A balloon-borne coded aperture telescope for ARC-minute angular resolution at hard X-ray energies

Abstract

We describe the development of a new balloon-borne telescope known as MARGIE (Minute-of-Arc Resolution Gamma ray Imaging Experiment). It is a coded aperture telescope designed to image photons (in various configurations) over the 20–600 keV range with an angular resolution approaching 1′. MARGIE will use one (or both) of two different detection plane technologies. One such technology involves the use of Cadmium Zinc Telluride (CZT) strip detectors, for which we have successfully demonstrated a spatial resolution of < 375 μm. A second detector option is based on CsI microfiber arrays coupled to a large area silicon CCD readout array, providing spatial resolutions comparable to that of the CZT prototype. In one possible configuration, the coded mask would be 0.5 mm thick tungsten, with 0.5 mm pixels at a distance of 1.5 m from the central detector, giving an angular resolution of 1′ and a fully coded FoV of 12°.