Damage morphology of Kr ion tracks in apatite: Dependence on thermal annealing

In this study, we have characterized the isothermal annealing (300 degrees C) of Kr-86(32+) ion tracks in Durango fluoroapatite by means of channeling Rutherford backscattering spectrometry (CRBS) and chemical etching. The CR BS results were obtained for four Kr-86(32+) irradiation energies chosen in the electronic stopping power range: 1.83, 0.73, 0.22 and 0.10 MeV u(-1). It was shown that the nuclear track effective radius (R-e) decreases with t he annealing time. In that way, the crystalline reorganization phenomenon o f previously amorphized bulk near the ion path is quantified for several io n energies. Chemical etching experiments associated with CRBS allowed us to qualitatively interpret the damage morphology evolution of nuclear tracks versus thermal treatment. It appears that crystal reorganization produces a defect fragmentation phenomenon, which is highlighted by chemical etching. This phenomenon is similar to the one previously detected during the slowi ng down of incident ions. In both casts, each type of track morphology can be defined by appropriate R-e values. The experimental results were then ap plied to determine the evolution of the U-238 fission-track structure under thermal annealing. (C) 2000 Elsevier Science B.V. All rights reserved.