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 教授東京大学大学院 理学系研究科 物理学専攻 教授量子場計測システム国際拠点(QUP) (主任研究者)北里大学大学院 理学研究科 客員教授
- 学位
- 博士（理学）(1996年3月 東京大学)
- ORCID ID
https://orcid.org/0000-0003-4885-5537- J-GLOBAL ID
- 200901003330670433
- Researcher ID
- C-2252-2008
- researchmap会員ID
- 5000019022
- 外部リンク
経歴
2-
2002年7月 - 2018年1月
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1993年 - 2002年
学歴
2-
1989年4月 - 1993年3月
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1985年4月 - 1989年3月
委員歴
2-
2017年10月 - 2023年9月
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2014年10月 - 2017年9月
論文
240-
Publications of the Astronomical Society of Japan 66(2) 2014年 査読有りThe quantitative measurement of O VII line intensity is a powerful method for understanding the soft X-ray diffuse background. By systematically analyzing the O VII line intensity in 145 high-latitude Suzaku/XIS observations, the flux of O I fluorescent line in the XIS spectrum, contaminating the O VII line, is found to have an increasing trend with time especially after 2011. For these observations, the O VII line intensity would be overestimated unless taking into consideration the O I fluorescent line contamination. Since the O I line emission originates from solar X-rays, this increase suggests that the flux of incident solar X-rays at the O I fluorescence energy tend to be larger than that in the early phase of Suzaku observations (2005-2010). © 2014 The Author.
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Journal of Low Temperature Physics 176(5-6) 733-740 2014年 査読有りLiteBIRD is a next-generation satellite mission to measure the polarization of the cosmic microwave background (CMB) radiation. On large angular scales the B-mode polarization of the CMB carries the imprint of primordial gravitational waves, and its precise measurement would provide a powerful probe of the epoch of inflation. The goal of LiteBIRD is to achieve a measurement of the characterizing tensor to scalar ratio r to an uncertainty of δr = 0.001. In order to achieve this goal we will employ a kilo-pixel superconducting detector array on a cryogenically cooled sub-Kelvin focal plane with an optical system at a temperature of 4 K. We are currently considering two detector array options transition edge sensor (TES) bolometers and microwave kinetic inductance detectors. In this paper we give an overview of LiteBIRD and describe a TES-based polarimeter designed to achieve the target sensitivity of 2 μK arcmin over the frequency range 50-320 GHz. © 2014 Springer Science+Business Media New York.
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Cryogenics 64 182-188 2014年 査読有りAstro-H is the Japanese X-ray astronomy satellite to be launched in 2015. The Soft X-ray Spectrometer (SXS) on board Astro-H is a high energy resolution spectrometer utilizing an X-ray micro-calorimeter array, which is operated at 50 mK by the ADR with the 30 liter superfluid liquid helium. The mechanical cryocoolers, 4 K-class Joule Thomson (JT) cooler and 20 K-class double-staged Stirling (2ST) cooler, are key components of the SXS cooling system to extend the lifetime of LHe cryogen beyond 3 years as required. Higher reliability was therefore investigated with higher cooling capability based on the heritage of existing cryocoolers. As the task of assessing further reliability dealt with the pipe-choking phenomena by contaminant solidification of the on-orbit SMILES JT cryocooler, outgassing from materials and component parts used in the cryocoolers was measured quantitatively to verify the suppression of carbon dioxide gas by their storage process and predict the total accumulated carbon dioxide for long-term operation. A continuous running test to verify lifetime using the engineering model (EM) of the 4 K-JT cooler is underway, having operated for a total of 720 days as of June 2013 and showing no remarkable change in cooling performance. During the current development phase, prototype models (PM) of the cryocoolers were installed to the test SXS dewar (EM) to verify the overall cooling performance from room temperature to 50 mK. During the EM dewar test, the requirement to reduce the transmitted vibration from the 2ST cooler compressor was recognized as mitigating the thermal instability of the SXS microcalorimeter at 50 mK.
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Journal of Low Temperature Physics 176(3-4) 578-583 2014年 査読有りA four-pixel-array superconducting transition-edge sensor (TES) microcalorimeter with a mushroom-shaped absorber was developed for energy dispersive spectroscopy performed on a transmission electron microscope. The TES consists of a bilayer of Au/Ti with either a 120- or 50-nm thickness. The absorber is made from a Au layer and its stem is deposited in the center of the TES surface. A Ta22O5 insulating layer of 100-nm thickness is inserted between the overhang region of the absorber and the TES surface. Two types of microcalorimeter were fabricated with differing absorber thicknesses of 0.5 and 5.0 μ m. An energy resolution of 15 eV FWHM with 5.9-keV X-rays was obtained using the 0.5- μ m-type microcalorimeter. © 2014 Springer Science+Business Media New York.
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Journal of Low Temperature Physics 176(3-4) 400-407 2014年 査読有りWe are developing frequency-division multiplexing (FDM) systems with baseband feedback for TES X-ray microcalorimeter arrays for use with the DIOS mission. To meet the requirement of limited cooling capacity at cryogenic temperatures, we developed low-power and FDM-optmized dc-SQUIDs. To make maximum use of the SQUIDs, we also developed digital electronics using FPGA evaluation boards and ADC/DAC FMC daughter cards, and evaluated signal-to-noise ratios and gain-bandwidth products. © 2014 Springer Science+Business Media New York.
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Publications of the Astronomical Society of Japan 65(2) 2013年4月25日 査読有りLong-term time variabilities of the OVII (0.57 keV) emission in the soft X-ray diffuse background were studied using six Suzaku annual observations of the blank sky towards the Lockman Hole made from 2006 to 2011. After time intervals in which the emission was enhanced on time scales of a few tens of ks were removed, the OVII intensity was found to be constant from 2006 to 2009 within 90% statistical errors. The intensity in 2010 and 2011 was higher by 2-3 LU (= photons s-1 cm-2 sr-1) than the earlier values. The most plausible origin of the fast variable component is Solar wind charge exchange (SWCX). The intensity increase is not positively correlated with the proton flux at the L1 point. Since all of the observations were made in the same season of a year, the variation cannot be explained by parallax of the SWCX-induced X-ray emission from the Heliosphere. We consider that it is related to geometrical changes of slow and fast solar wind structures associated with the 11 year solar activity. The observed variation was compared with that expected from the SWCX-induced X-ray emission model. © 2013 Astronomical Society of Japan.
