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 准教授
- 学位
- 博士(理学)(2004年3月 東京大学)
- 研究者番号
- 60446599
- ORCID ID
https://orcid.org/0000-0003-0441-7404- J-GLOBAL ID
- 202001021434500706
- researchmap会員ID
- R000012970
研究キーワード
6経歴
2-
2022年3月 - 現在
-
2006年7月 - 2022年2月
学歴
3-
2001年4月 - 2004年3月
-
1999年4月 - 2001年3月
-
1995年4月 - 1999年3月
受賞
2論文
217-
SPACE TELESCOPES AND INSTRUMENTATION 2012: ULTRAVIOLET TO GAMMA RAY 8443 2012年MeV and sub-MeV energy band from similar to 200 keV to similar to 2 MeV contains rich information of high-energy phenomena in the universe. The CAST (Compton Telescope for Astro and Solar Terrestrial) mission is planned to be launched at the end of 2010s, and aims at providing all-sky map in this energy-band for the first time. It is made of a semiconductor Compton telescope utilizing Si as a scatterer and CdTe as an absorber. CAST provides all-sky sub-MeV polarization map for the first time, as well. The Compton telescope technology is based on the design used in the Soft Gamma-ray Detector (SGD) onboard ASTRO-H, characterized by its tightly stacked semiconductor layers to obtain high Compton reconstruction efficiency. The CAST mission is currently planned as a candidate for the small scientific satellite series in ISAS/JAXA, weighting about 500 kg in total. Scalable detector design enables us to consider other options as well. Scientific outcome of CAST is wide. It will provide new information from high-energy sources, such as AGN and/or its jets, supernova remnants, magnetors, black-hole and neutron-star binaries and others. Polarization map will tell us about activities of jets and reflections in these sources, as well. In addition, CAST will simultaneously observe the Sun, and depending on its attitude, the Earth.
-
Physics Procedia 37 859-866 2012年© 2012 Shin'ichiro Takeda. By using a new Compton camera consisting of a silicon double-sided strip detector (Si-DSD) and a CdTe doublesided strip detector (CdTe-DSD), originally developed for the ASTRO-H satellite mission, an experiment involving imaging radioisotopes was conducted to study their feasibility for hotspot monitoring. In addition to the hotspot imaging already provided by commercial imaging systems, identification of various radioisotopes is possible thanks to the good energy resolution obtained by the semiconductor detectors. Three radioisotopes of 133Ba (356 keV), 22Na (511 keV) and 137Cs (662 keV) were individually imaged by applying event selection in the energy window and the gamma-ray images were correctly overlapped by an optical picture. Detection efficiency of 1.68 ×10-4 (effective area: 1.7×10-3 cm2) and angular resolution of 3.8 degrees were obtained by stacking five detector modules for a 662 keV gamma ray. The higher detection efficiency required in specific use can be achieved by stacking more detector modules.
-
Proceedings of SPIE - The International Society for Optical Engineering 8443 2012年The imaging and spectral performance of CdTe double-sided strip detectors (CdTe-DSDs) was evaluated for the ASTRO-H mission. The charcterized CdTe-DSDs have a strip pitch of 0.25 mm, an imaging area of 3.2 cm×3.2 cm and a thickness of 0.75 mm. The detector was successfully operated at a temperature of -20°C and with an applied bias voltage of 250 V. By using two-strip events as well as one-strip events for the event reconstruction, a good energy resolution of 2.0 keV at 59.5 keV and a sub-strip spatial resolution was achieved. The hard X-ray and gamma-ray response of CdTe-DSDs is complex due to the properties of CdTe and the small pixel effect. Therefore, one of the issues to investigate is the response of the CdTe-DSD. In order to investigate the spatial dependence of the detector response, we performed fine beam scan experiments at SPring-8, a synchrotron radiation facility. From these experiments, the depth structure of the electric field was determined as well as properties of carriers in the detector and successfully reproduced the experimental data with simulated spectra. © 2012 SPIE.
-
IEEE Nuclear Science Symposium Conference Record 1727-1730 2012年We are developing an integrated simulation framework based on Geant4 to estimate in-orbit performance of instruments onboard ASTRO-H, the international X-ray observatory to be launched in 2014. One of the most important purposes of our simulation is to estimate radiation background of the Hard X-ray Imager (HXI) and the Soft Gamma-ray Detector (SGD), both of which are composed of CdTe and silicon. We developed a new code based on Geant4 to handle the generation and the decay of radioactive nuclei and to estimate the activation of CdTe detector. In addition, to verify simulation results, we performed beam irradiation experiments at NIRS HIMAC using 150 MeV protons, which is typical energy of protons reaching to the CdTe detectors placed in the shielding materials, and measured the activation background spectra for several months. Our simulation results show good agreements with the experimental data. © 2012 IEEE.
-
AIP Conference Proceedings 1505 809-812 2012年The hard X-ray imager (HXI) is the focal plane detector onboard ASTRO-H to be launched in 2014. By combining with the hard X-ray telescope, the HXI will realize the focusing imaging in the energy range from 5 up to 80 keV. The sensitivity of the HXI for an isolated point source will be two orders of magnitude better compared with previous missions. The hybrid structure composed of four layers of double-sided silicon strip detectors (DSSD) and one layer of cadmium telluride double-sided strip detector (CdTe-DSD) enables high detection efficiency in the hard X-ray band. The DSSD and CdTe-DSD for ASTRO-H have been developed, and their spectral and imaging performances were evaluated. By using two-strip events for the reconstructions of spectra and images, energy resolution of 1.0 keV at 13.9 keV and 2.0 keV at 59.5 keV, and sub-strip spatial resolution were achieved. © 2012 American Institute of Physics.
-
IEEE Nuclear Science Symposium Conference Record 4199-4204 2012年Dust containing radioactive materials dispersed following the Fukushima nuclear power plant accident in March 2011. Gamma-rays are emitted in the process when unstable nuclei in the materials decay. Based on the technology of Si/CdTe Compton Camera, we have manufactured a quick prototype model for the use in the field. The camera, now called a 'Ultra-Wide-Angle Compton Camera' was successfully applied to visualize the distribution of radio-active substances in the Fukushima area. © 2012 IEEE.
