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 教授総合研究大学院大学 先端学術院 宇宙科学コース 教授東京工業大学 理学院 特定教授
- 学位
- 博士（理学）(東京大学)修士(東京大学)
- 研究者番号
- 20280555
- ORCID ID
https://orcid.org/0000-0002-2374-7073- J-GLOBAL ID
- 200901095989600566
- researchmap会員ID
- 1000363020
研究キーワード
6経歴
8-
2024年6月 - 現在
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2024年3月 - 現在
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2023年6月 - 2024年6月
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2023年6月 - 現在
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2008年4月 - 2023年5月
学歴
4-
1991年4月 - 1995年3月
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- 1995年
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1987年4月 - 1991年3月
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- 1991年
委員歴
2-
2009年4月 - 2011年3月
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2009年 - 2010年
受賞
2-
2010年
論文
155-
Cryogenics 139 103831-103831 2024年4月 査読有り
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Journal of Astronomical Telescopes, Instruments, and Systems 9(1) 14003-14003 2023年
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Journal of Low Temperature Physics 209(5-6) 971-979 2022年12月
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Space Telescopes and Instrumentation 2022: Ultraviolet to Gamma Ray 12181 2022年8月31日
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Ground test results of the micro-vibration interference for the x-ray microcalorimeter onboard XRISMProceedings of SPIE - The International Society for Optical Engineering 12181 2022年Resolve is a payload hosting an x-ray microcalorimeter detector operated at 50 mK in the X-Ray Imaging and Spectroscopy Mission (XRISM), which is currently under development by an international collaboration and is planned to be launched in 2023. One of the technical concerns is the micro-vibration interference to the sensitive microcalorimeter detector by the spacecraft bus components. We verified this in a series of the ground tests in 2021–2022, the results of which are reported here. We defined the micro-vibration interface between the spacecraft and the Resolve instrument. In the instrument-level test, we tested the flight-model hardware against the interface level by injecting micro-vibration using vibrators and evaluated the instrument response using the 50 mK stage temperature stability, the ADR magnet current consumption rate, and the detector noise spectra. We found the strong responses when injecting micro-vibration at ∼200, 380, and 610 Hz. In the former two cases, the beat among the injected frequency and the cryocooler frequency harmonics are also observed in the detector noise spectra. In the spacecraft-level test, we measured the acceleration and the instrument responses with and without suspending the entire spacecraft. The reaction wheels and the inertial reference units, two major sources of micro-vibration among the bus components, were operated. We found that the observed Resolve responses are within acceptable levels.
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X-RAY, OPTICAL, AND INFRARED DETECTORS FOR ASTRONOMY X 12191 2022年The Resolve instrument onboard the XRISM satellite is equipped with 6 x 6 x-ray microcalorimeter detectors aiming at an energy resolution of 7 eV (FWHM) at 5.9 keV. It is currently under development by an international collaboration and will be launched in 2023. The detectors are operated at 50 mK, which is achieved by a combination of four Stirling coolers (STC), one Joule-Thomson cooler (JTC), three-stage adiabatic demagnetization refrigerators, and superfluid helium inside the dewar. The cryocoolers (STC and JTC) are significant sources of microphonic noise against the detector performance. To understand and characterize the microphonic propagation, we monitored the level of vibration throughout the ground instrument-level tests in 2019-2022, yielding a rich and unique data set of the accelerometers and the detector at 50 mK amounting to 1720 hours (6.2 Ms). In this article, we report the result of classifying thermal and non-thermal microcalorimeter noise, distinguishing the origin of the noise, and the method for optimizing the cooler drive frequency that minimizes the effect of the noise originating from the cooler.