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Publications of the Astronomical Society of Japan 65(2) 44-1-12 2013年 査読有り
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Sensors and Actuators, A: Physical 188 411-416 2012年12月 査読有りWe report on our first X-ray imaging test of our novel ultra-lightweight and high-resolution MEMS X-ray optics for future space astronomical missions. We have fabricated a single-stage test optic made of Si from a Si (1 1 1) wafer with a thickness of 300 μm. We conducted a dry etching and made 20 μm line and space through holes to use their side walls for X-ray mirrors. We have smoothed the side walls by annealing and plastically bending the wafer to a spherical shape with a curvature of radius of 1000 mm.We have irradiated Al Kα 1.49 keV to the test optic and, for the first time, have verified X-ray focusing. An evaluated angular resolution ranged from 26 to 130 arcmin, which is two orders of magnitude worse than our goal of 15 arcsec. We found that this degraded resolution is mainly due to a large surface roughness of the side walls > 10 μm scale and possibly the deformation process. An estimated X-ray reflectivity was also an order of magnitude lower than the theoretical value assuming flat side walls. We concluded that this could be due to the loss of the reflective area by the rough surface. Therefore, the future improvement on the large scale surface roughness is indispensable for the better angular resolution and effective area. © 2012 Elsevier B.V. All rights reserved.
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Experimental Astronomy 34(2) 519-549 2012年10月 査読有りORIGIN is a proposal for the M3 mission call of ESA aimed at the study of metal creation from the epoch of cosmic dawn. Using high-spectral resolution in the soft X-ray band, ORIGIN will be able to identify the physical conditions of all abundant elements between C and Ni to red-shifts of z = 10, and beyond. The mission will answer questions such as: When were the first metals created? How does the cosmic metal content evolve? Where do most of the metals reside in the Universe? What is the role of metals in structure formation and evolution? To reach out to the early Universe ORIGIN will use Gamma-Ray Bursts (GRBs) to study their local environments in their host galaxies. This requires the capability to slew the satellite in less than a minute to the GRB location. By studying the chemical composition and properties of clusters of galaxies we can extend the range of exploration to lower redshifts (z ~0. 2). For this task we need a high-resolution spectral imaging instrument with a large field of view. Using the same instrument, we can also study the so far only partially detected baryons in the Warm-Hot Intergalactic Medium (WHIM). The less dense part of the WHIM will be studied using absorption lines at low redshift in the spectra for GRBs. The ORIGIN mission includes a Transient Event Detector (coded mask with a sensitivity of 0. 4 photon/cm2/s in 10 s in the 5-150 keV band) to identify and localize 2000 GRBs over a five year mission, of which ~65 GRBs have a redshift > 7. The Cryogenic Imaging Spectrometer, with a spectral resolution of 2. 5 eV, a field of view of 30 arcmin and large effective area below 1 keV has the sensitivity to study clusters up to a significant fraction of the virial radius and to map the denser parts of the WHIM (factor 30 higher than achievable with current instruments). The payload is complemented by a Burst InfraRed Telescope to enable onboard red-shift determination of GRBs (hence securing proper follow up of high-z bursts) and also probes the mildly ionized state of the gas. Fast repointing is achieved by a dedicated Controlled Momentum Gyro and a low background is achieved by the selected low Earth orbit. © 2011 Springer Science+Business Media B.V.
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Journal of Low Temperature Physics 167(3-4) 226-231 2012年6月 査読有りA 3×3+1 superconducting transition-edge sensor (TES) microcalorimeter- array has been developed for the energy dispersive spectrometer performed on a transmission electron microscope. For increasing sensitive area, each TES microcalorimeter consisted of a Ti/Au bilayer and a mushroom shaped absorber. The mushroom shaped absorber is made from a Au layer of 0.5 μm thick. Geometrical dimensions of the surface area of the TES and the absorber are 350 μm × 350 μm and 330 μm × 330 μm, respectively. The absorber stem of 150 μm × 150 μm in the cross sectional area is deposited on the center of the TES surface. A Ta2O5 insulating layer of 0.1 μm thick is inserted between the overhang layer of the absorber and the TES surface. One pixel of the TES microcalorimeter was operated for detecting X-ray photons emitted from an 55Fe source. © Springer Science+Business Media, LLC 2012.
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Journal of Low Temperature Physics 167(3-4) 435-441 2012年6月 査読有りFor future X-ray astronomy, a microcalorimeter array that has both megapixel imaging capability and eV-level high energy-resolution is desirable. In order to realize it, thermometers with negligible self-heating, multiplexing readout and close packing are essential components. We propose a novel detector concept, a dielectric microcalorimeter (DMC) and present current design studies. The DMC uses dielectric pixels as thermometers which form LC resonators in GHz band. The signals from many pixels can be easily multiplexed in a similar way to kinetic inductance detectors. The dielectric pixels are easy to be integrated into large and dense arrays. However, dielectrics with temperature-dependent permittivity below 2 K were not known. We evaluated quantum ferroelectric strontium titanate (STO) used in a capacitive thermometer higher than 2 K as a suitable dielectric for the DMC pixels. We fabricated STO capacitors and measured their capacitance from 2 K down to 80 mK. As a result, we found that their capacitive thermometer sensitivity at 100 mK are d logC/d log T ∼ 10-3, and they can be sensitive enough to detect X-ray with a resonator. We report the concepts, the measurement details, expected response to X-ray irradiation and our designs of the DMC. © Springer Science+Business Media, LLC 2012.
