BEAMS OF SHORT-LIVED NUCLEI PRODUCED BY SELECTIVE LASER IONIZATION INA GAS CELL

An on-line laser ion source has been developed for the production of e lemental and isobaric pure beams of radioactive ions. It is based on s elective resonant laser ionization of nuclear reaction products therma lized and neutralized in a noble gas at high pressure. The ion source has been tested in a wide range of recoil energies going from 1.3 MeV to similar to 90 MeV, Efficient schemes of two step laser ionization t hrough autoionizing states have been found for nickel, cobalt and rhod ium. Residence times of the reaction products in a gas cell have been measured for helium and argon as buffer gas, Elementally pure beams of Ni-54,Ni-55 and Co-54, produced in a light-ion induced fusion-evapora tion reaction, and of Rh-113, produced in proton-induced fission of U- 238, were obtained. An efficiency of the ion source of 6.6% for fusion reactions and of 0.22% for fission reactions has been obtained. A sel ectivity of the ion source of 300 for fusion and 50 for fission reacti ons has been achieved.