UNIFIED THEORY OF EDGE TURBULENCE IN HIGH-DENSITY AND LOW-DENSITY TOKAMAKS

A new theoretical model, which includes density and temperature gradie nts and impurity radiation effects, for the edge turbulence in high- a nd low-density tokamaks is established on the magnetohydrodynamics. Th e different drive effects in the turbulent evolution are discussed and the mechanism of nonlinear saturation is investigated. The fluctuatio n levels and the associated diffusion coefficients at the turbulent sa turation state are analytically given. The theoretical results are in agreement with the experimental observations on both high- and low-den sity tokamaks.