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 教授総合研究大学院大学 先端学術院 宇宙科学コース 教授東京工業大学 理学院物理学系物理学コース 特定教授関西学院大学 大学院理工学研究科 客員教授
- 学位
- 理学博士(東京大学)
- J-GLOBAL ID
- 200901025041369206
- researchmap会員ID
- 1000144439
専門はＸ線天文学。特に、中性子星やブラックホールを含むX線連星の観測的研究および衛星搭載X線CCDカメラの開発研究。
受賞
1-
1996年
論文
201-
Cryogenics 138 103795-103795 2024年3月
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Journal of Low Temperature Physics 209(5-6) 1097-1103 2022年12月The radio frequency interference (RFI) due to the X-band telecommunication with the LiteBIRD spacecraft was computed using a 3D electromagnetic field simulator to evaluate its field strength at the instrument detectors. First, the level of RFI with different materials for the spacecraft main body was evaluated. The attenuation effects for aluminum (Al) and carbon-fiber-reinforced plastic (CFRP) in comparison with a perfect electric conductor (PEC) were 1.5 dB and 10.5 dB, respectively. Then, the electric field strength for various shield plate structures on the solar panels was evaluated. In the best case, the RFI level could be attenuated by another 31 dB with an optimum design. Finally, the frequency dependence of the RFI was evaluated across the X-band, giving an attenuation slope of − 10 dB/oct, leading to an electric field intensity of − 116.8 dBV/m at the detector position for a frequency of 8.4 GHz.
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Progress of Theoretical and Experimental Physics 2023(4) 2022年11月21日Abstract LiteBIRD the Lite (Light) satellite for the study of B-mode polarization and Inflation from cosmic background Radiation Detection, is a space mission for primordial cosmology and fundamental physics. The Japan Aerospace Exploration Agency (JAXA) selected LiteBIRD in May 2019 as a strategic large-class (L-class) mission, with an expected launch in the late 2020s using JAXA’s H3 rocket. LiteBIRD is planned to orbit the Sun-Earth Lagrangian point L2, where it will map the cosmic microwave background (CMB) polarization over the entire sky for three years, with three telescopes in 15 frequency bands between 34 and 448 GHz, to achieve an unprecedented total sensitivity of 2.2 μK-arcmin, with a typical angular resolution of 0.5○ at 100 GHz. The primary scientific objective of LiteBIRD is to search for the signal from cosmic inflation, either making a discovery or ruling out well-motivated inflationary models. The measurements of LiteBIRD will also provide us with insight into the quantum nature of gravity and other new physics beyond the standard models of particle physics and cosmology. We provide an overview of the LiteBIRD project, including scientific objectives, mission and system requirements, operation concept, spacecraft and payload module design, expected scientific outcomes, potential design extensions and synergies with other projects. Subject Index LiteBIRD cosmic inflation, cosmic microwave background, B-mode polarization, primordial gravitational waves, quantum gravity, space telescope
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Publications of the Astronomical Society of Japan 75(1) 30-36 2022年11月12日Abstract 2S 0921−630 is an eclipsing low-mass X-ray binary (LMXB) with an orbital period of ∼9 d. Past X-ray observations have revealed that 2S 0921−630 has an extended accretion disk corona (ADC), from which most of the X-rays from the system are emitted. We report the result of our Suzaku archival data analysis of 2S 0921−630. The average X-ray spectrum is reproduced with a blackbody emission (kTbb ∼ 0.3 keV) Comptonized by optically thick gas (“Compton cloud”; optical depth τ ∼ 21) with a temperature of ∼2 keV, combined with 13 emission lines. We find that most of the emission lines correspond to highly ionized atoms: O, Ne, Mg, Si, S, Ar, and Fe. A Kα emission line and an absorption edge of semi-neutral iron (Fe textsci– textscxvii) are also detected. The semi-neutral iron Kα line is significantly broad, with a width of 0.11 ± 0.02 keV in sigma, which corresponds to the Doppler broadening by the Kepler motion at a radius of ∼109 cm. We suggest that the observed semi-neutral iron line originates at the inner part of the accretion disk in the immediate outside of the Compton cloud, i.e., the Compton cloud may have a radius of ∼109 cm.
MISC
200-
Space Telescopes and Instrumentation 2020: Optical, Infrared, and Millimeter Wave 2020年12月21日
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Space Telescopes and Instrumentation 2020: Optical, Infrared, and Millimeter Wave 11443 2020年12月15日LiteBIRD is a JAXA-led Strategic Large-Class mission designed to search for the existence of the primordial gravitational waves produced during the inflationary phase of the Universe, through the measurements of their imprint onto the polarization of the cosmic microwave background (CMB). These measurements, requiring unprecedented sensitivity, will be performed over the full sky, at large angular scales, and over 15 frequency bands from 34 GHz to 448 GHz. The LiteBIRD instruments consist of three telescopes, namely the Low-, Medium-and High-Frequency Telescope (respectively LFT, MFT and HFT). We present in this paper an overview of the design of the Medium-Frequency Telescope (89{224 GHz) and the High-Frequency Telescope (166{448 GHz), the so-called MHFT, under European responsibility, which are two cryogenic refractive telescopes cooled down to 5 K. They include a continuous rotating half-wave plate as the first optical element, two high-density polyethylene (HDPE) lenses and more than three thousand transition-edge sensor (TES) detectors cooled to 100 mK. We provide an overview of the concept design and the remaining specific challenges that we have to face in order to achieve the scientific goals of LiteBIRD.