-
Proceedings of SPIE - The International Society for Optical Engineering 8443 2012年The LOFT mission concept is one of four candidates selected by ESA for the M3 launch opportunity as Medium Size missions of the Cosmic Vision programme. The launch window is currently planned for between 2022 and 2024. LOFT is designed to exploit the diagnostics of rapid X-ray flux and spectral variability that directly probe the motion of matter down to distances very close to black holes and neutron stars, as well as the physical state of ultradense matter. These primary science goals will be addressed by a payload composed of a Large Area Detector (LAD) and a Wide Field Monitor (WFM). The LAD is a collimated (<1 degree field of view) experiment operating in the energy range 2-50 keV, with a 10 m2 peak effective area and an energy resolution of 260 eV at 6 keV. The WFM will operate in the same energy range as the LAD, enabling simultaneous monitoring of a few-steradian wide field of view, with an angular resolution of <5 arcmin. The LAD and WFM experiments will allow us to investigate variability from submillisecond QPO's to yearlong transient outbursts. In this paper we report the current status of the project. © 2012 SPIE.
-
Astrophysical Journal 740(2) 2011年10月10日Strong iron fluorescence at 6.4 keV and hard-X-ray emissions from giant molecular clouds in the Galactic center region have been interpreted as reflections of a past outburst of the Sgr A* supermassive black hole. Careful treatment of multiple interactions of photons in a complicated geometry is essential to modeling the reprocessed emissions from the dense clouds. We develop a new calculation framework of X-ray reflection from molecular clouds based on Monte Carlo simulations for accurate interpretation of high-quality observational data. By utilizing this simulation framework, we present the first calculations of morphologies and spectra of the reflected X-ray emission for several realistic models of Sgr B2, which is the most massive molecular cloud in our Galaxy. The morphology of scattered hard X-rays above 20 keV is significantly different from that of iron fluorescence due to their large penetrating power into dense regions of the cloud, probing the structure of the cloud. High-resolution spectra provide quantitative evaluation of the iron line including its Compton shoulder to constrain the mass and the chemical composition of the cloud as well as the luminosity of the illuminating source. These predictions can be checked in the near future with future X-ray missions such as NuStar (hard X-rays) and ASTRO-H (both iron lines and hard X-rays).
-
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 652(1) 149-152 2011年10月1日Schottky CdTe diode detectors suffer from a polarization phenomenon, which is characterized by degradation of the spectral properties over time following exposure to high bias voltage. This is considered attributable to charge accumulation at deep acceptor levels. A Schottky CdTe diode was illuminated with an infrared light for a certain period during a bias operation, and two opposite behaviors emerged. The detector showed a recovery when illuminated after the bias-induced polarization had completely progressed. Conversely, when the detector was illuminated before the emergence of bias-induced polarization, the degradation of the spectral properties was accelerated. Interpretation of these effects and discussion on the energy level of deep acceptors are presented. © 2011 Elsevier B.V.
-
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 650(1) 88-91 2011年9月11日We have developed a photon-counting-type CdTe pixel detector (SP8-01). SP8-01 was designed as a prototype of a high-energy X-ray imaging detector for experiments using synchrotron radiation. SP8-01 has a CdTe sensor of 500μm thickness, which has an absorption efficiency of almost 100% up to 50 keV and 45% even at 100 keV. A full-custom application specific integrated circuit (ASIC) was designed as a readout circuit of SP8-01, which is equipped with a window-type discriminator. The upper discriminator realizes a low-background measurement, because X-ray beams from the monochromator contain higher-order components beside the fundamental X-rays in general. ASIC chips were fabricated with a TSMC 0.25μm CMOS process, and CdTe sensors were bump-bonded to the ASIC chips by a gold-stud bonding technique. Beam tests were performed at SPring-8. SP8-01 detected X-rays up to 120 keV. The capability of SP8-01 as an imaging detector for high-energy X-ray synchrotron radiation was evaluated with its performance characteristics. © 2010 Elsevier B.V. All rights reserved.
-
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 648(SUPPL. 1) 2011年8月21日We are constructing a three-dimensional imaging system for medical and biological applications. The system will allow simultaneous imaging at high spatial and energy resolutions across a wide energy range, from several tens of keV to a few MeV. The system relies on a Si/CdTe semiconductor Compton camera, incorporating state-of-the-art space-observation technology developed by ISAS/JAXA. The Si/CdTe Compton camera was developed for use at moderate temperatures. Moreover, the solid, thin scattering layer allows the target to be placed close to the camera, a good angular resolution corresponds directly to a good spatial resolution. These aspects allow the construction of a compact medical system. In this work, we have developed a prototype head module for a multi-head system. The performance of the prototype was evaluated with a sealed Ba-133 radiation source. The experiments confirmed that the imaging results were consistent with source positioning. The experimental results were also compared with those of a Monte Carlo simulation. © 2011 Elsevier B.V. All rights reserved.
-
IEEE Transactions on Nuclear Science 58(4 PART 2) 2039-2046 2011年8月The Focusing Optics X-ray Solar Imager (FOXSI) is a NASA sounding rocket mission which will study particle acceleration and coronal heating on the Sun through high sensitivity observations in the hard X-ray energy band (5-15 keV). Combining high-resolution focusing X-ray optics and fine-pitch imaging sensors, FOXSI will achieve superior sensitivity; two orders of magnitude better than that of the RHESSI satellite. As the focal plane detector, a Double-sided Si Strip Detector (DSSD) with a front-end ASIC (Application Specific Integrated Circuit) will fulfill the scientific requirements of spatial and energy resolution, low energy threshold and time resolution. We have designed and fabricated a DSSD with a thickness of 500 μm and a dimension of 9.6 mm × 9.6 mm, containing 128 strips with a pitch of 75 μm, which corresponds to 8 arcsec at the focal length of 2 m. We also developed a low-noise ASIC specified to FOXSI. The detector was successfully operated in the laboratory at a temperature of -20°C and with an applied bias voltage of 300 V. Extremely good energy resolutions of 430 eV for the p-side and 1.6 keV for the n-side at a 14 keV line were achieved for the detector. We also demonstrated fine-pitch imaging successfully by obtaining a shadow image. Hence the implementation of scientific requirements was confirmed. © 2006 IEEE.
