DETERMINATION OF LOCAL TOKAMAK PARAMETERS BY MAGNETOHYDRODYNAMIC SPECTROSCOPY

The influence of local equilibrium parameters on the Alfven spectrum i s studied. The aim is to solve the inverse problem: identification of the plasma profiles, and especially the safety factor profile, using m easurements of magnetohydrodynamic (MHD) waves. A study case is presen ted to determine what the possible uses of MHD spectroscopy are. The d ependence of the TAE (Toroidicity induced Alfven Eigenmode) frequency on the safety factor at the edge is shown. The possible use of Alfven continuum modes near the edge is investigated. A very accurate determi nation of the safety factor on axis will be presented for plasmas wher e core-localized TAE's are present. It will be shown how measurements of mode structures can provide information on plasma parameters at par ticular points in the plasma. The numerical findings will be compared to experimental results from the Joint European Torus (JET) [P. ii. Re but and the JET Team, Plasma Physics and Controlled Nuclear Fusion Res earch 1984 (International Atomic Energy Agency,Vienna, 1985), Vol. 1, p. 11] active Alfven wave diagnostic.