Studying Alpha Irradiated CR39 Using Positron Annihilation Spectroscopy

Abstract

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  Ф  of 2.6 · 10⁸,  5.27 · 10⁸,  7.91 · 10⁸,  1.3 ·10⁹,  1.84 · 10⁹,  and  3.6 · 10⁹ α/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  τ₃ and the parameters S and W as a function of the fluence Ф. 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 τ₃ , 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 τ₃ , S and W parameters, and free volume radius has been noted when compared to the non-etched samples.