Status of the All-sky Medium Energy Gamma-ray Observatory Prototype

The study of gamma rays from a few hundred keV to hundreds of MeV is challenging due to high gamma-ray backgrounds, multiple scattering within the detector, and the fact that there are two competing interactions in this regime, Compton scattering and pair production, with cross-sections which crossover at ~15 MeV. As such, this regime, known as the MeV gap, has been largely unexplored since the pioneering measurements made by COMPTEL aboard CGRO (1991-2000). The All-sky Medium Energy Gamma-ray Observatory (AMEGO) is a NASA Probe-class mission concept designed to operate at energies from ~200 keV to > 10 GeV. AMEGO comprises four subsystems: a silicon tracker for measuring the energy and track of Compton recoil electrons and electron/positron pairs, a CZT calorimeter for measuring the energy and interaction location of Compton scattered photons, a CsI calorimeter for measuring the energy of the electron/positron pair-production products at high energies, and an anticoincidence detector for rejecting cosmic-ray events. Prototypes of the subsystems are under development at the NASA Goddard Space Flight Center and the Naval Research Laboratory; in this contribution we provide details on the development of the various subsystems in preparation for beam tests and a balloon flight.