-
Publications of the Astronomical Society of Japan 63(SPEC. ISSUE 3) 2011年7月25日Improvements of in-orbit calibration of GSO scintillators in the Hard X-ray Detector on board Suzaku are reported. To resolve an apparent change of the energy scale of GSO which appeared across the launch for unknown reasons, consistent and thorough re-analyses of both pre-launch and in-orbit data have been performed. With laboratory experiments using spare hardware, the pulse height offset, corresponding to zero energy input, was found to change by ~0.5 of the full analog voltage scale, depending on the power supply. Furthermore, by carefully calculating all the light outputs of secondaries from activation lines used in the in-orbit gain determination, their energy deposits in GSO were found to be effectively lower, by several percent, than their nominal energies. Taking both these effects into account, the in-orbit data agrees with the on-ground measurements within ~5%, without employing the artificial correction introduced in the previous work (Kokubun et al. 2007). With this knowledge, we updated the data processing, the response, and the auxiliary files of GSO, and reproduced the HXD-PIN and HXD-GSO spectra of the Crab Nebula over 12-300 keV by a broken powerlaw with a break energy of ~110 keV.
-
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 636(1 SUPPL.) 2011年4月Single X-ray photon counting pixel detectors have become the most advanced detector technology in synchrotron radiation experiments recently. In particular, the PILATUS detector based on a silicon sensor has reached a very mature state and represents the world's largest detector in this field. This paper first reports on threshold energy calibrations and the capability of applying an energy-resolved X-ray imaging with PILATUS. Second the design of a cadmium telluride (CdTe) pixel detector is described. A high density and high-atomic number sensor material is required in high energy X-ray applications available at SPring-8. For this purpose we are developing a CdTe pixel detector with the SP8-01 readout ASIC covering a wide dynamic range between 10 and 100 keV and containing lower and upper discriminators. © 2010 Elsevier B.V.
-
Proceedings of the 25th Workshop on Radiation Detectors and Their Uses 196-203 2011年
-
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 624(2) 303-309 2010年12月11日We have developed an integrated response generator based on Monte Carlo simulation for Compton cameras composed of silicon (Si) and cadmium telluride (CdTe) semiconductor detectors. In order to construct an accurate detector response function, the simulation is required to include a comprehensive treatment of the semiconductor detector devices and the data processing system in addition to simulating particle tracking. Although CdTe is an excellent semiconductor material for detection of soft gamma rays, its ineffective charge transport property distorts its spectral response. We investigated the response of CdTe pad detectors in the simulation and present our initial results here. We also performed the full simulation of prototypes of Si/CdTe semiconductor Compton cameras and report on the reproducibility of detection efficiencies and angular resolutions of the cameras, both of which are essential performance parameters of astrophysical instruments. © 2010 Elsevier B.V. All rights reserved.
-
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 623(1) 425-427 2010年11月1日We have been developing a hard X-ray imager and soft gamma-ray detector as on board instruments of the ASTRO-H mission. The Hard X-ray Imager (HXI) is one of the three focal plane detectors of ASTRO-H, which is aimed to realize the focusing imaging of hard X-ray photons in combination with hard X-ray telescopes. By use of the hybrid structure composed of double-sided silicon strip detectors and a cadmium telluride strip detector, it fully covers the energy range up to 80 keV with a high quantum efficiency. High spatial resolutions of 250μm pitch and energy resolutions of 12 keV (FWMH) are at the same time achieved with low noise front-end ASICs. The Soft Gamma-ray Detector (SGD) is a novel and unique detector which is characterized by semiconductor Compton cameras surrounded by narrow field-of-view active shields, and covers a higher energy range (30600 keV) than that of HXI. It consists of four Compton Cameras constructed with many layers of Silicon and CdTe pad detectors. With its multi-layer structure and Compton reconstruction capability, in addition to the BGO active shields read by Avalanche photo-diodes, this detector will achieve an extremely high background rejection efficiency in the orbit. We report the current status of hardware development including the design requirement, expected performance, and technical readinesses of key technologies. © 2010 Elsevier B.V. All rights reserved.
-
Japanese Journal of Applied Physics 49(11) 2010年11月By reading out both anode and cathode strips, double-sided CdTe strip detectors can achieve a large area and a high position resolution with few readout channels, which makes them very attractive for X-ray and γ-ray imaging and spectroscopy. We have developed double-sided CdTe strip detectors, 1:28 × 1:28 cm2 in size and 0.5 and 2.0mm in thickness. Both electrodes are divided into 32 orthogonal strips with a pitch of 400 μm. For a detector of 0.5mm thickness, the energy resolution was measured to be 1.5 keV (FWHM) at 60 keV. For the 2.0-mm-thick detector, an energy resolution of 8.0 keV (FWHM) at 662 keV was obtained using only the anode signal. By combining both the anode and cathode signals, we successfully improved the spectral performance and measured an energy resolution of 5.9 keV (FWHM) at 662 keV. © 2010 The Japan Society of Applied Physics.
-
Proceedings of SPIE - The International Society for Optical Engineering 7732 2010年10月24日The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly successful X-ray missions initiated by the Institute of Space and Astronautical Science (ISAS). ASTRO-H will investigate the physics of the high-energy universe by performing high-resolution, high-throughput spectroscopy with moderate angular resolution. ASTRO-H covers very wide energy range from 0.3 keV to 600 keV. ASTRO-H allows a combination of wide band X-ray spectroscopy (5-80 keV) provided by multilayer coating, focusing hard X-ray mirrors and hard X-ray imaging detectors, and high energy-resolution soft X-ray spectroscopy (0.3-12 keV) provided by thin-foil X-ray optics and a micro-calorimeter array. The mission will also carry an X-ray CCD camera as a focal plane detector for a soft X-ray telescope (0.4-12 keV) and a non-focusing soft gamma-ray detector (40-600 keV) . The micro-calorimeter system is developed by an international collaboration led by ISAS/JAXA and NASA. The simultaneous broad bandpass, coupled with high spectral resolution of Delta E ~7 eV provided by the micro-calorimeter will enable a wide variety of important science themes to be pursued.
-
Proceedings of SPIE - The International Society for Optical Engineering 7732 2010年10月24日ASTRO-H is the next generation JAXA X-ray satellite, intended to carry instruments with broad energy coverage and exquisite energy resolution. The Soft Gamma-ray Detector (SGD) is one of ASTRO-H instruments and will feature wide energy band (40-600 keV) at a background level 10 times better than the current instruments on orbit. SGD is complimentary to ASTRO-H's Hard X-ray Imager covering the energy range of 5-80 keV. The SGD achieves low background by combining a Compton camera scheme with a narrow field-of-view active shield where Compton kinematics is utilized to reject backgrounds. The Compton camera in the SGD is realized as a hybrid semiconductor detector system which consists of silicon and CdTe (cadmium telluride) sensors. Good energy resolution is afforded by semiconductor sensors, and it results in good background rejection capability due to better constraints on Compton kinematics. Utilization of Compton kinematics also makes the SGD sensitive to the gamma-ray polarization, opening up a new window to study properties of gamma-ray emission processes. The ASTRO-H mission is approved by ISAS/JAXA to proceed to a detailed design phase with an expected launch in 2014. In this paper, we present science drivers and concept of the SGD instrument followed by detailed description of the instrument and expected performance.
