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 9904 2016年 査読有り© 2016 SPIE. LiteBIRD is a next generation satellite aiming for the detection of the Cosmic Microwave Background (CMB) B-mode polarization imprinted by the primordial gravitational waves generated in the era of the inflationary universe. The science goal of LiteBIRD is to measure the tensor-to-scaler ratio r with a precision of δr < 10-3♦, oering us a crucial test of the major large-single-field slow-roll inflation models. LiteBIRD is planned to conduct an all sky survey at the sun-earth second Lagrange point (L2) with an angular resolution of about 0.5 degrees to cover the multipole moment range of 2 ≤ ℓ ≤ 200. We use focal plane detector arrays consisting of 2276 superconducting detectors to measure the frequency range from 40 to 400 GHz with the sensitivity of 3.2 μK·arcmin. including the ongoing studies.
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Proceedings of SPIE - The International Society for Optical Engineering 9906 2016年 査読有り© 2016 SPIE. Polarized patterns in the cosmic microwave background (CMB) radiation contains rich knowledge for early stage of the universe. In particular their odd-parity patterns at large angular scale (> 1), primordial B-modes, are smoking-gun evidence for the cosmic inflation. The GroundBIRD experiment aims to detect these B-modes with a ground-based apparatus that includes several novel devices: A high-speed rotational scan system, cold optics, and microwave kinetic inductance detectors (MKIDs). We plan to start observations in the Canary Islands in 2017. In this paper, we present the status of the development of our instruments. We established an environment that allows operation of our MKIDs in an optical configuration, in which the MKIDs observe radiations from the outside of the telescope aperture. We have also constructed MKID prototypes, and we are testing them in the optical configuration.
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Proceedings of SPIE - The International Society for Optical Engineering 9914 2016年 査読有り© 2016 SPIE. We demonstrate a design of octave-band circular waveguide coupled planar ortho-mode transducer (OMT) with Microwave Kinetic Inductance Detector (MKID) for LiteBIRD mission, a small-size satellite for cosmic microwave background (CMB) polarization signal full-sky mapping. In our 4-pixel prototype design, each single pixel is sensitive to two frequency bands (90 GHz and 150 GHz) corresponding to atmospheric window. Silicon on insulator (SOI) has been selected for OMT structure and a broadband coplanar waveguide (CPW) 180-degree hybrid is designed to cancel higher modes of a circular waveguide and add two signals from the fundamental mode together. After a microstrip bandpass diplexer, a microstrip line to coplanar waveguide transition structure couples signal to MKID. MKIDs are designed with Nb ground plane and Al/Ti bilayer center strip line to achieve low frequency response and high sensitivity. A 4-pixel module is under test and we plan to deploy these multichroic polarimeters on Nobeyama 45m telescope.
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Proceedings of SPIE - The International Society for Optical Engineering 9914 2016年 査読有り© 2016 SPIE. A focal plane based on MKID has been designed for cosmic microwave background (CMB) B-mode polarization experiments. We are designing and developing a focal plane with broadband corrugated horn array, planar OMT, 180 degree hybrid, bandpass filters, and MKIDs. The focal plane consists of 3 octave bands (55 - 108 GHz, 80 - 160 GHz, 160 - 320 GHz), 10 hexagonal modules. Broadband corrugated horn-array has been directly machined from an Al block and measured to have a good beam shape which is consistent with electromagnetic field simulations in octave bands. The horn array is designed to be low standing-wave, light weight, and electromagnetic shield. The broadband 4 probes ortho-mode transducer (OMT) is fabricated on Si membrane of an SOI wafer. A broadband 180 degree hybrid made with coplanar waveguide (CPW) is used to reduce higher modes of the circular waveguide. Two bandpass filters of each polarization are patterned with Nb microstrip. A prototype of the broadband corrugated horn coupled MKIDs has been fabricated and tested.
