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We describe a new method for estimating the beam range in heavy-ion radiation therapy by measuring the ion beam bremsstrahlung. We experimentally confirm that the secondary electron bremsstrahlung process provides the dominant bremsstrahlung contribution. A Monte Carlo simulation shows that the number of background photons from annihilation gamma rays is about 1% of the bremsstrahlung strength in the low-energy region used in our estimation (63-68 keV). Agreement between the experimental results and the theoretical prediction for the characteristic shape of the bremsstrahlung spectrum validates the effectiveness of our new method in estimating the ion beam range.

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.

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 highenergy universe via a suite of four instruments, covering a very wide energy range, from 0.3 keV to 600 keV. These instruments include a high-resolution, high-Throughput spectrometer sensitive over 0.3-12 keV with high spectral resolution of ?E 5 7 eV, enabled by a micro-calorimeter array located in the focal plane of thin-foil X-ray optics; hard X-ray imaging spectrometers covering 5-80 keV, located in the focal plane of multilayer-coated, focusing hard X-ray mirrors; a wide-field imaging spectrometer sensitive over 0.4-12 keV, with an X-ray CCD camera in the focal plane of a soft X-ray telescope; and a non-focusing Compton-camera type soft gamma-ray detector, sensitive in the 40-600 keV band. The simultaneous broad bandpass, coupled with high spectral resolution, will enable the pursuit of a wide variety of important science themes. © 2012 SPIE.

All-sky observations from hard X-ray to soft gamma-ray band is very important to study non-thermal processes for many bright astronomical objects such as Gamma-ray Bursts (GRBs), soft gamma-ray repeaters (SGRs), and solar flares. The Wide-band All-sky Monitor (WAM) onboard Suzaku enables unique observations utilizing its wide energy coverage between 50 keV to 5000 keV with very large effective area of 400 cm(2) even at 1 MeV. After six year observations, the WAM has detected more than 850 GRBs. Thanks to its largest effective area above 300 keV among all all-sky instruments, many data with good photon statistics is available even for both time-resolved spectroscopy and short duration GRBs and some implications for emission mechanism and physical condition of emission region of GRBs have been suggested. The WAM also observed many solar flares and SGRs. We summarized the observational results from 105 solar flares and their characteristics and addressed discussion on particle acceleration and heating process in solar flares. In addition to above transient objects, many bright gamma-ray sources such as Crab, Cyg X-1, GRB 1915-105, and NGC 4541 are monitored by the WAM using earth occultation technique.

By using a new Compton camera consisting of a silicon double-sided strip detector (Si-DSD) and a CdTe double-sided 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 Ba-133 (356 keV), Na-22 (511 keV) and Cs-137 (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 x10(-4) (effective area : 1.7 x10(-3) cm(2)) 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. (C) 2012 Published by Elsevier B.V. Selection and/or peer review under responsibility of the organizing committee for TIPP 11.

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.

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 IDMAC 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.

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 x 3.2 cm and a thickness of 0.75 mm. The detector was successfully operated at a temperature of -20 degrees 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.

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.

ASTRO-H is an X-ray astronomy satellite to be launched in 2014. The data acquisition system of this mission is realized with a standard network protocol, SpaceWire. Although the protocol itself is well designed, a new concept to grantee the quality of service will be installed to the ASTRO-H data acquisition system. Therefore, the verification of the design of the concept is essential in the initial phase of the development. The time assignment function is one of the important issues for the SpaceWire development. The accuracy of the absolute time of about 30 μs is required from science goals. The key point of the time assignment with SpaceWire network in the ASTRO-H system is how accurately sharing the time information. In this paper, our design of the time distribution and assignment system for ASTRO-H is shown. The results of our measurements of timing accuracy are also presented to show that the design will fulfill the goal of absolute timing accuracy. © 2011 IEEE.

The Hard X-ray Imager (HXI) is one of the four detectors on board the ASTRO-H mission (6th Japanese X-ray satellite), which is scheduled to be launched in 2014. Using the hybrid structure composed of double-sided silicon strip detectors and a cadmium telluride double-sided strip detector, both with a high spatial resolution of 250 mu m. Combined with the hard X-ray telescope (HXT), it consists a hard X-ray imaging spectroscopic instrument covering the energy range from 5 to 80 keV with an effective area of >300 cm(2) in total at 30 keV. An energy resolution of 1-2 keV (FWHM) and lower threshold of 5 keV are both achieved with using a low noise front-end ASICs. In addition, the thick BGO active shields surrounding the main detector package is a heritage of the successful performance of the Hard X-ray Detector on board the Suzaku satellite. This feature enables the instrument to achieve an extremely good reduction of background caused by cosmic-ray particles, cosmic X-ray background, and in-orbit radiation activation. In this paper, we present the detector concept, design, latest results of the detector development, and the current status of the hardware.

