Selection of RIB targets using ion implantation at the Holifield Radioactive Ion Beam Facility

Among several major challenges posed by generating and accelerating adequate intensities of RIBs, selection of the most appropriate target material is perhaps the most difficult because of the requisite fast and selective thermal release of minute amounts of the short-lived product atoms from the ISOL target in the presence of bulk amounts of target material. Experimental studies are under way at the Oak Ridge National Laboratory (ORNL) which are designed to measure the time evolution of implanted elements diffused from refractory target materials which are candidates for forming radioactive ion beams (RIBs) at the Holifield Radioactive Ion Beam Facility (HRIBF). The diffusion coefficients are derived by comparing experimental data with numerical solutions to a one-dimensional form of Fick's second equation for ion implanted distributions. In this report, we describe the experimental arrangement, experimental procedures, and provide time release data and diffusion coefficients for releasing ion implanted Cl-37 from Zr5Si3 and As-75, Br-79, and Se-78 from Zr,Ge, and estimates of the diffusion coefficients for Cl-35, Cu-63, Cu-69, Ga-69, and Ga-71 diffused from BN; Cl-35, Cu-63, Cu-65, Ga-69, As-75, and Se-78 diffused from C; Cl-35, Cu-68, Ga-69, As-75, and Se-78 diffused from Ta.