Analysis of Minute Nuclear Tracks with Atomic Force Microscopy

Abstract

  This is a feasibility experimental study to apply an atomic force microscope (AFM) to observe and analyze minute etch pits on CR-39 plastic nuclear track detectors. This method makes it possible to observe more than 10⁷/cm² etch pit density produced by 135MeV/n carbon ions. It is applicable to the flux, LET and dose measurements for carbon ion cancer treatments, because the order of the ion particle density is 10⁶/cm². It is impossible to do this kind of measurements with ordinary optical microscope observation, because almost all etch pits overlap each other.

  It is observed that the etch rate ratio of carbon ions is significantly small for the very surface layer (depth ～0.1μm) of CR-39 plastic detectors comparing with that for the deeper layer (depth ～40μm). This difference in track formation sensitivity is probably due to a surface effect of the detector material itself.