Study of fossil tracks due to 50 <= Z <= 92 Galactic cosmic ray nuclei in meteoritic crystals: Results and perspectives

A pew approach to the problem of investigation of charge and energy spectra of ultra heavy Galactic cosmic ray nuclei, based on fossil track study of extraterrestrial olivine crystals has been developed. The results of an inv estigation of ultra heavy Galactic cosmic ray nuclei (Z=50-92) in meteoriti c olivine crystals are presented. The technique was based on calibration of olivine crystals with accelerated Xe, Au, Pb and U ions and well-controlled partial annealing of "fresh" and "fossil' tracks. It allows us to determine the charge spectra and abundanc es of cosmic ray nuclei based on fossil track length study in meteoritic an d Moon crystals. The comparative studies of the spectra of "fossil' tracks and tracks due to Pb-208 and U-238 nuclei have shown that the group of 210 mu m "fossil" tracks, first observed in 1980 at JINR is due to Th-U nuclei- products of recent r-process nucleosyntesis in our Galaxy. The method in principle allows one to resolve Pt-Pb peaks in fossil tracks, to establish the upper limit of the abundance of Z>110 nuclei in the Galac tic cosmic rays at the level less than or equal to 10(-3) to the abundance of actinide nuclei and to get information on the history of Z>50 cosmic ray nuclei in time interval up to 220 M.Y.