated with a one‐pair field‐aligned current that consists of downward (upward) currents at the poleward (equatorward) edge of the patch. This current structure is maintained even if the auroral patch is latitudinally elongated.
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Geophysical Research Letters 2023年12月28日 査読有り
MISC
139-
地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM) 126th ROMBUNNO.B009-P019 2009年
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地球電磁気・地球惑星圏学会総会及び講演会予稿集(CD-ROM) 126th ROMBUNNO.B006-15 2009年
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Publications of the Astronomical Society of Japan 59(1 SPEC. ISS.) 2007年4月8日The Hard X-ray Detector (HXD) on board Suzaku covers a wide energy range from 10keV to 600 keV by the combination of silicon PIN diodes and GSO scintillators. The HXD is designed to achieve an extremely low in-orbit background based on a combination of new techniques, including the concept of a well-type active shield counter. With an effective area of 142cm 2 at 20keV and 273cm 2 at 150keV, the background level at sea level reached ∼ 1 × 10 -5 cts s -1 cm -2 keV -1 at 30 keV for the PIN diodes, and ∼ 2 × 10 -5 cts s -1 cm -2 keV -1 at 100keV, and ∼ 7 × 10 -6 cts s -1 cm -2 keV -1 at 200keV for the phoswich counter. Tight active shielding of the HXD results in a large array of guard counters surrounding the main detector parts. These anti-coincidence counters, made of ∼ 4cm thick BGO crystals, have a large effective area for sub-MeV to MeV x-rays. They work as an excellent y-ray burst monitor with limited angular resolution (∼ 5°). The on-board signal-processing system and the data transmitted to the ground are also described. © 2007. Astronomical Society of Japan.
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Publications of the Astronomical Society of Japan 59(1 SPEC. ISS.) 2007年4月8日The in-orbit performance and calibration of the Hard X-ray Detector (HXD) on board the X-ray astronomy satellite Suzaku are described. Its basic performances, including a wide energy bandpass of 10-600 keV, energy resolutions of ∼ 4 keV (FWHM) at 40 keV and ∼ 11% at 511 keV, and a high background rejection efficiency, have been confirmed by extensive in-orbit calibrations. The long-term gains of PIN-Si diodes have been stable within 1% for half a year, and those of scintillators have decreased by 5-20%. The residual non-X-ray background of the HXD is the lowest among past non-imaging hard X-ray instruments in energy ranges of 15-70 and 150-500 keV. We provide accurate calibrations of energy responses, angular responses, timing accuracy of the HXD, and relative normalizations to the X-ray CCD cameras using multiple observations of the Crab Nebula. © 2007. Astronomical Society of Japan.
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日本惑星科学会秋季講演会予稿集 2007 134-134 2007年比較的安価な小型月着陸実験機でピンポイントに月面の目標地点に着陸し，科学探査を行う小型ミッションを検討している．観測機器の重量制限，ミッション期間が最長で月の昼間に限定，月の表側のみに着陸可能など，制約は多い．しかし，単目的でも小回りの利く探査は，大型で高価な周回衛星や着陸機と相補的な役割を果たすことができ，さらに将来の惑星表面探査への技術ステップとしても重要性は高い．本研究では、小型月着陸機による探査構想とミッション候補の検討、搭載機器の可能性を検討した結果を報告する。
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日本惑星科学会秋季講演会予稿集 2007 133-133 2007年「かぐや（セレーネ）」搭載蛍光エックス線分光計（XRS）による月面元素分析手法の開発を進めている．本報告では、その手法の概要について紹介する．特に，われわれは月表面のラフネスによる蛍光X線強度への影響とその補正方法について検討してきている．ラフネスには２種類あり，X線吸収長程度の微小凹凸による影響と，より大きな地形的凹凸による影響がある．さらに，鉱物サイズが無視できないことによる効果も検討している．これらを定式化することが大量データで解析する上で重要であり，それらの検討を進めている．その現状についても紹介する．
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日本惑星科学会秋季講演会予稿集 2007 132-132 2007年月・惑星の起源や進化を解き明かす際、その元素組成・分布を明らかにすることは、最も基本的かつ重要な観測である。高精度ガンマ線分光計をローバーへ搭載することにより、細かな地形に応じた元素地図が取得できる。これを実現するために、我々は小型で高いエネルギー分解能を実現できるテルル化カドミウム半導体を用いたガンマ線検出器の開発を進めている。本発表では検出器の基礎的な特性と搭載機器の基礎設計について紹介する。
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日本物理学会講演概要集 60(2) 29-29 2005年8月19日
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日本物理学会講演概要集 60(2) 29-29 2005年8月19日
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Proceedings of SPIE - The International Society for Optical Engineering 5922 1-11 2005年We have been developed Si/CdTe semiconductor Compton telescope to explore the universe in the energy band from several 10 keV to a few MeV. In our Si/CdTe Compton telescope, a stacked thin CdTe pixel detector is a key component to achieve higher detection efficiency for MeV gamma-rays maintaining high energy resolution. In this paper, results from a prototype stacked CdTe pixel detector are reported, which consists of three layers of CdTe pixel detectors and one CdTe pixel detector at their side. With this prototype detector, we succeeded in Compton reconstruction of images and spectra in the energy band from 122 keV to 662 keV. The energy resolution (FWHM) of reconstructed spectra is 7.3 keV at 511 keV and 3.1 keV at 122 keV, respectively.