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Cryogenics 52(4-6) 158-164 2012年4月 査読有りAstro-H is the Japanese X-ray astronomy satellite planned for launch in 2014. The Soft X-ray Spectrometer (SXS) onboard Astro-H, is a high energy resolution spectrometer utilizing an X-ray micro-calorimeter array, which is operated at 50 mK by the ADR with the 30-L superfluid liquid helium (LHe). The mechanical cryocoolers, 4 K-class Joule Thomson (JT) cooler and 20 K-class double-staged Stirling (2ST) cooler are key components to achieve a LHe lifetime for over 3 years in orbit (5 years as a goal). Based on the existing cryocoolers onboard Akari (2006) and JEM/SMILES (2009), modifications for higher cooling power and reliability had been investigated. In the present development phase, the Engineering Models (EMs) of these upgraded cryocoolers are fabricated to carry out verification tests for cooling performance, mechanical performance and lifetime. Nominal cooling power of 200 mW at 20 K for the 2ST cooler and 40 mW at 4.5 K for the JT cooler were demonstrated with temperature and power margin. Mechanical performance test for the 2ST cooler units proves tolerability for pyro shock and vibration environment of the Astro-H criteria. Continuous running of the 4 K-class JT cooler combined with the 2ST precooler for lifetime test has achieved over 5000 h without any degradation of cooling performance. © 2012 Elsevier Ltd. All rights reserved.
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日本原子力学会 年会・大会予稿集 2012 77-77 2012年我々は透過型電子顕微鏡に搭載するエネルギー分散型X線検出器として、超伝導転移端温度センサー(TES)型X線検出器の開発研究を展開している。本研究では、4ピクセル配置のTES型X線検出器を試作した。個々のピクセルは、TESの全面を厚さ0.5μmのAu吸収体層が覆い、TESとの間に厚さ0.1μmのTa2O5絶縁層が挿入されている。選択した2ピクセルについてX線検出特性を測定した。
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Journal of Low Temperature Physics 167(5-6) 759-764 2012年 査読有りWe have been improving our TEM-EDS for elemental microanalysis after a successful achievement of a high energy resolution (7.8 eV at 1.7 keV) using a TES microcalorimeter. The improvements fall into a 3D superconductive wiring and a high-speed processing (∼3,000 cps). We are implementing a 10-ch TES array for higher count rate and a broader dynamic range. The shape of a probe needs to be a small polygonal rod with an approximate size of 1 cm × 1 cm× 10 cm, and hence the placing and wiring of the TES array and read-out circuits at the cryogenic stage were very demanding. We overcame those difficulties by 3D photolithography and electrodeposition. With these new technologies, we developed the OFC probe with solder-plated 3D wiring, and successfully observed a superconductivity at the temperature of liquid helium. As a required count rate per channel is ∼300 cps, the overall system count rate is ∼3,000 cps, which is incomparably higher than before. In the last model, we used an embedded system to process waveforms from a 4-ch 14-bit 1 MS/s ADC due to a small signal bandwidth, but this time we parallelized three identical ADCs and transfer raw waveforms by Ethernet lines to a host to achieve the required system count rate. © Springer Science+Business Media, LLC 2012.
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PASJ : publications of the Astronomical Society of Japan 64(1) "18-1"-"18-14" 2012年 査読有り
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Journal of Low Temperature Physics 167(5-6) 795-802 2012年 査読有りThe science and an overview of the Soft X-ray Spectrometer onboard the STRO-H mission are presented. The SXS consists of X-ray focusing mirrors and a microcalorimeter array and is developed by international collaboration lead by JAXA and NASA with European participation. The detector is a 6 × 6 format microcalorimeter array operated at a cryogenic temperature of 50 mK and covers a 3' × 3' field of view of the X-ray telescope of 5.6 m focal length. We expect an energy resolution better than 7 eV (FWHM, requirement) with a goal of 4 eV. The effective area of the instrument will be 225 cm2 at 7 keV by a factor of about two larger than that of the X-ray microcalorimeter on board Suzaku. One of the main scientific objectives of the SXS is to investigate turbulent and/or macroscopic motions of hot gas in clusters of galaxies. © Springer Science+Business Media, LLC 2012.
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Astrophysical Journal Letters 742(2) 2011年12月1日 査読有りA bright, nearby edge-on starburst galaxy, NGC253, was studied using the Suzaku, XMM, and Chandra X-ray observatories. With Suzaku and XMM we detected complex line structure of Fe K, which is resolved into three lines (FeI at 6.4keV, FeXXV at 6.7keV, and FeXXVI at 7.0keV) around the center of NGC253. Especially, the FeI and FeXXVI lines are the first clear detections, with a significance of > 99.99% and 99.89% estimated by a Monte Carlo procedure. Imaging spectroscopy with Chandra revealed that the emission is distributed in ∼60arcsec2 region around the nucleus, which suggests that the source is not only the buried active galactic nucleus. The flux of highly ionized Fe lines can be explained by the accumulation of 10-1000 supernova remnants that are the result of high star-forming activity, while the FeI line flux is consistent with the fluorescent line emission expected with the molecular clouds in the region. © 2011. The American Astronomical Society. All rights reserved..
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Publications of the Astronomical Society of Japan 63 S889-S901 2011年 査読有りWe present a detailed spectroscopic study of the hot gas toward the galactic bulge along the 4U 1820-303 sight line by a combination analysis of emission and absorption spectra. In addition to the absorption lines of O VII K alpha, O VII K beta, O VIII K alpha, and Ne IV K alpha by Chandra LTGS, as shown by previous studies. Suzaku clearly detected the emission lines of O VII, O VIII, Ne IX, and Ne X from the vicinity. We used simplified plasma models with constant temperature and density. An evaluation of the background and foreground emission was carefully performed, including the stellar X-ray contribution based on the recent X-ray observational results and the stellar distribution simulator. If we assume that one plasma component exists in front of 4U 1820-303 and the other one at the back, the obtained temperatures are T = (1.7 +/- 0.2) x 10(6) K for the front-side plasma and T = (3.9(-0.3)(+0.4)) x 10(6) K for the back-side. This scheme is consistent with a hot and thick ISM disk, as suggested by extragalactic source observations and an X-ray bulge around the galactic center.
