ELECTRON-MICROSCOPY ANALYSIS OF KRYPTON ION TRACKS INDUCED IN DURANGOAPATITE

The, track annealing phenomenon, which occurs in a heated mineral cont aining uranium like apatite, is analysed using the transmitted electro n microscopy (TEM) associated to the platinium shadowed carbon replica method. The diameters of 86Kr (1,66 MeV/nucleon) ion tracks induced n ormally to the observation plane are measured during an etching stage with a very low concentrated etchant (HNO3 1%). The distribution of tr ack diameters in a sample, and its variation following the annealing a mount the apatite knew, lead us to agree with the track registration m odel which let appear more than one microscopic defect structure (Dart yge et al., 1981). This model cannot be observed with only unannealed etched tracks, but is clearly highlighted by the thermal annealing of nuclear tracks in this mineral. The opening track profile is analysed as a determination of the etching speed variation versus the distance to the ion trajectory. The variation is shown to be dependent on the c ristallogaphy of the apatite. The different etching speeds, relative t o the orientation with the c-axis of the apatite, influence the track shape for long etching times. The etched pit figure is not symetrical, and present in the c-axis direction a much more width opening than th e etched track diameter. Finaly, the lateral track shape and the etche d pit are supposed to be sensitive to the etchant strength.