Avalanche photodiode arrays for a high-angular resolution X-ray and gamma-ray imaging telescopes

Avalanche photodiodes (APDs) have been investigated as the basis for a very high angular resolution coded aperture telescope with sensitivity over a wide energy range. Using custom electronics, software and a unique shadow-masking technique, we have achieved angular resolution from an X-ray point source of about 30 arcsec. In addition we have demonstrated imaging of higher gamma-ray energies by coupling to a CsI scintillator. Imaging from energies from few keV to an MeV with <1 arcsec resolution are achievable.