Effects of Internal Disruptions on Impurity Transport in Tokamaks

The effects of diffusion, convection, and internal disruptions on impurity profile evolution in tokamaks are investigated by use of experimental measurements, numerical simulations, and a new analytic eigenfunction formalism for confinement times and profile shapes. Experimental observations on the Alcator-$C$ tokamak show that internal disruptions flatten radial profiles of impurity densities in the plasma core, and theoretical calculations indicate that periodic internal disruptions should significantly decrease impurity confinement times under some circumstances.