The effect of infrared laser of wavelength (λ=1064 nm), pulse energy of 40 mJ/pulse at a repetition rate of 10 Hz, on the activation energy of CR-39 polymer, solid state nuclear track detector, has been investigated. Fifteen detectors were divided into three sets of equal numbers. The first set (un-exposed to laser beam), used as a reference set, was irradiated in close contact with an alpha source (241Am). The second set (post-exposed) was first exposed to alpha radiation in close contact to the same 241Am source and then treated in air with laser at energy intensity 8 J/cm2. For the third set (pre-exposed), the process was reversed (laser+alpha) under the same conditions. The activation energies of bulk etch (EB) for unexposed, post-exposed and pre-exposed are found to be equal to 0.98, 0.91, and 1.0 eV, respectively. The respective activation energies of track etch (ET) for unexposed, post-exposed and pre-exposed are found to be equal to 0.71, 0.75, and 0.97 eV.These results show that EB for post-exposed and pre-exposed samples remain, to within the experimental uncertainty, comparable to that of un-exposed sample which indicates that laser irradiation has a small effect on EB. Also, the results of ET for post-exposed and un-exposed samples are in close proximity with a slight increase for the former. The increase in ET of pre-exposed CR-39 polymer due to IR exposure is discussed on the basis of cross linking processes occurring during the exposure. This increase in ET leads to the hardening of the detector material of the pre-exposed sample. The hardening of the detector material is crucial in applications of CR-39 polymer such as in cosmic ray and cold fusion research.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment Volume 680, 11 July 2012, Pages 82–85