A pair production telescope for medium-energy gamma-ray polarimetry

We describe the science motivation and development of a pair production telescope for medium-energy (∼5–200MeV) gamma-ray polarimetry. Our instrument concept, the Advanced Energetic Pair Telescope (AdEPT), takes advantage of the Three-Dimensional Track Imager, a low-density gaseous time projection chamber, to achieve angular resolution within a factor of two of the pair production kinematics limit (∼0.6° at 70MeV), continuum sensitivity comparable with the Fermi-LAT front detector (<3×10−6MeVcm−2s−1 at 70MeV), and minimum detectable polarization less than 10% for a 10mCrab source in 106s.