Investigation of free radicals induced by light ions in CR-39 using ESR spectroscopy

In previous investigations the formation of radicals induced by γ-irradiation in CR-39 samples has been studied by electron spin resonance (ESR) spectroscopy. On the other hand, all attempts fail to detect radicals in samples irradiated by particles (p, α and neutrons). The present work succeeded in detection of radicals produced by charged particle radiation in CR-39 (TASTRAK). The detectors were irradiated with protons of 7 MeV and α-particles of 3 MeV with fluences in the order of 1011-1012 particles/cm2. The observed ESR signal is composed of at least four different resonance lines for each of which we determined the amplitudes, g-factors, lifetimes and the G-value. The amplitude of the total ESR signal decreases rapidly with a short and a longer lifetime. About 5 days after irradiation the ESR intensity decreased to an undetectable value. The lowest detectable dose (LDD) is of the order of 1 kGy.