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Japanese Journal of Applied Physics 54(9) 2015年9月1日 査読有り© 2015 The Japan Society of Applied Physics. Amorphous NbTiN is widely applied in superconducting electronic devices owing to its merits of wide energy gap, high T<inf>c</inf>, and mitigated requirement in fabrication. Its highly disordered feature yields considerable kinetic inductance, making it an ideal material for parametric amplification. To build up the correspondence between the fabrication conditions and the desirable electrical performance, we designed, fabricated, and measured NbTiN microstrip resonators at microwave frequencies. The principal result is that the unloaded Q factor of the resonators does not depend on the film normal state resistivity, which largely depends on the sputtering pressure. This result is consistent with the dirty superconductor theories.
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IEEE TRANSACTIONS ON TERAHERTZ SCIENCE AND TECHNOLOGY 5(3) 456-463 2015年5月We have been developing a superconductive detector array for terahertz astronomical observation using Microwave Kinetic Inductance Detector (MKID) technology. MKID is accomplished by making a strip of superconductor part of a microwave resonant circuit, and monitoring the phase and amplitude of a probe signal transmitted through the resonator. Frequency-domain multiplexing will allow up to thousands of resonators to be read out through a single line. We developed a 600-pixel 220 GHz detector array and a 102-pixel 440-GHz detector array. We have developed a new scheme readout system for the detector arrays, and which uses a frequency-sweeping probe signal instead of a fixed-frequency probe signal. This scheme enables us a direct measurement of the changed resonance frequency after optical loading.
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電子情報通信学会技術研究報告 = IEICE technical report : 信学技報 115(13) 35-41 2015年4月22日
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Journal of Astronomical Telescopes, Instruments, and Systems 1(2) 2015年 査読有り© 2015 Society of Photo-Optical Instrumentation Engineers (SPIE). A wide-field Nasmyth optical system that connects a planned 10-m Ritchey-Chrétien telescope to a submillimeter camera is reported. This diffraction-limited system has a 1-deg field of view at 850 GHz, filled with a more than 20,000-pixel camera. The system enables us to carry out large field surveys of distant galaxies within reasonable time scales. The size of the Nasmyth optics is reasonably compact and its cryogenic part including the vacuum window, cryogenic lens, and IR block filters can be built using existing technologies at a reasonable cost. This type of optical system can be applied for the optical design of millimeter, terahertz, and other submillimeter instruments.
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Journal of Astronomical Telescopes, Instruments, and Systems 1(2) 2015年 査読有り© 2015 Society of Photo-Optical Instrumentation Engineers (SPIE). We have been developed 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 camera due to its high refractive index and low dielectric loss at low temperatures. The camera is an antenna-coupled Al coplanar waveguide on a Si substrate. Thus the lens and the device are made of the same material. We report a fabrication method of a 721-pixel Si lens array with an antireflection (AR) coating. The Si lens array was fabricated with an ultraprecision 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 arithmetic average roughness (Ra) of 1.8 μm. The mixed epoxy was used as an AR coating to adjust the refractive index. It was shaved to yield a thickness of 185 μm for 220 GHz. Narrow grooves were made between the lenses to prevent cracking due to the different thermal expansion coefficients of Si and the epoxy. The surface roughness of the AR coating was Ra of 2.4 to 4.2 μm.
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26th International Symposium on Space Terahertz Technology, ISSTT 2015 2015年 査読有りAn MKID focal plane array has been designed for LiteBIRD, which is a future satellite to probe B-mode polarization of cosmic microwave background radiation. Octaveband corrugated horn arrays and planar OMTs are designed for the feed. Three kinds of feed modules detect photons from 55 GHz to 330 GHz with 6 frequency bands. This focal plane array consists of 2780 MKID detectors.
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26th International Symposium on Space Terahertz Technology, ISSTT 2015 2015年 査読有りAmorphous NbTiN is widely applied in superconducting electronic device due to the merits of wide energy gap, high Tc and mitigated requirement in fabrication. Its highly disordered feature also makes it a candidate material for parametric amplification. It is found that the resistivity and film stress of NbTiN film strongly depend on fabrication conditions. To build up the correspondence between the fabrication conditions and the desirable electrical performance, we designed, fabricated and measured NbTiN microstrip resonators. The principal result is that the unloaded Q factor of the resonators does not depend on the film normal state resistivity. This result is consistent with the dirty superconductor theories given by Pippard, Ginsberg-Landau, and Mattis-Bardeen. Our study also provides an accurate method to determine the gap energy of NbTiN.
