Slow positron production using the RIKEN AVF cyclotron

Using the RIKEN AVF cyclotron, various targets were irradiated with proton or deuteron beams to produce beta(+)-decay radioisotopes. Slow positrons are extracted backward at an angle of 30 degrees to the incident ion beam using a well annealed W film, with a thickness of 10 mu m, as a moderator. This geometry was chosen to allow for both the use of various kinds of target materials and the in-beam slow positron extraction during ion beam irradiation. In preliminary experiments, a slow e(+) intensity of similar to 5.6 x 10(4) e(+)/s was obtained from BN by irradiating protons with an energy of 14 MeV and a current of 4 mu A. From an Al target irradiated with a proton beam with an energy of 10 MeV and a current 3.6 mu A, a slow e(+) intensity of similar to 5.5 X 10(2) e(+)/s was also obtained. By irradiating a deuteron beam with 8 MeV energy and 1.3 mu A current, slow e(+) intensities of similar to 4.2 X 10(3) e(+)/s and similar to 3.4 X 10(3) e(+)/s were obtained from carbon and Si3N4 respectively. Using a pulsed ion beam, background noise was eliminated almost completely in three-coincidence measurement.