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
-
1993年 - 2002年
学歴
2-
1989年4月 - 1993年3月
-
1985年4月 - 1989年3月
委員歴
2-
2017年10月 - 2023年9月
-
2014年10月 - 2017年9月
論文
257-
Journal of Astronomical Telescopes, Instruments, and Systems 4(2) 2018年4月1日 査読有りThe Soft X-ray Spectrometer onboard the Astro-H (Hitomi) orbiting x-ray observatory featured an array of 36 silicon thermistor x-ray calorimeters optimized to perform high spectral resolution x-ray imaging spectroscopy of astrophysical sources in the 0.3-To 12-keV band. Extensive preflight calibration measurements are the basis for our modeling of the pulse height-energy relation and energy resolution for each pixel and event grade, telescope collecting area, detector efficiency, and pulse arrival time. Because of the early termination of mission operations, we needed to extract the maximum information from observations performed only days into the mission when the onboard calibration sources had not yet been commissioned and the dewar was still coming into thermal equilibrium, so our technique for reconstructing the per-pixel time-dependent pulse height-energy relation had to be modified. The gain scale was reconstructed using a combination of an absolute energy scale calibration at a single time using a fiducial from an onboard radioactive source and calibration of a dominant time-dependent gain drift component using a dedicated calibration pixel, as well as a residual time-dependent variation using spectra from the Perseus cluster of galaxies. The energy resolution was also measured using the onboard radioactive sources. It is consistent with instrument-level measurements accounting for the modest increase in noise due to spacecraft systems interference. We use observations of two pulsar wind nebulae to validate our models of the telescope area and detector efficiency and to derive a more accurate value for the thickness of the gate-valve Be window, which had not been opened by the time mission operations ceased. We use observations of the Crab nebula to refine the pixel-To-pixel timing and validate the absolute timing.
-
Cryogenics 91 27-35 2018年4月1日 査読有りASTRO-H was an X-ray astronomy satellite that the Japan Aerospace Exploration Agency (JAXA) developed to study the evolution of the universe and physical phenomena yet to be discovered. The primary scientific instrument of ASTRO-H was the Soft X-ray Spectrometer (SXS). Its detectors were to be cooled to 50 m K using a complex cryogenic system with a multistage adiabatic demagnetization refrigerator (ADR) developed by the National Aeronautics and Space Administration (NASA), and a cryogenic system developed by Sumitomo Heavy Industries, Ltd. (SHI). SHI's cryogenic system was required to cool the ADR's heatsink to 1.3 K or less in orbit for three years or longer. To meet these requirements, SHI developed a hybrid cryogenic system consisting of a liquid helium tank, a 4 K Joule-Thomson cooler, and two two-stage Stirling coolers. ASTRO-H was launched from Tanegashima Space Center on February 17, 2016. The initial operation of the SXS cryogenic system in orbit was completed successfully. The cooling performance was as expected and could have exceeded the lifetime requirement of three years. This paper describes results of ground tests, results of top-off filling of superfluid liquid helium just before launch, and cooling performance in orbit.
-
IEEE Transactions on Nuclear Science 65(2) 758-765 2018年2月1日 査読有りWe created a simple simulation model of transmitted X-rays in polycapillary optics for improved understanding of the transmission characteristics and to aid in the design of the geometrical parameters of the polycapillary optics. New polycapillary optics for a 64-pixel array transition-edge sensor (TES) microcalorimeter energy-dispersive spectrometer system that was installed in a scanning transmission electron microscope (STEM) were developed using the simulation model. The characteristic X-rays that are emitted from the STEM specimen were transmitted and focused on the pixel array TES microcalorimeter by the polycapillary optics. The experimental X-ray transmission characteristics of the manufactured polycapillary optics agreed with the simulated results.
-
Journal of Astronomical Telescopes, Instruments, and Systems 4(1) 2018年We summarize all of the in-orbit operations of the soft x-ray spectrometer (SXS) onboard the ASTRO-H (Hitomi) satellite. The satellite was launched on February 17, 2016, and the communication with the satellite ceased on March 26, 2016. The SXS was still in the commissioning phase, in which the set-ups were progressively changed. This paper is intended to serve as a concise reference of the events in orbit in order to properly interpret the SXS data taken during its short lifetime and as a test case for planning the in-orbit operation for future microcalorimeter missions.
-
Astrophysical Journal 862(1) 2018年 査読有りThe formation mechanism of the hot gaseous halo associated with the Milky Way is still under debate. We report new observational constraints on the gaseous halo using 107 lines of sight of the Suzaku X-ray observations at 75°< l < 285° and with a total exposure of 6.4 Ms. The gaseous halo spectra are represented by a singleerature plasma model in collisional ionization equilibrium. The median temperature of the observed fields is 0.26 keV (3.0 × 106 K) with a typical fluctuation of ∼30%. The emission measure varies by an order of magnitude and marginally correlates with the Galactic latitude. Despite the large scatter of the data, the emission measure distribution is roughly reproduced by a disk-like density distribution with a scale length of ∼7 kpc, a scale height of ∼2 kpc, and a total mass of ∼5 × 107 M. In addition, we found that a spherical hot gas with the β-model profile hardly contributes to the observed X-rays but that its total mass might reach 109 M. Combined with indirect evidence of an extended gaseous halo from other observations, the hot gaseous halo likely consists of a dense disk-like component and a rarefied spherical component; the X-ray emissions primarily come from the former, but the mass is dominated by the latter. The disk-like component likely originates from stellar feedback in the Galactic disk due to the low scale height and the large scatter of the emission measures. The median [O/Fe] of ∼0.25 shows the contribution of the core-collapse supernovae and supports the stellar feedback origin.
