Track detector of CR-39-DAP-copolymer with variable threshold to detect trans-iron nuclei in galactic cosmic rays

摘要

Observation of trans-iron nuclei in galactic cosmic rays (Z >= 30) requires a high performance cosmic ray detector telescope with a large expoSUre area because of their extremely low fluxes. A solid-state track detector SUch as CR-39 has the advantage of easy extension of expoSUre area, but it SU necessary to raSUe the Z/beta detection threshold in order to SUppress background tracks produced by galactic cosmic rays with Z/beta< 30. The track regSUtration sensitivity and detection threshold for heavy ions with various Z*/beta were verified by using track detectors of copolymers of CR-39 and DAP (diallyl phthalate) with various DAP concentration. We found that it SU possible to control the Z*/beta detection threshold of copolymers by changing DAP concentration. In order to detect heavy ions with Z*/beta >= 30. the optimum DAP concentration was found to be approximately 50%.