-
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 622(3) 619-627 2010年10月21日A Compton camera has been developed based on Si and CdTe semiconductor detectors with high spatial and spectral resolution for hard X- and γray astrophysics applications. A semiconductor Compton camera is also an excellent polarimeter due to its capability to precisely measure the Compton scattering azimuth angle, which is modulated by linear polarization. We assembled a prototype Compton camera and conducted a beam test using nearly 100% linearly polarized γrays at SPring-8. © 2010 Elsevier B.V. All rights reserved.
-
2010 IEEE NUCLEAR SCIENCE SYMPOSIUM CONFERENCE RECORD (NSS/MIC) 2004-2007 2010年 査読有りIn this study, the counting rate performance of a newly developed Compton camera for biological and medical applications was investigated; further, the sensitivity profile of this highly complicated imaging system was measured using Na-22 and F-18 point gamma-ray sources. Na-22 was used to assess the imaging ability of this camera against the point source, and the intense F-18 point source of 200 MBq was used to measure the sensitivity profiles of this camera for a range of counting rates over a short period.
-
2010 IEEE NUCLEAR SCIENCE SYMPOSIUM CONFERENCE RECORD (NSS/MIC) 1491-1493 2010年 査読有りIn this paper, we report the estimations of the lower detection limits of gamma ray energy for a newly developed Compton camera for applications to nuclear medicine imaging. We performed simulation studies to investigate the relationship of the distance between the scatterer and absorber detectors with the lower detection limit. In addition, imaging tests were performed by using multiple sources.
-
2010 IEEE Sensors Applications Symposium, SAS 2010 - Proceedings 170-174 2010年A semiconductor Compton camera with wide-band imaging capability and high energy resolution is expected to provide new in-vivo data that enables tracking of multiple RI-labeled molecular probes. In our previous works, we have constructed prototype Compton cameras composed of Si and CdTe semiconductor detectors, and demonstrated wide-band imaging of 60-662 keV gamma-rays with a spatial resolution on the order of millimeters for a 2-D target. The feasibility of 3-D imaging is studied by Monte Carlo simulations that were validated in our previous work, in order to apply this camera to in-vivo molecular imaging and clinical use. © 2009 IEEE.
-
Proceedings of SPIE - The International Society for Optical Engineering 7732 2010年We are developing an ASTRO-H data analysis framework with the Geant4-based Monte Carlo simulation core, and numerical models of the on-orbit environmental radiation and full-satellite mass structure. In addition, the framework also includes a mechanism to connect and control data processing modules that are developed independently and data communication channels among them, which has been technically proven by simulations and analysis of the Suzaku HXD, many other detectors and astrophysical issues. © 2010 SPIE.
-
Proceedings of SPIE - The International Society for Optical Engineering 7732 2010年The Focusing Optics X-ray Solar Imager (FOXSI) is a rocket experiment scheduled for January 2011 launch. FOXSI observes 5 - 15 keV hard X-ray emission from quiet-region solar flares in order to study the acceleration process of electrons and the mechanism of coronal heating. For observing faint hard X-ray emission, FOXSI uses focusing optics for the first time in solar hard X-ray observation, and attains 100 times higher sensitivity than RHESSI, which is the present solar hard X-ray observing satellite. Now our group is working on developments of both Double-sided Silicon Strip Detector (DSSD) and read-out analog ASIC "VATA451" used for FOXSI. Our DSSD has a very fine strip pitch of 75 μm, which has sufficient position resolution for FOXSI mirrors with angular resolution (FWHM) of 12 arcseconds. DSSD also has high spectral resolution and efficiency in the FOXSI's energy range of 5 - 15 keV, when it is read out by our 64-channel analog ASIC. In advance of the FOXSI launch, we have established and tested a setup of 75 μm pitch DSSD bonded with "VATA451" ASICs. We successfully read out from almost all the channels of the detector, and proved ability to make a shadow image of tungsten plate. We also confirmed that our DSSD has energy resolution (FWHM) of 0.5 keV, lower threshold of 5 keV, and position resolution less than 63 μm. These performance satisfy FOXSI's requirements. © 2010 SPIE.
-
Proceedings of SPIE - The International Society for Optical Engineering 7732 2010年Hard X-ray Detector (HXD) onboard Suzaku, the Japanese 5th X-ray observatory, consists of 64 PIN photo diodes with 2 mm thickness (10-70 keV) and 16 phoswich detectors using 5 mm-thick GSO scintillators and BGO active collimators (40-600 keV), and these are surrounded by 20 units of BGO Active shields. All the detector units have been working well with no significant troubles in four and a half years since the launch on July 2005, and given many important scientific results. In this paper, we report the recent status of onorbit calibrations for PIN/GSO detectors. For the PIN, analog/digital threshold levels of both in-orbit and on-ground are raised up to avoid the increasing noise events due to in-orbit radiation damage. For the GSO, the accuracy of the energy scale and modeling of gain variations are improved, and newly calibrated data set including background files and response matrices are released on April 2010. © 2010 SPIE.
-
Proceedings of SPIE - The International Society for Optical Engineering 7732 2010年The Soft Gamma-ray Detector onboard the ASTRO-H satellite, scheduled for launch in 2014, is a Si/CdTe Compton telescope surrounded by a thick BGO active shield. The SGD covers the energy range from 40 to 600 keV and studies non-thermal phenomena in the universe with high sensitivity. For the success of the SGD mission, careful examination of the expected performance, particularly the instrumental background in orbit, and optimization of the detector configuration are essential. We are developing a Geant4-based Monte Carlo simulation framework on the ANL++ platform, employing the MGGPOD software suite to predict the radioactivation in orbit. A detailed validation of the simulator through the comparison with literature and the beam test data is summarized. Our system will be integrated into the ASTRO-H simulation framework. © 2010 SPIE.
