Critical Impurity Concentrations for Power Multiplication in Beam-Heated Toroidal Fusion Reactors

Abstract

Using the most recent evaluations of power loss by impurity radiation, we have calculated the maximum permitted impurity concentration for various species as a function of Q, the ratio of deuterium-tritium (D-T) fusion power to injected beam power. These criteria for maximum impurity concentration must be satisfied before applying the usual n_eτ_E versus T_i conditions for obtaining a given Q value. For , the critical impurity concentration f_cz varies as Z^{−2.2 to −2.5}. The tolerable concentration of medium- and high-Z impurities for operation at low can be at least one order of magnitude larger than the concentration allowed for ignition, provided that the plasma temperature is maintained by reacting ion beams.