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IEEE TRANSACTIONS ON TERAHERTZ SCIENCE AND TECHNOLOGY 5(1) 49-56 2015年1月 査読有りWe have developed an optics for 220 GHz observations, which is a compact cold re-imaging one from a telescope focal plane, with F / # = 6 to a detector plane with F / # = 1 at 100 mK. It employs two high refractive lenses, high purity alumina (n = 3.1) and silicon (n = 3.4). To reduce the incident stray light into the detector, a cold nested baffle composed of four reflectors with the same spherical shape has been developed. The stray light power is simulated to be 0.2 mu W which corresponds a quarter of that of a without-baffles case. The total transmittance of three kinds of IR blocking filters is 0.78 at the observation frequency, and less than 10(-10) above 6 THz. Thermal flow power into the detector, including the stray light power, is about 0.7 mu W. The cold optics with an 600 pixels MKID camera has been cooled down to 100 mK.
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電子情報通信学会総合大会講演論文集 2014(2) "SS-38"-"SS-41" 2014年3月4日
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電子情報通信学会技術研究報告 = IEICE technical report : 信学技報 113(401) 67-72 2014年1月23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。
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電子情報通信学会技術研究報告 = IEICE technical report : 信学技報 113(401) 73-77 2014年1月23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。
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8th European Conference on Antennas and Propagation, EuCAP 2014 2407-2408 2014年 査読有り© 2014 European Association on Antennas and Propagation. Wide field-of-view (FoV) MKID cameras for millimeter and sub millimeter astronomy have been developed at the Advanced Technology Center of NAOJ. To observe large scale structure of the universe, thousands of pixels with high sensitive detectors are required. We demonstrate key technologies, such as 700 pixel 220 GHz MKID camera, Si lens array, anti-reflection (AR) coating for Si and Alumina lens, wide FoV cryogenic optics, and read-out circuit for MKID cameras.
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Proceedings of SPIE - The International Society for Optical Engineering 9153 2014年 査読有り© 2014 SPIE. Wide field cryogenic optics and millimeter-wave Microwave Kinetic Inductance Detector (MKID) cameras with Si lens array have been developed. MKID is a Cooper-pair breaking photon detector and consists of supercon-ducting resonators which enable microwave (∼GHz) frequency multiplexing. Antenna-coupled Aluminum CPW resonators are put in a line on a Si substrate to be read by a pair of coaxial cables. A 220 GHz-600 pixels MKID camera with anti-reflection (AR) coated Si lens has been demonstrated in an 0.1 K cryostat. A compact cryogenic system with high refractive index materials has been developed for the MKID camera.
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Proceedings of SPIE - The International Society for Optical Engineering 9153 2014年 査読有り© 2014 SPIE. We designed wide FoV (1 degree) Nasmyth optics which transformed the f/6 Nasmyth focus to f/1 at a 850GHz superconducting camera for a planning 10-m Ritchey-Chrétien telescope. This optical system consists of reflecting mirrors at room temperature and a refractive lens at 4K. It enables us to carry out wide FoV imaging observations at the diffraction limit (Strehl ratio < 0.89) with a more than 100,000 pixel camera equipped in a 10-m telescope. The size of this system is reasonably compact (whole size:1.6 mx3.3 mx2.6 m, cryogenic part:0.7 mx0.7 mx1.0 m). The cryogenic part of this system such as vacuum window, cryogenic lens and IR block filters can be made with existing technologies at reasonable cost. The optical system can extend to the millimeter wave and the terahertz domain.
