Results of a high energy gamma telescope

Abstract

We report on experimental results obtained using a new type of detector for high energy gamma astrophysics. The apparatus can detect gamma-rays in the GeV range, with an angular resolution of a few mrad and an acceptance of 50°. The telescope is based on the imaging of the Cherenkov light produced in a dense medium (liquid or solid) backed by a parabolic or spherical reflecting surface. The high energy electrons, produced at the start of the electromagnetic shower, generate a ring-shaped photon image which may produce tens or hundreds of photoelectrons on an appropriate photon imaging detector placed at the focal plane of the system on the entrance surface of the converter. A prototype consisting of a liquid radiator (C 6F 14), a multistep parallel-plate avalanche chamber and an optical readout system has been tested in a 1–10 GeV c charged particle beam. The analysed data indicate that the initial direction of particles can be reconstructed with an angular resolution of approximatelly 3.5 mrad. Furthermore, the capability of such a detector to separate e π in the GeV range seems promising. Possible use of the apparatus in a space-borne experiment for distinct gamma-ray sources is also discussed.