Radiation Interaction with Solid Material Surface in Radioisotope Plasmas

在这项研究中，辐射粒子（β-射线和γ-射线）的固体表面相互作用的放射性同位素（RI）和/或外部源进行了研究。放射性同位素被认为是气体放电中的一种元素。我们打算弄清楚辐射粒子与固体材料的相互作用过程，旨在开发以下技术：（1）用等离子体方法固定可处置的放射性同位素;（2）用等离子体CVD方法在固体表面上沉积薄膜的新型辐射探测器。我们试图测量由γ射线（或X射线）入射引起的沉积膜中的传导电流，以证明在评估膜的性质时对辐射的检测。本文用蒙特卡罗方法模拟了γ射线在固体材料层中的行为和电子在气体等离子体中的行为。主要结果如下：1.用等离子体CVD法在Al_2O_3和塑料等固体绝缘体上制备的TiO_2薄膜可以作为γ射线的良好探测器。2.研究了TiO_2薄膜的导电机理。3.研究了TiO_2薄膜的导电机理。结果表明，TiO_2薄膜的导电机理是：（1）在固体绝缘体上制备的TiO_2薄膜是γ射线的理想探测器;（2）在固体绝缘体上制备的TiO_2薄膜是γ射线的理想探测器;（3）在气体等离子体上制备的TiO_2薄膜是γ射线的理想探测器2薄膜的光子和电子的Monte Carlo模拟，使用EGS 4代码进行了分析。结果表明，导致电流传导的空穴-电子对的产生过程主要由康普顿电子控制。3.考虑到放射性同位素等离子体中重要的气体--水分子，我们将这些气体的电子碰撞截面嵌入到蒙特卡罗程序中。

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.