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SPACE TELESCOPES AND INSTRUMENTATION 2022: ULTRAVIOLET TO GAMMA RAY 12181 2022年Resolve is an X-ray microcalorimeter spectrometer on the X-Ray Imaging and Spectroscopy Mission (XRISM) to be launched in Japanese fiscal year 2022. Resolve is required to achieve an energy resolution of 7 eV at FWHM at 6 keV. To satisfy this requirement, it is necessary to correct the in-orbit gain drift. For this purpose, Resolve is equipped with multiple gain tracking calibration sources, including the modulated X-ray sources (MXS). The MXS will be operated in a pulsed mode, in which calibration X-rays illuminating the detector array are emitted at a duty cycle of similar to 1%. The low duty cycle allows us to monitor the gain drift with a small loss of the observing efficiency. However, the use of the MXS has drawbacks such as increase in the instrumental background due to exponentially decaying afterglow emission following each MXS pulse and the loss of throughput due to changes in the event-grade branching ratio. To minimize these effects, an optimization of the MXS operating parameters is needed. Based on the results of the MXS component-level tests, we established an analytical model that describes the MXS pulse and afterglow count rates. We obtained the optimal pulse parameters for various gain tracking intervals and estimated the effects of using the MXS on observation data. We further studied the trade-off between these effects and resolution degradation using the actual in-orbit drift observed with the Soft X-ray Spectrometer on the Hitomi satellite. Our study forms the basis of strategies for the in-orbit gain drift correction of Resolve.
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Publications of the Astronomical Society of Japan 73(3) 584-595 2021年6月 査読有りWe represent a joint X-ray, weak-lensing, and optical analysis of the optically-selected merging cluster, HSC J085024+001536, from the Subaru HSC-SSP survey. Both the member galaxy density and the weak-lensing mass map show that the cluster is composed of southeast and northwest components. The two-dimensional weak-lensing analysis shows that the southeast component is the main cluster, and the sub- and main-cluster mass ratio is $0.32^{+0.75}_{-0.23}$. The northwest subcluster is offset by $\sim700$ kpc from the main cluster center, and their relative line-of-sight velocity is $\sim1300\,{\rm km s^{-1 } }$ from spectroscopic redshifts of member galaxies. The X-ray emission is concentrated around the main cluster, while the gas mass fraction within a sphere of $1'$ radius of the subcluster is only $f_{\mathrm{gas } }=4.0^{+2.3}_{-3.3}\%$, indicating that the subcluster gas was stripped by ram pressure. X-ray residual image shows three arc-like excess patterns, of which two are symmetrically located at $\sim550$ kpc from the X-ray morphological center, and the other is close to the X-ray core. The excess close to the subcluster has a cold-front feature where dense-cold gas and thin-hot gas contact. The two outer excesses are tangentially elongated about $\sim 450-650$ kpc, suggesting that the cluster is merged with a non-zero impact parameter. Overall features revealed by the multi-wavelength datasets indicate that the cluster is at the second impact or later. Since the optically-defined merger catalog is unbiased for merger boost of the intracluster medium, X-ray follow-up observations will pave the way to understand merger physics at various phases.
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Space Telescopes and Instrumentation 2020: Ultraviolet to Gamma Ray 2020年12月13日
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Proceedings of SPIE - The International Society for Optical Engineering 11444 2020年We are studying an improved DIOS (Diffuse Intergalactic Oxygen Surveyor) program, Super DIOS, which is accepted for establishing the Research Group in ISAS/JAXA, for a launch year after 2030. The aim of Super DIOS is an X-ray quantitative exploration of”dark baryon” over several scales from circumgalactic medium, cluster outskirt to warm-hot intergalactic medium along the Cosmic web with mapping redshifted emission lines from mainly oxygen and other ions. These observations play key roles for investigating the physical condition, such as the energy flow and metal circulation, of most baryons in the Universe. This mission will perform wide field X-ray spectroscopy with a field of view of about 0.5-1 degree and energy resolution of a few eV with TES microcalorimeter, but with much improved angular resolution of about 10-15 arcseconds. We will also consider including a small gamma-ray burst monitor and a fast repointing system. We will have an international collaboration with US and Europe for all the onboard instruments.
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Monthly Notices of the Royal Astronomical Society 491(3) 3411-3418 2020年 査読有りA double source plane (DSP) system is a precious probe for the density profile of distant galaxies and cosmological parameters. However, these measurements could be affected by the surrounding environment of the lens galaxy. Thus, it is important to evaluate the cluster-scale mass for detailed mass modelling. We observed the Eye of Horus, a DSP system discovered by the Hyper Suprime-Cam Subaru Strategic Survey (HSC-SSP), with XMM-Newton. We detected two X-ray extended emissions, originating from two clusters, one centred at the Eye of Horus, and the other located similar to 100 arcsec north-east to the Eye of Horus. We determined the dynamical mass assuming hydrostatic equilibrium, and evaluated their contributions to the lens mass interior of the Einstein radius. The contribution of the former cluster is 1.1(-0.5)(+1.2) x 10(12) M-circle dot, which is 21-76 per cent of the total mass within the Einstein radius. The discrepancy is likely due to the complex gravitational structure along the line of sight. On the other hand, the contribution of the latter cluster is only similar to 2 per cent on the Eye of Horus. Therefore, the influence associated with this cluster can be ignored.
