HARPO—A gaseous TPC for high angular resolution -ray astronomy and polarimetry from the MeV to the TeV

We propose a “thin” detector as a high-angular-precision telescope and polarimeter for cosmic γ - rays above the pair-creation threshold. We have built a demonstrator based on a gaseous TPC. We are presently characterizing the detector with charged cosmic rays in the laboratory. Here we present some of its properties.