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 宇宙物理学研究系東京大学 大学院理学系研究科 天文学専攻
- J-GLOBAL ID
- 200901049964309113
- researchmap会員ID
- 5000001980
- 外部リンク
研究キーワード
5経歴
1-
2017年10月 - 現在
主要な論文
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Applied Optics 2024年8月8日
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Journal of Astronomical Telescopes, Instruments, and Systems 9(02) 2023年4月19日
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Journal of Astronomical Telescopes, Instruments, and Systems 9(02) 2023年4月12日
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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 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 $2.2\, \mu$K-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.
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Space Telescopes and Instrumentation 2022: Optical, Infrared, and Millimeter Wave 2022年8月27日
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Space Telescopes and Instrumentation 2022: Optical, Infrared, and Millimeter Wave 2022年8月27日
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SPACE TELESCOPES AND INSTRUMENTATION 2022: OPTICAL, INFRARED, AND MILLIMETER WAVE 12180 2022年LiteBIRD is a JAXA-led international project that aims to test representative inflationary models by performing an all-sky cosmic microwave background radiation (CMB) polarization survey for 3 years at the Sun-Earth Lagrangian point L2. We aim to launch LiteBIRD in the late 2020s. The payload module (PLM) is mainly composed of the Low-Frequency Telescope (LFT), the Mid-Frequency Telescope and High-Frequency Telescope (MHFT), and a cryo-structure. To conduct the high-precision and high-sensitivity CMB observations, it is required to cool the telescopes down to less than 5 K and the detectors down to 100 mK. The high temperature stability is also an important design factor. It is essential to design and analyze the cryogenic thermal system for PLM. In this study, the heat balance, temperature distribution, and temperature stability of the PLM for the baseline design are evaluated by developing the transient thermal model. The effect of the Joule-Thomson (JT) coolers cold tip temperature variation, the periodical changes in subK Adiabatic Demagnetization Refrigerator (ADR) heat dissipation, and the satellite spin that generates the variable direction of solar flux incident are implemented in the model. The effect of contact thermal conductance in the LFT and the emissivity of the V-groove on the temperature distribution and heat balance are investigated. Based on the thermal analysis, it was confirmed that the PLM baseline design meets the requirement of the temperature and the cooling capability of the 4K-JT cooler. In addition, the temperatures of the V-groove and the LFT 5-K frame are sufficiently stable for the observation. The temperature stability of the Low Frequency Focal Plane (LF-FP) is also discussed in this paper.
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Proceedings of SPIE - The International Society for Optical Engineering 11453 2020年© 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.
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Proceedings of SPIE - The International Society for Optical Engineering 11453 2020年© COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only. We are developing a 100-GHz band 109-pixel MKID camera for the Nobeyama 45-m telescope. The camera optics contains plano-convex silicon (Si) lenses with 300-and 154-mm diameters located at the 4-K and 1-K stages, and a vacuum window of 320-mm diameter. Antireflective subwavelength structures (SWSs) for the Si lenses and the vacuum window were designed to reduce surface reflection. Cyclo olefin polymer (COP) was chosen as the base material for vacuum window as the dielectric loss is comparable with high-density polyethylene and it is easy to fabricate. Antireflective SWSs optimized for 100-GHz band were simulated using ANSYS HFSS. A one-layer rectangular pillar was designed for a Si lens of 300-mm diameter and a 320-mm diameter COP window to examine the fabrication process in large areas. For 154-mm diameter Si lens, a 1.2-mm depth tapered structure was used to obtain broadband characteristics. These designed structures were fabricated on both sides using a three-Axis numerically-controlled machine. An end mill and a metal-bonded dicing blade were used for cutting the COP and Si, respectively. W-band vector network analyzer was used for S-parameter measurements of the SWS formed flat surface at an ambient temperature. Average surface reflectance of Si lenses and transmittance of the COP window in the 90-110 GHz range were found at approximately 1% and 98%, respectively.
