The reactor physics requirements are outlined in terms of characteristic performance measures. Four reactor designs of different scope are taken as examples. ITER is based on the ELMy H-mode as an operating regime demonstrated over many energy confinement times. Designs for power producing reactors require higher power densities and bootstrap current fractions, and therefore higher values of normalized . The capability of different enhanced confinement regimes, combining internal transport barriers with the L- or H-mode edge to satisfy these demands, together with the requirements on helium pumping and divertor power load, is discussed.
Possible divertor solutions for a fusion reactor.: Part I. Physical aspects based on present day divertor operation