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Publications of the Astronomical Society of Japan 72(1) 2020年 査読有りWe present the first results of a pilot X-ray study of 37 rich galaxy clusters at 0.1 < z < 1.1 in the Hyper Suprime-Cam Subaru Strategic Program field. Diffuse X-ray emissions from these clusters were serendipitously detected in the XMM-Newton fields of view. We systematically analyze X-ray images of 37 clusters and emission spectra of a subsample of 17 clusters with high photon statistics by using the XMM-Newton archive data. The frequency distribution of the offset between the X-ray centroid or peak and the position of the brightest cluster galaxy was derived for the optical cluster sample. The fraction of relaxed clusters estimated from the X-ray peak offsets in 17 clusters is 29 +/- 11(+/- 13)%, which is smaller than that of the X-ray cluster samples such as HIFLUGCS. Since the optical cluster search is immune to the physical state of X-ray-emitting gas, it is likely to cover a larger range of the cluster morphology. We also derive the luminosity-temperature relation and found that the slope is marginally shallower than those of X-ray-selected samples and consistent with the self-similar model prediction of 2. Accordingly, our results show that the X-ray properties of the optical clusters are marginally different from those observed in the X-ray samples. The implication of the results and future prospects are briefly discussed.
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Proceedings of SPIE - The International Society for Optical Engineering 10699 2018年© 2018 SPIE. 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 × 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.
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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.
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Publications of the Astronomical Society of Japan 70(2) 2018年 査読有り
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Journal of Low Temperature Physics 193(5-6) 991-995 2018年The X-ray Astronomy Recovery Mission (XARM) is a recovery mission of ASTRO-H/Hitomi, which is expected to be launched in Japanese Fiscal Year of 2020 at the earliest. The Resolve instrument on XARM consists of an array of 6 × 6 silicon-thermistor microcalorimeters cooled down to 50 mK and a high-throughput X-ray mirror assembly with the focal length of 5.6 m. Hitomi was launched into orbit in February 2016 and observed several celestial objects, although the operation of Hitomi was terminated in April 2016. The soft X-ray spectrometer (SXS) on Hitomi demonstrated high-resolution X-ray spectroscopy of ~ 5 eV FWHM in orbit for most of the pixels. The Resolve instrument is planned to mostly be a copy of the Hitomi SXS and soft X-ray telescope designs, though several changes are planned based on the lessons learned from Hitomi. We report a brief summary of the SXS performance and the status of the Resolve instrument.
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Journal of Astronomical Telescopes, Instruments, and Systems 4(1) 2018年 査読有り
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Journal of Astronomical Telescopes, Instruments, and Systems 4(1) 2018年 査読有り
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Cryogenics 91 2018年 査読有り
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Journal of Astronomical Telescopes, Instruments, and Systems 4(1) 2018年 査読有り
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Journal of Astronomical Telescopes, Instruments, and Systems 4(2) 2018年 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. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License.
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Journal of Astronomical Telescopes, Instruments, and Systems 4(1) 2018年 査読有り
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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.
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Publications of the Astronomical Society of Japan 70(3) 2018年 査読有り
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Journal of Astronomical Telescopes, Instruments, and Systems 4(2) 2018年 査読有り
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Journal of Astronomical Telescopes, Instruments, and Systems 4(2) 2018年 査読有り
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Journal of Astronomical Telescopes, Instruments, and Systems 4(1) 2018年 査読有り
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Journal of Astronomical Telescopes, Instruments, and Systems 4(2) 2018年
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Journal of Astronomical Telescopes, Instruments, and Systems 4(2) 2018年
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Publications of the Astronomical Society of Japan 69(3) 2017年
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SPACE TELESCOPES AND INSTRUMENTATION 2016: ULTRAVIOLET TO GAMMA RAY 9905 2016年 査読有りThe Soft X-ray Spectrometer instrument on the Astro-H observatory contains a 6x6 array of x-ray microcalorimeters, which is cooled to 50 mK by an adiabatic demagnetization refrigerator (ADR). The ADR consists of three stages in order to provide stable detector cooling using either a 1.2 K superfluid helium bath or a 4.5 K Joule-Thomson (JT) cryocooler as its heat sink. When liquid helium is present, two of the ADR's stages are used to single-shot cool the detectors while rejecting heat to the helium. After the helium is depleted, all three stages are used to cool both the helium tank (to about 1.5 K) and the detectors (to 50 mK) using the JT cryocooler as its heat sink. The Astro-H observatory, renamed Hitomi after its successful launch in February 2016, carried approximately 36 liters of helium into orbit. On day 5, the helium had cooled sufficiently (<1.4 K) to allow operation of the ADR. This paper describes the design, operation and on-orbit performance of the ADR.
