中平 聡志

MAXI, the first astronomical payload on JEM-EF of ISS, began operation on August 3, 2009 for monitoring all-sky X-ray images every ISS orbit (92 min). All instruments as well as two main X-ray slit cameras, the GSC and SSC, worked well as expected for one month test operation. The MAXI has been operated since August, 2009 and monitored more than 300 X-ray sources, which include Galactic black holes and black hole candidates (BH/BHC), transient X-ray pulsars, X-ray novae, X-ray bursts, CVns, a considerable number of AGNs and so on. Automatic nova-alert and rapid report system is starting up, while we have published more than 30 results publicly on GCN and ATel with manual analysis. We are also releasing daily data more than 200 targets publicly. Now MAXI has continued steady operation since the beginning of 2010 although capability of a part of X-ray detectors is going down from initial ability. We have obtained some remarkable results concerning BH/BHC, X-ray pulsars and AGNs. As one of the results XTE J1752-223, an X-ray nova accompanying a black hole candidate, has revealed an evolution of accretion disc and high energy plasma from the data for seven-month observations. In this paper we report the operation status of MAXI on the ISS as well as early several astronomical results. © 2010 SPIE.

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.

The Monitor of All-sky X-ray Image (MAXI) mission is the first astronomical payload to be installed on the Japanese Experiment Module - Exposed Facility (JEM-EF or Kibo-EF) on the International Space Station. It has two types of X-ray slit cameras with wide FOVs and two kinds of X-ray detectors consisting of gas proportional counters covering the energy range of 2 to 30 keV and X-ray CCDs covering the energy range of 0.5 to 12 keV. MAXI will be more powerful than any previous X-ray All Sky Monitor payloads, being able to monitor hundreds of Active Galactic Nuclei. A realistic simulation under optimal observation conditions suggests that MAXI will provide all-sky images of X-ray sources of ∼20 mCrab (∼7 × 10-10ergcm-2s-1 in the energy band of 2-30 keV) from observations during one ISS orbit (90 min), ∼4.5 mCrab for one day, and ∼2 mCrab for one week. The final detectability of MAXI could be ∼0.2 mCrab for two years, which is comparable to the source confusion limit of the MAXI field of view (FOV). The MAXI objectives are: (1) to alert the community to X-ray novae and transient X-ray sources, (2) to monitor long-term variabilities of X-ray sources, (3) to stimulate multi-wavelength observations of variable objects, (4) to create unbiased X-ray source cataloges, and (5) to observe diffuse cosmic X-ray emissions, especially with better energy resolution for soft X-rays down to 0.5 keV. © 2009. Astronomical Society of Japan.

A gamma-ray burst monitor fot the CALorimetric Electron Telescope (CALET) is under development. The aim of the CALET GRB Monitor (CALET-GBM) is to obtain a wide-band energy spectrum of GRB over an unprecedented nine decades in energy (from several keV to a few TeV) together with the CALET Imaging Calorimeter (IMC) and the Total Absorption Calorimeter (TASC). The GBM is under designing so as to have a sensitivity from several keV to 20 MeV. Furthermore our undergoing plan is to use six LaBr3(Ce) crystals from several keV to about 1 MeV measurement (one BGO for higher energy), in which light yield is about twice as large as that of NaI(Tl). LaBr3(Ce) is very attractive material, but this crystal has not been used yet as a detector for long exposure in space. Therefore its radiation hardness and proton induced background due to incoming protons are not fully understood. To evaluate its performance in high radiation environment of ISS orbit, we carried out proton beam irradiation tests. Proton- induced radioactive gamma-rays were measured from a few minutes after the irradiation to a period longer than two months by a Germanium detector, and most of radioactive nuclei induced by protons are identified. We have manufactured a proto-type model of LaBr3(Ce) that is of 3 inch diameter and half inch thick with 220 μm beryllium entrance window. In preliminary measurements, 6.4 keV Fe Kα fluorescence line is clearly detected. We expect that the lower energy threshold is around 4 ke V or even lower. © 2009 The Physical Society of Japan.

The CALET mission is a Japanese-led effort involving candidate experiments on the International Space Station, planned for launch in 2013. The CALET main detector is a pair conversion telescope which is dedicated to observing high energy electrons and gamma-rays in the GeV-TeV range. CALET can observe gamma-ray bursts over an unprecedented 9 decade energy range from ∼keV to ∼TeV with a combination of a gamma-ray burst monitor (GBM) with low energy coverage. GBM is now designed as multiple scintillators made of BGO and LaBr3 (Ce) scintillators. The prototype LaBr3(Ce) crystal with 3 inch diameter and 0.5 inch thickness displays a very good performance: 2.9±0.1 % FWHM energy resolution at 662 keV and 4 keV lower energy threshold. Furthermore, degradations in performance by the anticipated proton irradiation in the orbit are not significant. Results on proton-induced background are also presented. © 2009 American Institute of Physics.