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Proceedings of SPIE - The International Society for Optical Engineering 9145 2014年 査読有り© 2014 SPIE. We have developed a 30-cm submillimeter-wave telescope intended to survey the Milky Way in 500 GHz emission lines at the Dome Fuji station in Antarctic plateau. Transportability and low power consumption are required while keeping low system noise temperature for the operation in Antarctica. The telescope is designed to be divided into five components and to operate with less than 2.5 kW of electric power. Its receiver noise temperature is less than 85 K in SSB at 461 and 492 GHz. We succeeded in operating the telescope at -30°C in laboratory that is a typical temperature of the Dome Fuji in summer.
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Proceedings of SPIE - The International Society for Optical Engineering 9153 2014年 査読有り© 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.
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ISSTT 2014 - 25th International Sympsoium on Space Terahertz Technology, Proceedings 49-51 2014年 査読有りAn optics which we have developed for 220 GHz observations is a compact cold re-imaging one from a telescope focal plane with F/# = 6 to a detector plane with F/# = 1 at 100 mK. It employs two high refractive lenses, high purity alumina (n=3.1) and silicon (n=3.4). To reduce the incident stray light into the detector, a cold nested baffle composed of 4 reflectors with the same spherical shape has been developed. The stray light power is simulated to be 0.2 μW which corresponds a quarter of that of a without-baffles case. The total transmittance of three kinds of IR blocking filters is 0.78 at the observation frequency, and less than 10 -10 above 6 THz. Thermal flow power into the detector, including the stray light power, is about 0.7 μW. The cold optics with an 600 pixels MKID camera has been cooled down to 100 mK.
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Proceedings of SPIE - The International Society for Optical Engineering 9143 2014年 査読有り© 2014 SPIE. We present the mission design of LiteBIRD, a next generation satellite for the study of B-mode polarization and inflation from cosmic microwave background radiation (CMB) detection. The science goal of LiteBIRD is to measure the CMB polarization with the sensitivity of δr = 0:001, and this allows testing the major single-field slow-roll inflation models experimentally. The LiteBIRD instrumental design is purely driven to achieve this goal. At the earlier stage of the mission design, several key instrumental specifications, e.g. observing band, optical system, scan strategy, and orbit, need to be defined in order to process the rest of the detailed design. We have gone through the feasibility studies for these items in order to understand the tradeoffs between the requirements from the science goal and the compatibilities with a satellite bus system. We describe the overview of LiteBIRD and discuss the tradeoffs among the choices of scientific instrumental specifications and strategies. The first round of feasibility studies will be completed by the end of year 2014 to be ready for the mission definition review and the target launch date is in early 2020s.
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日本物理学会講演概要集 67 135-135 2012年
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Physics Procedia 36 318-323 2012年 査読有り© 2012 Published by Elsevier B.V. Selection and/or peer-review under responsibility of the Guest Editors. The Mattis-Bardeen theory for the anomalous skin effect in the superconductors has been extended taking the complex gap energy into account and the surface impedance of superconductors has been calculated using the extended Mattis- Bardeen theory. It is found that the surface resistance of the superconductor increases with increasing magnitude of the imaginary part of the gap energy. It is demonstrated that the calculated surface resistance for a NbN film quantitatively agrees with the measured one. It is also found that temperature dependence of Q values of superconducting resonators is well described by those calculated by the extended Mattis-Bardeen equation.
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Proceedings of SPIE - The International Society for Optical Engineering 8452 2012年 査読有りA precise measurement of the Cosmic Microwave Background (CMB) provides us a wealth of information about early universe. LiteBIRD is a future satellite mission lead by High Energy Accelerator Research Organization (KEK) and its scientific target is detection of the B-mode polarization of the CMB, which is a footprint of primordial gravitational waves generated during inflation era, but has not been successfully observed so far due to lack of sensitivity. Microwave Kinetic Inductance Detector (MKID) is one candidate of sensitive millimeterwave camera which will be able to detect the B-mode polarization. We have been developing MKID at National Astronomical Observatory of Japan (NAOJ) in cooperation with KEK and RIKEN for the focal plane detector of the LiteBIRD. The developed technologies are: fabrication process of MKIDs with epitaxially-formed aluminum (Al) on silicon (Si) wafer; optical system of the camera consisting of double-slot antenna with Si lens array; and readout circuit utilizing Fast Fourier Transform Spectrometer (FFTS). With these technologies, we designed a prototype MKIDs camera for the LiteBIRD. © 2012 SPIE.
