Development of ion source for JAEA-ISOL-I

According to the JAEA-KEK joint radioactive nuclear beam (RNB) project, we have improved a surface-ionization type integrated-Uranium-target-ion source (U-SIS) system to separate neutron-rich indium nuclei with particle-induced fission of 238U. Yields and release times of mass-separated indium nuclei were examined. An overall efficiency for 126In separation was 0.08% by a previous version of U-SIS. We considered this very low efficiency was caused by the low temperature of a thick ionizer. Therefore, we used a thin ionizer for the improved version of U-SIS. A uranium carbide target was prepared at a uranium density of 630-mg/cm2U. The target was bombarded with a 33-MeV proton beam with intensity of about 100 nA. For the separation yield measurements of fission products, the mass separated products were collected on an aluminized Mylar tape in a tape transport system and were periodically transported to a measuring position where an HPGe detector was placed for γ-ray measurements. Separation yields of indium nuclei were derived from γ-ray measurements. The overall efficiency for 126In separation was about ten times improved. Release time of In ion was also measured. (author)