Applicability of Polyimide Films as Etched-Track Detectors for Ultra-Heavy Cosmic Ray Components

The track registration property in polyimide Kapton has been examined for heavy ions, including 2.3 GeV Fe and 24 GeV Xe ions. Conventional track formation criteria fail to predict the thresholds of etch pit formation, while a chemical criterion stating that etchable tracks are formed when two adjacent diphenyl ethers are broken in the vicinity of the ion's trajectory should be more appropriate. Discriminative detections of ultra-heavy components in cosmic rays, such as Bi, Th, and U ions, are possible by measuring the recorded track length.