HARPO - A Gaseous TPC for High Angular Resolution Gamma-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 gamma-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. 
Denis Bernard
astro-ph.IM physics.ins-det