Demonstration of Tokamak Ohmic Flux Saving by Transient Coaxial Helicity Injection on NSTX

Transient Coaxial Helicity Injection (CHI) started discharges in NSTX have attained peak currents up to 300 kA and when these discharges are coupled to induction, it has produced up to 200 kA additional current over inductive-only operation. CHI in NSTX has shown to be energetically quite efficient, producing a plasma current of about 10 A/Joule of capacitor bank energy. In addition, for the first time, the CHI produced toroidal current that couples to induction continues to increase with the energy supplied by the CHI power supply at otherwise similar values of the injector flux, indicating the potential for substantial current generation capability by CHI in NSTX and in future toroidal devices.