-
Journal of Astronomical Telescopes Instruments and Systems 4(1) 2018年 査読有りThe soft x-ray spectrometer (SXS) onboard ASTRO-H (named Hitomi after launch) is a microcalorimeter-type spectrometer, installed in a dewar to be cooled at 50 mK. The energy resolution of the SXS engineering model suffered from microvibration from cryocoolers mounted on the dewar. This is mitigated for the flight model (FM) by introducing vibration isolation systems between the cryocoolers and the dewar. The detector performance of the FM was verified before launch of the spacecraft in both ambient condition and thermal-vacuum condition, showing no detectable degradation in energy resolution. The in-orbit detector spectral performance and cryocooler cooling performance were also consistent with that on ground, indicating that the cryocoolers were not damaged by launch environment. The design and performance of the vibration isolation system along with the mechanism of how the microvibration could degrade the cryogenic detector is shown. Lessons learned from the development to mitigate unexpected issues are also described. (c) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License.
-
Journal of Astronomical Telescopes, Instruments, and Systems 4(1) 2018年1月1日 査読有りThe soft x-ray spectrometer (SXS) onboard the Hitomi satellite achieved a high-energy resolution of ∼4.9 eV at 6 keV with an x-ray microcalorimeter array cooled to 50 mK. The cooling system utilizes liquid helium, confined in zero gravity by means of a porous plug (PP) phase separator. For the PP to function, the helium temperature must be kept lower than the λ point of 2.17 K in orbit. To determine the maximum allowable helium temperature at launch, taking into account the uncertainties in both the final ground operations and initial operation in orbit, we constructed a thermal mathematical model of the SXS dewar and PP vent and carried out time-series thermal simulations. Based on the results, the maximum allowable helium temperature at launch was set at 1.7 K. We also conducted a transient thermal calculation using the actual temperatures at launch as initial conditions to determine flow and cooling rates in orbit. From this, the equilibrium helium mass flow rate was estimated to be ∼34 to 42 μg/s, and the lifetime of the helium mode was predicted to be ∼3.9 to 4.7 years. This paper describes the thermal model and presents simulation results and comparisons with temperatures measured in the orbit.
-
Journal of Low Temperature Physics 193(3-4) 618-625 2018年 査読有り
-
Publications of the Astronomical Society of Japan 70(2) 2018年 査読有り
-
Publications of the Astronomical Society of Japan 70(2) 2018年 査読有り
-
Publications of the Astronomical Society of Japan 70(6) 2018年 査読有りWe present the results from the Hitomi Soft Gamma-ray Detector (SGD) observation of the Crab nebula. The main part of SGD is a Compton camera, which in addition to being a spectrometer, is capable of measuring polarization of gamma-ray photons. The Crab nebula is one of the brightest X-ray / gamma-ray sources on the sky, and, the only source from which polarized X-ray photons have been detected. SGD observed the Crab nebula during the initial test observation phase of Hitomi. We performed the data analysis of the SGD observation, the SGD background estimation and the SGD Monte Carlo simulations, and, successfully detected polarized gamma-ray emission from the Crab nebula with only about 5 ks exposure time. The obtained polarization fraction of the phase-integrated Crab emission (sum of pulsar and nebula emissions) is (22.1% +/- 10.6%), and, the polarization angle is 110.degrees 7 + 13.degrees 2 /-13.degrees 0 in the energy range of 60-160 keV (The errors correspond to the 1 sigma deviation). The confidence level of the polarization detection was 99.3%. The polarization angle measured by SGD is about one sigma deviation with the projected spin axis of the pulsar, 124.degrees 0 +/- 0.degrees 1.
-
SPACE TELESCOPES AND INSTRUMENTATION 2018: ULTRAVIOLET TO GAMMA RAY 10699 2018年 査読有りThe ASTRO-H mission was designed and developed through an international collaboration of JAXA, NASA, ESA, and the CSA. It was successfully launched on February 17, 2016, and then named Hitomi. During the in-orbit verification phase, the on-board observational instruments functioned as expected. The intricate coolant and refrigeration systems for soft X-ray spectrometer (SXS, a quantum micro-calorimeter) and soft X-ray imager (SXI, an X-ray CCD) also functioned as expected. However, on March 26, 2016, operations were prematurely terminated by a series of abnormal events and mishaps triggered by the attitude control system. These errors led to a fatal event: the loss of the solar panels on the Hitomi mission. The X-ray Astronomy Recovery Mission (or, XARM) is proposed to regain the key scientific advances anticipated by the international collaboration behind Hitomi. XARM will recover this science in the shortest time possible by focusing on one of the main science goals of Hitomi, "Resolving astrophysical problems by precise high-resolution X-ray spectroscopy".(1) This decision was reached after evaluating the performance of the instruments aboard Hitomi and the mission's initial scientific results, and considering the landscape of planned international X-ray astrophysics missions in 2020's and 2030's.Hitomi opened the door to high-resolution spectroscopy in the X-ray universe. It revealed a number of discrepancies between new observational results and prior theoretical predictions. Yet, the resolution pioneered by Hitomi is also the key to answering these and other fundamental questions. The high spectral resolution realized by XARM will not offer mere refinements; rather, it will enable qualitative leaps in astrophysics and plasma physics. XARM has therefore been given a broad scientific charge: "Revealing material circulation and energy transfer in cosmic plasmas and elucidating evolution of cosmic structures and objects". To fulfill this charge, four categories of science objectives that were defined for Hitomi will also be pursued by XARM; these include (1) Structure formation of the Universe and evolution of clusters of galaxies; (2) Circulation history of baryonic matters in the Universe; (3) Transport and circulation of energy in the Universe; (4) New science with unprecedented high resolution X-ray spectroscopy. In order to achieve these scientific objectives, XARM will carry a 6 x 6 pixelized X-ray micro-calorimeter on the focal plane of an X-ray mirror assembly, and an aligned X-ray CCD camera covering the same energy band and a wider field of view. This paper introduces the science objectives, mission concept, and observing plan of XARM.