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23rd International Symposium on Space Terahertz Technology 2012, ISSTT 2012 105-108 2012年 査読有りWe have developed a transportable 30-cm submillimeter-wave telescope to operate at the Dome Fuji station in Antarctic plateau. Transportability is an important requirement in the design; the telescope can be divided into several components by hands. The maximum weight of the components is restricted to be below 60 kg, so that the telescope can be assembled without a lifting machine. A small 4K mechanical cooler is used for cooling down a SIS mixer. Total power consumption was designed to be less than 2.5 kW. The 30-cm offset Cassegrain antenna produces a 9′ beam that is same angular resolution of those of the Columbia-CfA and U. Chile CO (J=1-0) survey. The optical system is designed to satisfy the frequency independent matching condition at the subreflector and the feed horn of the SIS mixer, so we could accommodate a higher frequency receiver without changing mirrors. A quasi-optical filter was employed for single the sideband operation in observation of the CO (J=4-3) line at 461 GHz and the [CI] (3P1-3Po) line at 492 GHz. It is equipped with a 1 GHz width spectrometer that covers a velocity width of 600 km·s -1 with a velocity resolution of 0.04 km·s-1 at 461 GHz. We carried out test observations at a 4400-m altitude site in northern Chile during winters of 2010 and 2011. The typical system noise temperature including atmospheric loss was 3000 K (SSB) at 461 GHz that is mainly limited by atmospheric opacity. The beam size was measured to be 9′.4 ± 0′.4 by cross scanning of the sun. We estimated the main beam efficiency to be 87 ± 5% by observing the new moon. We succeeded in mapping Orion Molecular Cloud A and M17 SW in CO (J=4-3) followed by test observations toward Orion KL in both CO (J=4-3) and [CI] (3P1-3Po). Index Terms-Antarctic plateau, transportable telescope, submillimeter astronomy.
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23rd International Symposium on Space Terahertz Technology 2012, ISSTT 2012 39-41 2012年 査読有りWe have developed 220 GHz camera using microwave kinetic inductance detectors (MKIDs) for astronomical observations. The optical system of the MKID camera is based on double slot antennas and an extended hemispherical silicon lens array. The diameter of the lens was determined as three times larger than the wavelength at 220 GHz. The 220 GHz camera has 9 pixels. The silicon lens array has been directly machined by highspeed spindle on an ultra-precision machine. The shape fabrication error and the surface roughness of the top of the lens were less than 20 urn (Peak-to-Valley) and about 0.7 urn (rms), respectively. The beam patterns of the MKID camera were measured and are in good agreement with the calculations.
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Publications of the Astronomical Society of Japan 61(5) 1065-1080 2009年 査読有りA beam waveguide system for connecting the ALMA front-end, which has been designed for the Cassegrain focus of the ALMA 12-m antenna, with the ALMA/ACA 7-m antenna was designed. The beam waveguide system, covering 30-950 GHz, consists of flat mirrors or prisms to modify the boresight tilt angle from the front-end, and recovers more than the half of the sensitivity loss caused by a misalignment between the front-end optics and the 7-m antenna. No mechanical alignment procedure is needed for installation of the beam waveguide system, and thus it does not impact on the maintenance/operation scheme of the front-end system. Beam-pattern measurements in the frequency ranges of ALMA bands 4 (144 GHz), 6 (252 GHz), and 8 (385 GHz) have confirmed that directions of the radiation patterns transmitted to the subreflector are successfully shifted by the beam waveguide system without any serious deformation of the beam. The aperture efficiencies calculated from the measured radiation patterns were determined to be 84.6% at 144GHz, 86.1% at 252 GHz, and 84.8% at 385 GHz, which are consistent with those of a simulated radiation pattern. © 2009. Astronomical Society of Japan.
