Production of slow positrons with a 100-MeV electron linac

Intense, pulsed beams of low-energy positrons have been produced by a high-energy beam from an electron linac. The production mechanism has been studied near 100-MeV incident energy and several characteristics that affect slow-positron production have been identified. These characteristics include the geometry of the electron-positron converter and positron moderator, the thickness of the converter, and the energy of the electron beam. The production efficiency for producing low-energy positrons has been determined experimentally. The results imply that low-energy positron beams from a linac can be of much higher intensity than those beams currently derived from radioactive sources.