-
Proceedings of SPIE - The International Society for Optical Engineering 7732 2010年The Hard X-ray Imager (HXI) is one of the instruments onboard International X-ray Observatory (IXO), to be launched into orbit in 2020s. It covers the energy band of 10-40 keV, providing imaging-spectroscopy with a field of view of 8×8 arcmin2. The HXI is attached beneath the Wide Field Imager (WFI) covering 0.1-15 keV. Combined with the super-mirror coating on the mirror assembly, this configuration provides observation of X-ray source in wide energy band (0.1-40.0 keV) simultaneously, which is especially important for varying sources. The HXI sensor part consists of the semiconductor imaging spectrometer, using Si in the medium energy detector and CdTe in the high energy detector as its material, and an active shield covering its back to reduce background in orbit. The HXI technology is based on those of the Japanese-lead new generation X-ray observatory ASTRO-H, and partly from those developed for Simbol-X. Therefore, the technological development is in good progress. In the IXO mission, HXI will provide a major assets to identify the nature of the object by penetrating into thick absorbing materials and determined the inherent spectral shape in the energy band well above the structure around Fe-K lines and edges. © 2010 SPIE.
-
Proceedings of SPIE - The International Society for Optical Engineering 7732 2010年Soft Gamma-ray Detector (SGD:40-600 keV) will be mounted on the 6th Japanese X-ray observatory ASTRO-H to be launched in 2014. The main part of the SGD is a Compton camera with a narrow field of view and surrounded by BGO active shields (SGD-BGO). Via this combination, the SGD can achieve sensitivity more than ten times superior to the Suzaku/HXD. The BGO active shield will also function as a gamma-ray burst monitor as proven by the wide-band all-sky monitor (WAM) of the Suzaku/HXD. Avalanche Photodiodes (APDs) are used to read out scintillation lights from the BGO. The size of the former also means we need to focus on collecting light from large, complex-shaped BGO blocks. The significant leakage current of the APD means a lower temperature is preferred to minimize the noise while a higher temperature is preferred to simplify the cooling system. To optimize the BGO shape and the operating temperature, we tested the performance of the BGO readout system with various BGO shapes under different operating temperatures. We also apply waveform sampling by flash-ADC and digital filter instead of a conventional analog filter and ADC scheme to reduce the space and power of the circuit with increased flexibilities. As an active shield, we need to achieve a threshold level of 50-100 keV. Here, we report on the studies of threshold energy of active shield under various conditions and signal processings. © 2010 SPIE.
-
Experimental results of the gamma-ray imaging capability with a Si/CdTe semiconductor compton cameraIEEE Transactions on Nuclear Science 56(3) 783-790 2009年6月A semiconductor Compton camera that combines silicon (Si) and Cadmium Telluride (CdTe) detectors was developed, and its imaging capability was examined with various kinds of gamma-ray targets such as a point source, arranged point sources and an extended source. The camera consists of one double-sided Si strip detector and four layers of CdTe pad detectors, and was designed to minimize the distance between a scatterer and the target. This is because the spatial resolution with Compton imaging improves as the target approaches the scatterer. This new camera realizes a minimum distance of 25 mm. By placing the target at a distance of 30 mm from the detector, resolving power better than 3 mm was demonstrated experimentally for a 364 keV (131I) gamma-ray. Positional determination with accuracy of 1 mm was also demonstrated. As a deconvolution method, we selected the iteration algorithm (called List-Mode Expectation-Maximizing Maximum Likelihood), and applied it to several kinds of experimental data. The Compton back projection images of the arranged point sources and an extended object were successfully deconvolved. © 2006 IEEE.
-
Publications of the Astronomical Society of Japan 61(SUPPL. 1) 2009年1月5日Suzaku Hard X-ray Detector (HXD) achieved the lowest background level than any other previously or currently operational missions sensitive in the energy range of 10--600 keV, by utilizing PIN photodiodes and GSO scintillators mounted in the BGO active shields to reject particle background and Compton-scattered events as much as possible. Because it does not have imaging capability nor rocking mode for the background monitor, the sensitivity is limited by the reproducibility of the non X-ray background (NXB) model. We modeled the HXD NXB, which varies with time as well as other satellites with a low-earth orbit, by utilizing several parameters, including particle monitor counts and satellite orbital/attitude information. The model background is supplied as an event file in which the background events are generated by random numbers, and can be analyzed in the same way as the real data. The reproducibility of the NXB model depends on the event selection criteria (such as cut-off rigidity and energy band) and the integration time, and the 1sigma systematic error is estimated to be less than 3% (PIN 15--40 keV) and 1% (GSO 50--100 keV) for more than 10 ksec exposure.
-
2008 IEEE NUCLEAR SCIENCE SYMPOSIUM AND MEDICAL IMAGING CONFERENCE (2008 NSS/MIC), VOLS 1-9 5247-+ 2009年 査読有りWe developed double-sided CdTe strip detectors and studied their performances. By readout from both anode and cathode strips, a double-sided CdTe strip detector can achieve large area and high position resolution with a small number of readout channels. Therefore it is very attractive for gamma-ray imaging and spectroscopy. We developed double-sided CdTe strip detectors with Al/CdTe/Pt electrode configulation. The detectors have a size of 1.28 cm x 1.28 cm and a thickness of 0.5 mm and 2.0 mm. Both electrodes are divided into orthogonal 32 strips surrounded by guard-ring electrodes. The strip pitch is 400 mu m. We successfully operated the detectors at a temperature or -20 degrees C and a bias voltage of 500 V, and obtained spectra of gamma-ray from radio isotope sources. By using the detector with a thickness of 0.5 mm, energy resolutions of 1.8 keV (FWHM) for 60 keV gamma-ray was obtained from each side. From both signals from anode and cathode for each photons, we successfully reconstructed incident photon energy, and obtained energy resolutions (FWHM) of 1.5 keV for 60 keV. By using the detector with a thickness of 2.0 mm, the energy resolution of 8.0 keV (FWHM) for 662 keV was obtained by anode signals. We successfully estimated incident photon energy from the relation anode and cathode signals, and we achieved the energy resolution of 6.2 keV (FWHM) for 662 keV.
