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The Monitor of All‐sky X‐ray Image (MAXI) is the unprecedentedly sensitive all‐sky X‐ray monitor. Gas Slit Camera (GSC) of MAXI is sensitive for 2–30 keV bands and sweeps almost the whole sky once every 90 minutes with long narrow fields of view (FoV). We developed the PSF(Point Spread Function)‐fitting method for the scanning data of MAXI/GSC to calculate the position and flux of X‐ray point sources. This method is useful both to determine the position of a transient source like GRBs and to calculate the fluxes of sources located in a crowded region. For transients whose duration is shorter than one scan (about 30 sec–4 min), other method is applied to determine the position without assumption of constancy of X‐ray flux. The locations of two short X‐ray transients discovered by MAXI/GSC (ATel ♯2321 and ♯2415) were determined by these methods.

There have been two different multielement detectors developed at the SPring‐8 facility for high energy SR X‐ray experiments beyond 100 keV, i.e., the 128‐channel microstrip Germanium detector and the YAP imager. The farmer one is optimized for spectroscopy required in Compton scattering experiments, the latter for imaging in time‐resolved diffraction pattern observation. With latest experimental results obtained with these two detectors, the design concepts are discussed together with some technical issues needed for further research.

We have developed a new X‐ray beam intensity monitor based upon rare gas scintillation in order to solve (i) the non‐ion‐saturation problem occurring ionization chambers when irradiated with high flux X‐ray beams and (ii) the slow time response of ionization chambers. When argon gas is used, it has been confirmed that the scintillation output was proportional to an X‐ray intensity up to 1015 xph/sec, and responded to an X‐ray beam with a time resolution better than 50 nsec. The rare gas scintillation X‐ray beam monitor developed is compatible to ionization chamber in terms of its readout electronics and the physical size, so that it can easily substitute existing ionization chambers when needed.