We have investigated the effect of ion implantation on structural modification and the electrical conductivity of Bakeliteresistive plate chamber (RPC) detector material used in high energy physics experiments. Samples of Bakelite polymer were exposed to 100 keV and 150 keV oxygen ions in the fluence of 10 12 to 10 15 ions cm 22 . Ion implantation induced microstructural changes have been studied using positron annihilation lifetime spectroscopy, X-ray diffraction and Fourier transform infrared techniques. Positron lifetime parameters viz., o-Ps lifetime and its intensity showed formation of radicals, secondary ions due to the creation of interior tracks by high-energy ions followed by chain scission at lower fluence of 100 keV implantation. The decreased free volume size at 150 keV ion implantation is an indication of crosslinking and filling up of interior tracks by the implanted ions. Variation of ac conductivity with frequency obeys Jonscher power law at 100 keV and the conduction mechanism is explained by barrier hopping model.

To explore the structural modifications in terms of crosslink density and electrical conductivity in polymer based Bakelite RPC detector material was exposed to 8 MeV electron beam with the irradiation doses of 20 kGy to 100 kGy in steps of 20 kGy. The microstructural changes of Bakelite upon electron beam irradiation have been studied using Positron Annihilation Lifetime Spectroscopy (PALS), X-ray Diffraction (XRD) and Fourier Transform Infrared (FTIR) Spectroscopy. Positron lifetime parameters viz., o-Ps lifetime and its intensity showed chain scission at lower doses (at 20 kGy and 40 kGy) followed by crosslinking due to the radical reactions. These changes are effectively explained with the help of FTIR and XRD parameters. The reduction in electrical conductivity of Bakelite material beyond 60 kGy is correlated between conducting pathways and crosslinks in the polymer matrix. The appropriate dose of electron beam on Bakelite might reduce the leakage current of Bakelite RPC detector material and hence improves the performance of the detector.

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