Studies on the nuclear tracks in CR-39 plastics

Abstract

A review was given for our recent studies on the latent tracks in CR-39 nuclear track detector. The radial size of track core has been determined through UV spectral measurements combined to the model of track overlapping and by AFM observations of slightly etched detectors. The track core radius was found to be about a few nano-meters and almost proportional to the cubic root of stopping power. As a control study, the etching properties of CR-39, irradiated by low-LET radiation, has been examined. The observed depth-dependence and dose-rate dependence of the bulk etch rate of the irradiated CR-39 were explained that the damage formation process was governed by the reaction between the radiation induced radicals and the oxygen supplied from the air. This indicated that latent tracks in CR-39 are produced through local radiation induced oxidation process along the ion paths. Studies on vibration spectra, Near-IR, FT-IR and Raman spectra, of CR-39 have been also carried out to estimate the chemical structure of the latent tracks. The creation of OH group in irradiated CR-39 has been confirmed.

Sudden Increase of the Radiation Chemical Yield for Loss of Carbonate Ester in PADC Detector where the Track Overlapping of 28 MeV Electrons Becomes Significant

“…As listed in Table I, the removal cross sections for the both groups in the multi-hits zone are equally 1.4×10 -17 cm 2 , which correspond to the effective track radius of 0.021 nm. In our previous studies, we obtained the core radius based on the track overlapping model and the fluence dependence of UV spectra of PADC exposed to protons and heavy ions [12]. The results were concordant to that of loss of ether within the experimental error [3].…”

Track core size estimation for heavy ions in CR-39 by AFM and UV methods

“…The CR-39 is well known as the most sensitive etched nuclear track detector for more than 25 years [1]. However, there are some unresolved aspects in the track formation process occurring in this material [2]. Determination of the radial size of the latent tracks in CR-39 should be one of the important objects in order to understand the track formation mechanism [3,4].…”

The Optical and Chemical Response of Thermal Neutron-Irradiated CR-39 Polymeric Track Detector after Annealing

“…The soggy vibrations of these molecules give rise to absorption bonds at low energies falling in the region of infrared radiations [25] . Under irradiation, the energy transferred to the molecules of the polymers results in the breaking of covalent bonds and may also result in the molecular fragments recombination to form new molecular bonds [31] . These two different processes are found to be dependent on the irradiation dose in general.…”