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Publications of the Astronomical Society of Japan 62(6) 1445-1454 2010年12月25日 査読有りWe studied the temperature and metal abundance distributions of the intra-cluster medium (ICM) in a group of galaxies, NGC 1550, observed with Suzaku. NGC 1550 is classified as a fossil group, which has few bright member galaxies, except for the central galaxy. Thus, such a type of galaxy is important to investigate how metals are enriched to the ICM. With the Suzaku XIS instrument, we directly measured not only the Si, S, and Fe lines, but also the O and Mg lines, and obtained those abundances to an outer region of ∼0.5r180 for the first time, and confirmed that the metals in the ICM of such a fossil group are indeed extending to a large radius. We found steeper gradients for the Mg, Si, S, and Fe abundances, while O showed an almost flat abundance distribution. Abundance ratios of α-elements to Fe were similar to those of the other groups and poor clusters. We calculated the number ratio of type II to type Ia supernovae for the ICM enrichment to be 2.9±0.5 within 0.1r180 the value is consistent with those for the other groups and poor clusters observed with Suzaku. We also calculated the metal mass-to-light ratios (MLRs) for Fe, O, and Mg with the B-band and K-band luminosities of the member galaxies of NGC 1550. The derived MLRs are comparable to those of the NGC 5044 group in the r < 0.1r180 region, while those of NGC 1550 are slightly higher than those of NGC 5044 in the outer region. © 2010. Astronomical Society of Japan.
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Cryogenics 50(9) 597-602 2010年9月 査読有りWe report a development of a portable dewar with a double-stage ADR in it, and its cooling test results. The purpose of this system is to establish a cooling cycle of double-stage adiabatic demagnetization from 4.2 K to 50 mK, which is strongly desired for future space science missions. In our test dewar, two units of ADR are installed in parallel at the bottom of a liquid He tank. We used 600 g of GGG (Gadolinium Gallium Garnet) for the higher temperature stage (4 Tesla) and ∼90 g of CPA (Chromic Potassium Alum) for the lower temperature stage (3 Tesla). A passive gas-gap heat switch (PGGHS) is used between these two stages, while a mechanical heat switch between the He tank and the GGG stage. Using this system, 50 mK was achieved, and various kinds of cooling cycles with different operating temperatures and different sequences of magnetization were tested. We also evaluated the performance of the PGGHS, and interference of the magnetic field with each other during a stable temperature control. © 2010 Elsevier Ltd. All rights reserved.
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Cryogenics 50(9) 488-493 2010年9月 査読有りThe Soft X-ray Spectrometer (SXS) is a cryogenic high resolution X-ray spectrometer onboard the X-ray astronomy satellite Astro-H which will be launched in 2014. The detector array is cooled down to 50 mK using an adiabatic demagnetization refrigerator (ADR). The cooling chain from the room temperature to the ADR heat-sink is composed of superfluid liquid He, a Joule-Thomson cryocooler, and double-stage Stirling cryocoolers. It is designed to keep 30 l of liquid He for more than 5 years in the normal case, and longer than 3 years even if one of the cryocoolers fails. Cryogen-free operation is also possible in the normal case. It is fully redundant from the room temperature to the ADR heat-sink. © 2010 Elsevier Ltd. All rights reserved.
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Publications of the Astronomical Society of Japan 62(4) 981-986 2010年8月25日 査読有りWe report on the detection of a time variable O VII line emission in a deep 100ks Suzaku X-ray Imaging Spectrometer spectrum of the galactic ridge X-ray emission. The observed line intensity is too strong (11 ±2 line unit or photon cm-2 s-1 sr-1) to be emitted inside the heavily obscured galactic disk. It showed a factor of two time variation that showed a significant (∼4σ) correlation with the solar-wind O 7+ ion flux. The high line intensity and good time correlation with the solar wind strongly suggests that it originated from geocoronal solar-wind charge-exchange emission. We discuss the X-ray line intensity while considering a line-of-sight direction and also theoretical distribution models of the neutral hydrogen and solar wind around Earth. Our results indicate that X-ray observations of geocoronal solar-wind charge-exchange emission can be used to constrain these models. © 2010. Astronomical Society of Japan.
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Microsystem Technologies 16(8-9) 1633-1641 2010年8月 査読有りWe are developing novel ultra light-weight and high-resolution X-ray micro pore optics for space X-ray telescopes. In our method, curvilinear micro pore structures are firstly fabricated by silicon deep reactive ion etching (DRIE) or X-ray LIGA processes. Secondly, side walls of the micro structures are smoothed by magnetic field assisted finishing and/or hydrogen annealing techniques for high reflectivity mirrors. Thirdly, to focus parallel X-ray lights from astronomical objects, these structures are elastically or plastically bent into a spherical shape. Fourthly, the bent structures are stacked to form a multistage X-ray telescope. In this paper, we report on fabrication and X-ray reflection tests of silicon and nickel X-ray mirrors using the DRIE and LIGA processes, respectively. For the first time, X-ray reflections were confirmed on both of the mirrors. Estimated rms roughnesses were 5 nm and 3 nm for the silicon and nickel mirrors, respectively. © 2009 Springer-Verlag.
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Applied Optics 49(18) 3511-3521 2010年6月20日 査読有りX-ray astronomy research is often limited by the size, weight, complexity, and cost of functioning x-ray optics. Micropore optics promises an economical alternative to traditional (e.g., glass or foil) x-ray optics however, many manufacturing difficulties prevent micropore optics from being a viable solution. Ezoe et al. introduced microelectromechanical systems(MEMS)micropore optics having curvilinear micropores in 2008. Madeby either deep reactive ion etching or x-ray lithography, electroforming, and molding (LIGA), MEMSmicropore optics suffer from high micropore sidewall roughness (10-30 nm rms) which, by current standards, cannot be improved. In this research, a new alternating magnetic-field-assisted finishing process was developed using a mixture of ferrofluid and microscale abrasive slurry. A machine was built, and a set of working process parameters including alternating frequency, abrasive size, and polishing time was selected. A polishing experiment on a LIGA-fabricated MEMS micropore optic was performed, and a change in micropore sidewall roughness of 9:3 ± 2:5 nm rms to 5:7 ± 0:7 nm rms was measured. An improvement in x-ray reflectancewas also seen. This research shows the feasibility and confirms the effects of this new polishing process on MEMS micropore optics. © 2010 Optical Society of America.
