Behaviour of the particle transport coefficients near the density limit in the microwave tokamak experiment

The perturbed particle transport coefficients have been obtained in MTX with the use of a gas modulation technique for a scan of densities at constant Ip and Bt. Near the Greenwald density limit there is a dramatic increase in both the perturbed diffusion coefficient and the convection coefficient, which is most pronounced in the outer portion of the plasma but also extends well into the plasma core. The coefficient profiles provide evidence that the mechanism responsible is confined to regions of relatively low temperature and causes the particle transport coefficients to increase through an inverse dependence on Te and/or LTe. (author). 24 refs, 7 figs