EQUILIBRIUM RECONSTRUCTION OF THE SAFETY FACTOR PROFILE IN TOKAMAKS FROM MOTIONAL STARK-EFFECT DATA

The motional Stark effect (MSE) diagnostic has been used to obtain accurate measurements of the internal magnetic pitch angle tan-1(B(Z)/B(T)) in finite-pressure tokamaks. The MSE data, together with external magnetic probe data, are used to reconstruct self-consistently the equilibrium safety factor (q) profile and, hence, the plasma current density, in the Tokamak Fusion Test Reactor (TFTR) [Plasma Phys. Controlled Nucl. Fusion Res. 1, 51 (1986)] and the Princeton Beta Experiment-Modified (PBX-M) tokamak [Phys. Fluids B 2, 1271 (1990)]. An efficient computational scheme, based on an inverse coordinate representation of the magnetic field, has been developed to solve the coupled nonlinear equations describing both the magnetohydrodynamic (MHD) equilibrium and the q profile, which best match all the experimental data.