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Vibration isolation system for cryocoolers of Soft X-ray Spectrometer (SXS) onboard ASTRO-H (Hitomi)SPACE TELESCOPES AND INSTRUMENTATION 2016: ULTRAVIOLET TO GAMMA RAY 9905 2016年 査読有り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 micro-vibration from cryocoolers mounted on the dewar. This is mitigated for the flight model by introducing vibration isolation systems between the cryocoolers and the dewar. The detector performance of the flight model was verified before launch of the spacecraft in both ambient condition and thermal-vac condition, showing no detectable degradation in energy resolution. The in-orbit performance was 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 micro-vibration could degrade the cryogenic detector is shown.
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Review of Scientific Instruments 87(11) 2016年 査読有り
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SPACE TELESCOPES AND INSTRUMENTATION 2016: ULTRAVIOLET TO GAMMA RAY 9905 99053R 2016年The Soft X-ray Spectrometer (SXS) onboard ASTRO-H (Hitomi) achieved a high energy resolution of similar to 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-g by means of a porous plug phase separator. For the porous plug to function, the helium temperature must be kept lower than the lambda point of 2.17 K in orbit. To determine the maximum allowable helium temperature at launch, taking into account uncertainties in both the final ground operations and initial operation in orbit, we constructed a thermal mathematical model of the SXS dewar and porous plug 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 on orbit. From this, the equilibrium helium mass flow rate was estimated to be similar to 34-42 mu g/s, and the life time of the helium mode was predicted to be similar to 3.9-4.7 years. This paper describes the thermal model, and presents simulation results and comparisons with temperatures measured in the orbit.
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SPACE TELESCOPES AND INSTRUMENTATION 2016: ULTRAVIOLET TO GAMMA RAY 9905 2016年 査読有りThe Soft X-ray Spectrometer (SXS) is a cryogenic high-resolution X-ray spectrometer onboard the ASTRO-H satellite, that achieves energy resolution better than 7 eV at 6 keV, by operating the detector array at 50 mK using an adiabatic demagnetization refrigerator. The cooling chain from room temperature to the ADR heat sink is composed of 2-stage Stirling cryocoolers, a He-4 Joule-Thomson cryocooler, and superfluid liquid He, and is installed in a dewar. It is designed to achieve a helium lifetime of more than 3 years with a minimum of 30 liters. The satellite was launched on 2016 February 17, 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 He 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 cryocoolers.
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Proceedings of SPIE - The International Society for Optical Engineering 9905 2016年 査読有りSuppression of super fluid helium flow is critical for the Soft X-ray Spectrometer onboard ASTRO-H (Hitomi). In nominal operation, a small helium gas flow of ∼30 μg/s must be safely vented and a super fluid film flow must be sufficiently small < 2 μg/s. To achieve a life time of the liquid helium, a porous plug phase separator and a film flow suppression system composed of an orifice, a heat exchanger, and knife edge devices are employed. In this paper, design, on-ground testing results and in-orbit performance of the porous plug and the film flow suppression system are described.
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日本物理学会講演概要集 71 367-367 2016年<p>2016年2月17日に打ち上げられたASTRO-H (ひとみ) 衛星に搭載された精密X線分光装置 SXS (Soft X-ray Spectrometer) は，40日弱の限られた期間ではあったが，軌道上において正常に動作し，天体のデータも取得できた．SXS の軌道上での性能について報告する．</p>
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SPACE TELESCOPES AND INSTRUMENTATION 2016: ULTRAVIOLET TO GAMMA RAY 9905 2016年We present the overall design and performance of the Astro-H (Hitomi) Soft X-Ray Spectrometer (SXS). The instrument uses a 36-pixel array of x-ray microcalorimeters at the focus of a grazing-incidence x-ray mirror Soft X-Ray Telescope (SXT) for high-resolution spectroscopy of celestial x-ray sources. The instrument was designed to achieve an energy resolution better than 7 eV over the 0.3-12 keV energy range and operate for more than 3 years in orbit. The actual energy resolution of the instrument is 4-5 eV as demonstrated during extensive ground testing prior to launch and in orbit. The measured mass flow rate of the liquid helium cryogen and initial fill level at launch predict a lifetime of more than 4 years assuming steady mechanical cooler performance. Cryogen-free operation was successfully demonstrated prior to launch. The successful operation of the SXS in orbit, including the first observations of the velocity structure of the Perseus cluster of galaxies, demonstrates the viability and power of this technology as a tool for astrophysics.
