THE STOCHASTIC DIFFUSION PROCESS IN REVERSED-FIELD PINCH

The stochastic diffusion process has been carefully analysed for the R everse Field Pinch (RFP) equilibrium configuration. Three different ap proaches to the problem have been used, i.e, the direct calculation of the stochastic diffusion coefficient (D-st) from the radial evolution of an ensemble of field lines, an indirect determination using a Gaus sian-fit to the field line probability distribution function and final ly the relationship of D-st with the maximum Lyapunov exponent of the system. Different perturbation spectra have been also considered and c ompared and the quasi-linear approximation has been tested. (C) 1996 A merican Institute of Physics.