Generation of hot closed helical bands by electron cyclotron resonance heating of rational-q tokamak flux surfaces

The r.f. heating of three classes of Tokamak flux surfaces which intersect the electron cyclotron resonance heating region is discussed. On irrational-q surfaces, the degree of heating is the same for all electrons. On and near rational-q surfaces, heating is localised to closed helical bands of electrons. These hot bands support local enhancements of current density, and act as current-carrying filaments within the plasma. The poloidal magnetic field associated with these currents has X-points. The use of ECRH as a current drive mechanism will enhance these effects, as will an increase in the size of Tokamak major radius. (author)