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2009 3RD EUROPEAN CONFERENCE ON ANTENNAS AND PROPAGATION, VOLS 1-6 2341-+ 2009年 査読有りIn this paper, the optical performance of the ALMA Band 8 (385-500 GHz) cartridge receiver (S/N 01), which is the first one of 80 shipments, was investigated. ALMA Band 8 cartridge receiver consists of a corrugated horn, an Ortho-Mode Transducer, an elliptical mirror, a local oscillator, IF amplifiers, and superconducting-insulator-superconducting (SIS) mixers which cover IF frequency range from 4 to 8 GHz. The amplitude and phase of electric field at near-field were probed, and then the far-field co-polar and cross-polar patterns of the receiver were transferred. The far-field patterns are symmetrical, low side-lobe and compatible with physical optics simulations down to -30 dB. We confirmed that the aperture efficiency at sub-reflector of 12-m antenna are around 80 %-and cross-pol. efficiency are about 20 dB at five frequencies.
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LOW TEMPERATURE DETECTORS LTD 13 1185 393-+ 2009年 査読有りWe describe the development of large format array of superconducting tunnel junction detectors that is readout by SONY GaAs-JFET cryogenic integrated circuits. High quality SIS photon detectors have high dynamic impedance that can be readout by low gate leakage GaAs-JFET circuits. Our imaging array design, with niobium SIS photon detectors and GaAs-JFET cryogenics electronics, uses integrating amplifiers, multiplexers and shift-registers to readout large number of pixels that is similar to CMOS digital cameras. We have designed and fabricated GaAs-JFET cryogenic integrated circuits, such as AC-coupled capacitive trans-impedance amplifier, multiplexers with sample-and-holds and shift-registers, for 32-channel readout module. The Advanced Technology Center of National Astronomical Observatory of Japan have started extensive development program for large format array of SIS photon detectors.
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2009 34TH INTERNATIONAL CONFERENCE ON INFRARED, MILLIMETER, AND TERAHERTZ WAVES, VOLS 1 AND 2 526-+ 2009年 査読有りIn this paper, the optical design of astronomical detector array with SIS for 600 - 700 GHz is proposed. A unit has 127 pixel, and SIS junctions are coupled to double slot antennas and extended hemisphere lens made from Silicon or Alumina ceramics. A lens with multi-pixel system is compared to 1 lens with 1 antenna system (fly-eye)from the view point of antenna spacing, aberration, and beam efficiency.
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 60(5) 1199-1207 2008年10月 査読有りWe have developed a cartridge-type receiver covering the frequency band of 385-500GHz as a qualification model of Atacama Large Millimeter/submillimeter Array (ALMA) band 8. It receives two orthogonal polarizations and down-converts the sideband-separated signals to intermediate frequencies (IF) of between 4 and 8GHz. The cartridge-type receiver consists of cold optics, two feed horns, a wire grid, mirrors, two sideband-separating SIS mixers, cryogenic multipliers of a local oscillator (LO), cryogenic and warm IF amplifiers, a cartridge body, and sensors/wirings. These components were individually tested, and then the cartridge was integrated and tested as a complete assembly. We have also developed equipment for efficiency tests of both the components and the integrated receiver. The single sideband (SSB) noise temperature of this receiver is 100K at the band center and 300K at the band edges. The beam pattern and cross-polarization pattern are consistent with a physical optical calculation. The amplitude stability is around 3 x 10(-4) in 1 s. The phase stability is less than 2.degrees 0 on a time scale of 0.1 s to 10 min. These results are promising for a receiver in the ALMA.