Improvements of the in-orbit calibration of GSO scintillators in the Hard X-ray Detector aboard Suzaku are reported. To resolve an apparent change in 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 similar to 0.5% of the full analog voltage scale, depending on the power supply. Furthermore, by carefully calculating all of 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 of these effects into account, the in-orbit data agree with the on-ground measurements within similar to 5%, without employing the artificial correction introduced in previous work (Kokubun et al. 2007, PASJ, 59, S53). 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 power-law with a break energy of similar to 110 keV.

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 m and a dimension of 9.6 mm 9.6 mm, containing 128 strips with a pitch of 75 mu m, 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 degrees 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.

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 key 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. (c) 2011 Elsevier B.V. All rights reserved.

The anomalous X-ray pulsar 4U 0142+61 was observed with Suzaku on 2007 August 15 for a net exposure of similar to 100 ks, and was detected in a 0.4 to similar to 70 keV energy band. The intrinsic pulse period was determined to be 8.68878 +/- 0.00005 s, in agreement with art extrapolation from previous measurements. The broadband Suzaku spectra enabled a first simultaneous and accurate measurement of the soft and hard components of this object by a single satellite. The former can be reproduced by two blackbodies, or slightly better by a resonant cyclotron scattering model. The hard component can be approximated by a power-law of photon index of Gamma(h) similar to 0.9 when the soft component is represented by the resonant cyclotron scattering model, and its high-energy cutoff is constrained as > 180 keV. Assuming an isotropic emission at a distance of 3.6 kpc, the unabsorbed 1-10 keV and 10-70 keV luminosities of the soft and hard components were calculated to be 2.8 x 10(35) erg s(-1) and 6.8 x 10(34) erg s(-1), respectively. Their sum becomes similar to 10(3) times as large as the estimated spin-down luminosity. On a time scale of 30 ks, the hard component exhibited evidence of variations either in its normalization or pulse shape.

The FD-SOI technology is a fascinating LSI fabrication process as a possible radiation-tolerant device. In order to confirm benefits of the FD-SOI and expand application ranges in front-end electronics, we experimentally designed an analog front-end ASIC for X-ray CCD readout with the FD-SOI process. The circuit design was submitted to OKI Semiconductor Co., Ltd. via the multi-chip project as a part of the SOI pixel-detector R&D program in KEK. The ASIC contains seven readout channels using the correlated double sampling technique, and includes key circuit elements for a low-noise LSI. This paper describes the circuit design and the performance of the ASIC together with the radiation tolerance. (C) 2010 Elsevier B.V. All rights reserved.

The Focusing Optics x-ray Solar Imager (FOXSI) is a sounding rocket payload funded under the NASA Low Cost Access to Space program to test hard x-ray (HXR) focusing optics and position-sensitive solid state detectors for solar observations. Today's leading solar HXR instrument, the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) provides excellent spatial (2 arcseconds) and spectral (1 keV) resolution. Yet, due to its use of an indirect imaging system, the derived images have a low dynamic range (typically <10) and sensitivity. These limitations make it difficult to study faint x-ray sources in the solar corona which are crucial for understanding the particle acceleration processes which occur there. Grazing-incidence x-ray focusing optics combined with position-sensitive solid state detectors can overcome both of these limitations enabling the next breakthrough in understanding impulsive energy release on the Sun. The FOXSI project is led by the Space Sciences Laboratory at the University of California, Berkeley. The NASA Marshall Space Flight Center is responsible for the grazing-incidence optics, while the Astro-H team at JAXA/ISAS has provided double-sided silicon strip detectors. FOXSI is a pathfinder for the next generation of solar hard x-ray spectroscopic imagers. Such observatories will be able to image the non-thermal electrons within the solar flare acceleration region, trace their paths through the corona, and provide essential quantitative measurements such as energy spectra, density, and energy content in accelerated electrons.

ASTRO-H is an X-ray astronomy satellite to be launched in 2014. The data acquisition system of this mission is realized with a standard network protocol, SpaceWire. Although the protocol itself is well designed, a new concept to grantee the quality of service will be installed to the ASTRO-H data acquisition system. Therefore, the verification of the design of the concept is essential in the initial phase of the development. The time assignment function is one of the important issues for the SpaceWire development. The accuracy of the absolute time of about 30 mu s is required from science goals. The key point of the time assignment with SpaceWire network in the ASTRO-H system is how accurately sharing the time information. In this paper, our design of the time distribution and assignment system for ASTRO-H is shown. The results of our measurements of timing accuracy are also presented to show that the design will fulfill the goal of absolute timing accuracy.

