Analysis of classical impurity transport

Abstract

This work is an application of Braginskii's classical theory of particle transport to partially ionized plasmas in cylindrical geometry or toroidal geometry in the Pfirsch-Schlüter regime. Particular attention is given to the steady state, for which density and flux distributions are determined, and the re-cycling phenomenon is analysed. On the assumption of coronal equilibrium, numerical computation shows that, although the centrifugal and centripetal fluxes of ions of a particular ionization degree may be large, the electron and global ion fluxes are usually small, in contrast with experimental results. Possible anomalous fluxes are necessarily linked with violation of coronal equilibrium; in this case, a transport equation for the mean ionization degree is given as a substitute to the coronal hypothesis. Numerical simulation also shows the significance of friction between ions of the same impurity and different impurities, for common impurity concentrations.