Tokamak MHD equilibrium generation by narrow-spectrum fast-wave current drive

Abstract

One key to achieving high beta in a tokamak may be the proper control of the plasma pressure and current density profiles. In principle, if steady-state RF current drive is used, the current density may be tailored by a careful selection of the wave frequency and the power spectrum. This study uses the selfconsistent theory of RF current drive in an axisymmetric torus to compute the MHD equilibrium generated by the fast (magnetosonic) wave current driver. This is accomplished by iterations in a calculation of the MHD equilibrium for a given diamagnetism function, F(ψ) = RBt, and a ray-tracing calculation which determines F(ψ). The various wave and plasma characteristics which determine the equilibrium are examined, and it appears possible to create a large diversity of equilibria.