The Soft Gamma-ray Detector (SGD) on board ASTRO-H (Japanese next high-energy astrophysics mission) is a Compton telescope with narrow field-of-view, which utilizes Compton kinematics to enhance its background rejection capabilities. It is realized as a hybrid semiconductor detector system which consists of silicon and CdTe (cadmium telluride) detectors. It can detect photons in a wide energy band (50-600 keV) at a background level 10 times better than that of the Suzaku Hard X-ray Detector, and is complimentary to the Hard X-ray Imager on board ASTRO-H with an energy coverage of 5-80 keV. Excellent energy resolution is the key feature of the SGD, allowing it to achieve good background rejection capability taking advantage of good angular resolution. An additional capability of the SGD, its ability to measure gamma-ray polarization, opens up a new window to study properties of gamma-ray emission processes. Here we describe the instrument design of the SGD, its expected performance, and its development status. ©2009 IEEE.

Monitor of All Sky X-ray Image (MAXI) is the first astronomical payload on the International Space Station (ISS). MAXI was activated on 3 August 2009 by receiving electric power, circulated coolant, and data links from Japanese Experiment Module (JEM) "Kibo" Exposed Facility of ISS. All MAXI instruments have successfully passed the post-activation health check. MAXI has two types of X-ray cameras, GSC (Gas Slit Camera covering 2-30 keV with twelve proportional counters) and SSC (Solid state Slit Camera covering 0.5-12 keV with 32 X-ray CCD chips), and three support sensors, VSC (Visual Star Camera), RLG (Ring Laser Gyro), and GPSR (GPS Receiver). MAXI transfers telemetry data to the ground via data relay satellites. Having accumulated the GSC data for one ISS orbit (92 minutes), we released, on 18 August 2009, the "first light" image in which we can easily recognize about 20 bright Galactic sources. A preliminary analysis suggests that GSC achieved about 20-30 mCrab sensitivity in one orbit, mostly consistent with the pre-flight estimation. In January 2010, we started the public release of the MAXI light curves and images at http://maxi.riken.jp/ . We are preparing the automatic Internet transmission of the MAXI source detection alerts (MAXI Nova/Burst Alerts). The nominal mission life is five years.

The Hard X-ray Imager (HXI) is one of three focal plane detectors on board the NeXT (New exploration X-ray Telescope) mission, which is scheduled to be launched in 2013. 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 of photons collected with the hard X-ray telescope up to 80 keV with a high quantum efficiency. High spatial resolutions of 400 micron pitch and energy resolutions of 1-2 keV (FWMH) are at the same time achieved with low noise front-end ASICs. In addition, thick BGO active shields compactly surrounding the main detection part, as a heritage of the successful performance of the Hard X-ray Detector (HXD) on board Suzaku satellite, enable to achive an extremely high background reduction for the cosmic-ray particle background and in-orbit activation. The current status of hardware development including the design requirement, expected performance, and technical readinesses of key technologies are summarized.

We propose to provide a gamma-ray burst monitor (GBM) for the CALET mission to monitor gamma-ray bursts (GRBs) together with the CALET Imaging Calorimeter detector. The major purpose is to derive a wide-band energy spectrum of GRBs over an unprecedented 9 decades of energy (from a few keV to a few TeV) in combination with the CALET tower detector. Hence it is desirable to have the CALET-GBM covering an energy range from a few keV to about 20 MeV to avoid a gap in the observational energy bands. The design of GBM is underway to fulfill this requirement. The current detector candidate is BGO, and a LaBr (Ce) scintillator which has a superior energy resolution to that of NaI(Tl). In this paper, design and expected performance of the CALET-GBM is shown. © 2008 American Institute of Physics.

We propose to provide a gamma-ray burst monitor (GBM) for the CALET mission to monitor gamma-ray bursts (GRBs) simultaneously with the CALET main detector. The major purpose is to derive a wide-band energy spectrum of GRB over an unprecedented 9 decades of energy (from a few keV to a few TeV) in combination with the CALET tower detector. Hence it is desirable to have the CALET-GBM covering an energy range from a few keV to about 20 MeV to avoid a gap in observational energy band. The design of GBM is underway to fulfill this requirement. The current detector candidate is LaBr3(Ce) scintillator which has a superior energy resolution to that of NaI(Tl). The design and expected performance of the CALET-GBM will be presented in this paper.

We propose a gamma-ray burst detector (GRB) detector combining the silicon drift detector (SDD) array and scintillators with broadband X-ray and gamma-ray coverage (0.5-1000 keV or more), high energy resolution (2-10 %) and high time resolution (∼ μs) in space. To realize such compact high-performance detector without photomultiplier tubes, we constructed proto-type model using KETEK SDD with a detection area of 1 cm2 and BGO crystal. Signals from both detectors are clearly separated by the double integration method. The detector shows a very good performance. Obtained FWHM energy resolution was 191 eV at 5.9 keV in the SDD, while 6.5 % at 662 keV in the BGO at -30 degree C. Evaluation of the 7 channel SDD array and development of analog ASIC for its readout are also presented.