EFFUSIVE FLOW DELAY TIMES FOR GASEOUS SPECIES IN A COMPACT RF ION-SOURCE

A rf ion source is presently being developed and evaluated as a potent ial candidate for use in generating radioactive ion beams (RIBs) for t he experimental research program at the Holifield Radioactive Ion Beam Facility (HRIBF) now under construction at the Oak Ridge National Lab oratory. For this application, any time delays that are excessively lo ng with respect to the half-life of the radioactive species of interes t can result in significant losses of the RIB intensity; therefore the times for effusive flow through the ion source are of fundamental imp ortance since they set limits on the minimum half-life of radioactive species that can be processed in the source. Complementary experimenta l and computational techniques have been developed which can be used t o determine the characteristic delay times for gaseous species in low- pressure ion source assemblies. These techniques are used to character ize the effusive delay times for the stable counterparts of various at omic and molecular radioactive species in the ORNL-rf source: He, Ne, Ar, Kr, Xe, H-2, CO, CO2, N-2, N2O, and O-2. (C) 1996 American Institu te of Physics.