SUBMICROSCOPIC ANALYSIS OF TRACKS IN MICA

Tracks of 49 MeV Cl-35 ions in muscovite mica were analyzed by transmi ssion electron microscopy up to 10 Angstrom resolution applying the tr ack replica method. The enlargement of the track diameter is measured as a function of etching time. The track shape evolution shows circula r tracks for very short etching times. By increasing the etching time the tracks gradually become ovals. For longer etching times, tracks sh ow the characteristic rhombic shape of the bulk region. A non monotono us decrease of the track velocity vs. radius is reported. Formation of a low velocity shell in the intermediate region between the central a morphous zone and the non-perturbed crystalline lattice is suggested.