Enhanced electromagnetic showers initiated by 20-180 GeV gamma rays on aligned thick germanium crystals

The distribution of the energy released in a silicon detector placed on the downstream side of thick germanium single crystals bombarded by 20-180 GeV gamma rays along directions close to the 〈1 1 0〉 axis or along a random direction has been investigated. A large enhancement of the shower for axial incidence of the gamma rays has been found. The response of the system composed of a germanium crystal and a silicon detector to single gamma rays as a function of their energy has been deduced and compared with existing Monte Carlo simulations.