TPC in gamma-ray astronomy above pair-creation threshold

Abstract

We examine the performance of a TPC as a gamma-ray telescope above the pair-creation threshold. The contributions to the photon angular resolution are studied and their dependence on energy is obtained. The effective area per detector unit mass for such a thin detector is the conversion mass attenuation coefficient. The differential sensitivity for the detection of a point-like source is then derived. Finally, the measurement of track momentum from deflections due to multiple scattering is optimized. These analytical results are exemplified numerically for a few sets of detector parameters. TPCs show an impressive improvement in sensitivity with respect to existing pair-creation-based telescopes in the [MeV - GeV] energy range, even with the modest detector parameters of this study. In addition, gas TPCs allow an improvement in angular resolution of about one order of magnitude.

This is the long version of a work presented at the 5th International Symposium on High-Energy Gamma-Ray Astronomy (Gamma2012) July 9-13 2012, in Heidelberg, Germany. To appear in Nuclear Inst. and Methods in Physics Research, A

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