Annealing effects of helium implanted single crystals and polycrystalline magnesium aluminate spinel

The effects of transmutation produced alpha -particles and the thermal beha viour of the incorporated helium is simulated by 900 keV He-3 ion implantat ions at 2 mum depth in (100) surface oriented single crystals and in polycr ystalline samples. Thermal Helium Desorption Spectrometry (THDS) and Neutro n Depth Profiling (NDP) have been applied to study the release rate of heli um and changes in the depth profile, respectively, during isothermal anneal ing. Release of the helium took place in at least two stages in a wide temp erature interval ranging from 600 to 1600 K. For polycrystalline spinel an additional high temperature release stage at T> 1300 K was ascribed to trap ping in pores. For the high dose implanted single crystals mainly helium re lease in bursts was observed due to thermally induced flaking. (C) 2001 Pub lished by Elsevier Science Ltd. All rights reserved.