-
Publications of the Astronomical Society of Japan 70(3) 2018年 査読有り
-
Journal of Low Temperature Physics 193(5-6) 1282-1286 2018年 査読有りA detector head for an energy-dispersive X-ray spectroscopy (EDS) for a scanning transmission electron microscope (STEM) was designed, fabricated, and tested. A 64-pixel TES X-ray microcalorimeter and 64 SQUID array amplifiers (SAAs) are mounted on a detector head which is cooled to about 100 mK. The body of the detector head is a copper rod of about 1 cm(2) cross section and 10 cm length with 3 cm cubic structure at the bottom. The TES microcalorimeter is mounted at the top of the rod while the SAAs are mounted on the four side surfaces of the cubic structure. In order to reduce the number of wire bondings, we adopted a flip-chip bonding for the SAAs. In order to reduce the stress imposed on the flip-chip bondings due to the difference in the linear thermal expansion of the SAA chip and the mounting surfaces, we mounted the SAAs and connectors to the room-temperature electronics on sapphire circuit board and mounted the SAAs and connectors using a superconducting flip-chip bonding technology. Then, both the TES and the sapphire circuit board were mounted on the rod and are connected to the print circuit like superconducting wires, which are created on the multiple surfaces of the rod, with A1 wire bondings. We reduced the number of wire bondings from 768 to 256. The yield of the flip-chip bonding was not perfect but relatively high. We installed the detector head in the STEM EDS system, confirmed that the energy resolution and counting requirements, Delta E < 10 eV with 5 kcps were fulfilled.
-
Publications of the Astronomical Society of Japan 70(2) id 11 p1-id11 p30 2018年 査読有り
-
Journal of Astronomical Telescopes, Instruments, and Systems 4(1) 11208 2018年1月1日 査読有りThe soft x-ray spectrometer (SXS) was a cryogenic high-resolution x-ray spectrometer onboard the Hitomi (ASTRO-H) satellite that achieved energy resolution of 5 eV at 6 keV, by operating the detector array at 50 mK using an adiabatic demagnetization refrigerator (ADR). The cooling chain from room temperature to the ADR heat sink was composed of two-stage Stirling cryocoolers, a 4He Joule-Thomson cryocooler, and superfluid liquid helium and was installed in a dewar. It was designed to achieve a helium lifetime of more than 3 years with a minimum of 30 L. The satellite was launched on February 17, 2016, and the SXS worked perfectly in orbit, until March 26 when the satellite lost its function. It was demonstrated that the heat load on the helium tank was about 0.7 mW, which would have satisfied the lifetime requirement. This paper describes the design, results of ground performance tests, prelaunch operations, and initial operation and performance in orbit of the flight dewar and the cryocoolers.
-
Journal of Astronomical Telescopes, Instruments, and Systems 4(1) 2018年1月1日 査読有りThe soft x-ray spectrometer (SXS) onboard the Hitomi satellite achieved a high-energy resolution of ∼4.9 eV at 6 keV with an x-ray microcalorimeter array cooled to 50 mK. The cooling system utilizes liquid helium, confined in zero gravity by means of a porous plug (PP) phase separator. For the PP to function, the helium temperature must be kept lower than the λ point of 2.17 K in orbit. To determine the maximum allowable helium temperature at launch, taking into account the uncertainties in both the final ground operations and initial operation in orbit, we constructed a thermal mathematical model of the SXS dewar and PP vent and carried out time-series thermal simulations. Based on the results, the maximum allowable helium temperature at launch was set at 1.7 K. We also conducted a transient thermal calculation using the actual temperatures at launch as initial conditions to determine flow and cooling rates in orbit. From this, the equilibrium helium mass flow rate was estimated to be ∼34 to 42 μg/s, and the lifetime of the helium mode was predicted to be ∼3.9 to 4.7 years. This paper describes the thermal model and presents simulation results and comparisons with temperatures measured in the orbit.
-
Publications of the Astronomical Society of Japan 70(2) 2018年 査読有りThe X-Ray Spectrometer (XRS) instrument of Suzaku provided the first measurement of the non-X-ray background (NXB) of an X-ray calorimeter spectrometer, but the data set was limited. The Soft X-ray Spectrometer (SXS) instrument of Hitomi was able to provide a more detailed picture of X-ray calorimeter background, with more than 360 ks of data while pointed at the Earth, and a comparable amount of blank-sky data. These data are important not only for analyzing SXS science data, but also for categorizing the contributions to the NXB in X-ray calorimeters as a class. In this paper, we present the contributions to the SXS NXB, the types and effectiveness of the screening, the interaction of the screening with the broad-band redistribution, and the residual background spectrum as a function of magnetic cut-off rigidity. The orbit-averaged SXS NXB in the range 0.3-12 keV was 4 x 10(-2) counts s(-1) cm(-2). This very low background in combination with groundbreaking spectral resolution gave SXS unprecedented sensitivity to weak spectral lines.
