Investigation of positron generation by relativistic electrons in aligned crystals

Abstract An experiment to investigate the positron production efficiency by electrons moving in axially oriented tungsten and silicon single crystals has been conducted. The electron energy was 1.2 GeV. The positron yield from the aligned crystal ∼0.35 r.l. in thickness was 2.8 times that from the randomly oriented crystals for tungsten and 1.8 times higher for silicon. A simple model has been designed to simulate positron production by coherent bremsstrahlung (CB) photons. Comparison of the calculation with the experiment has shown that most contribution to the positron production in thick crystals comes from CB.