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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 108(100) 117-121 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。
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 60(3) 407-419 2008年6月 査読有りThe "integral-shaped filament" of the Orion A giant molecular cloud was mapped in N2H+, and its nor-them end, the OMC-2/3 region, was also observed in HC3N and CCS. The results were compared with maps of other molecular lines and the dust continuum emission. The N2H+ distribution is similar to the dust continuum distribution, except for the central part of the Orion Nebula. The distribution of (HCO+)-C-13 holds a resemblance to that of the dust continuum, but the N2H+ distribution looks more similar to the dust continuum distribution. The N-bearing molecules, N2H+ and NH3, seem to be more intense in OMC-2, compared with the, (HCO+)-C-13 and CS distribution. This suggests that OMC-2 has a higher abundance of N-bearing molecules, or a higher filling factor of the quiescent gas. We identified 34 cloud cores from N2H+ data. Over the Orion Nebula region, the N2H+ linewidth is large (1.1-2.1 km s(-1)). In the OMC-2/3 region, it becomes moderate (0.5-1.3 km s(-1)), and it is smaller (0.3-1.1 km s(-1)) in the south of the Orion Nebula. On the other hand, the gas kinetic temperature of the quiescent cores observed in N2H+ is rather constant (similar to 20 K) over the integral-shaped filament. We detected no CCS emission in the OMC-2/3 region. In general, the N2H+ and HC3N distribution is quite similar in the OMC-2/3 region, but we observed a displacement between N2H+ and HC3N over a 2' scale in OMC-3, which has a chain of Class 0-I protostars (candidates).
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Astrophysics and Space Science Proceedings (202419) 359-359 2008年 査読有り
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Proceedings of the 19th International Symposium on Space Terahertz Technology, ISSTT 2008 498-503 2008年 査読有りWe measured corrugated horns, OMTs [1] (Orthomode Transducer), optics blocks at room temperature with a vector near field measurement system. The amplitude and phase measured at near-field are transformed to far-field pattern, and compared to calculations with Grasp 9 and CORRUG The co-polar beams were found to be consistent with the simulations at 385, 442, 500 GHz, and the calculated taper efficiency at the sub-reflector of ALMA 12-m antenna was greater than 92 %. Side lobe was less than-30 dB. The peak of cross-polar relative to co-polar found to be less than-20.5 dB. In addition, to evaluate accuracy of measurements, we studied both effects of standing wave and stability of the amplitude and phase. The error of the far-field was found to be less than 0.2dB between 0 and-20 dB range.
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Proceedings of the 19th International Symposium on Space Terahertz Technology, ISSTT 2008 234-238 2008年 査読有りWe have developed a cartridge-type receiver covering from 385 to 500 GHz for pre-production of ALMA Band 8. It receives two orthogonal polarizations and down-converts the sideband-separated signals to intermediate frequencies (IF) between 4 and 8 GHz. The cartridge-type receiver consists of a cold optics, a feed horn, an OMT, two sideband-separating SIS mixers, cryogenic multipliers of local oscillator (LO). These components were individually tested and then the cartridge was integrated and tested as a complete assembly. We have also developed equipment to test both components and the integrated receiver. The single sideband (SSB) noise temperature of this receiver is 130 K at the band center and 180 K at the band edges. The beam pattern and cross-polarization pattern are consistent with physical optical calculation. These results are promising for receiver production to the Atacama Large Millimeter/submillimeter Array (ALMA).
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Proceedings of the 19th International Symposium on Space Terahertz Technology, ISSTT 2008 521-526 2008年 査読有りWe report on the development of an orthomode transducer (OMT) for ALMA Band 8 (385-500 GHz). The OMT is a scaled model of that of ALMA Band 4 (125-163 GHz), which has a Bifot junction and a double ridge. The transmission loss of the OMT at 4 K was derived to be 0.4-0.5 dB from noise measurements with an SIS mixer. The polarization isolation was measured to be larger than 20 dB from quasioptical measurements. For electromagnetic design, effects of mechanical errors have been studied and then a robust design with allowable mechanical errors of 10 μm has been obtained.
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INTERNATIONAL JOURNAL OF INFRARED AND MILLIMETER WAVES 28(11) 1039-1042 2007年11月 査読有り
講演・口頭発表等
78共同研究・競争的資金等の研究課題
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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
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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
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専任大学名東京大学（University of Tokyo)
