A measurement of hydrogen ion transport parameters in Tokamak discharges

By modulating the small gas feed required to maintain a steady-state Tokamak discharge a small density perturbation may be induced from whose propagation particle transport parameters may be adduced. Experiments in TEXT show that the phenomena may be adequately described by a simple model with constant diffusion plus inward convection except near the density limit. Diffusion coefficients and convective velocities has been determined for a broad range of hydrogen discharges and found to scale approximately as (nq) -1 . The results are plausibly related to impurity transport parameters, thermal diffusivity, and particle confinement times. Diffusion coefficients for deuterium are systematically lower than for hydrogen.