The damage profile in Mo bombarded with Ni++ and Ni++ + He ions

High-rate sputter deposition has been used to increase the thickness of ion-bombarded specimens such that TEM specimens can be obtained parallel to the ion beam direction. By using this technique the complete damage profile has been observed in Mo bombarded at 10000C with Ni++ ions or Ni++ + He+ ions. The damage is less than expected near the ion entry surface, but extends to a greater distance than displacement damage calculations would indicate. These observations can be rationalized when long-range diffusion of point defects from their point of origin is considered. The concurrent injection of He and Ni results in a smaller void size and higher void density than in the irradiations without He. There is little effect of helium on void volume fraction. The deposited Ni atoms (in solution) also appeared to affect the formation of voids in the Mo. (author)