Development of supermirror hard X-ray telescope and the results of the first InFOCuS flight observation

The development of hard X-ray focusing optics is widely recognized as one of key technologies for future X-ray observatory missions such as NeXT(Japan), Constellation-X(US) and possibly XEUS(Europe). We have developed hard X-ray telescope employing depth-graded multilayers, so-called supermirrors. Its benefit is to reflect hard X-rays by Bragg reflection at incidence angles larger than the critical angle of total external reflection. InFOCμS is an international balloon-borne hard X-ray observation experiment initiated by NASA/GSFC. InFOCμS hard X-ray telescope has been jointly developed by Nagoya University and GSFC. The telescope is conical approximation of Wolter-I optics with 8 m focal length and 40 cm diameter. It consists of 255 nested ultra-thin reflector pairs with incidence angles of 0.10 to 0.36 deg. Reflectors are coated with Pt/C supermirrors with periodic length of 2.9 to 13 nm and bi-layer number of 25 to 65, depending on incidence angles. The effective area and imaging quality are expected as 100 cm² at 30 keV and 2 arcmin in Half Power Diameter, respectively. The InFOCμS experiment was launched on July 5, 2001, from National Scientific Balloon Facility in Texas, USA. We successfully observed Cyg X-1, chosen for a calibration target, in 20-40 keV energy band. We are planning to carry out next flight for scientific observations as soon as additional telescopes, detectors, and upgraded gondola system are implemented.