The Gamma-Ray Observation of Winter Thunderclouds (GROWTH) experiment, consisting of two radiation detection subsystems, has been operating since 2006 on the premises of Kashiwazaki-Kariwa nuclear power plant located at the coastal area of Japan Sea. By February 2010, GROWTH detected seven long-duration γray emissions associated with winter thunderstorms. Of them, two events, obtained on 13 December 2007 and 25 December 2008, are reported. On both occasions, all inorganic scintillators (NaI, CsI, and BGO) of the two subsystems detected significant γ ray signals lasting for &gt 1 min. Neither of these two events were associated with any lightning. In both cases, the γray energy spectra extend to 10 MeV, suggesting that the detected γrays are produced by relativistic electrons via bremsstrahlung. Assuming that the initial photon spectrum at the source is expressed by a power law function, the observed photons can be interpreted as being radiated from a source located at a distance of 290-560 m for the 2007 event and 110-690 m for the 2008 one, both at the 90% confidence level. Employing these photon spectra, the number of relativistic electrons is estimated as 10&lt sup&gt 9&lt /sup&gt -10 &lt sup&gt 11&lt /sup&gt . The estimation generally agrees with those calculated on the basis of the relativistic runaway electron avalanche model. A GROWTH photon spectrum, summed over three individual events including the present two events and another reported previously, has similar features including a cutoff energy, to an averaged spectrum of terrestrial γ ray flashes. Copyright 2011 by the American Geophysical Union.

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 (C) 2009 Elsevier B V All rights reserved

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 key with a high quantum efficiency. High spatial resolutions of 250 mu m pitch and energy resolutions of 1-2 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 (30-600 key) 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 read messes of key technologies. (C) 2010 Elsevier B.V. All rights reserved.

A Compton camera has been developed based on Si and CdTe semiconductor detectors with high spatial and spectral resolution for hard X- and gamma-ray 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 gamma-rays at SPring-8. (C) 2010 Elsevier B.V. All rights reserved.

We observed the soft gamma repeater SGR 0501+4516 with Suzaku for similar to 51 ks on 2008 August 26-27, about 4 days after its discovery. Following the first paper, which reported on the persistent soft X-ray emission and the wide-band spectrum of an intense short burst, this paper presents an analysis of the persistent broadband (1-70 keV) spectra of this source in outburst, taken with the X-ray Imaging Spectrometer (XIS) and the Hard X-ray Detector (HXD). Pulse-phase folding in the 12-35 keV HXD-PIN data on an ephemeris based on multi-satellite timing measurements at soft X-rays revealed the pulsed signals at greater than or similar to 99% confidence in the hard X-ray band. The wide-band spectrum clearly consists of a soft component and a separate hard component, crossing over at similar to 7 keV. When the soft component is modeled by a blackbody plus a Comptonized blackbody, the hard component exhibits a 20-100 keV flux of 4.8(-0.6)(+0.8) (stat.)(-0.4)(+ 0.8) (sys.) x 10(-11) erg s(-1) cm(-2) and a photon index of Gamma = 0.79(-0.18)(+ 0.01) (sys.). The hard X-ray data are compared with those obtained by INTEGRAL about 1 day later. Combining the present results with those on other magnetars, we discuss a possible correlation between the spectral hardness of magnetars and their characteristic age and magnetic field strengths.

We present X-ray observations of the northern outskirts of the relaxed galaxy cluster A 1413 with Suzaku, whose XIS instrument has the low intrinsic background needed to make measurements of these low surface brightness regions. We excised 15 point sources superimposed on the image above a flux of 1 x 10(-14)erg cm(-2) s(-1) (2-10 keV) using XMM-Newton and Suzaku images of the cluster. We quantified all known systematic errors as part of our analysis, and showed that our statistical errors encompass them for the most part. Our results extend previous measurements with Chandra and XMM-Newton, and show a significant temperature drop to about 3 keV at the virial radius, r(200). Our entropy profile in the outer region (>0.5 r(200)) joins smoothly onto that of XMM-Newton, and shows a flatter slope compared with simple models, similar to a few other clusters observed at the virial radius. The integrated mass of the cluster at the virial radius is approximately 7.5 x 10(14) M-circle dot, and varies by about 30%, depending on the particular method used to measure it.

© 2010 SPIE. 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 ΔE ~7 eV provided by the micro-calorimeter will enable a wide variety of important science themes to be pursued.

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 x 8 arcmin(2). 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.

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.

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 on-orbit 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.