-
Publications of the Astronomical Society of Japan 70(2) 2018年 査読有り© The Author(s) 2017. Published by Oxford University Press on behalf of the Astronomical Society of Japan. To search for giant X-ray pulses correlated with the giant radio pulses (GRPs) from the Crab pulsar, we performed a simultaneous observation of the Crab pulsar with the X-ray satellite Hitomi in the 2-300 keV band and the Kashima NICT radio telescope in the 1.4-1.7 GHz band with a net exposure of about 2 ks on 2016 March 25, just before the loss of the Hitomi mission. The timing performance of the Hitomi instruments was confirmed to meet the timing requirement and about 1000 and 100 GRPs were simultaneously observed at the main pulse and inter-pulse phases, respectively, and we found no apparent correlation between the giant radio pulses and the X-ray emission in either the main pulse or inter-pulse phase. All variations are within the 2 σ fluctuations of the X-ray fluxes at the pulse peaks, and the 3 σ upper limits of variations of main pulse or inter-pulse GRPs are 22% or 80% of the peak flux in a 0.20 phase width, respectively, in the 2-300 keV band. The values for main pulse or inter-pulse GRPs become 25% or 110%, respectively, when the phase width is restricted to the 0.03 phase. Among the upper limits from the Hitomi satellite, those in the 4.5-10 keV and 70-300 keV bands are obtained for the first time, and those in other bands are consistent with previous reports. Numerically, the upper limits of the main pulse and inter-pulse GRPs in the 0.20 phase width are about (2.4 and 9.3) × 10−11 erg cm−2, respectively. No significant variability in pulse profiles implies that the GRPs originated from a local place within the magnetosphere. Although the number of photon-emitting particles should temporarily increase to account for the brightening of the radio emission, the results do not statistically rule out variations correlated with the GRPs, because the possible X-ray enhancement may appear due to a >0.02% brightening of the pulse-peak flux under such conditions.
-
Publications of the Astronomical Society of Japan 70(2) 2018年 査読有り
-
Publications of the Astronomical Society of Japan 70(2) 2018年 査読有り
-
Publications of the Astronomical Society of Japan 70(2) 2018年 査読有り
-
Journal of Astronomical Telescopes, Instruments, and Systems 4(1) 2018年1月1日 査読有りThe calorimeter array of the JAXA Astro-H (renamed Hitomi) soft x-ray spectrometer (SXS) was designed to provide unprecedented spectral resolution of spatially extended cosmic x-ray sources and of all cosmic x-ray sources in the Fe-K band around 6 keV. The properties that made the SXS array a powerful x-ray spectrometer also made it sensitive to photons from the entire electromagnetic band as well as particles. If characterized as a bolometer, it would have had a noise equivalent power of < 4 × 10 ? 18 W / (Hz)0.5. Thus, it was imperative to shield the detector from thermal radiation from the instrument and optical and UV photons from the sky. In addition, it was necessary to shield the coldest stages of the instrument from the thermal radiation emanating from the warmer stages. These needs were addressed by a series of five thin-film radiation-blocking filters, anchored to the nested temperature stages, that blocked long-wavelength radiation while minimizing x-ray attenuation. The aperture assembly was a system of barriers, baffles, filter carriers, and filter mounts that supported the filters and inhibited their potential contamination. The three outer filters also had been equipped with thermometers and heaters for decontamination. We present the requirements, design, implementation, and performance of the SXS aperture assembly and blocking filters.
-
Journal of Astronomical Telescopes, Instruments, and Systems 4(1) 2018年1月1日 査読有りThe soft x-ray spectrometer was designed to operate onboard the Japanese Hitomi (ASTRO-H) satellite. In the beam of this instrument, there was a filter wheel containing x-ray filters and active calibration sources. This paper describes this filter wheel. We show the purpose of the filters and the preflight calibrations performed. In addition, we present the calibration source design and measured performance. Finally, we conclude with prospects for future missions.
-
Publications of the Astronomical Society of Japan 70(2) 2018年 査読有り
-
Publications of the Astronomical Society of Japan 70(2) 2018年 査読有り
-
Cryogenics 89 85-94 2018年1月1日 査読有りIn the framework of the ESA X-ray mission ATHENA, scheduled for launch in 2028, an ESA Core Technology Program (CTP) was started in 2016 to build a flight like cryostat demonstrator in parallel with the phase A studies of the ATHENA/X-IFU instrument [1,2]. As part of this CTP, called the Detector Cooling System (DCS), design, manufacturing and test of a cryostat including existing space coolers will be done. In addition to the validation of thermal performance, a Focal Plan Assembly (FPA) demonstrator using Transition Edge Sensors (TES) detector technology will be also integrated and its performance characterized versus the environment provided by the cryostat. This is a unique opportunity to validate many crucial issues of the cryogenic part of such a sensitive instrument. A dedicated activity within this CTP-DCS is the demonstration of the 300 K–50 mK cooling chain in a Ground System Equipment (GSE) cryostat. The studies are focused on the operation of the space coolers, which is made possible by the use of a ground cooler for cooling cryogenic shields and mechanical supports. Thanks to the modularity of the cryostat, several cooling chains could be tested. In the base line configuration described here, the low temperature stage is the CEA hybrid sorption/ADR 50 mK cooler with thermal interfaces at 4 K and 2 K. 4 K cooling is accomplished by a 4 K Joule-Thomson (JT) cryocooler and its Stirling precooler provided by JAXA. Regarding the 2 K stage, at first a 2 K JT from JAXA will be used. Alternatively, a 2 K JT cooler from RAL could replace the JAXA 2 K JT. In both cases new prototype(s) of a 2 K JT will be implemented, precooled by the EM 15 K pule tube cooler from Air Liquide. This test program is also the opportunity to validate the operation of the cryochain with respect to various requirements, such as time constant and temperature stabilities. This would bring us valuable inputs to integrate the cryochain in DCS cryostat or for the X-IFU phase A studies. This cryochain demonstration is also a critical milestone for the SPICA mission [3]. The design of the cryostat and first thermal validations both before and after integration of the JAXA JT coolers are presented in this paper.