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Applied Optics 49(6) 1007-1011 2010年2月20日 査読有りThe x-ray reflectivity of an ultralightweight and low-cost x-ray optic using anisotropic wet etching of Si (110) wafers is evaluated at two energies, C Kα 0:28 keV and Al Kα 1:49 keV. The obtained reflectivities at both energies are not represented by a simple planar mirror model considering surface roughness. Hence, an geometrical occultation effect due to step structures upon the etched mirror surface is taken into account. Then, the reflectivities are represented by the theoretical model. The estimated surface roughness at C Kα (∼6nmrms) is significantly larger than ∼1nm at Al Kα. This can be explained by different coherent lengths at two energies. © 2010 Optical Society of America.
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Journal of Electron Microscopy 59(1) 17-26 2010年2月 査読有りA new energy dispersive X-ray spectrometer (EDS) with a mi- crocalorimeter detector equipped with a transmission electron microscope (TEM) has been developed for high- accuracy compositional analysis in the nanoscale. A superconducting transition-edge-sensor-type microcalorimeter is applied as the detector. A cryogen-free cooling system, which consists of a mechanical and a dilution refrigerator, is selected to achieve long-term temperature stability. In order to mount these detector and refrigerators on a TEM, the cooling system is specially designed such that these two refrigerators are separated. Also, the detector position and arrangement are carefully designed to avoid adverse affects between the superconductor detector and the TEM lens system. Using the developed EDS system, at present, an energy resolution of 21.92 eV full-width-at-half maximum has been achieved at the Cr Kα line. This value is about seven times better than that of the current typical commercial Si(Li) detector, which is usually around 140 eV. The developed microcalorimeter EDS system can measure a wide energy range, 1-20 keV, at one time with this high energy resolution that can resolve peaks from most of the elements. Although several further developments will be needed to enable practical use, highly accurate compositional analysis with high energy resolution will be realized by this microcalorimeter EDS system.
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Publications of the Astronomical Society of Japan 62(3) 723-733 2010年 査読有りWe present a detailed spectroscopic study of the hot gas in the Galactic halo toward the direction of a blazer PKS 2155-304 (z = 0.117). The O vil and O vIII absorption lines were measured with the Low and High Energy Transmission Grating Spectrographs aboard Chandra, and the O VII, O vIII, and Ne IX emission lines produced in an adjacent field of the PKS 2155-304 direction were observed with the X-ray Imaging Spectrometer aboard Suzaku. Assuming vertically exponential distributions of the gas temperature and the density, we performed a combined analysis of the absorption and emission data. The gas temperature and the density at the galactic plane were determined to be (2.5+0.3 +0.6) × 106K and (1.4-0.4+0.5) × 10-3cm-3, and the scale heights of the gas temperature and density were 5.6-4.2+7.4 kpc and 2.3 -0.8+0.9kpc, respectively. These values are consistent with those obtained in the LMC X-3 direction. © 2010. Astronomical Society of Japan.
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IEEE Journal of Quantum Electronics 46(9) 1309-1312 2010年 査読有りWe have been developing novel microelectromechanical systems X-ray optics for future satellites. It can be ultra-lightweight and of high-resolution. For the first time, we fabricated a spherical test optics made of silicon. We used the dry etching and hot plastic deformation method. We conducted imaging tests to examine whether it can focus a parallel beam of light. Visible light was selected instead of X-rays because of the convenience of testing. The focusing was confirmed with a fullwidth at half-maximum focal size of 2 arcmin. Since the focus is affected by optical diffraction, a smaller focus can be expected in future X-ray imaging tests. © 2010 IEEE.
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PASJ : publications of the Astronomical Society of Japan 62(6) 1423-1433 2010年 査読有り
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IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 19(3) 456-459 2009年6月 査読有りWe fabricated 16 16 format arrays of 180 square Ti/Au superconducting transition edge X-ray microcalorimeters of which transition temperatures range from 130 to 220 mK. All pixels are wired with Al, and stand on SiO(2) and SiN(x) membranes that work as a weak thermal link. The membrane structure is formed by deep reactive ion etching. Energy resolution of a pixel in the array without a Au absorber was 11 eV (FWHM) at 5.9 keV, while the baseline resolution is about 3.7 eV.
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EXPERIMENTAL ASTRONOMY 23(1) 67-89 2009年3月How structures of various scales formed and evolved from the early Universe up to present time is a fundamental question of astrophysical cosmology. EDGE (Piro et al., 2007) will trace the cosmic history of the baryons from the early generations of massive stars by Gamma-Ray Burst (GRB) explosions, through the period of galaxy cluster formation, down to the very low redshift Universe, when between a third and one half of the baryons are expected to reside in cosmic filaments undergoing gravitational collapse by dark matter (the so-called warm hot intragalactic medium). In addition EDGE, with its unprecedented capabilities, will provide key results in many important fields. These scientific goals are feasible with a medium class mission using existing technology combined with innovative instrumental and observational capabilities by: (a) observing with fast reaction Gamma-Ray Bursts with a high spectral resolution. This enables the study of their star-forming and host galaxy environments and the use of GRBs as back lights of large scale cosmological structures; (b) observing and surveying extended sources (galaxy clusters, WHIM) with high sensitivity using two wide field of view X-ray telescopes (one with a high angular resolution and the other with a high spectral resolution). The mission concept includes four main instruments: a Wide-field Spectrometer (0.1-2.2 eV) with excellent energy resolution (3 eV at 0.6 keV), a Wide-Field Imager (0.3-6 keV) with high angular resolution (HPD = 15") constant over the full 1.4 degree field of view, and a Wide Field Monitor (8-200 keV) with a FOV of A1/4 of the sky, which will trigger the fast repointing to the GRB. Extension of its energy response up to 1 MeV will be achieved with a GRB detector with no imaging capability. This mission is proposed to ESA as part of the Cosmic Vision call. We will outline the science drivers and describe in more detail the payload of this mission.
