Improvement of charge resolution for trans-iron nuclei (Z >=30) in CR-39 plastic nuclear track detectors using trajectory tracing technique

Charge identification of trans-iron nuclei (nuclear charge: Z>=30) using CR-39 plastic nuclear track detector (PNTD) is essential as a part of an effort to our future measurements of the projectile charge changing cross sections for galactic cosmic ray nuclei, but extremely hard. Therefore, an improvement method of the charge resolution (sZ) for 350 MeV/n Ge in CR-39 PNTD using the trajectory tracingtechnique with averaging the signals of nuclear tracks for each ion was studied. Eight sheets of CR-39 PNTDs were aligned and exposed to Ge beam behind a graphite target to produce projectile fragments. Average of the nuclear track data was taken over 16 detector surfaces for each ion, then the sZ of Ge was successfully improved from 0.31 charge unit on single surface to 0.15 charge unit in rms, which isgood enough for making the precise cross section measurements and no other experiments using CR-39 PNTDs or the other passive detectors have achieved such a good sZ for the trans-iron nuclei with Z/beta