Gamma-ray and Hard X-ray Imaging of Solar Flares

We discuss the scientific and technical aspects of high-resolution γ-ray and X-ray imaging of solar flares. The scientific necessity for imaging observations of solar flares and the implications of future observations for the study of solar flare electrons and ions are considered. Performance parameters for a future hard X-ray and γ-ray imager are then summarized. We briefly survey techniques for high-energy photon imaging including direct collimation imaging, coded apertures, and modulation collimators. We then discuss in detail the technique of Fourier-transform imaging. The basic formalism is presented, followed by a discussion of several practical aspects of the technique. We conclude our discussion of imaging techniques with a description of the options for detectors and grid fabrication. Several planned future high-energy imagers are described including the Solar-A hard X-ray imager, the balloon-borne GRID γ-ray imager, and the Pinhole/Occulter Facility.