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日本物理学会講演概要集 64 254-254 2009年
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LOW TEMPERATURE DETECTORS LTD 13 1185 757-+ 2009年 査読有りThe International X-Ray Observatory (IXO) is under formulation by NASA, ESA and JAXA for deployment in 2022. IXO emerged over the last 18 months as the NASA Constellation-X and ESA/JAXA X-Ray Evolving Universe Spectrometer (XEUS) missions were combined. The driving performance requirements for the X-Ray Microcalorimeter Spectrometer (XMS) are a spectral resolution of 2.5 eV over the central 2'x2' in the 0.3-7.0 keV band, and 10 eV to the edge of the 5'x5' field of view (FOV). The XMS is now based on a microcalorimeter array of Transition-Edge Sensor (TES) thermometers with Au/Bi absorbers and a SQUID MUX readout. One of the concepts studied as part of the mission formulation has a core 40x40 array corresponding to a 2'x2' FOV with 3 '' pixels surrounded by an outer, annular 52 x 52 array of 6 '' pixels that extends the field of view to 5.4'x5.4' with better than 10 eV resolution. There are several options for implementing the readout and cooling system of the XMS under study in the US, Europe and Japan. The ADR system will have from two to five stages depending on the performance of the cryocooler. Mechanical coolers with sufficient cooling power at 4K are available now, and similar to 2K coolers are under development. In this paper we give an overview of the XMS instrument, and some of the tradeoffs to be addressed for this observatory instrument.
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Astrophysical Journal 690(1) 143-153 2009年 査読有りWe present Suzaku spectra of X-ray emission in the fields just off the LMC X-3 sight line. O VII, O VIII, and Ne IX emission lines are clearly detected, suggesting the presence of an optically thin thermal plasma with an average temperature of 2.4 × 106 K. This temperature is significantly higher than that inferred from existing X-ray absorption line data obtained with Chandra grating observations of LMC X-3, strongly suggesting that the gas is not isothermal. We then jointly analyze these data to characterize the spatial and temperature distributions of the gas. Assuming a vertical exponential Galactic disk model, we estimate the gas temperature and density at the Galactic plane and their scale heights as 3.6(2.9, 4.7) × 106 K and 1.4(0.3, 3.4) × 10-3 cm-3 and 1.4(0.2, 5.2) kpc and 2.8(1.0, 6.4) kpc, respectively. This characterization can account for all the O VI line absorption, as observed in a Far Ultraviolet Spectroscopy Explorer spectrum of LMC X-3, but only predicts less than one-tenth of the O VI line emission intensity typically detected at high Galactic latitudes. The bulk of the O VI emission most likely arises at interfaces between cool and hot gases. © 2009. The American Astronomical Society. All rights reserved.
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 61 2009年 査読有り
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Superconductor Science and Technology 22(11) 2009年 査読有りA microcalorimeter array based on a transition-edge sensor (TES) thermometer is a promising imaging spectrometer for use in future x-ray astronomy missions. A TES microcalorimeter achieves eV energy resolution and an array of > 100 pixels also provides a moderate imaging capability. For a large format array, signal multiplexing at the low temperature stage is mandatory in order to reduce heat loads from cold stage preamplifiers and through wirings. We are developing frequency division multiplexing (FDM). In FDM, each TES is ac-biased with a different carrier frequency. Signals from several pixels are summed and then read out by one dc SQUID (superconducting quantum interference device). The maximum number of multiplexed pixels is limited by the bandwidth of a SQUID in a flux-locked loop. Assuming 1m cable length between the room temperature and the cold stage, the bandwidth is only < 1MHz with a standard flux-locked loop, due to the delay and phase shift of wirings. We report our development of baseband feedback, a new feedback scheme that overcomes the bandwidth limitation. In baseband feedback, the signal (kHz) from the TES is sent back to the SQUID after the phase of carrier frequency (∼1MHz) has been adjusted. We demonstrated open-loop gain of 8 for 10kHz signal at 5MHz carrier frequency, which indicates the possibility of ∼40-pixel multiplexing of the TES signal. © 2009 IOP Publishing Ltd.
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Publications of the Astronomical Society of Japan 61(4) 805-823 2009年 査読有りThe soft diffuse X-ray emission of twelve fields observed with Suzaku are presented together with two additional fields from previous analyses. All have galactic longitudes 65° < ℓ < 295° to avoid contributions from the very bright diffuse source that extends at least 30° from the Galactic center. The surface brightnesses of the Suzaku nine fields for which apparently uncontaminated ROSAT All Sky Survey (RASS) were available were statistically consistent with the RASS values, with an upper limit for differences of 17 × 10-6c s-1 arcmin-2 in R45-band. The O VII and O VIII intensities are well correlated to each other, and O VII emission shows an intensity floor at ∼ 2 photons s-1cm -2str-1 (LU). The high-latitude O VIII emission shows a tight correlation with excess of O VII emission above the floor, with (O VIII intensity) = 0.5 × [(O VII intensity) - 2 LU], suggesting that temperatures averaged over different line-of-sight show a narrow distribution around ∼ 0.2 keV. We consider that the offset intensity of O VII arises from the Heliospheric solar wind charge exchange and perhaps from the local hot bubble, and that the excess O VII (2-7 LU) is emission from more distant parts of the Galaxy. The total bolometric luminosity of this galactic emission is estimated to be 4 × 1039ergs-1, and its characteristic temperature may be related to the virial temperature of the Galaxy. © 2009. Astronomical Society of Japan.
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PASJ : publications of the Astronomical Society of Japan 61(1) S291-S298 2009年 査読有り
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PASJ : publications of the Astronomical Society of Japan 61(1) S353-S363 2009年 査読有り
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 61(SP1) S225-S232 2009年 査読有りIn order to elucidate the origin of galactic ridge X-ray emission, we analyzed Suzaku data taken at various regions along the galactic plane, and studied their Fe-K emission line features. Suzaku resolved the Fe line complex into three narrow lines at similar to 6.4 keV, similar to 6.7 keV and similar to 6.97 keV, which are K-lines from neutral (or low-ionized), He-like, and H-like iron respectively. The 6.7 keV line is clearly seen in all of the observed regions, and its longitudinal distribution is consistent with that determined from previous observations. The 6.4 keV emission line was also found in various galactic plane regions (b similar to 0 degrees). Differences in the flux ratios of the 6.4 keV/6.7 keV and 6.97 keV/6.7 keV lines between the galactic plane and the galactic center regions were studied and its implication was discussed.
