A new concept kinetic-ejection negative-ion source for rib generation

Chemically active radioactive species are often released from target-materials in a variety of molecular forms. For example, F-17, is principally released from Al2O3 target-material as (AlF)-F-17. 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 F-17(-) beams for use in the astrophysics research program at the Holifield Radioactive Ion Beam Facility (HRIBF) using the O-16(d,n)F-17 reaction. The mechanical design features, principles of operation, operational parameters, beam quality information (emittance data) and efficiencies for forming intense beams of F-17(-) during off-line and on-line operation of the source are presented in this report. (C) 2000 Elsevier Science B.V. All rights reserved.