Studying Alpha Irradiated CR39 Using Positron Annihilation Spectroscopy

The monitoring of the alpha irradiation effect on the microstructural deformation of CR39 via the variation of free volumes has been studied. CR39 samples have been irradiated with alpha particles at fluencies phi of 2.6 x 108, 5.27 x 108, 7.91 x 108, 1.3 x 109, 1.84 x 109, and 3.6 x 109 alpha/cm2. The samples have been investigated with positron annihilation lifetime spectroscopy and Doppler broadening spectroscopy. The analysis of positron annihilation spectra has shown a variation of the ortho-positronium component 73 and the parameters S and W as a function of the fluence phi. This variation is related to a change in the size and number of free volumes, which is created via the evolution of chemical chains. From the values of 73, the free volume radius has been estimated using the Tao-Eldrup model. Moreover, theoretical calculation of the radial dose distribution has been also performed using the Waligorski formulation to get the track core radius. After an etching of 5 min, the positron annihilation spectroscopy technique was again used to investigate the microstructural changes in etched samples subjected to alpha radiation. A clear variation of 73, S and W parameters, and free volume radius has been noted when compared to the non-etched samples.