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IEEE Transactions on Terahertz Science and Technology 9(6) 598-605 2019年11月 査読有り© 2019 IEEE. Polarization of the cosmic microwave background (CMB) has crucial information on the inflationary universe. To detect these signals, it is necessary to suppress far sidelobes of a telescope, which contaminate the CMB signals with strong foreground radiation, such as the Galactic plane. LiteBIRD is the only funded CMB observation satellite for the 2020s, and the low frequency telescope (LFT; 34-161 GHz) is one of its telescopes. We measured near-field antenna patterns of the LFT using its 1/4-scaled model and examined far sidelobes up to 60° from the peaks. To cover the 20° field of view of the LFT, we investigated the antenna patterns at the edges of the focal plane as well as at the center. The measurement frequencies were 140-220 GHz, which correspond to the lowest bands (35-55 GHz) of the full-scale LFT. The measurements were consistent with the simulated far-sidelobe patterns at least -50 dB level, and showed that far sidelobes for two orthogonal polarization directions are consistent with each other down to -40 dB level. We also measured the cross-polarization patterns, and their peak level was less than -20 dB.
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Journal of Astronomical Telescopes, Instruments, and Systems 5(4) 2019年10月1日 査読有り© 2019 Society of Photo-Optical Instrumentation Engineers (SPIE). Radiative cooling with thermal isolation shields can provide a reliable cooling system for instruments onboard satellites in orbit. We report the optimization study for the cryogenic architecture of the LiteBIRD satellite using radiative cooling. A trade study that changed the number of thermal shields and shield emissivity were conducted. The heat flow from 300 to 4.5 K, including active cooling by mechanical cryocoolers, was evaluated among the trade designs. We found that the design that consists of low-emissivity four-layer thermal shields is optimum in terms of thermal performance and system design. The optimum design achieved a heat load of 29.9 mW for the 4.5-K cooling stage, whereas the requirement was 30 mW with the assumed cryogenic system.
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Proceedings of SPIE - The International Society for Optical Engineering 10698 2018年 査読有り© COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only. LiteBIRD is a candidate for JAXA's strategic large mission to observe the cosmic microwave background (CMB) polarization over the full sky at large angular scales. It is planned to be launched in the 2020s with an H3 launch vehicle for three years of observations at a Sun-Earth Lagrangian point (L2). The concept design has been studied by researchers from Japan, U.S., Canada and Europe during the ISAS Phase-A1. Large scale measurements of the CMB B-mode polarization are known as the best probe to detect primordial gravitational waves. The goal of LiteBIRD is to measure the tensor-to-scalar ratio (r) with precision of r < 0:001. A 3-year full sky survey will be carried out with a low frequency (34 - 161 GHz) telescope (LFT) and a high frequency (89 - 448 GHz) telescope (HFT), which achieve a sensitivity of 2.5 μK-arcmin with an angular resolution 30 arcminutes around 100 GHz. The concept design of LiteBIRD system, payload module (PLM), cryo-structure, LFT and verification plan is described in this paper.
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IEEE Transactions on Applied Superconductivity 25(3) 2015年6月1日 査読有り© 2002-2011 IEEE. We developed SIS mixers for Atacama large millimeter/submillimeter array (ALMA) Band 8 (385-500 GHz) receiver cartridges and evaluated their performance. DC IV curves of the SIS mixers showed small leakage current at the high current density. The current density and quality factor (R-{sg}/R-{n}) of the Band 8 SIS junction were 13 \hbox{kA/cm}{2} and approximately 20, respectively. Double-sideband noise temperature of the 266 SIS mixers was 92.8 K at 4.0 K bath temperature on the average from 385 to 500 GHz with a standard deviation of 7.0%. A couple of sideband-separating (2SB) mixers for dual polarizations were used in the Band 8 receiver cartridge. The 73 receivers have met ALMA specifications of the noise temperature. Single-sideband noise temperature and image rejection ratio of the receivers were 139.5 K and 20.5 dB on the average from 385 to 500 GHz, respectively. These test results of the receivers indicate high quality and uniformity of the 2SB mixers.
