Search for cosmic gamma radiation with a vidicon spark chamber

Abstract

A vidicon spark chamber flown in a high-altitude balloon has been used to search for primary gamma radiation (E > 100 MeV). No celestial gamma-ray source was detected. The new upper limit to the flux from the Crab nebula was found to be 3.1 × 10⁻⁵ cm⁻² s⁻¹, and the flux from the quiet sun to be [Formula: see text]. A solar flare (type 2) also occurred during the flight, of flux [Formula: see text], which is also a new upper limit. The gamma-ray background flux and energy spectrum at 4 g cm⁻² altitude were measured.