Electron Beam Induced Microstructural Changes and Electrical Conductivity in Bakelite RPC Detector Material

Abstract

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.

Influence of oxygen ion implantation on the free volume parameters and electrical conductivity of a polymer‐based bakelite RPC detector material

“…The formation of crosslinks occurs by the induced radical reactions between the polymeric chains of Bakelite. These reactions are carried by the radicals formed during the scission of polymeric chains in the initial stages of O + ion implantation …”

“…The structural alterations in the ion‐implanted polymers are resulted due to drastic changes in the chemical and physical properties of the polymer network. The changes in the microstructural and physical properties of the ion‐implanted polymers are mainly due to the crosslinking, chain scission, chain aggregation, double bond formation and molecular emission by radical reactions . These processes depend on the structure of polymer matrix, ion implantation energy, and the energy transfer mechanism .…”

“…Based on our previous studies on electron beam irradiation induced structural changes, it has been found that it is more significant to conduct experimental investigations on the ion implantation induced microstructural changes of Bakelite RPC detector material. We expect that the implantation of lighter ions such as oxygen and argon with low energy may modify the microstructure of Bakelite without damaging the actual properties of the material.…”

“…In polymers, ortho ‐positronium ( o ‐Ps) lifetime is an important parameter of positron annihilation lifetime studies as o ‐Ps trapped and annihilated in free volume sites and therefore determines the size of free volume holes in the polymer matrix, which has direct bearing on the microstructure. These free volume holes provide pathways for thermal motion of the chain segments.…”

Room temperature X-ray and positron annihilation lifetime spectroscopic studies of cavansite crystals

“…The comprehensive experimental elucidation can be found in our earlier publications. 14,[16][17][18][19][20][21][22] All the free volume hole sizes were obtained by o-Ps lifetime (τ 3 ) with the technique illustrated in a previous publication. 23) The o-Ps lifetime (τ 3 ) was illustrated according to the previous reported hypothetical models for molecular liquids.…”