Presentation #404.04 in the session “MeV Gamma Rays and Multi-messenger Astronomy”.
I will describe a future gamma-ray mission concept called the Advanced Particle-astrophysics Telescope (APT), and a funded NASA suborbital mission called the Antarctic Demonstrator for APT (ADAPT). The APT instrument combines a pair tracker and Compton telescope in one relatively simple monolithic design. By using scintillating fibers for the tracker and wavelength-shifting fibers to readout CsI detectors, the instrument could achieve an order of magnitude improvement in sensitivity compared with Fermi at GeV energies, and several orders of magnitude improvement in MeV sensitivity compared while fitting within the cost envelope for a mid-sized or probe class mission. The ultimate goal of the development would be the deployment of an observatory in a 10-year mission in a sun-Earth Lagrange orbit, providing near all-sky sensitivity and order of magnitude improvement in effective area compared to the Fermi Gamma-ray Space Telescope, but extending the energy reach from 1 MeV to TeV energies. While the mission would have a broad impact on astroparticle physics, the primary science drivers for the mission include: (1) probing WIMP dark matter across the entire natural mass range and annihilation cross section for a thermal WIMP, (2) providing a nearly all-sky instantaneous FoV, with prompt sub-degree localization and polarization measurements for gamma-rays transients such as neutron-star mergers and (3) tmaking measurements of rare utra-heavy cosmic ray nuclei to distinguish between n-star merger and SNae r-process synthesis of the heavy elements.