Thermophysical investigation of Gafchromic EBT2 films using photoacoustic spectroscopy

The thermophysical properties of EBT2 films exposed to different doses of x-ray were investigated. The doses ranged from 2 to 818 cGy. The films were irradiated by a Varian linear accelerator using a 6 MV photon beam. The thermal conductivity (k) was obtained by measuring the thermal diffusivity (α) and thermal effusivity (e) using the photoacoustic (PA) technique. The α, e, and k values clearly indicated their dependence on the dose from 0 to 818 cGy. The results demonstrate that the PA technique can detect variations in the thermal diffusivity at doses as low as approximately 3 cGy. The thermal conductivity for the film exposed to 818 cGy of radiation increased by a factor of approximately 3.70 compared to the non-exposed film. The PA spectroscopic technique displayed good reproducibility, with a relative standard deviation of less than 5%. (paper)