-
Cryogenics 88 70-77 2017年12月1日 査読有りMechanical cryocoolers for space applications are required to have high reliability to achieve long-term operation in orbit. ASTRO-H (Hitomi), the 6th Japanese X-ray astronomy mission, has a major scientific instrument onboard—the Soft X-ray Spectrometer (SXS) with several 20K-class two-stage Stirling (2ST) coolers and a 4K-class Joule Thomson (JT) cooler, which must operate for 3 years to ensure the lifetime of liquid helium as a cryogen for cooling of its detectors [1,2]. Other astronomical missions such as SPICA [3,4], LiteBIRD [5], and Athena [6] also have top requirements for these mechanical cryocoolers, including a 1K-class JT cooler to be operated for more than 3–5 years with no cryogen system. The reliability and lifetime of mechanical cryocoolers are generally understood to depend on (1) mechanical wear of the piston seal and valve seal, and (2) He working gas contaminated by impurity outgases, mainly H2O and CO2 released from the materials in the components of the cryocoolers. The second factor could be critical relative to causing blockage in the JT heat exchanger plumbing and the JT orifice or resulting in blockage in the Stirling regenerator and thereby degrading its performance. Thus, reducing the potential for outgassing in the cryocooler design and fabrication process, and predicting the total amount of outgases in the cryocooler are very important to ensure cryocooler lifetime and cooling performance in orbit. This paper investigates the outgas analysis of the 2ST and the 1K/4K-JT coolers for achieving a long lifetime. First, gas analysis was conducted for the materials and components of the mechanical cryocoolers, focusing on non-metallic materials as impurity gas sources. Then gas analysis of the mechanical wear effect of the piston seal materials and linear ball bearings was investigated. Finally, outgassing from a fully assembled cryocooler was measured to evaluate whether the outgas reduction process works properly to meet the requirement levels.
-
Nature 551(7681) 478-480 2017年11月23日 査読有りThe metal abundance of the hot plasma that permeates galaxy clusters represents the accumulation of heavy elements produced by billions of supernovae. Therefore, X-ray spectroscopy of the intracluster medium provides an opportunity to investigate the nature of supernova explosions integrated over cosmic time. In particular, the abundance of the iron-peak elements (chromium, manganese, iron and nickel) is key to understanding how the progenitors of typical type Ia supernovae evolve and explode. Recent X-ray studies of the intracluster medium found that the abundance ratios of these elements differ substantially from those seen in the Sun, suggesting differences between the nature of type Ia supernovae in the clusters and in the Milky Way. However, because the K-shell transition lines of chromium and manganese are weak and those of iron and nickel are very close in photon energy, high-resolution spectroscopy is required for an accurate determination of the abundances of these elements. Here we report observations of the Perseus cluster, with statistically significant detections of the resonance emission from chromium, manganese and nickel. Our measurements, combined with the latest atomic models, reveal that these elements have near-solar abundance ratios with respect to iron, in contrast to previous claims. Comparison between our results and modern nucleosynthesis calculations disfavours the hypothesis that type Ia supernova progenitors are exclusively white dwarfs with masses well below the Chandrasekhar limit (about 1.4 times the mass of the Sun). The observed abundance pattern of the iron-peak elements can be explained by taking into account a combination of near- A nd sub-Chandrasekhar-mass type Ia supernova systems, adding to the mounting evidence that both progenitor types make a substantial contribution to cosmic chemical enrichment.
-
2016 IEEE Nuclear Science Symposium, Medical Imaging Conference and Room-Temperature Semiconductor Detector Workshop, NSS/MIC/RTSD 2016 2017- 2017年10月16日 査読有りAn energy dispersive spectrometer with a superconducting transition edge sensor (TES) microcalorimeter mounted on a scanning transmission electron microscope (STEM) has been developed to improve the accuracy of nanoscale material analysis. Because of the magnetic field generated by the STEM objective lens, a TES microcalorimeter cannot be placed in a STEM column. Therefore, a polycapillary optics is used for collecting X-rays emitted by a STEM specimen on the TES microcalorimeter. The counting rate of 300 cps was insufficient for a practical application to the STEM. To achieve the counting rate larger than 5000 cps, we are now conducting development of a 64-pixel TES microcalorimeter system operating on the STEM. We developed a new polycapillary optics for a 64-pixel TES microcalorimeter with using a X-ray transmission simulation model that we made. We performed energy spectrum measurements of X-rays transmitted by the fabricated new polycapillary optics for evaluating the X-ray transmission characteristics.
-
IEEE Transactions on Applied Superconductivity 27(4) 2017年6月1日 査読有りTES microcalorimeters show a nonlinear pulse-height-to-energy relation, reflecting their nonlinear resistance-to-temperature relation on the transition edge. In some of TES applications, such as energy dispersive X-ray spectroscopy, a wide energy range (e.g. 0.5-15 keV) and a good energy calibration (e.g. within a few eV) are required. We have studied the method to calibrate the nonlinear pulse-height-to-energy and to correct for it in the data analysis. We irradiated a TES microcalorimeter with three radio isotopes simultaneously to obtain continuum-free line spectra covering from 3.3 to 17.8 keV. X-ray lines from those isotopes are, respectively, a line complex containing fine structures and/or satellite lines, which cannot be fully separated with TES microcalorimeters. Thus, a special treatment is necessary. We first established a method to estimate the relation between PHA (pulse height analyzed value by optimum filtering) and X-ray energy of the line complex precisely: we assumed that the relation could be approximated with a linear function, PHA = aE +b , locally in the narrow energy range containing one of the line complex, and determined a and b from the model fit of the PHA spectrum of the line complex. Then, from the PHA-to-energy relations of six line complexes, we determined an approximation formula which represented the global PH-to-energy relation. We then applied the global relation to convert PHA values of all pulses to energy equivalent value, which we call PI (pulse invariant). We then fitted the PI spectra with the model function to check the consistency of energy. We have done these processes starting from two different forms of data TES current as a function of time, and TES resistance as a function of time. The nonlinearity of PHA-to-energy was smaller for TES resistance pulses, and a better energy calibration is obtained. We found that the PI spectra obtained from TES resistance pulses reproduced the X-ray energies within ±3 eV uncertainty, while the uncertainties becomes as large as 10 eV for the PI spectra obtained from TES current pulses.
