The soft x-ray photon-counting telescope for solar observations

Abstract

We present overview and development activities of a soft X-ray photon-counting spectroscopic imager for the solar corona that we conceive as a possible scientific payload for future space solar missions including Japanese Solar-C. The soft X-ray imager will employ a Wolter I grazing-incidence sector mirror with which images of the corona (1 MK to beyond 10 MK) will be taken with the highest-ever angular resolution (0.5"/pixel for a focal length of 4 m) as a solar Xray telescope. In addition to high-resolution imagery, we attempt to implement photon-counting capability for the imager by employing a backside-illuminated CMOS image sensor as the focal-plane device. Imaging-spectroscopy of the X-ray corona will be performed for the first time in the energy range from ~0.5 keV up to 10 keV. The imaging-spectroscopic observations with the soft X-ray imager will provide a noble probe for investigating mechanism(s) of magnetic reconnection and generation of supra-thermal (non-thermal) electrons associated with flares. Ongoing development activities in Japan towards the photon-counting imager is described with emphasis on that for sub-arcsecond-resolution grazing-incidence mirrors.