SLOW POSITRON BEAM PRODUCTION BY IRRADIATION OF P(+), D(+) AND HE2+ ON VARIOUS TARGETS

Slow positron beams were extracted by irradiating various targets with p(+), d(+) and He2+ ion beams from the AVF (azimuthally varying field ) cyclotron of RIKEN. The targets were selected considering the large cross section and high maximum energy of the beta(+)-decay. Two differ ent geometries elf the target and moderator (one W sheet) arrangement, reflection-type and transmission-type were used and a Field of simila r to 10(4) slow e(+)/s/mu A was obtained However, in both geometries l oss of a fraction of the fast positrons by self-absorption in the targ et is unavoidable. For increasing the number of available fast positro ns we have designed a gas target (N-2) system. The estimated slow posi tron yield is 1.5 x 10(5) e(+)/S/mu A using a 16 MeV proton beam and a one W foil moderator.