Characteristics of CR-39 for detection of cosmic ray particles

A stack of CR-39 sheets has been exposed to 96 MeV/n and 2.1 GeV/n Ar beams in order to study uniformity of response and the response curve. Variation in response of the area of about 50 cm × 50 cm for one sheet was within 1.5 %. Roughness of the surface after 27 hr etching and the charge resolution were improved by changing temperature-time curing cycles. Steeper response curve at high REL region was observed and it was confirmed that our CR-39 has higher sensitivity in the recording of nuclear tracks down to Z/β ≃ 6 for vertical incidence.