On the Possibility of Further Heating of a Tokamak Plasma by Microwave Injection-The Effects of Impurities

Abstract

The possibility of further heating of a Tokamak plasma by means of microwave is estimated from the energy balance equations, taking into account of the effects of impurities. For a higher density plasma the ion temperature is expected to rise with the electron temperature because of electron-ion coupling, even when all the wave power is derectly absorbed by the electrons.The high-Z element impurity fraction in the plasma must, however, be limited to a low level to obtain an efficient ion heating. For example, the fraction of molybdenum impurity must be lower than about 0.01 %, when a 60 m3 plasma of density of 8 ×1013 cm-3 is to be heated up to 4 keV of the ion temperature by 10 MW microwave injection.