First result from a ground calibration of the Hard X-ray Telescope (HXT) onboard ASTRO-H satellite

We report a first result from a ground-based X-ray calibration of the ASTRO-H Hard X-ray Telescope (HXT) at a synchrotron radiation facility SPring-8. ASTRO-H, to be launched in 2015, is Japan’s sixth X-ray satellite mission following to Suzaku satellite. One of the features of ASTRO-H is a simultaneous observation between 0.3 keV to 600 keV with several instruments. ASTRO-H will carry two HXTs to cover hard x-rays up to 80 keV. HXT, which is one of the key instruments in ASTRO-H, is the conically approximated Wolter-I grazing incidence optics similar to the Suzaku X-ray telescope. Reflector surfaces are coated with depth-graded Platinum and Carbon multilayer to reflect hard X-rays efficiently. The integrations of the flight optics of HXT-1 and HXT- 2 were completed, and we performed a ground calibration of HXT-1 at a synchrotron facility, SPring-8 beamline BL20B2 to build a response function of HXT. We use a raster scan method with a pencil beam at the baseline length of 215m. A point spread function and effective area were measured at 30, 40, 50, 60, 70keV. From a preliminary analysis of the data, an angular resolution of 1.5 - 1.9 arcmin. was obtained at five energy band in the full telescope. The effective area is 170 cm 2 at 30 keV and 82 cm 2 at 50 keV, respectively. The effective area at 30 and 50 keV are about 13 % and 50 % larger than expected, respectively. We also measured the stray light from outside of field of view at 12’ and 20’ of-axis angle. We confirmed the effectiveness of pre-collimator to reduce the stray lights.