Imaging properties of the MEGA prototype

The tracking Medium Energy Gamma-ray Astronomy telescope MEGA, which can detect gamma-rays via Compton scattering and pair creation, has been calibrated with lab sources (511 keV up to 1836 keV) from January to March 2003 and during April/May 2003 at the High Intensity Gamma Source (HIγS) at Duke University (Durham, North Carolina). The latter calibration was performed with monoenergetic (dE/E < 2%) and 100% polarized pencil beams in the energy range from 710 keV up to 48.9 MeV for different incident angles (0°, 30°. 60°, 80°, 120°, 180°). This paper describes preliminary results of the imaging properties of the telescope, including angular resolution, point source location accuracy, field of view, and polarization detection. Laboratory measurements of extended sources as well as of multiple sources in the near-field of the telescope are also presented.