Studies of electrical properties of microchannel plates during and after high-temperature vacuum bakeout

During the present investigation, attempts have been made to gain an insight into the nature of physical phenomena which are responsible for causing reversible and irreversible changes in the electrical characteristics of microchannel plates (MCP's) as a result of high-temperature vacuum bakeout. It has been found that during the vacuum bakeout of an MCP there exists a transition temperature which determines the occurrence of reversible and irreversible changes in the electrical characteristics of an MCP. At temperatures below the transition temperature, the electrical conduction in an MCP is primarily through the surface and the observed changes are associated with outgassing alone and are reversible in nature. At temperatures above the transition temperature, the electrical conduction in an MCP is found to be through the bulk and predominantly ionic in nature. Such ionic movements through the bulk, it is believed, are responsible for causing the observed irreversible changes in the electrical properties of an MCP. An empirical formula for the variation of MCP strip current as a function of its temperature below the transition temperature has been obtained. The room-temperature values of strip current and electron gain of various MCP's before and after the high-temperature vacuum bakeout have been compared.