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IEEE Nuclear Science Symposium Conference Record 7 4286-4290 2004年12月1日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 stacked 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 80 keV to 662 keV. The energy resolution (FWHM) is 10 keV and 16 keV at 356 keV and 511 keV, respectively. © 2004 IEEE.
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IEEE Nuclear Science Symposium Conference Record 7 4392-4396 2004年12月1日Employing Fourier-synthesis optics and one-dimensional position-sensitive detectors, we are developing a novel hard X-ray imager which can work in the ∼10 keV to ∼200 keV range either as a telescope or a microscope. As the detection part of our imager, we have developed a strip detector made of Schottky CdTe diode, with its cathode divided into 64 channels of 150 μm pitch. Electrodes of all channels are gold-stud bonded to a fanout board, and connected to low noise analog ASIC. We read out signals from all channels simultaneously. As the grid optics elements, one-dimensional modulation collimator grids of 1 mm thick tungsten have been manufactured, with 10 grid pitches ranging from 0.2 mm to 2 mm with harmonic ratios. Combining the CdTe strip detector and the modulation collimators, we have verified hard X-ray imaging performance of this system. Specifically, by observing an241Am source, we have successfully obtained an image in the 10-70 keV range. © 2004 IEEE.
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IEEE Nuclear Science Symposium Conference Record 1 314-321 2004年12月1日The Soft Gamma-ray Detector (SGD) on board NeXT (Japanese future high energy astrophysics mission) is a Compton telescope with narrow field of view (FOV), which utilizes Compton kinematics to enhance its background rejection capabilities. It is realized as a hybrid semiconductor gamma-ray detector which consists of silicon and CdTe (Cadmium Telluride) detectors. It can detect photons in a wide energy band (0.05-1 MeV) at a background level of 5 × 10-7counts/s/cm2/keV; the silicon layers are required to improve the performance at a lower energy band (<0.3 MeV). Excellent energy resolution is the key feature of the SGD, allowing to achieve both high angular resolution and good background rejection capability. An additional capability of the SGD, its ability to measure gamma-ray polarization opens up a new window to study properties of astronomical objects. We will present the development of key technologies to realize the SGD; high quality CdTe, low noise front-end ASIC and bump bonding tecnology. Energy resolutions of 1.7 keV (FWHM) for CdTe pixel detectors and 1.1 keV for Si strip detectors have been measured. We also present the validation of MC simulation used to evaluate the performance of the SGD. © 2004 IEEE.
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IEEE TRANSACTIONS ON NUCLEAR SCIENCE 51(5) 1991-1996 2004年10月We summarize significant improvements which have been achived in the development of Astro-E2 Hard X-ray Detector (HXD-II). An expanded energy range and better energy resolution have been achieved from progresses in device materials and redesigning of the front-end electronics. An improved estimation for the detector background in orbit has also been conducted based upon results from our proton irradiation experiment. The sensitivity of HXD-II can be expected to reach an order of 10(-6) [c s(-1) keV(-1) cm(-2)].
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IEEE TRANSACTIONS ON NUCLEAR SCIENCE 51(5) 2004-2007 2004年10月We are developing a medium energy particle detector in a high-count rate environment, in order to solve the acceleration mechanism and the process of high-energy particles in the collision less plasma shock region in the space. The key observation is to measure the maximum energy of accelerated particles correctly. It is important to reduce the pile-up events, in order to measure the correct maximum energy. The new developed detector for the high-count rate environment consists of the double-sided silicon strip detector (DSSD) and the readout Application Specific Integrated Circuit (ASIC) chips VA32TA, made by IDEA. The performance of the new DSSD system for charged particles was tested using proton beams with an energy of 6 MeV from the medium-energy accelerator in the Heavy Ion Medical Accelerator in Chiba (HIMAC) of the National Institute for Radiological Science. The result is that the new DSSD system works well and has high performance in detecting not only X-rays, but also charged particles. It is certain that this new DSSD system can measure the correct energy of incident particles in high-count rate environments using the accelerator.