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SPACE TELESCOPES AND INSTRUMENTATION 2016: ULTRAVIOLET TO GAMMA RAY 9905 2016年We summarize all the in-orbit operations of the Soft X-ray Spectrometer (SXS) onboard the ASTRO-H (Hitomi) satellite. The satellite was launched on 2016/02/17 and the communication with the satellite ceased on 2016/03/26. The SXS was still in the commissioning phase, in which the setups were progressively changed. This article is intended to serve as a reference of the events in the orbit to properly interpret the SXS data taken during its short life time, and as a test case for planning the in-orbit operation for future micro-calorimeter missions.
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Journal of Low Temperature Physics 184(1-2) 2016年
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Temperature Control and Noise Reduction in our Compact ADR System for TES Microcalorimeter OperationJournal of Low Temperature Physics 184(3-4) 2016年
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SPACE TELESCOPES AND INSTRUMENTATION 2014: ULTRAVIOLET TO GAMMA RAY 9144 2014年We present the development status of the Soft X-ray Spectrometer (SXS) onboard the ASTRO-H mission. The SXS provides the capability of high energy-resolution X-ray spectroscopy of a FWHM energy resolution of < 7eV in the energy range of 0.3 - 10 keV. It utilizes an X-ray micorcalorimeter array operated at 50 mK. The SXS microcalorimeter subsystem is being developed in an EM-FM approach. The EM SXS cryostat was developed and fully tested and, although the design was generally confirmed, several anomalies and problems were found. Among them is the interference of the detector with the micro-vibrations from the mechanical coolers, which is the most difficult one to solve. We have pursued three different countermeasures and two of them seem to be effective. So far we have obtained energy resolutions satisfying the requirement with the FM cryostat.
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Publications of the Astronomical Society of Japan 70(2) 2018年We report a Hitomi observation of IGR J16318-4848, a high-mass X-ray binary<br /> system with an extremely strong absorption of N_H~10^{24} cm^{-2}. Previous<br /> X-ray studies revealed that its spectrum is dominated by strong fluorescence<br /> lines of Fe as well as continuum emission. For physical and geometrical insight<br /> into the nature of the reprocessing material, we utilize the high spectroscopic<br /> resolving power of the X-ray microcalorimeter (the soft X-ray spectrometer;<br /> SXS) and the wide-band sensitivity by the soft and hard X-ray imager (SXI and<br /> HXI) aboard Hitomi. Even though photon counts are limited due to unintended<br /> off-axis pointing, the SXS spectrum resolves Fe K{\alpha_1} and K{\alpha_2}<br /> lines and puts strong constraints on the line centroid and width. The line<br /> width corresponds to the velocity of 160^{+300}_{-70} km s^{-1}. This<br /> represents the most accurate, and smallest, width measurement of this line made<br /> so far from any X-ray binary, much less than the Doppler broadening and shift<br /> expected from speeds which are characteristic of similar systems. Combined with<br /> the K-shell edge energy measured by the SXI and HXI spectra, the ionization<br /> state of Fe is estimated to be in the range of Fe I--IV. Considering the<br /> estimated ionization parameter and the distance between the X-ray source and<br /> the absorber, the density and thickness of the materials are estimated. The<br /> extraordinarily strong absorption and the absence of a Compton shoulder<br /> component is confirmed. These characteristics suggest reprocessing materials<br /> which are distributed in a narrow solid angle or scattering primarily with warm<br /> free electrons or neutral hydrogen.
