Empirical Tokamak scaling

Experimental results from a large number of Tokamaks have been collected. It is shown that the measured energy-confinement times are consistent in the sense that they may be represented (accurately) by simple empirical formulas. These formulas are used in predicting the ohmically heated temperatures in future Tokamaks. The predicted temperatures are similar to but slightly lower than those in present machines. The central electron temperature is about 0.5 to 1 keV. This result emphasizes the point that substantial additional heating will be required for the attainment of ignition temperature.