Date/Time
Date(s) - 22/01/2014
3:30 pm - 4:30 pm

Title: A Pair Production Telescope for Medium-Energy Gamma-Ray Polarimetry

Speaker: Dr. Stanley D Hunter

Institute: National Aeronautics and Space Administration
Goddard Space Flight Center

Location: ABB 102

Description:

Since the launch of the AGILE and Fermi gamma-ray telescopes, the scientific progress in highenergy
(>200 MeV) gamma-ray astrophysics has been dramatic. Neither telescope, however,was optimized for observations below ~200 MeV where many astronomical objects exhibit
unique, transitory behavior, such as spectral breaks, bursts, and flares. While progress will continue at high energies, there remains a significant sensitivity gap in the medium-energy (~0.1â??200 MeV) regime, which remains largely unexplored. The astrophysics objectives of a
future medium-energy telescope require a major improvement in sensitivity and high angular resolution gamma-ray imaging. The imaging goal is angular resolution limited by the pairproduction kinematics rather than Coulomb scattering of the electron-positron pair. This goal
can only be met with a low-density homogenous conversion medium and accurate 3-D tracking of electron-positron pairs.
The Advanced Energetic Pair Telescope (AdEPT), a new pair production telescope, is being developed at GSFC to explore the medium-energy (5â??200 MeV) range. The enabling
technology for AdEPT is the Three-Dimensional Track Imager (3-DTI) detector. The 3-DTI consists of a gaseous time projection chamber (TPC) with 2-D cross-strip micro-well detector (MWD) readout. The 3-DTI detector provides the large volume, low-density, and high spatial resolution 3-D electron tracking required for AdEPT to achieve the science objectives of a future medium-energy gamma-ray telescope. The low density of the 3-DTI detector further enables
AdEPT to be the first gamma-ray telescope to have high gamma-ray polarization sensitivity, a new tool to study astrophysical phenomena, and to take advantage of triplet production (pair production on electrons) for gamma-ray imaging. The development and expected performance
of the AdEPT telescope is described.