Modelling of plasma and impurity behaviour in a tokamak with a stochastic layer1

Transport of charged particles and heat in a stochastic layer at the plasma edge are discussed. Results of numerical modelling by the one-dimensional code RITM of particle and energy balance in Tore–Supra discharges with and without ergodic divertor are presented and compared with the experimental data. The effects of stochastization on the radiation losses from impurities and on impurity concentration in the plasma core are analyzed on the basis of simple analytical models.