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Publications of the Astronomical Society of Japan 61(5) 1093-1098 2009年 査読有りWe showed that if the non-thermal emission from the galactic center in the range 14-40 keV is due to inverse bremsstrahlung emission of subrelativistic protons, their interactions with hot and cold fractions of the interstellar medium are equally important. Our estimation shows that about 30% of the total non-thermal flux from the GC in the range 14-40 keV is generated in regions of cold gas while the rest is produced by proton interaction with hot plasma. From the spatial distribution of 6.7 keV iron line we concluded the spatial distribution of hot plasma is strongly non-uniform that should be taken into account in analysis of proton propagation in the GC. From the Suzaku data we got independent estimates for the diffusion coefficient of subrelativistic protons in the GC, which was in the range 1026-1027cm 2s-1. © 2009. Astronomical Society of Japan.
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Publications of the Astronomical Society of Japan 61(5) 1099-1105 2009年 査読有りWe analyse new results of Chandra and Suzaku Observatories which found a flux of hard X-ray emission from the compact region around Sgr A * (r ∼ 100 pc). We suppose that this emission is generated by accretion processes onto the central supermassive blackhole when an unbound part of captured stars obtains an additional momentum. As a result a flux of subrelativistic protons is generated near the galactic center which heats the background plasma up to temperatures about 6-10 keV and produces by inverse bremsstrahlung a flux of non-thermal X-ray emission in the energy range above 10 keV. © 2009. Astronomical Society of Japan.
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Publications of the Astronomical Society of Japan 61(4) 901-907 2009年 査読有りWe analyze the 6.4 keV line and continuum emission from the molecular cloud SgrB2 and the source HESS J1745-303, which is supposed to be a complex of molecular gas. From the HESS results it follows that Sgr A* is a source of high energy protons, which penetrate into molecular clouds producing there a TeV gamma-ray flux. We present arguments that Sgr A may also produce a flux of subrelativistic protons which generate the 6.4 keV line and bremsstrahlune continuum emission from the clouds. © 2009. Astronomical Society of Japan.
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Journal of Low Temperature Physics 151(3-4) 946-951 2008年5月 査読有りWe report on performance of 8-input superconducting quantum interference devices (SQUIDs) for multiplexing transition-edge sensor signals by using frequency-domain multiplexing. We found the typical critical current and the flux noise to be 17-19 μA and 0.7-1.1 μΦ0/Hz, respectively. We also measured the crosstalk current between the input coils of the SQUIDs, and found that the mutual inductance was consistent with the design value, 800 pH. We confirmed that the cross talk current due to the mutual inductance was reduced by the flux-locked-loop (FLL) feedback, and its reduction rate was consistent with 1/(1+L), where L is the FLL feedback gain. We also show the result of 2-channel DC-driven TES signals readout using the 8-input SQUIDs. © Springer Science+Business Media, LLC 2008.
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Journal of Low Temperature Physics 151(3-4) 733-739 2008年5月 査読有りThe EURECA project aims to demonstrate technological readiness of a micro-calorimeter array for application in future X-ray astronomy missions, like Constellation-X, EDGE, and XEUS. The prototype instrument consists of a 5 × 5 pixel array of TES-based micro-calorimeters read out by two SQUID-amplifier channels using frequency-domain-multiplexing (FDM) with digital base-band feedback. The detector array is cooled by a cryogen-free cryostat consisting of a pulse tube cooler and a two stage ADR. Initial tests of the system at the PTB beam line of the BESSY synchrotron showed stable performance and an X-ray energy resolution of 1.5 eV at 250 eV for read-out of one TES-pixel only. Next step is deployment of FDM to read-out the full array. Full performance demonstration is expected end 2008. © Springer Science+Business Media, LLC 2008.
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Journal of Low Temperature Physics 151(3-4) 997-1002 2008年5月 査読有りA digital processing system for a TES microcalorimeter array is being developed based on "SpaceWire" interface. In this system, we introduced a trigger logic which can handle double-pulse events due to high count rate in future X-ray missions and several application on the ground experiments. The detailed design and performance of this system is described. © Springer Science+Business Media, LLC 2008.
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Journal of Low Temperature Physics 151(1-2) 185-189 2008年4月 査読有りWe fabricated the TES microcalorimeter with TES(Ti/Au) and gold absorber, and obtained FWHM energy resolution of 4.8±0.3 eV at 5.9keV. The baseline resolution, i.e. the resolution determined by noise, was 4.1±0.1 eV. From the noise spectra we found that the square of the baseline resolution could be approximately decomposed into contributions of three noise components. They are estimated to be (2.5 eV) 2 (the intrinsic noise), (1.5 eV) 2 (the readout noise), and (3.0 eV) 2 (so-called excess noise). There is additional broadening of (2.5 eV) 2 from the baseline resolution. The excess noise is the largest limiting factor of the energy resolution of the device. © Springer Science+Business Media, LLC 2008.
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Journal of Low Temperature Physics 151(1-2) 345-350 2008年4月 査読有りWe report on the performance of two types of SQUID gradiometers developed for the readout of magnetic calorimeters. Our previously developed low dissipation SQUID gradiometer optimized for low temperature operation has demonstrated the flux noise level of ∼μΦ0/√Hz under a magnetic field of 2.5 mT and 150 mK. With a cylindrical Au:Er paramagnetic sensor mounted inside the octagonal pickup washer of the SQUID gradiometer, we succeeded in detecting X-ray signals. However, our achieved energy resolution was 47.2±2.1 eV at 5.9 keV limited by the high operating temperature of 150 mK and by a magnetic field, small for that temperature, due to the limited critical current of the field coils. Based on these results, we fabricated new arrays of SQUID gradiometer by tuning the line width and the number of turns of the field coils and shunt resistance to realize a lower noise level and a larger magnetic field. Furthermore, arrays of SQUID gradiometer with meander patterned pickup washer was fabricated which provides a stronger coupling between the paramagnetic sensor and the pickup washer, and a larger magnetic field at the sensor. © Springer Science+Business Media, LLC 2008.
