RA1. RIB Development
(Y. Liu, C. Havener and D. Stracener)
A novel technique using lasers is being developed at HRIBF for efficient suppression of isobaric contaminants in negative ion beams. Progress on this project has been described in earlier HRIBF Newsletters but the data below are from a redesigned system that will be implemented at HRIBF soon after the commissioning of the new RIB Injector (IRIS2). Lasers shined on the negative ion beam can be tuned in frequency so that their light is absorbed by contaminant negative ions only, which then eject their extra electron and their negative charge. They can then easily be separated from the negatively charged ions of interest. In a recent experiment, the feasibility of near 100% suppression of isobar contaminants in negative ion beams was demonstrated. In this work, negative ions of 58Ni and 59Co were neutralized using a pulsed Nd:YAG laser beam at 1064 nm. A gas-filled radio-frequency quadrupole ion guide was employed to slow down the negative ions and dramatically increase the interaction time of the ions with the laser. This substantially increased the efficiency of removing the extra electron. More than 99.99% of the contaminant 59Co- ions were removed with less than 3W of laser power, while less than a 20% loss of the 58Ni- ions was observed under identical conditions. This technique will be used at HRIBF to purify the radioactive ion beams of 56Ni, 17,18F and 33,34Cl isotopes. A U.S. patent on this technique has been granted (U.S. Patent 7,335,878, Feb. 2008, Beene, Liu, and Havener).
Figure RA1: The fraction of 59Co and 58Ni negative ions transmitted through the RF quadrupole ion guide as a function of laser power. The ion guide was operated at about 6 Pa He buffer gas and 2.76 MHz RF frequency.