Annealing studies of tracks in crystals

The influence of crystallographic structure of the annealing of fission-fragment tracks in muscovite has been reported in the past, but the possibility of such an effect in other minerals has received little attention. We have investigated the annealing behaviour of tracks in bronzite, using collimated beams of ²⁵²Cf fission fragments, and heavy ions (Fe and Kr of 9·6 MeV/nucleon) employing the ‘L-R plot’ technique. No influence of structure on the annealing of these tracks is found. The annealing behaviour of fossil-fission tracks in apatite is also studied from this aspect, and here significant crystallographic effects are found. After reduction of track density to 0·25 of the original unannealed value, the great majority of tracks are aligned with the c-axis of the crystal prism. However, the overall significance of this effect, in terms of track densities, seems to be small.