Radiation losses from oxygen and iron impurities in a high-temperature plasma

Abstract

Radiation and ionization losses due to impurities present in a high-temperature plasma have been calculated for a light element (oxygen), which is completely stripped in the core of existing tokamak discharges, and a heavy one (iron), which is only partially stripped. Two extreme cases have been treated: a) corona equilibrium is attained; the radiated power is then equal to the product of electron density n_e, impurity density n_imp, and a function of the electron temperature, T_e; b) impurities re-cycle with a constant radial velocity v₀ (either inwards or outwards) in a background plasma (represented by the radial profiles of n_e and T_e). In this case, radiation and ionization losses are proportional to the impurity flux ψ_imp and are a decreasing function of the diffusion velocity v₀. The results presented can be used to evaluate losses in a practical case.