On the determination of the track age of some natural crystals

The detailed investigations of annealing behaviour of fission fragment tracks in muscovite mica, apatite and whitlocite crystals have been performed. For muscovite mica the annealing procedure has been applied to single fission fragment tracks, for apatite and whitlocite crystals - for binary events. As it has been observed, the controlled annealing produced the shortening down of fission fragment track length. Such procedure provides more direct comparison of the track length spectra due to spontaneous fission of 238U and due to thermal neutron induced fission of 235U in the same crystal; it allows one to obtain a more correct value of the track age. (Author)