MISC
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Proceedings of SPIE - The International Society for Optical Engineering 1734 44-55 1992年 査読有りWe have developed a low background hard x-ray/γ-ray telescope for balloon-borne experiments. The telescope called Welcome-1 (well type compound eye) utilizes newly developed well-type phoswich counters. In the well-type phoswich counter, the background from external and internal (nuclear activation) sources are reduced significantly. Welcome-1 is designed for observation in the energy range from 60 keV to 800 - 1000 keV. The effective area of Welcome-1 is 740 cm2 at 122 keV and 222 cm2 at 511 keV line. We flew Welcome-1 from Cachoeira Paulista, Brazil in 1990 and 1991 to detect hard x rays from SN1987A, PSR1509-58, Cen-A, and others. The background levels at an altitude of 4 g/cm2 are 1 × 10-4/cm2/s/keV at 122 keV and 4 × 10-5/cm2/s/keV at 511 keV. The data obtained during the flight shows that the detector in fact has the 3σ sensitivity of approximately a few × 10-6/cm2/s/keV and approximately 10-4/cm2/s in a 104s observation for the continuum spectrum and line spectrum, respectively. Crab nebula has been observed with S/N ratio better than unity between 100 and 200 keV.
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Proceedings of SPIE - The International Society for Optical Engineering 1734 2-13 1992年 査読有りWe have developed a new kind of phoswich counters that are capable of detecting low flux hard x ray/γ ray from localized sources. The counter consists of a small inorganic scintillator with a fast decay time (the detection part) glued to the interior bottom surface of a well-shaped block of another inorganic scintillator with a slow decay time (the shielding part). The well-shaped shielding part acts as an active collimator as well as an active shield. The whole assembly is viewed by a phototube from the exterior bottom surface of the shielding part. By using an appropriate pulse-shape discriminator (PSD), hard x rays/γ rays that have deposited energy only in the detection part can be selected. The first counter was built by using a new scintillator (GSO) for the detection part and CsI(Tℓ) for the shielding part. A detector system consisting of 64 such phoswich counters (total area approximately 740 cm2) was flown three times on board a balloon, setting a limit to the 57Co line flux from SN1987A at around 10-4 cm-2s, determining the pulsating hard x/γ ray flux of PSR1509-58, determining the hard x/γ ray spectra of CenA and GX339-04. Analyses have revealed the fact that background counts due to the Compton scattering, nuclear reactions, and β-γ radioactivities in the detector are largely suppressed because they are likely to register at least one extra count in the shielding part. The ultimate sensitivity of the detector is then determined by the level of radioactive contamination. Other scintillator combinations such as GSO/BGO, NaI(Tℓ)/CsI(Tℓ), and YAlO3/BGO also have been studied. Efforts to reduce the radioactive contamination in scintillators also have been actively pursued. In the near future we expect to reach a sensitivity (3σ) around a few times 10-7 cm-2s-1keV-1 for continuum in a
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SCIENTIFIC BALLOONING 13 165-168 1992年We have developed a new kind of phoswich counters that will be capable of detecting low flux hard X-rays/gamma-rays from astronomical objects. The new phoswich counter consists of a small inorganic scintillator with a fast decay time (the detection part) glued to the interior bottom surface of a rectangular well-shaped block of another inorganic scintillator with a slow decay time (the shielding part). Here, the well-shaped shielding part acts as an active collimator as well as an active shield. We have built a detector system consisting of 64 such phoswich counters: newly developed scintillator (GSO) is used for the detection part and CsI(Tl) is used for the shielding part. The total geometrical area of the 64 detection parts is about 740cm 2 and its 3σ sensitivity is expected to reach below 10 -5 cm -2 s -1 keV -1 up to 700keV. With several improvements such detectors will be able to detect hard X-rays/gamma-rays at a flux level around 10 -6 cm -2 s -1 keV -1 upto 2 MeV. © 1992.
講演・口頭発表等
78共同研究・競争的資金等の研究課題
8-
日本学術振興会 科学研究費助成事業 2023年6月 - 2027年3月
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日本学術振興会 科学研究費助成事業 2023年4月 - 2027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(A) 2017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 新学術領域研究(研究領域提案型) 2015年6月 - 2020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(S) 2015年5月 - 2020年3月
社会貢献活動
1● 指導学生等の数
1-
年度2021年度(FY2021)博士課程学生数1修士課程学生数1インターンの人数9
● 指導学生の表彰・受賞
1-
指導学生名高倉隼人所属大学東京大学受賞内容（タイトル、団体名等）B-mode from space受賞年月日2019-12-5
● 専任大学名
1-
専任大学名東京大学（University of Tokyo)
