Application of polyimide films as a nuclear track detector (2): A latent track structure study with Fourier transform infrared spectroscopy

This paper reports the relation between latent track structure and the detection threshold of etch pits formation in UPILEX-S (R) and Kapton. At the similar stopping power value, effective track core radii and G values for heavier ions are lower than those of lighter ions. These results would be due to the difference of the radial dose distribution for low- and high-velocity ions. The G value starts more rapidly rising above 600 and 1000 keV/mu m for Kapton and UPILEX-S (R), respectively. The detection threshold of UPILEX-S is 4000 keV/mu m for Ar ions, at which effective track core radii of all functional groups are larger than 2 nm. Since the length of a molecule unit of UPILEX-S (R) is about 1.4 nm, at least more than two molecule units have to be damaged for the etch pit formation. A similar discussion is applicable to Kapton, whose detection threshold is significantly lower than UPILEX-S (R).