Observation and simulations of the backsplash effects in high-energy γ-ray telescopes containing a massive calorimeter

Beam test and simulation results are presented for a study of the backsplash effects produced in a high-energy γ-ray detector containing a massive calorimeter. An empirical formula is developed to estimate the probability (per unit area) of backsplash for different calorimeter materials and thicknesses, different incident particle energies, and at different distances from the calorimeter. The results obtained are applied to the design of the Anti-Coincidence Detector (ACD) for the Large Area Telescope (LAT) on the Gamma-ray Large Area Space Telescope (GLAST).