Improving the energy resolution of high-pressure Xe cylindrical ionization chambers

Results are presented on the development of high-pressure (>50 atm) Xe cylindrical ionization chambers for hard X-ray and low energy gamma-ray astronomy. Two methods to improve the energy resolution of these devices have been tested. One uses a shielding mesh and the other employs no mesh but substitutes a rise-time correction. Both techniques can give similar resolutions, with 2.2% FWHM being measured at 662 keV and 2.4% at 511 keV.