The effect of infrared laser on the activation energy of CR-39 polymeric detector

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/cm ². For the third set (pre-exposed), the process was reversed (laseralpha) under the same conditions. The activation energies of bulk etch (E _B) 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 (E _T) 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 E _B 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 E _B. Also, the results of E _T for post-exposed and un-exposed samples are in close proximity with a slight increase for the former. The increase in E _T 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 E _T 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.