Retention of ion-implemented-xenon in olivine - Dependence on implantation dose

The diffusion of Xe in olivine, a major mineral in both meteorites and linear samples, was studied. Xe ions were implanted at 200 keV into single-crystal synthetic-forsterite targets and the depth profiles were measured by alpha particle backscattering before and after annealing for 1 hour at temperatures up to 1500 C. The fraction of implanted XE retained following annealing was strongly dependent on the implantation dose. Maximum retention of 100 percent occurred for an implanting dose of 3 x 10 to the 15th power Xe ions/sq cm. Retention was less at lower doses, with approximately more than or = 50 percent loss at one hundred trillion Xe ions/sq cm. Taking the diffusion coefficient at this dose as a lower limit, the minimum activation energy necessary for Xe retention in a 10 micrometer layer for ten million years was calculated as a function of metamorphic temperature. Previously announced in STAR as N83-18528