EFFICIENT LINAC-BASED PRODUCTION OF SLOW POSITRONS

A novel technique for efficient production of slow positrons is propos ed. It is based on the trapping of electroproduced relativistic positr ons in a high field magnetic bottle. By introducing a small drift moti on the emitted positrons are prevented from re-striking the production target and they undergo extended radiative cooling. By adding high vo ltage electrostatic trapping the cooling can proceed down to very smal l transverse momenta. In the simplest version of the method the wide d istribution of final longitudinal momenta is conserved until a dedicat ed extraction procedure converts the trapped positrons into a quasi-co ntinuous beam of very low energy. What comes out is a slow positron be am with the same quality as that obtained with the standard moderation scheme. The conversion efficiency is mound 0.01 e(+)/e(-) and beam in tensities exceeding 10(11) e(+)/s can be obtained with a moderate lina c average current.