A Survey of Microwave Electron Density Measuring Systems Used in Controlled Fusion Research

A survey of microwave electron density measuring systems, with a brief introducticn to laser plasma diagnostics, is presented. Resonant cavity techniques, both cylindrical and Fabry-Perot types, are treated. Broad coverage of microwave interferometers is given indicating the advantages and disadvantages of the various schemes. A summary table is presented to aid the experimentalist to select the most appropriate measuring system for the prevailing experimental conditions i. e. density range of interest, steady state or transient conditions, large or small plasmas etc.