-
Astrophysical Journal Letters 837(1) 2017年3月1日 査読有りHigh-resolution X-ray spectroscopy with Hitomi was expected to resolve the origin of the faint unidentified E ≈ 3.5 keV emission line reported in several low-resolution studies of various massive systems, such as galaxies and clusters, including the Perseus cluster. We have analyzed the Hitomi first-light observation of the Perseus cluster. The emission line expected for Perseus based on the XMM-Newton signal from the large cluster sample under the dark matter decay scenario is too faint to be detectable in the Hitomi data. However, the previously reported 3.5 keV flux from Perseus was anomalously high compared to the sample-based prediction. We find no unidentified line at the reported high flux level. Taking into account the XMM measurement uncertainties for this region, the inconsistency with Hitomi is at a 99% significance for a broad dark matter line and at 99.7% for a narrow line from the gas. We do not find anomalously high fluxes of the nearby faint K line or the Ar satellite line that were proposed as explanations for the earlier 3.5 keV detections. We do find a hint of a broad excess near the energies of high-n transitions of S xvi (E ≃ 3.44 keV rest-frame) - a possible signature of charge exchange in the molecular nebula and another proposed explanation for the unidentified line. While its energy is consistent with XMM pn detections, it is unlikely to explain the MOS signal. A confirmation of this interesting feature has to wait for a more sensitive observation with a future calorimeter experiment.
-
IEICE Electronics Express 14(11) 2017年 査読有りWe have succeeded in the first demonstration of a simple and accurate resonator-superconducting quantum interference device (SQUID) coupling for microwave SQUID multiplexers. A simple theory shows our direct coupling with adjustable fractional inductance in the SQUID loop can decrease the deviation of resonance frequencies from designed values in contrast to a conventional inductive coupling. Our direct coupling provides the individual coupling that can be optimized with keeping identical structure, shape, and dimension of the SQUID among all pixels on the same chip. It covers experimentally three or potentially more factors of a frequency band that is larger than that of cryogenic high electron mobility transistor amplifiers. The deviation of experimental fractional inductance from the designed one is less than −3/+10%.
-
Cryogenics 88 143-146 2017年 査読有りSoft X-ray Spectrometer instrument (SXS) is one of the primary scientific instruments of ASTRO-H. SXS has a cold detector that is cooled to 50 mK by using a multi-stage Adiabatic Demagnetization Refrigerator (ADR). SXS Dewar containing ADR provides 1.3 K heat sink by using liquid helium in nominal operation. After liquid helium is dried up, 4 K heat sink is provided by using mechanical coolers. Both nominal operation and cryogen free operation were successfully demonstrated. This paper describes the test result of cryogen free operation and cool-down performance from room temperature by using only mechanical coolers without liquid helium. The coolers on the Dewar cooled down cold mass from around 300 K to 4 K with 260 W electric power in 40 days. Cold mass is 35 kg in 4 K area including the helium tank, ADR and detector assembly.
-
Journal of Low Temperature Physics 184(3-4) 824-831 2016年8月1日 査読有りLiteBIRD is a proposed CMB polarization satellite project to probe the inflationary B-mode signal. The satellite is designed to measure the tensor-to-scalar ratio with a 68 % confidence level uncertainty of σr< 10 - 3, including statistical, instrumental systematic, and foreground uncertainties. LiteBIRD will observe the full sky from the second Lagrange point for 3 years. We have a focal plane layout for observing frequency coverage that spans 40–402 GHz to characterize the galactic foregrounds. We have two detector candidates, transition-edge sensor bolometers and microwave kinetic inductance detectors. In both cases, a telecentric focal plane consists of approximately 2 × 10 3 superconducting detectors. We will present the mission overview of LiteBIRD, the project status, and the TES focal plane layout.
-
Journal of Low Temperature Physics 184(3-4) 688-693 2016年8月1日 査読有りWe present the latest update and progress on the future Japanese X-ray satellite mission Diffuse Intergalactic Oxygen Surveyor (DIOS). DIOS is proposed to JAXA as a small satellite mission, and would be launched with an Epsilon rocket. DIOS would carry on the legacy of ASTRO-H, which carries semiconductor-based microcalorimeters and is scheduled to be launched in 2016, in high-resolution X-ray spectroscopy. A 400-pixel array of transition-edge sensors (TESs) would be employed, so DIOS would also provide valuable lessons for the next ESA X-ray mission ATHENA on TES operation and cryogen-free cooling in space. We have been sophisticating the entire design of the satellite to meet the requirement for the Epsilon payload for the next call. The primary goal of the mission is to search for warm-hot intergalactic medium with high-resolution X-ray spectroscopy by detecting redshifted emission lines from OVII and OVIII ions. The results would have significant impacts on our understanding of the nature of “dark baryons,” their total amount and spatial distribution, as well as their evolution over cosmological timescales.
-
Nature 535(7610) 117-121 2016年7月6日 査読有りClusters of galaxies are the most massive gravitationally bound objects in the Universe and are still forming. They are thus important probes of cosmological parameters and many astrophysical processes. However, knowledge of the dynamics of the pervasive hot gas, the mass of which is much larger than the combined mass of all the stars in the cluster, is lacking. Such knowledge would enable insights into the injection of mechanical energy by the central supermassive black hole and the use of hydrostatic equilibrium for determining cluster masses. X-rays from the core of the Perseus cluster are emitted by the 50-million-kelvin diffuse hot plasma filling its gravitational potential well. The active galactic nucleus of the central galaxy NGC 1275 is pumping jetted energy into the surrounding intracluster medium, creating buoyant bubbles filled with relativistic plasma. These bubbles probably induce motions in the intracluster medium and heat the inner gas, preventing runaway radiative cooling - a process known as active galactic nucleus feedback. Here we report X-ray observations of the core of the Perseus cluster, which reveal a remarkably quiescent atmosphere in which the gas has a line-of-sight velocity dispersion of 164 ± 10 kilometres per second in the region 30-60 kiloparsecs from the central nucleus. A gradient in the line-of-sight velocity of 150 ± 70 kilometres per second is found across the 60-kiloparsec image of the cluster core. Turbulent pressure support in the gas is four per cent of the thermodynamic pressure, with large-scale shear at most doubling this estimate. We infer that a total cluster mass determined from hydrostatic equilibrium in a central region would require little correction for turbulent pressure.
