Double-Helix Current Drive for Tokamaks

Double sets of $m=1\mathrm{}$ helical coils fed by appropriately phased radio-frequency currents are shown theoretically to be capable of driving both toroidal and poloidal currents in a toroidal plasma by means of the nonlinear Hall effect. It is shown that total toroidal current is optimized when the ratio of the plasma circumference to the pitch length of the helical coils is 1.35.