Non-inductive current generation in NSTX using coaxial helicity injection

Abstract

Coaxial Helicity Injection (CHI) on the National Spherical Torus Experiment (NSTX) has produced 240kA of toroidal current without the use of the central solenoid.Values of the current multiplication ratio (CHI produced toroidal current / injector current) up to 10 were obtained, in agreement with predictions.The discharges which lasted for up to 200ms, limited only by the programmed waveform are more than an order of magnitude longer in duration that any CHI discharges previously produced in a Spheromak or a Spherical Torus (ST).