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
147-
Applied Optics 2024年8月8日
-
Journal of Astronomical Telescopes, Instruments, and Systems 9(02) 2023年4月19日
-
Journal of Astronomical Telescopes, Instruments, and Systems 9(02) 2023年4月12日
-
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.
-
Space Telescopes and Instrumentation 2022: Optical, Infrared, and Millimeter Wave 2022年8月27日
-
Space Telescopes and Instrumentation 2022: Optical, Infrared, and Millimeter Wave 2022年8月27日
-
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.
-
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.
-
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.
-
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.
-
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.
-
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.
-
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
206講演・口頭発表等
78-
電子情報通信学会技術研究報告 = IEICE technical report : 信学技報 2014年1月23日
-
電子情報通信学会技術研究報告. SCE, 超伝導エレクトロニクス 2014年1月16日我々は、宇宙マイクロ波背景放射観測衛星LiteBIRDや南極望遠鏡に搭載するミリ波、サブミリ波を直接検出する超伝導共振器(Microwave Kinetic Inductance Detector,MKID)の開発を進めている。MKIDに入射した光子のエネルギーが超伝導体のギャップエネルギーより大きいとき、超伝導体中のクーパー対を破壊し準粒子が生じるため、力学的インダクタンスが変化する。この変化により共振器の共振周波数が変わり、MKIDはこの共振周波数の変化を以って光子を検出する。これまでは、ミリ波を検出するために、転移温度が1.2K、ギャップエネルギーが〜90GHzのアルミニウムを用いていた。ニオブ層の上にアルミ層をのせた積層型のMKIDを用いることで、近接効果によりアルミニウム膜よりも高い転移温度が得られる積層型MKIDをリフトオフにより製作した。またこの積層型のMKIDのQ値の温度依存性はアルミニウム、ニオブ単層膜と異なる振る舞いをした。
-
電子情報通信学会技術研究報告. SCE, 超伝導エレクトロニクス 2014年1月16日超伝導ギャップ内状態を占有する準粒子の存在を仮定した理論を提案し、超伝導体の表面抵抗の過剰成分や超伝導共振器のQ値のの解析を行った。ギャップ内の準粒子状態密度はギャップエネルギを複素数とすることにより記述でき、これを用いてMattis-Bardeen方程式を複素積分化することにより表面抵抗を求めた。こうして求めたNbN超伝導薄膜の表面抵抗やNb空洞共振器のQ値は実験値を良く説明できることが明らかになった。また、Al薄膜共振器中の残留準粒子数は、トンネル接合のI-V特性のフィッティングから求めた準粒子状態密度を用いて求めた準粒子数と定量的に一致することが明らかになった。
-
Proceedings of SPIE - The International Society for Optical Engineering 2014年1月1日© 2014 SPIE. We have been developing a lens-integrated superconducting camera for millimeter and submillimeter astronomy. High-purity silicon (Si) is suitable for the lens array of the Microwave Kinetic Inductance Detector (MKID) camera due to the high refractive index and the low dielectric loss at low temperature. The camera is antenna-coupled Al coplanar waveguides on a Si substrate. Thus the lens and the device are made of the same material. We report a fabrication method of 721 pixel Si lens array with anti-reflection coating. The Si lens array was fabricated with an ultra-precision cutting machine. It uses TiAlN coated carbide end mills attached with a high-speed spindle. The shape accuracy was less than 50 μm peak-to-valley and the surface roughness was Ra 1.8 μm. The mixed epoxy was used as anti-reflection coating to adjust the refractive index. It was shaved to make the thickness of 185 μm for 220 GHz. Narrow grooves were made between the lenses to prevent cracking due to different thermal expansion coefficients of Si and the epoxy. The surface roughness of the anti-reflection coating was Ra 2.4 ∼ 4.2 μm.
-
電子情報通信学会技術研究報告. SANE, 宇宙・航行エレクトロニクス 2008年6月19日ALMA(Atacama Large Millimeter Submillimeter Array)は、日本・北米・欧州が国際協力により、南米チリのアタカマ砂漠(標高5000m)に建設する大型のミリ波サブミリ波干渉計である。超高精度(鏡面精度20μm r.m.s.以下)サブミリ波アンテナ12m鏡および7m鏡を計80台設置し、ハッブル宇宙望遠鏡やすばる望遠鏡の角度分解能〜0.1秒角を上回る0.01秒角を達成する。観測周波数30GHz-950GHzを大気の窓に対応した10個の周波数バンドに分割し、それぞれをカートリッジ型受信機でカバーする。ALMAの観測装置は、日本・北米・欧州がそれぞれの最先端技術や英知を結集して開発している。本講演では、日本が担当する低雑音の超伝導サブミリ波受信機の開発について紹介する。既存のミリ波干渉計に比べて2桁高い性能をもつALMAは、2010年より数素子にて部分運用をおこない、2012年より本格的な観測が始まる。
-
電子情報通信学会技術研究報告. SANE, 宇宙・航行エレクトロニクス 2004年6月18日ALMA (Atacama Large Millimeter Submillimeter Array)計画は、日本・北米・欧州が国際協力により、南米チリのアタカマ砂漠に建設する大型ミリ波サブミリ波干渉計である。建設予定地は標高5000mの高地で、比較的平坦な上地で、直径14kmに分布する干渉計の建設が可能である。超高精度(鏡面精度20μm r.m.s.以下)サブミリ波アンテナ12m鏡および7m鏡を合計80台設置し、ハッブル宇宙望遠鏡やすばる望遠鏡の角度分解能〜0.1秒角を上回る0.01秒角を達成する。観測周波数30GHz-950GHzを大気の窓に対応した10個の周波数バンドに分割し、それぞれをカートリッジ型受信機でカバーする。ALMAの装置は、日本・北米・欧州がそれぞれの最先端技術や英知を結集して開発している。本講演では、日本が担当する超伝導サブミリ波受信機の開発や光電気変換デバイスを用いた干渉計用参照信号源(Photonic Local Oscillator)などの装置開発についても紹介する。その結果、既存のミリ波干渉計に比べて2桁高い性能をもつ。ALMAは2007年より数素子にて部分運用をおこない、2012年より本格的な観測が始まる。
-
電子情報通信学会総合大会講演論文集 2004年3月8日
-
電子情報通信学会技術研究報告. A・P, アンテナ・伝播 2004年1月16日サブミリ波アンテナとして広帯域,高利得かつ低損失コルゲートアンテナの設計を行ったので報告する.従来からコルゲートホーンアンテナは放射パターンの対称性が良く,交差偏波が非常に小さいことが知られているため,電波望遠鏡等の低損失アンテナとして用いられてきた.しかし,円形ホーンアンテナの内側に単純にコルゲーションと呼ばれる溝を施すだけでの設計では,広帯域において高効率かつ低交差偏波特性を有するアンテナ設計は容易ではない.特に電波天文学において観測に用いるサブミリ波電波望遠鏡の受信機ホーンに必要な性能を有する設計は非常に困難であった.我々は,コルゲートホーンアンテナの給電部とフレア部の間に独特のモード変換部を設ける事により,非常に高性能なサブミリ波ホーンアンテナを設計することができたので報告する.
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
-
日本学術振興会 科学研究費助成事業 2023年4月 - 2027年3月
-
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
-
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
-
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)
