Measurement of local ion diffusion coefficients in the tokamak fusion testreactor

The perturbations in ion temperature, density and parallel velocity resulti ng from sawtooth disruptions in TFTR are measured with a novel diagnostic. The local ion thermal diffusivity, particle diffusivity and parallel moment um diffusivity are determined in a high power discharge at r/a = 0.64 by fi tting the observed pulses to a simple model of the radial diffusive propaga tion of heat, particles and momentum caused by the crash. The incremental i on thermal diffusivity, chi(i)(inc), is found to be similar in amplitude to the ion and electron thermal diffusivities obtained from a steady state 1- D power balance analysis, and the particle and parallel momentum diffusivit ies are found to be an order of magnitude smaller than chi(i)(inc).