Current sustainment by synchrotron radiation in a tokamak device

Current drive using anisotropic synchrotron radiation in a tokamak device is considered. A relativistic formulation of the current drive efficiency, which includes both momentum transfer and asymmetric resistivity, is presented. The explicit computation of the current drive efficiency is performed for a Maxwellian plasma using Trubnikov’s theory of radiation [in Reviews of Plasma Physics, edited by M. A. Leontovich (Consultants Bureau, New York, 1979), Vol. 7, p. 345]. The effect of the various synchrotron harmonics on the total generated current is examined, and it is shown that most of the contribution comes from a few harmonics near n=ω/ωc≫1 for which the corresponding resonant velocities are in the same direction. The general properties of the synchrotron radiation and its capability to generate current in a reactor are also briefly discussed.