PLASMA EDGE DIAGNOSTICS BY OPTICAL METHODS

The extension of the plasma edge in a tokamak may be roughly defined by the ionization length of the atomic hydrogen. The physical quantities to be measured and their expected ranges of magnitude are approximately identified. Requiring that the diagnostic methods be non-disturbing one is left mainly with characteristic radiation and ionization processes in the plasma edge region. In this paper, the authors discuss naturally occurring processes like the radiation of hot surfaces and those due to electron impact and electron capture. Considering, in addition, processes activated by laser photons or by injected particles, it does appear possible to solve most of the tasks of plasma edge diagnostics even if one relies only on the presently available light and particle sources and detection techniques. Practical experiences with the application of these methods will be presented and expected developments will be discussed.