-
Journal of Low Temperature Physics 184(1-2) 250-256 2016年7月1日 査読有りThe dielectric micro calorimeter (DMC) is a novel radiation detector utilizing a GHz resonator with dielectric thermometer (Sekiya et al. in J Low Temp Phys 167:435, 2012). The advantage of using a DMC is that the detection mechanism is based on a phonon mediation without Johnson noise and quasi-particle decay process. A large format array of DMCs can be easily multiplexed by a resonator circuit in the readout at GHz band width. We describe the design of a DMC as an X-ray photon counter. It is optimized to detect photon at 5.9 keV energy. We consider 18O-doped SrTiO3 (STO18) and Nb-doped KTa( 1 - x )NbxO3 (KTN) as a candidate of dielectric thermometer. Dielectric materials which have sensitivity α(= dlog Cel/ dlog T) are also ideal for our application. We check that both STO18 and KTN have α∼ 10 3 at 100 mK. If we assume a DMC resonator operating at 100 mK, we need a Q value of a resonator to be 2000 for X-ray detection.
-
Journal of Low Temperature Physics 184(1-2) 257-262 2016年7月1日 査読有りWe report the fabrication and evaluation of the Cu/Bi bilayer absorber with electrodeposition. We designed the Cu/Bi absorber to satisfy the requirements for scanning transmission electron microscope (STEM). The residual resistivity ratios of films of Cu and Bi with electrodeposition was 5.91 ± 0.49 and 2.06 ± 0.33 , respectively these values are sufficient for the requirements of STEM. We found that the Cu/Bi bilayer absorber TES microcalorimeter experienced a pulse-shape variation and we considered that these variations were caused by the quality of the contact surface between the absorber and TES. In addition, we examined the structure of the absorber using focus ion beam analysis and STEM. The results suggest that an oxidation between the Cu and seed layer, in which the layer is an electrode for electrodeposition, yielded variations. Moreover, thermal simulation suggests that the thermal conduction between the absorber and TES caused variations. The results of this study will improve the process of Bi electrodeposition.
-
Journal of Low Temperature Physics 184(1-2) 519-526 2016年7月1日 査読有りWe are developing the frequency-division multiplexing (FDM) readout system aimed to realize the 400-pixel transition edge sensor (TES) microcalorimeter array for the DIOS mission as well as large-format arrays with more than a thousand of TES for future space missions such as the ATHENA mission. The developed system consists of the low-power superconducting quantum interference device (SQUID), the digital FDM electronics, and the analog front-end to bridge the SQUID and the digital electronics. Using the developed readout system, we performed a TES readout experiment and succeeded to multiplex four TES signals with the single-staged cryogenic setup. We have experienced two issues during the experiment: an excess noise and crosstalk. The brief overview of the developed system and the details, results, and issues of the TES multiplexing readout experiment is discussed.
-
Journal of Low Temperature Physics 184(1-2) 91-96 2016年7月1日 査読有りWe discuss the design and performance of a transition edge sensor (TES) X-ray microcalorimeter array for scanning transmission electron microscope (STEM)–energy dispersive X-ray spectroscopy (EDS). The TES X-ray microcalorimeter has better energy resolution compared to conventional silicon drift detector and STEM–EDS utilizing a TES detector makes it possible to map the distribution of elements on a specimen in addition to analyze the composition. The requirement for a TES detector is a high counting rate (> 20 kcps), wide energy band (0.5–15 keV) and good energy resolution (< 10 eV) full width at half maximum. The major improvement of this development is to increase the maximum counting rate. In order to accommodate the high counting rate, we adopted an 8 × 8 format, 64-pixel array and common biasing scheme for the readout method. We did all design and fabrication of the device in house. With the device we have fabricated most recently, the pulse decay time is 40 μ s which is expected to achieve 50 kcps. For a single pixel, the measured energy resolution was 7.8 eV at 5.9 keV. This device satisfies the requirements of counting rate and energy resolution, although several issues remain where the performance must be confirmed.
-
Journal of Low Temperature Physics 184(1-2) 454-459 2016年7月1日 査読有りA transition edge sensor (TES) microcalorimeter array as an X-ray sensor for a scanning transmission electron microscope system is being developed. The technical challenge of this system is a high count rate of ∼ 5000 counts/second/array. We adopted a 64 pixel array with a parallel readout. Common SQUID bias, and common TES bias are planned to reduce the number of wires and the resources of a room temperature circuit. The reduction rate of wires is 44 % when a 64 pixel array is read out by a common bias of 8 channels. The possible degradation of the energy resolution has been investigated by simulations and experiments. The bias fluctuation effects of a series connection are less than those of a parallel connection. Simple calculations expect that the fluctuations of the common SQUID bias and common TES bias in a series connection are 10 - 7 and 10 - 3, respectively. We constructed 8 SQUIDs which are connected to 8 TES outputs and a room temperature circuit for common bias readout and evaluated experimentally. Our simulation of crosstalk indicates that at an X-ray event rate of 500 cps/pixel, crosstalk will broaden a monochromatic line by about 0.01 %, or about 1.5 eV at 15 keV. Thus, our design goal of 10 eV energy resolution across the 0.5–15 keV band should be achievable.
