Performance of a drift chamber detector for gamma-ray astronomy.

A 52 x 52 sq cm stack of drift chambers has been constructed in which the conventional field shaping wires are replaced by copper strips etched on copper-clad glass-epoxy. The performance as a detector for gamma-ray astronomy has been assessed using electron and gamma-ray beams at DESY, Hamburg. Particular emphasis is placed on the ability of the drift chambers to detect the two, simultaneous adjacent electron tracks produced by the gamma-ray. It is shown that an improvement of a factor of 4 in angular resolution can be achieved using the drift chamber technique, compared with the recent SAS-II and COS-B spark chamber gamma-ray telescopes.