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 60 S317-S331 2008年2月 査読有りThe compact group of galaxies HCG 62 (z = 0.0145) was observed for 120 ks with Suzaku XIS and HXD-PIN. The XIS spectra for four annular regions were fitted with a two-temperature vapec model with variable abundance, combined with the foreground Galactic component. The Galactic component was described by a two-temperature apec model, and constrained to have a common surface brightness among the four annuli. We confirmed the multitemperature nature of the intra-group medium, as reported previously, with a doughnut-like high temperature ring at radii 3'3-6'5. Abundances of Mg, Si, S, and Fe were well-constrained. We examined the possible "high-abundance arc" at'- 2; southwest from the center; however, Suzaku data did not confirm it. We suspect that it is a misidentification of an excess hot component in this region as the Fe line. Neither XIS (5-12 keV) nor HXD-PIN (12-40 keV) gave positive detection of the extended hard X-rays previously reported with ASCA, although our upper limit did not exclude the ASCA result. The 5-12 keV intensity in the r < 33 region turned out to be 70 19% higher than the nominal CXB level, and Chandra and Suzaku data suggest a concentration of hard X-ray sources with an average photon index of F = 1.3 8 0.06. The cumulative mass of 0, Fe, and Mg in the intra-group medium and the metal mass-to-light ratio were compared with those in other groups. The possible role of AGN or galaxy mergers in this group is also discussed.
MISC
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Space Telescopes and Instrumentation 2020: Optical, Infrared, and Millimeter Wave 2020年12月21日
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Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy X 2020年12月16日
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Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy X 2020年12月16日
担当経験のある科目(授業)
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2003年3月 - 現在宇宙物理学特論I (隔年開講，前期） (東京大学大学院)
所属学協会
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2010年 - 現在
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 学術変革領域研究(A) 2020年11月 - 2025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) 2019年4月 - 2022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) 2018年4月 - 2022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) 2018年4月 - 2021年3月
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日本学術振興会 科学研究費助成事業 基盤研究(S) 2014年5月 - 2019年3月
教育内容やその他の工夫
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件名宇宙研での大学院教育概要宇宙の構造形成の観測的研究を主に極低温観測技術を用いて行なっている。東京大学，北里大学から大学院学生をうけいれ，大学院では，新しい検出器の開発とその応用および観測的研究の専門教育を行なう。大学院では，「誰もやったことがないこと」を自ら行なう力をつけることを目標にする。
● 指導学生等の数
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年度2018年度(FY2018)博士課程学生数1修士課程学生数1
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年度2019年度(FY2019)博士課程学生数1修士課程学生数3
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年度2020年度(FY2020)博士課程学生数1修士課程学生数3
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年度2018年度(FY2018)博士課程学生数1修士課程学生数1
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年度2019年度(FY2019)博士課程学生数1修士課程学生数3
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年度2020年度(FY2020)博士課程学生数1修士課程学生数3
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年度2022年度(FY2022)博士課程学生数3修士課程学生数2
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年度2023年度(FY2023)博士課程学生数2修士課程学生数1
● 指導学生の顕著な論文
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指導学生名高久諒太所属大学東京大学著者名, ジャーナル名, 巻号ページ（出版年）Takaku et al. , Journal of Applied Physics, 128(22), id.225302, (2020)論文タイトルBroadband, millimeter-wave anti-reflective structures on sapphire ablatedwith femto-second laserDOIhttp://doi.org/10.1063/5.0022765
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指導学生名中島裕貴所属大学Univ. of Tokyo著者名, ジャーナル名, 巻号ページ（出版年）Nakashima et al. Applied Physics Letters, 117 122601 (2020)論文タイトルLow-noise microwave SQUID multiplexed readout of 38 x-ray transition-edge sensor microcalorimetersDOIhttp://doi.org/10.1063/5.0016333
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指導学生名紺野良平所属大学Kitasato Univ.著者名, ジャーナル名, 巻号ページ（出版年）Konno et al. Journal of Low Temperature Physics 199, 654 (2019)論文タイトルDevelopment of TES micsrocalorimters with solar-axion converterDOIhttp://doi.org/10.1007/s10909-019-02257-9
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指導学生名山本亮所属大学Univ. of Tokyo著者名, ジャーナル名, 巻号ページ（出版年）Yamamoto et al. , Journal of Cosmokogy and Astrophysics, 02 (2020) 011論文タイトルA Search for a Contribution from Axion-Like Particles to the X-Ray Diffuse Background Utilizing the Earth's Magnetic FieldDOIhttp://doi.org/10.1088/1475-7516/2020/02/011
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指導学生名関谷典央所属大学University. of Tokyo著者名, ジャーナル名, 巻号ページ（出版年）Sekiya, Yamasaki, and Mitsuda, Publications of Astronomical Society in Japan, 68(SP1), S31 (2016)論文タイトルSearch for a keV Signature of Radiatively Decaying Dark Matter with Suzaku XIS Observations of the X-ray Diffuse BackgroundDOIhttp://doi.org/10.1093/pasj/psv081
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指導学生名三石郁之所属大学Univ. of Tokyo著者名, ジャーナル名, 巻号ページ（出版年）Mitsuishi, Yamasaki, and Takei, Publications of Astronomical Society in Japan, 65, 44 (2013)論文タイトルAn X-Ray Study of the Galactic-Scale Starburst-Driven Outflow in NGC 253DOIhttp://doi.org/10.1093/pasj/65.2.44
● 専任大学名
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専任大学名東京大学（University of Tokyo)
● 所属する所内委員会
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所内委員会名ナノエレクトロニクスクリーンルーム運営委員会
