On the relation between radiation level, central impurity concentration and helium exhaust in a burning fusion plasma

For a stationary burning fusion plasma a relation is derived and discussed which describes the close link between energy confinement, He-exhaust efficiency, central impurity density and the corresponding radiation level from impurities at the plasma boundary. Such a coherent approach helps to identify crucial parameters. Possibilities for further optimization are deduced from scalings of the radiation level with respect to the electron density, transport coefficients, impurity charge Z and He-exhaust efficiency.