Improvement of charge resolution for intermediate energy heavy ion using CR-39 plastic nuclear track detector

It is essential for the study of galactic cosmic ray origin to measure precise cross section of projectile fragmentation for heavy ion on hy-drogen and helium target at intermediate energy between a few hundred and a few thousand MeV/nucleon in laboratory system. As charge identification determines the measurement preci-sion of cross section, an improvement of charge resolution for heavy ions with intermediate ener-gy using CR-39 PNTD has been made. We showed that a limitation of Z was about 20 for the identi-fication of nuclear charge Z with enough charge resolution < 0.15 charge units (cu) in rms) under optimized etching time, depending on the projec-tile energy. However, the charge resolution of the CR-39 PNTD is found to be drastically improved by averaging the measurement data of multiple layers of the CR-39. This improvement leads us an excellent charge resolution better than 0.15 cu. for a wide range of elements as for projectile. These results will support us to measure the fragmentation cross sections precisely using CR-39 PNTD.