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日本物理学会講演概要集 59(2) 63-63 2004年8月25日
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HIGH-ENERGY DETECTORS IN ASTRONOMY 5501 218-228 2004年We have developed a large CdTe pixel detector with dimensions of 23.7 x 13.0 mm(2) and a pixel size of 448 x 448 mum(2). The detector is based on recent technologies of an uniform CdTe single crystal, a two-dimensional ASIC, and stud bump-bonding to connect pixel electrodes on the CdTe surface to the ASIC. Good spectra are obtained from 1051 pixels out of total 1056 pixels. When we operate the detector at -50degreesC, the energy resolution is 0.67 keV and 0.99 keV at 14 keV and 60 keV, respectively. Week-long stability of the detector is confirmed at operating temperatures of both -50degreesC and -20degreesC. The detector also shows high uniformity: the peak positions for all pixels agree to within 0.82%, and the average of the energy resolution is 1.04 keV at a temperature of -50degreesC. When we normalized the peak area by the total counts detected by each pixel, a variation of 2.1% is obtained.
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HIGH-ENERGY DETECTORS IN ASTRONOMY 5501 286-295 2004年The Hard X-ray Detector (HXD-II), one of instruments onboard the Astro-E2 satellite to be launched in February 2005, is in the final stage of its development. The HXD-II probes the universe in the energy range of 10-600 keV with a sensitivity by an order of magnitude better than those of previous missions. The assembly of the HXD-II completed in January 2004, followed by a series of pre-launch qualification tests. As a result, the design goals of the HXD-II have been met. These include; a background level of 5x10(-6) counts/s/keV/cm(2) at 200 keV for GSO and 1x10(-5) counts/s/keV/cm(2) at 30 keV for PIN; energy resolutions of 2.9 keV (PIN diode, at 59.5 keV) and 10% (GSO scintillator, at 662 keV); and low energy thresholds of 10 keV for PIN diodes and 30 keV for GSO scintillators. The measured background predicts a continuum sensitivity of a few x10(-6) photons/s/keV/cm(2). Anti-Counter units surrounding the HXD-II provide 50 keV-5 MeV information on gamma-ray bursts and bright X-ray transients.
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HIGH-ENERGY DETECTORS IN ASTRONOMY 5501 229-240 2004年We are developing a Compton telescope based on high resolution Si and CdTe imaging devices in order to obtain a high sensitivity astrophysical observation in sub-MeV gamma-ray region. In this paper, recent results from the prototype Si/CdTe semiconductor Compton telescope are reported. The Compton telescope consists of a double-sided Si strip detector (DSSD) and CdTe pixel detectors, combined with low noise analog LSI, VA32TA. With this detector, we obtained Compton reconstructed images and spectra from line gamma-rays ranging from 81 keV up to 356 keV. The energy resolution is 3.8 keV and 7.9 keV at 122 keV and 356 keV, respectively, and the angular resolution is 9.9degrees and 5.7degrees at 122 keV and 356 keV, respectively.
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HIGH-ENERGY DETECTORS IN ASTRONOMY 5501 197-207 2004年A Semiconductor Multiple-Compton Telescope (SMCT) is expected to proceed a high-sensitivity soft gamma-ray observation in the energy range of 0.1-20 MeV. Double-sided silicon strip detector (DSSD) is one of key technologies for constructing SMCT, as well as the high-stopping semiconductor CdTe, because of its high energy resolution and high scattering efficiency. We have developed a low-noise system of DSSD and frontend LSI for SMCT, by optimizing geometrical structures of DSSD. We have thus obtained an energy resolution of 1.3 keV (FWHM) for 60 keV and 122 keV at -10degreesC in the multi-channel reading. Gamma-ray responses such as image flatness and charge splittings were found to be not problematic. We also demonstrated that our system achieved the good angular resolution close to the Doppler-broadening limit in the Compton imaging by two DSSDs.
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UV AND GAMMA-RAY SPACE TELESCOPE SYSTEMS, PTS 1 AND 2 5488 561-571 2004年Compton telescope is a promising technology to achieve very high sensitivity in the soft gamma-ray band (0.1-10 MeV) by utilizing Compton kinematics. Compton kinematics also enables polarization measurement which will open new windows to study gamma-ray production mechanism in the universe. CdTe and Si semiconductor technologies are key technologies to realize the Compton telescope in which their high energy resolution is crucial for high angular resolution and back-round rejection capability. We have assembled a prototype module using a double-sided silicon strip detector and CdTe pixel detectors. In this paper, we present expected polarization performance of a proposed mission (NeXT/SGD). We also report results from polarization measurements using polarized synchrotron light and validation of EGS4 MC simulation.
所属学協会
5共同研究・競争的資金等の研究課題
8-
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日本学術振興会 科学研究費助成事業 基盤研究(B) 2020年4月 - 2023年3月
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日本学術振興会 科学研究費助成事業 国際共同研究加速基金(国際共同研究強化(B)) 2018年10月 - 2021年3月
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日本学術振興会 科学研究費助成事業 基盤研究(C) 2018年4月 - 2021年3月
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日本学術振興会 科学研究費助成事業 2015年4月 - 2019年3月
