Current drive experiments in the HIT-II spherical tokamak

Abstract

The Helicity Injected Torus programme has made progress in understanding relaxation and helicity injection current drive. Helicity conserving MHD activity during the inductive (ohmic) current ramp demonstrates the profile flattening needed for coaxial helicity injection (CHI). Results from cathode and anode central column CHI pulses are consistent with the electron locking model of current drive from a pure n = 1 mode. Finally, low density CHI, compatible with ohmic operation, has been achieved. Some enhancement of CHI discharges with the application of ohmic heating is shown.