Plasma Boundary Diagnostics by Laser Induced Fluorescence

For an efficient control of the effects of plasma surface interaction improved diagnostics of the plasma edge region is needed. Laser induced fluorescence offers the possibility to measure the density, the velocity distribution and the flux density of neutral and ionized particles with good time and space resolution. In contrast to currently used probes it does not disturb the plasma and is not affected by it. A survey on results obtained with this technique in tokamaks and other magnetic confinement devices is presented. It is shown that fluxes of metal atoms emitted by the wall can be determined with good accuracy. In addition important information on processes of plasma surface interaction can be obtained. From the measured spatial distribution of particle densities the ionization length as well as T e can be derived and knowledge about the structure of the scrape off layer is gained. Using laser induced fluorescence on injected beams of suitable chosen metal atoms, n e and T e can be determined in the boundary layer even at low n e . Present limits of the method with respect to type and density of species to be detected and future prospects are discussed.