On the extrapolation to ITER of discharges in present tokamaks

An expression for the extrapolated fusion gainG=Pfusion/5Pheat(Pfusionbeing the total fusion power andPheatthe total heating power) of ITER in terms of the confinement improvement factor (H) and the normalized beta (βN) is derived in this paper. It is shown that an increase in normalized beta can be expected to have a negative or neutral influence onGdepending on the chosen confinement scaling law. Figures of merit like should be used with care, since large values of this quantity do not guarantee high values ofG, and might not be attainable with the heating power installed on ITER.