The tokamak plasma edge and its diagnostics

After a brief introduction to the edge plasma in tokamaks, an outline is given of the spectroscopic measurement of some of its most important parameters. Hydrogen and impurity atom fluxes are derived from radially integrated line intensities. The availability of the ionization and excitation rate coefficients needed for the evaluation of the observations is discussed. In order to obtain local electron densities and temperatures, He or Li atomic beams are injected into the plasma. The line intensities of the respective atoms yield the desired data. Measurement of ion temperatures is performed by the determination of the Doppler-widths of highly ionized C VI-lines excited by charge exchange with neutral H-atoms, injected by neutral beams (50 keV) or released by recycling from the limiter. Also injected energetic Li atomic beams are used. (orig.)