A Hard X - Ray Spectrometer for High Angular Resolution Observations of Cosmic Sources

LAXRIS (large area x-ray imaging spectrometer) is an experimental, balloon-borne, hard x-ray telescope that consists of a realigned array of x-ray imaging spectrometer modules capable of obtaining high angular resolution (1-3 arcminutes) with moderate energy resolution in the 20to 300-keV region. Each spectrometer module consists of a CsI(Na) crystal coupled to a position-sensitive phototube with a crossed-wire. resisitive readout Imaging is provided by a coded aperture mask with a 4-m focal length. The high angular resolution is coupled with rather large area (—800 cnr) to provide good sensitivity. Results are presented on performance and overall design. Sensitivity estimates are derived from a Monte-Carlo code developed to model the LAXRIS response to background encountered at balloon altitudes. We discuss a variety of observations made feasible by high angular resolution. For instance, spaiially resolving the nonthermal x-ray emission from clusters of galaxies is suggested as an ideal program for LAXRIS.