-
2009 IEEE NUCLEAR SCIENCE SYMPOSIUM CONFERENCE RECORD, VOLS 1-5 4001-+ 2009年 査読有りThe next generation of Compton Camera based on Si and CdTe semiconductor has been developed in Japan for cosmic gamma-ray observation in space. Angular resolution and hence sensitivity of Compton Cameras are improved by employing the imaging semiconductors with good energy and spatial resolution. Moreover, for the energy range from several tens keV to a few MeV, silicon is suitable for the scattering part of the Compton camera since Compton cross-section is relatively large in Si, compared with the photo absorption cross section. Also effects of Doppler broadening is small. On the other hand, CdTe is suitable for the absorbers because of its high photo-absorption efficiency for gamma rays in this energy region. The high angular resolution and high energy resolution of the Si/CdTe Compton camera is very attractive features for medical applications. In the previous simulation study, we reported that the Compton camera has a low spatial resolution along the longitudinal direction, but it can be inproved by using two camera heads. In the present work, we measured the spatial resolution of the Compton camera, especially for the longitudinal direction. The spatial resolutions are compared with the simulation study. The longitudinal resolution is measured to be about 27 mm and the lateral one is about 5 mm at the distance of 6 cm from the surface of the top detector. The simulation result and the experimental one agree well with each other. Moreover we demonstrate the capability of three-dimensional imaging by using multi-head system consisted of plural Compton cameras. The spatial resolutions are consistent with the simulation result. These results implies that clear 3D-image can be realized by using a multi-head system of Compton cameras.
-
2008 IEEE NUCLEAR SCIENCE SYMPOSIUM AND MEDICAL IMAGING CONFERENCE (2008 NSS/MIC), VOLS 1-9 3275-+ 2009年 査読有りWe have developed a prototype of Compton camera using Si/CdTe semiconductors for medical imaging. In the case where a Compton camera has a single head and therefore the detection area of the Compton camera is restricted to small region, position resolution of depth direction is expected to be low. To overcome this weakness, we propose multi-head Compton camera. In this work, we evaluated the position resolutions of single- and double-head Compton camera by using Monte Carlo simulation. Consequently, the position resolution is about 6 mm for double-head camera while the position resolution of depth direction is about 15 mm for single-head camera. These results indicate that the position resolution is improved and clear 3D-image is taken by using multi-head Compton camera.
-
Astrophysical Journal 694(1) 294-301 2008年11月24日We report the Suzaku observations of the high luminosity blazar SWIFT J0746.3+2548 (J0746) conducted in November 2005. This object, with z = 2.979, is the highest redshift source observed in the Suzaku Guaranteed Time Observer (GTO) period, is likely to show high gamma-ray flux peaking in the MeV range. As a result of the good photon statistics and high signal-to-noise ratio spectrum, the $Suzaku$ observation clearly confirms that J0746 has an extremely hard spectrum in the energy range of 0.3-24 keV, which is well represented by a single power-law with a photon index of 1.17 and Galactic absorption. The multiwavelength spectral energy distribution of J0746 shows two continuum components, and is well modeled assuming that the high-energy spectral component results from Comptonization of the broad-line region photons. In this paper we search for the bulk Compton spectral features predicted to be produced in the soft X-ray band by scattering external optical/UV photons by cold electrons in a relativistic jet. We discuss and provide constraints on the pair content resulting from the apparent absence of such features.
-
IEEE Transactions on Nuclear Science 56(3) 777-782 2008年11月4日 査読有り筆頭著者責任著者We developed CdTe double-sided strip detectors (DSDs or cross strip detectors) and evaluated their spectral and imaging performance for hard X-rays and gamma-rays. Though the double-sided strip configuration is suitable for imagers with a fine position resolution and a large detection area, CdTe diode DSDs with indium (In) anodes have yet to be realized due to the difficulty posed by the segmented In anodes. CdTe diode devices with aluminum (Al) anodes were recently established, followed by a CdTe device in which the Al anodes could be segmented into strips. We developed CdTe double-sided strip devices having Pt cathode strips and Al anode strips, and assembled prototype CdTe DSDs. These prototypes have a strip pitch of 400 micrometer. Signals from the strips are processed with analog ASICs (application specific integrated circuits). We have successfully performed gamma-ray imaging spectroscopy with a position resolution of 400 micrometer. Energy resolution of 1.8 keV (FWHM: full width at half maximum) was obtained at 59.54 keV. Moreover, the possibility of improved spectral performance by utilizing the energy information of both side strips was demonstrated. We designed and fabricated a new analog ASIC, VA32TA6, for the readout of semiconductor detectors, which is also suitable for DSDs. A new feature of the ASIC is its internal ADC function. We confirmed this function and good noise performance that reaches an equivalent noise charge of 110 e- under the condition of 3-4 pF input capacitance.
-
Astrophysical Journal 685(2) 988-1004 2008年6月9日We present results obtained from a series of observations of the supernova remnant RX J1713.7-3946 by the Suzaku satellite. The observations cover about two-thirds of the remnant surface. We successfully detected hard X-rays up to ~ 40 keV from each pointing. The hard X-ray spectra are described by power-law functions with photon indices of ~ 3.0, which are larger than those in the energy region below 10 keV. Connection of the spatially-integrated XIS and HXD spectra clearly reveals a spectral cutoff in the 0.4--40 keV X-ray spectrum. This cutoff is interpreted to correspond to the maximum acceleration energy of electrons emitting synchrotron radiation. The wide-band coverage of Suzaku for the first time allows us to derive the parent electron spectrum in the cutoff region, which shows good agreement with theoretical predictions. The inferred cutoff energy in the spatially-integrated X-ray spectrum indicates that particle acceleration in the remnant is so efficient that it is almost at the theoretical limit, the so-called Bohm limit. Based on the Suzaku data, we present results of multi-wavelength studies from spectral and morphological points of view. The spectral energy distribution favors the hadronic scenario rather than the leptonic scenario. For the morphology studies, we compare the surface brightness maps from the Suzaku XIS and the H.E.S.S. telescope. We confirm the strong correlation between X-ray and TeV gamma-ray emission. In addition to the correlation, we found that in the bright western rim regions the X-ray emission is brighter than expected from the general X-ray to gamma-ray correlation.