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Space Telescopes and Instrumentation 2020: Ultraviolet to Gamma Ray 11444 2020年12月13日Soft X-ray Imager (SXI) is the X-ray CCD camera onboard X-Ray Imaging and Spectroscopy Mission (XRISM) that is scheduled to be launched in Japanese fiscal year 2022. Combining the SXI with an X-ray mirror assembly, we realize the Soft X-ray Imaging Telescope (Xtend) with a focal length of 5.6 m and a field of view of 38 arcmin square. The high quantum efficiency of the focal-plane sensor, P-channel back-illumination type CCD, brings about the wide effective energy range from 0.4 to 13 keV with moderate energy resolution. Although the design of the SXI for XRISM is basically identical to that for Hitomi satellite, we have applied several improvements to the CCDs in terms of the charge transfer inefficiency (CTI) and the optical blocking performance. For the former issue, we introduce a notch implant in the charge transfer path to reduce the CTI increase in orbit. For the latter, we change the design of aluminum layers on the incident surface of the CCDs to decrease incoming visible light and/or infrared. Four flight model (FM) CCDs have been selected considering several items including energy resolution at 5.9 keV, CTI, dark current, etc. We have also completed calibration campaign for all the FM CCDs. Initial analyses show that the response function for monochromatic X-rays is basically the same as that of Hitomi CCDs. Front-end ASIC have been confirmed to properly function even after the long-term storage after the manufacture for Hitomi SXI. Then the analog electronics for driving CCDs and for processing the output analog signals have been implemented. Their functional tests have been completed with no problem. The focal plane including the single-stage Stirling cooler has been assembled. Production of key parts in SXI sensor body such as contamination blocking filter and onboard calibration source has been finished and they are waiting for assemble. The digitized signals of the CCD are corrected step by step before conversion to X-ray energy. We are preparing calibration database for the correction such as CTI, gain, and line redistribution function.
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Space Telescopes and Instrumentation 2020: Optical, Infrared, and Millimeter Wave 11443 2020年12月13日The electromagnetic interference (EMI) is becoming an increasingly important factor in the spacecraft design equipped with highly sensitive detectors. This is particularly the case for LiteBIRD, in which the TES bolometers are exposed to space through the optical path. A particular concern is radiative interference caused by the X-band transmission during the ground communication. As the end-to-end verification test will be conducted in a later phase of the development, we need to derisk the concern early using simulation. In this report, we present the result of the EMI effects in the 1-GHz frequency range based on the electromagnetic simulation using a finite difference time domain (FDTD) solver. We modeled the dominant large structures of the spacecraft, calculated the spatial transmission of the antenna power, and estimated the electric field strength at the detector focal plane. The simulation results helped constrain aspects of the LiteBIRD satellite, such as the forward/backward ratio of the transmission antenna, to reduce the coupling between the antenna and the detectors.
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Proceedings of SPIE - The International Society for Optical Engineering 11453 2020年12月© COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only. LiteBIRD has been selected as JAXA's strategic large mission in the 2020s, to observe the cosmic microwave background (CMB) B-mode polarization over the full sky at large angular scales. The challenges of LiteBIRD are the wide field-of-view (FoV) and broadband capabilities of millimeter-wave polarization measurements, which are derived from the system requirements. The possible paths of stray light increase with a wider FoV and the far sidelobe knowledge of-56 dB is a challenging optical requirement. A crossed-Dragone configuration was chosen for the low frequency telescope (LFT: 34-161 GHz), one of LiteBIRD's onboard telescopes. It has a wide field-of-view (18° x 9°) with an aperture of 400 mm in diameter, corresponding to an angular resolution of about 30 arcminutes around 100 GHz. The focal ratio f/3.0 and the crossing angle of the optical axes of 90a-▪ are chosen after an extensive study of the stray light. The primary and secondary reflectors have rectangular shapes with serrations to reduce the diffraction pattern from the edges of the mirrors. The reflectors and structure are made of aluminum to proportionally contract from warm down to the operating temperature at 5 K. A 1/4 scaled model of the LFT has been developed to validate the wide field-of-view design and to demonstrate the reduced far sidelobes. A polarization modulation unit (PMU), realized with a half-wave plate (HWP) is placed in front of the aperture stop, the entrance pupil of this system. A large focal plane with approximately 1000 AlMn TES detectors and frequency multiplexing SQUID amplifiers is cooled to 100 mK. The lens and sinuous antennas have broadband capability. Performance specifications of the LFT and an outline of the proposed verification plan are presented.
所属学協会
4-
2000年1月 - 現在
共同研究・競争的資金等の研究課題
15-
日本学術振興会 科学研究費助成事業 基盤研究(C) 2019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 新学術領域研究(研究領域提案型) 2012年6月 - 2017年3月
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日本学術振興会 科学研究費助成事業 2012年4月 - 2015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(B) 2010年4月 - 2013年3月
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日本学術振興会 科学研究費助成事業 特別研究員奨励費 2005年 - 2007年
● 指導学生等の数
1-
年度2021年度(FY2021)修士課程学生数2連携大学院制度による学生数2学術特別研究員数1
● 専任大学名
1-
専任大学名総合研究大学院大学（SOKENDAI)
