Low-Z impurity transport in tokamaks

Abstract

Low-Z impurity transport in tokamaks was simulated with a one-dimensional impurity transport model including both neoclassical and anomalous transports. The neoclassical fluxes are due to collisions between the background plasma and impurity ions as well as to collisions between the various ionization states. The evaluation of the neoclassical fluxes takes into account the different collisionality regimes of the background plasma and the impurity ions. A limiter scrape-off model is used to define the boundary condition for the impurity ions in the plasma periphery. To account for the spectroscopic measurements of power radiated by the lower ionization states, fluxes due to anomalous transport are included. The sensitivities of the results to uncertainties in rate coefficients and plasma parameters in the periphery are investigated. The implications of the transport model for spectroscopic evaluation of impurity concentrations, impurity fluxes, and radiated power from line emission measurements are discussed.