-
Astrophysical Journal 672(2) 787-799 2008年1月10日We present the results from a multiwavelength campaign conducted in 2006 August of the powerful γ-ray quasar PKS 1510-089 (z = 0.361). This campaign commenced with a deep Suzaku observation lasting 3 days for a total exposure time of 120 ks and continued with Swift monitoring over 18 days. Besides Swift observations, the campaign included ground-based optical and radio data and yielded a quasi-simultaneous broadband spectrum from 109 to 1019 Hz. The Suzaku observation provided a high signal-to-noise ratio X-ray spectrum, which is well represented by an extremely hard power law with a photon index of Γ ∼ 1.2, augmented by a soft component apparent below 1 keV, which is well described by a blackbody model with a temperature of kT ≃ 0.2 keV. Monitoring by Suzaku revealed temporal variability that differs between the low- and high-energy bands, again suggesting the presence of a second, variable component in addition to the primary power-law emission. We model the broadband spectrum, assuming that the high-energy spectral component results from Comptonization of infrared radiation produced by hot dust located in the surrounding molecular torus. The adopted internal shock scenario implies that the power of the jet is dominated by protons, but with a number of electrons and/or positrons that exceeds the number of protons by a factor of ∼10. We also find that inhomogeneities responsible for the shock formation prior to the collision may produce bulk Compton radiation, which can explain the observed soft X-ray excess and possible excess at ∼18 keV. We note, however, that the bulk Compton interpretation is not unique, as discussed briefly in the text. © 2008. The American Astronomical Society. All rights reserved.
-
Proceedings of SPIE - The International Society for Optical Engineering 7011 2008年The NeXT (New exploration X-ray Telescope), the new Japanese X-ray Astronomy Satellite following Suzakii, is an international X-ray mission which is currently planed for launch in 2013. NeXT is a combination of wide band X-ray spectroscopy (3-80 keV) provided by multi-layer coating, focusing hard X-ray mirrors and hard X-ray imaging detectors, and high energy-resolution soft X-ray spectroscopy (0.3-10 keV) provided by thin-foil X-ray optics and a micro-calorimeter array. The mission will also carry an X-ray CCD camera as a focal plane detector for a soft X-ray telescope and a non-focusing soft gamma-ray detector. With these instruments, NeXT covers very wide energy range from 0.3 keV to 600 keV. The micro-calorimeter system will be developed by international collaboration lead by ISAS/JAXA and NASA. The simultaneous broad bandpass, coupled with high spectral resolution of ΔE ∼7 eV by the micro-calorimeter will enable a wide variety of important science themes to be pursued.
-
Advances in Space Research 41(3) 411-415 2008年SN 1006 is one of the supernova remnants (SNRs) with relatively low-temperature electrons, considering the young age of just 1000 years. We carried out SN 1006 mapping observations with the X-ray Imaging Spectrometers (XIS) and the Hard X-ray Detector (HXD) onboard Suzaku, the fifth Japanese X-ray satellite. Thanks to the excellent spectral resolution of XIS in the soft X-ray band, H-like and He-like oxygen emission lines were clearly detected, and we could make a map of the line intensity, and as well as a flux and the photon index of nonthermal component. We found that these parameters have spatial dependences from region to region in the SNR; the north region is bright in nonthermal, while dim in thermal; the east region is bright in both nonthermal and thermal; the inner region shows dim nonthermal and bright thermal emission. The photon index is the smallest in the north region. © 2007.
-
Publications of the Astronomical Society of Japan 60(SPEC. ISS. 1) 2007年11月17日The hard X-ray detector (HXD) on board the X-ray satellite Suzaku is designed to have a good timing capability with a 61 $\mu$s time resolution. In addition to detailed descriptions of the HXD timing system, results of in-orbit timing calibration and performance of the HXD are summarized. The relative accuracy of time measurements of the HXD event was confirmed to have an accuracy of $1.9\times 10^{-9}$ s s$^{-1}$ per day, and the absolute timing was confirmed to be accurate to 360 $\mu$s or better. The results were achieved mainly through observations of the Crab pulsar, including simultaneous ones with RXTE, INTEGRAL, and Swift.
-
Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers 46(9 A) 6043-6045 2007年9月7日We developed a new Al Schottky CdTe pixel detector and measured its spectral performance. It has pixelated anodes made of aluminum and a common cathode made of platinum. Because of the low leakage current and the high bias voltage owing to the Schottky diode characteristic and the anode pixel configuration, a good spectral performance including a high energy resolution was achieved. When the pixel detector with a thickness of 0.75 mm was subjected to a bias voltage of 400 V and was operated at -20°C, the full-width-half-maximum (FWHM) energy resolution of 1.1 and 1.8 keV at 59.5 and 122 keV, respectively, were successfully obtained. The spectral performance obtained with the Al Schottky CdTe pixel detector exceeded that obtained with the conventional In Schottky CdTe pixel detector, which has an In common anode and Pt pixelated cathodes, under the same operating conditions. © 2007 The Japan Society of Applied Physics.
-
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 579(2 SPEC. ISS.) 871-877 2007年9月1日Si and CdTe semiconductor imaging detectors have been developed for use in a Si/CdTe Compton camera. Based on a previous study using the first prototype of a Si/CdTe Compton camera, new detector modules have been designed to upgrade the performance of the Compton camera. As the scatter detector of the Compton camera, a stack of double-sided Si strip detector (DSSD) modules, which has four layers with a stack pitch of 2 mm, was constructed. By using the stack DSSDs, an energy resolution of 1.5 keV (FWHM) was achieved. For the absorber detector, the CdTe pixel detector modules were built and a CdTe pixel detector stack using these modules was also constructed. A high energy resolution (Δ E / E ∼ 1 %) was achieved. The improvement of the detection efficiency by stacking the modules has been confirmed by tests of the CdTe stack. Additionally, a large area CdTe imager is introduced as one application of the CdTe pixel detector module. © 2007 Elsevier B.V. All rights reserved.
-
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 579(2 SPEC. ISS.) 859-865 2007年9月1日The low noise double-sided silicon strip detector (DSSD) technology is used to construct a next generation Compton telescope which is required to have both high-energy resolution and high-Compton reconstruction efficiency. In this paper, we present the result of a newly designed stacked DSSD module with high-energy resolution in highly packed mechanical structure. The system is designed to obtain good P-side and N-side noise performance by means of DC-coupled read-out. Since there are no decoupling capacitors in front-end electronics before the read-out ASICs, a high density stacked module with a pitch of 2 mm can be constructed. By using a prototype with four-layer of DSSDs with an area of 2.56 cm × 2.56 cm, we have succeeded to operate the system. The energy resolution at 59.5 keV is measured to be 1.6 keV (FWHM) for the P-side and 2.8 keV (FWHM) for the N-side, respectively. In addition to the DSSD used in the prototype, a 4 cm wide DSSD with a thickness of 300 μ m is also developed. With this device, an energy resolution of 1.5 keV (FWHM) was obtained. A method to model the detector energy response to properly handle split events is also discussed. © 2007.
