New concept kinetic-ejection negative-ion source for rib generation

Abstract

Chemically active radioactive species are often released from target-materials in a variety of molecular forms. For example, 17F, is principally released from Al2O3 target-material as Al17F. Because of the low probability of simultaneously dissociating such molecular carriers and efficiently ionizing their atomic constituents with conventional hot-cathode, electron-impact ion sources, species of interest are often distributed in several mass channels in the form of molecular side-band beams. Consequently, beam intensities of the desired radioactive species are diluted. The sputter negative-ion beam generation technique is particularly effective for simultaneously dissociating molecular carriers and efficiently ionizing highly electronegative atomic constituents. Therefore, a new concept kinetic-ejection negative-ion source (KENIS), based on this principle, was conceived to address this problem. The source has proven to be highly efficient for simultaneously dissociating and negatively ionizing sputter-ejected atomic fluorine from cesiated surfaces. The source has been successfully employed on-line to generate high intensity 17F- beams for use in the astrophysics research program at the Holifield Radioactive Ion Beam Facility (HRIBF) using the 16O(d,n)17F reaction. The mechanical design features, principles of operation, operational parameters, beam quality information (emittance data) and efficiencies for forming intense beams of 17F- during off-line and on-line operation of the source are presented in this report. Show more