On measuring the electron heat diffusion coefficient in a tokamak from sawtooth oscillation observations

A number of new methods are discussed for determining the electron heat conduction coefficient chisub(e) in a tokamak from the experimental observation of the space-time evolution of the temperature perturbations induced by internal disruptions. In the Oak Ridge Tokamak (ORMAK) the various average values of chisub(e) and the radial dependence of chisub(e) are found to be consistent with and more precise than the chisub(e)(r) determined by conventionally analysing the electron power balance equation. The net result of these measurements is to conclusively prove that the dominant radial electron heat transport mechanism in tokamaks is a microscopic, diffusive process. (author)