Density distributions of impurities and related energy losses in tokamak plasmas

Stationary density distributions of impurities as carbon, oxygen and iron in various states of ionization and related energy losses in tokamak plasmas are calculated numerically, taking into account cross-field classical and anomalous diffusions and ionization-recombination processes. The numerical model provides results in good agreement with ST and TFR experiments. The diffusion of impurity ions is not classical, and the energy losses by impurities cause the strong cooling of the plasma near the boundary. The energy losses will become more serious in a large tokamak of the next generation, since they amount to 0.1 MW/m3 of power loss at a concentration of 5-10% carbon, 2-5% oxygen or 0.1-0.3% iron. (auth.)