Runaway electrons as a diagnostic of magnetic fluctuations (invited)

The transport of runaway electrons in a hot plasma can be comparatively easily measured by perturbation experiments which provide a runaway electron diffusivity D. The diffusion can be interpreted in terms of a magnetic fluctuation level, from which an electron thermal diffusivity can be deduced. We find the runaway electron diffusion coefficient is determined by intrinsic magnetic fluctuations rather than electrostatic fluctuations because of the high energies involved. The results presented here demonstrate the efficacy of using runaway transport techniques for determining intrinsic magnetic fluctuations.