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 mu m, 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 mu m 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 mu m. These performance satisfy FOXSI's requirements.

© 2010 SPIE. 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 ΔE ~7 eV provided by the micro-calorimeter will enable a wide variety of important science themes to be pursued.

Soft Gamma-ray Detector (SGD:40-600 keV) will be mounted on the 6(th) 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.

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.

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.

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.

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 22Na and 18F point gamma-ray sources. 22Na was used to assess the imaging ability of this camera against the point source, and the intense 18F 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.

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.

Suzaku X-ray observations of a young supernova remnant, Cassiopeia A, were carried out. K-shell transition lines from highly ionized ions of various elements were detected, including Chromium (Cr-K alpha at 5.61 keV). The X-ray continuum spectra were modeled in the 3.4-40keV band, summed over the entire remnant, and were fitted with a simplest combination of the thermal bremsstrahlung and the non-thermal cut-off power-law models. The spectral fits with this assumption indicate that the continuum emission is likely to be dominated by non-thermal emission with a cut-off energy at > 1 keV. The thermal-to-non thermal fraction of the continuum flux in the 4-10 keV band is best estimated as similar to 0.1. Non-thermal-dominated continuum images in the 4-14 keV band were made. The peak of the non-thermal X-rays appears at the western part. The peak position of the TeV gamma-rays measured with HEGRA and MAGIC is also shifted at the western part with the I-sigma confidence. Since the location of the X-ray continuum emission was known to be presumably identified with the reverse shock region, the possible keV-TeV correlations give a hint that the accelerated multi-TeV hadrons in Cassiopeia A are dominated by heavy elements in the reverse shock region.

We showed that if the non-thermal emission from the galactic center in the range 14-40keV is due to inverse bremsstrahlung emission of subrelativistic protons, their interactions with hot and cold fractions of the interstellar medium are equally important. Our estimation shows that about 30% of the total non-thermal flux from the GC in the range 14-40keV is generated in regions of cold gas while the rest is produced by proton interaction with hot plasma. From the spatial distribution of 6.7 keV iron line we concluded the spatial distribution of hot plasma is strongly non-uniform that should be taken into account in analysis of proton propagation in the GC. From the Suzaku data we got independent estimates for the diffusion coefficient of subrelativistic protons in the GC, which was in the range 10(26)-10(27) cm(2) s(-1).

We analyse new results of Chandra and Suzaku Observatories which found a flux of hard X-ray emission from the compact region around Sgr A* (r similar to 100pc). We suppose that this emission is generated by accretion processes onto the central supermassive blackhole when an unbound part of captured stars obtains an additional momentum. As a result a flux of subrelativistic protons is generated near the galactic center which heats the background plasma up to temperatures about 6-10keV and produces by inverse bremsstrahlung a flux of non-thermal X-ray emission in the energy range above 10 keV.

X-ray data of the Centaurus cluster, obtained with XMM-Newton for 45 ks, were analyzed. Deprojected EPIC spectra from concentric thin-shell regions were reproduced equally well by a single-phase plasma emission model, or by a two-phase model developed by ASCA, both incorporating cool (1.7-2.0 keV) and hot (similar to 4 keV) plasma temperatures. However, EPIC spectra with higher statistics, accumulated over three-dimensional thick-shell regions, were reproduced better by the two-phase model than by the singe-phase one. Therefore, hot and cool plasma phases are inferred to co-exist in the cluster core region within similar to 70 kpc. The iron and silicon abundances of the plasma were reconfirmed to increase significantly toward the center, while that of oxygen was consistent with being radially constant. The implied nonsolar abundance ratios explain away the previously reported excess X-ray absorption from the central region. Although an additional cool (similar to 0.7 keV) emission was detected within similar to 20 kpc of the center, the RGS data gave tight upper limits on any emission with temperatures below similar to 0.5 keV. These results are compiled into a magnetosphere model, which interprets the cool phase as confined within closed magnetic loops anchored to the cD galaxy. When combined with the so-called Rosner-Tucker-Vaiana mechanism which applies to solar coronae, this model can potentially explain basic properties of the cool phase, including its temperature and thermal stability.

We analyze the 6.4 keV line and continuum emission from the molecular cloud Sgr B2 and the source HESS J1745-303, which is supposed to be a complex of molecular gas. From the HESS results it follows that Sgr A* is a source of high energy protons, which penetrate into molecular clouds producing there a TeV gamma-ray flux. We present arguments that Sgr A* may also produce a flux of subrelativistic protons which generate the 6.4 keV line and bremsstrahlung continuum emission from the clouds.

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 mu m. 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 mu m. 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.

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 ((131)I) 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.