MeV-cluster impacts and related phenomena

Point defect creation in 8.7 MeV C-5-cluster irradiated LiF crystals have been studied in a dose range from 2x10(10) up to 1x10(13) C-5(+)/cm(2) and compared to the defect creation in similar conditions with single energetic carbon ions. An enhancement of the primary defect creation (F-centres) and aggregation (F-2-centres) has been measured in a near surface region as deep as about 0.3 mu m corresponding to an energy per carbon atom of the incident cluster decreasing from 1.74 MeV at the impact down to 1.3 MeV. In this region, the carbon atoms of a cluster are confined in a track with a radius (similar to 100 nm) comparable to that of a single carbon ion track. This leads to a very high locally deposited energy density which is directly responsible of the enhanced defect production measured.