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Publications of the Astronomical Society of Japan 70(6) 2018年We present the results from the Hitomi Soft Gamma-ray Detector (SGD)<br /> observation of the Crab nebula. The main part of SGD is a Compton camera, which<br /> in addition to being a spectrometer, is capable of measuring polarization of<br /> gamma-ray photons. The Crab nebula is one of the brightest X-ray / gamma-ray<br /> sources on the sky, and, the only source from which polarized X-ray photons<br /> have been detected. SGD observed the Crab nebula during the initial test<br /> observation phase of Hitomi. We performed the data analysis of the SGD<br /> observation, the SGD background estimation and the SGD Monte Carlo simulations,<br /> and, successfully detected polarized gamma-ray emission from the Crab nebula<br /> with only about 5 ks exposure time. The obtained polarization fraction of the<br /> phase-integrated Crab emission (sum of pulsar and nebula emissions) is (22.1<br /> $\pm$ 10.6)% and, the polarization angle is 110.7$^o$ + 13.2 / $-$13.0$^o$ in<br /> the energy range of 60--160 keV (The errors correspond to the 1 sigma<br /> deviation). The confidence level of the polarization detection was 99.3%. The<br /> polarization angle measured by SGD is about one sigma deviation with the<br /> projected spin axis of the pulsar, 124.0$^o$ $\pm$0.1$^o$.
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Publications of the Astronomical Society of Japan 70(2) 2018年The present paper investigates the temperature structure of the X-ray<br /> emitting plasma in the core of the Perseus cluster using the 1.8--20.0 keV data<br /> obtained with the Soft X-ray Spectrometer (SXS) onboard the Hitomi Observatory.<br /> A series of four observations were carried out, with a total effective exposure<br /> time of 338 ks and covering a central region $\sim7'$ in diameter. The SXS was<br /> operated with an energy resolution of $\sim$5 eV (full width at half maximum)<br /> at 5.9 keV. Not only fine structures of K-shell lines in He-like ions but also<br /> transitions from higher principal quantum numbers are clearly resolved from Si<br /> through Fe. This enables us to perform temperature diagnostics using the line<br /> ratios of Si, S, Ar, Ca, and Fe, and to provide the first direct measurement of<br /> the excitation temperature and ionization temperature in the Perseus cluster.<br /> The observed spectrum is roughly reproduced by a single temperature thermal<br /> plasma model in collisional ionization equilibrium, but detailed line ratio<br /> diagnostics reveal slight deviations from this approximation. In particular,<br /> the data exhibit an apparent trend of increasing ionization temperature with<br /> increasing atomic mass, as well as small differences between the ionization and<br /> excitation temperatures for Fe, the only element for which both temperatures<br /> can be measured. The best-fit two-temperature models suggest a combination of 3<br /> and 5 keV gas, which is consistent with the idea that the observed small<br /> deviations from a single temperature approximation are due to the effects of<br /> projection of the known radial temperature gradient in the cluster core along<br /> the line of sight. Comparison with the Chandra/ACIS and the XMM-Newton/RGS<br /> results on the other hand suggests that additional lower-temperature components<br /> are present in the ICM but not detectable by Hitomi SXS given its 1.8--20 keV<br /> energy band.
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Publications of the Astronomical Society of Japan 70(2) 2018年The Hitomi SXS spectrum of the Perseus cluster, with $\sim$5 eV resolution in<br /> the 2-9 keV band, offers an unprecedented benchmark of the atomic modeling and<br /> database for hot collisional plasmas. It reveals both successes and challenges<br /> of the current atomic codes. The latest versions of AtomDB/APEC (3.0.8), SPEX<br /> (3.03.00), and CHIANTI (8.0) all provide reasonable fits to the broad-band<br /> spectrum, and are in close agreement on best-fit temperature, emission measure,<br /> and abundances of a few elements such as Ni. For the Fe abundance, the APEC and<br /> SPEX measurements differ by 16%, which is 17 times higher than the statistical<br /> uncertainty. This is mostly attributed to the differences in adopted<br /> collisional excitation and dielectronic recombination rates of the strongest<br /> emission lines. We further investigate and compare the sensitivity of the<br /> derived physical parameters to the astrophysical source modeling and<br /> instrumental effects. The Hitomi results show that an accurate atomic code is<br /> as important as the astrophysical modeling and instrumental calibration<br /> aspects. Substantial updates of atomic databases and targeted laboratory<br /> measurements are needed to get the current codes ready for the data from the<br /> next Hitomi-level mission.
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 基盤研究(C) 2023年4月 - 2026年3月
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