a Kinetic Model for Divertors and Pumped Limiters.

In divertors and pumped limiters, plasma flows along magnetic field lines from the scrape-off layer to a material wall where it is neutralized. The neutrals refluxing from the wall will undergo ionization and charge exchange, producing cold ions. These cold ions will increase the electric potential over that which would otherwise exist. Depending on the location of their production relative to the peak in the potential, the cold ions will flow down the potential gradient either towards the scrape-off zone or towards the wall. This problem has been examined using a largely analytical,. kinetic model. Both the case of a uniform magnetic field and the. case of a magnetic field possessing a constriction (as in a bundle. divertor) are presented. The effects of charge exchange are. discussed. Results are compared with numerical simulations by. Morse et al.('1) Simple models for use in transport codes are presented. ('1)P. Gierszewski, P. McKenty, J. McCullen, R. Morse, Phys. Rev. Lett. 49 (1982) 650.