Radiation Interaction with Solid Material Surface in Radioisotope Plasmas

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In this study, solid surface interactions of radiation particles (β-ray and γ-ray) from a radioisotope (RI) and/or external sources are investigated. The radioisotope is considered to be an element in the gas discharge. We intend to make clear the interaction processes of the radiation particles with solid materials aiming to develop the following techniques : (1)fixation of disposal RIs by plasma processes, (2)new type radiation detectors using thin films deposited by the plasma CVD method on solid surfaces.In experimental studies, we attempt to measure conduction currents in the deposited films induced by a γ-ray (or X-ray) incident for demonstrating a detection of radiation while the properties of the films are evaluated. The Monte Carlo method is employed to simulate the behaviors of γ-rays in solid material layers and of electrons in the gas plasmas.The outcomes of the project are summarized as below.1.It was shown that TiO_2 films produced by a triode plasma CVD on solid insulators such as Al_2O_3 and plastics can be good detectors for γ-rays.2.The conduction mechanism of the TiO_2 films was analyzed by a Monte Carlo simulation of photons and electrons using EGS4 code. The results suggest that the production process of hole-electron pairs causing the current conduction be dominated by the Compton electrons.3.The electron collision cross sections for Xe and water molecule were determined to be embedded in a Monte Carlo code (originally developed) since these gases are important in the radioisotope plasmas.