-
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 579(2 SPEC. ISS.) 878-885 2007年9月1日A Compton telescope with high angular resolution and high energy resolution is a promising detector for the next generation of astrophysics space missions aiming at hard X-rays and sub-MeV/MeV gamma-rays. We have been working on a semiconductor Compton camera based on silicon and cadmium telluride (Si/CdTe Compton telescope). The soft gamma-ray detector (SGD) employs a Si/CdTe Compton camera combined with a well-type active shield. It will be mounted on the NeXT mission, proposed to be launched around 2012. One Compton camera module in the SGD will consist of 24 layers of double-sided silicon strip detectors and four layers of CdTe pixel detectors. We carried out Monte Carlo simulations to investigate the basic performance of the detector. Design parameters of devices required in the simulation, such as energy resolution and position resolution of the detector, are based on the results from our prototype detector. From the simulation using current design parameters, the detection efficiency is found to be higher than 10% at ∼100 keV and the angular resolution to be 9° and 4.4° at 120 keV and 330 keV, respectively. The effects of changing the design parameters are also discussed. © 2007.
-
Publications of the Astronomical Society of Japan 60(SPEC. ISS. 1) 2007年8月15日We report on results from Suzaku broadband X-ray observations of the southwest part of the Galactic supernova remnant (SNR) RX J1713.7-3946 with an energy coverage of 0.4-40 keV. The X-ray spectrum, presumably of synchrotron origin, is known to be completely lineless, making this SNR ideally suited for a detailed study of the X-ray spectral shape formed through efficient particle acceleration at high speed shocks. With a sensitive hard X-ray measurement from the HXD PIN on board Suzaku, we determine the hard X-ray spectrum in the 12--40 keV range to be described by a power law with photon index Gamma = 3.2+/- 0.2, significantly steeper than the soft X-ray index of Gamma = 2.4+/- 0.05 measured previously with ASCA and other missions. We find that a simple power law fails to describe the full spectral range of 0.4-40 keV and instead a power-law with an exponential cutoff with hard index Gamma = 1.50+/- 0.09 and high-energy cutoff epsilon_c = 1.2+/- 0.3 keV formally provides an excellent fit over the full bandpass. If we use the so-called SRCUT model, as an alternative model, it gives the best-fit rolloff energy of epsilon_{roll} = 0.95+/- 0.04 keV. Together with the TeV gamma-ray spectrum ranging from 0.3 to 100 TeV obtained recently by HESS observations, our Suzaku observations of RX J1713.7-3946 provide stringent constraints on the highest energy particles accelerated in a supernova shock.
-
Astrophysical Journal 665(1 PART 1) 209-224 2007年8月10日A Suzaku observation of the nucleus of the radio-loud AGN Centaurus A in 2005 has yielded a broadband spectrum spanning 0.3-250 keV. The net exposure times after screening were 70 ks per X-ray Imaging Spectrometer (XIS) camera, 60.8 ks for the Hard X-ray Detector ( HXD) PIN, and 17.1 ks for the HXD GSO. The hard X-rays are fit by two power laws of the same slope, absorbed by columns of 1.5 and 7 × 1023 cm-2, respectively. The spectrum is consistent with previous suggestions that the power-law components are X-ray emission from the subparsec VLBI jet and from Bondi accretion at the core, but it is also consistent with a partial-covering interpretation. The soft band is dominated by thermal emission from the diffuse plasma and is fit well by a two-temperature VAPEC model, plus a third power-law component to account for scattered nuclear emission, jet emission, and emission from X-ray binaries and other point sources. Narrow fluorescent emission lines from Fe, Si, S, Ar, Ca, and Ni are detected. The Fe Ka line width yields a 200 It-day lower limit on the distance from the black hole to the line-emitting gas. Fe, Ca, and S K-shell absorption edges are detected. Elemental abundances are constrained via absorption edge depths and strengths of the fluorescent and diffuse plasma emission lines. The high metallicity ([Fe/H] = +0.1) of the circumnuclear material suggests that it could not have originated in the relatively metal-poor outer halo unless enrichment by local star formation has occurred. Relative abundances are consistent with enrichment from Type II and Ia supernovae. 2007. The American Astronomical Society. All rights reserved.
-
Publications of the Astronomical Society of Japan 60(SPEC. ISS. 1) 2007年8月1日We report on the wide band spectra of SN 1006 as observed by Suzaku. Thermal and nonthermal emission are successfully resolved thanks to the excellent spectral response of Suzaku's X-ray CCD XIS. The nonthermal emission cannot be reproduced by a simple power-law model but needs a roll-off at 5.7$\times 10^{16}$ Hz = 0.23 keV. The roll-off frequency is significantly higher in the northeastern rim than in the southwestern rim. We also have placed the most stringent upper limit of the flux above 10 keV using the Hard X-ray Detector.
-
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 573(1-2) 44-47 2007年4月Double-sided silicon strip detectors (DSSD) with an energy resolution of 1-2 keV full-width at half-maximum (FWHM) are attractive devices for future hard X-ray and soft γ-ray applications. For example, they are well suited as scatterer detectors for semiconductor Compton telescopes working in the sub-MeV to MeV band, as well as imaging spectrometers in the hard X-ray band. In this paper, the performance of newly developed 4-cm-wide DSSDs is presented.This DSSD has an active area of 38.4 mm times 38.4 mm, with a thickness of 300 μm. The stip pitch is 400 μm. The detector shows an average energy resolution of 1.5 keV (FWHM) for 59.5 keV γ-rays, operated at -20 °C with a bias of 100 V. A 22 keV hard X-ray image is also obtained with 400 μm resolution. © 2006 Elsevier B.V. All rights reserved.
MISC
208-
Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023) 2023年8月18日
講演・口頭発表等
93共同研究・競争的資金等の研究課題
15-
日本学術振興会 科学研究費助成事業 基盤研究(A) 2021年4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) 2020年4月 - 2024年3月
-
日本学術振興会 科学研究費助成事業 新学術領域研究(研究領域提案型) 2018年6月 - 2023年3月
-
日本学術振興会 科学研究費助成事業 新学術領域研究(研究領域提案型) 2018年6月 - 2023年3月
-
日本学術振興会 科学研究費助成事業 基盤研究(A) 2016年4月 - 2020年3月
