TOKAMAK PLASMA DIAGNOSIS BY ELECTRICAL PROBES

This paper reviews progress in the understanding and application of el ectrical probes for the diagnosis of tokamak edge plasmas. Langmuir pr obes are still one of the most commonly applied diagnostics in tokamak s but our understanding of how to interpret them in strong magnetic fi elds is still rather limited. Recent results from flush-mounted Langmu ir probes in divertor plates are used to highlight the problem areas, in particular non-saturation of the ion current and low electron to io n saturation current ratios. The importance of measuring the parallel flow velocity in the plasma edge is highlighted and recent development s in theories for interpretation of Mach probes are discussed. Finally , the importance of diagnostics for ion temperature and impurity conte nt is emphasized, and progress in the application of advanced electric al probes such as retarding field analysers and mass spectrometers to the tokamak boundary is reviewed in this context.