-
Publications of the Astronomical Society of Japan 68 S311-S3110 2016年6月1日 査読有りWe performed the deepest search for an X-ray emission line at between 0.5 and 7 keV from non-baryonic dark matter by the Suzaku XIS. Dark matter associated with the Milky Way was selected as the target to obtain the best signal-to-noise ratio. From the Suzaku archive, we selected 187 data sets of blank-sky regions that were dominated by the X-ray diffuse background. The data sets were from 2005 to 2013. The instrumental responses were adjusted by multiple calibration data sets of the Crab Nebula. We also improved the technique of subtracting lines of instrumental origin. These energy spectra were well described by X-ray emission due to charge exchange around the Solar System, hot plasma in and around the Milky Way, and the superposition of extra-galactic point sources. A signal of a narrow emission-line was searched for, and the significance of detection was evaluated in consideration of the blind search method (the Look-elsewhere Effect). Our results exhibited no significant detection of an emission line feature from dark matter. The 3 σ upper limit for the emission line intensity between 1 and 7 keV was ∼ 10-2 photons cm-2 s-1 sr-1, or ∼ 5 × 10-4 photons cm-2 s-1 sr-1 per M pc-2, assuming a dark matter distribution with the Galactic rotation curve. The parameters of sterile neutrinos as candidates of dark-matter were also constrained.
-
Cryogenics 74 10-16 2016年3月1日 査読有りASTRO-H is a Japanese X-ray astronomy satellite, scheduled to be launched in fiscal year 2015. The mission includes a soft X-ray spectrometer instrument (SXS), which contains an X-ray micro calorimeter operating at 50 mK by using an adiabatic demagnetization refrigerator (ADR). The heat sink of the ADR is superfluid liquid helium below 1.3 K. The required lifetime of the superfluid helium is 3 years or more. In order to realize this lifetime, we have improved the thermal performance from the engineering model (EM) while maintaining the mechanical performance. Then, we have performed a thermal test of the flight model (FM). The results were that the heat load to the helium tank was reduced to below 0.8 mW in the FM from 1.2 mW in the EM. Therefore, the lifetime of the superfluid helium is more than 3 years with 30 L of liquid helium. In this paper, the thermal design and thermal test results are described.
-
Cryogenics 74 47-54 2016年3月1日 査読有りThis paper reports on the development of a 1K-class Joule-Thomson (JT) cryocooler in Japan for application to upcoming next-generation astronomy missions. In this development, engineering models (EMs) were designed and manufactured for verification tests. The survival of the models in the mechanical and thermal vacuum environment tests of the JT compressors was proven to be possible with stable compression performance. In addition, the electromagnetic noise and disturbance force associated with the JT compressors were evaluated. Gas analysis showed that the estimated total amount of CO2 gas contaminant was less than the getter capacity for the required lifetime. A nominal cooling power of 10 mW at 1.7 K was verified using the EM test units.
-
Review of Scientific Instruments 87(11) 2016年 査読有り
-
Journal of Low Temperature Physics 181(1-2) 59-67 2015年10月24日 査読有りGHz LC resonators whose resonance frequency depends on temperature may be put to use as radiation detectors. We have demonstrated that a resonator utilizing STO (SrTiO$$_{3}$$3) at 4 and 2 K detected infrared light emitting diode (LED) light, by a shift of resonance frequency around 2 GHz. A suitable design of a resonator array with temperature-dependent dielectric material will be used as a large-format microcalorimeter array without or with only very small Johnson noise.
-
IEEE Transactions on Nuclear Science 62(4) 1918-1922 2015年8月1日 査読有りThis paper studies the polycapillary optics that are used to focus and transmit the X-rays emitted by a transmission electron microscope (TEM) specimen to an energy dispersive spectrometer using a superconducting transition edge sensor (TES) microcalorimeter. In this study, X-rays are collected from a TEM specimen and are then focused on a silicon drift detector, from which energy spectrum measurements of the polycapillary optics are taken and used to determine the transmission characteristics of the optics. When the polycapillary optics are used, an increase of 25.9 is seen in the intensity of 4.6 keV X-rays, while an increase of 6.0 is seen for 12.6 keV X-rays. The focal spot sizes of the X-ray beams from the polycapillary optics are found to be 382μm for the 4.6 keV X-rays and 156μm for the 12.6 keV X-rays. Further improvement of these characteristics can be achieved by improving the alignment of the optics to the detector and the collimator, which immediately precedes the detector, and by optimizing the collimator width.
MISC
189-
Space Telescopes and Instrumentation 2020: Optical, Infrared, and Millimeter Wave 2020年12月21日
-
Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy X 2020年12月16日
-
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)
1-
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
3-
2010年 - 現在
共同研究・競争的資金等の研究課題
22-
日本学術振興会 科学研究費助成事業 2020年11月 - 2025年3月
-
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
-
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
-
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
-
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
教育内容やその他の工夫
1-
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
8-
年度2018年度(FY2018)博士課程学生数1修士課程学生数1
-
年度2019年度(FY2019)博士課程学生数1修士課程学生数3
-
年度2020年度(FY2020)博士課程学生数1修士課程学生数3
-
年度2018年度(FY2018)博士課程学生数1修士課程学生数1
-
年度2019年度(FY2019)博士課程学生数1修士課程学生数3
-
年度2020年度(FY2020)博士課程学生数1修士課程学生数3
-
年度2022年度(FY2022)博士課程学生数3修士課程学生数2
-
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
6-
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
-
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
-
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
-
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
-
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
-
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
1-
専任大学名東京大学（University of Tokyo)
● 所属する所内委員会
1-
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
