Spheromak formation by steady inductive helicity injection

Since the last IAEA meeting, new understanding and parameters have been achieved on the Helicity Injected Torus with Steady Inductive helicity injection current drive (HIT-SI) experiment. The experiment has a bowtie shaped spheromak confinement region with two helicity injectors. The inductive injectors are 180 degree segments of a small, oval-cross-section RFP. The Taylor-state model is shown to agree with HIT-SI surface and internal magnetic profile measurements. Helicity balance predicts the peak magnitude of toroidal spheromak current and the threshold for spheromak formation. The model also accurately predicts the division of the applied loop voltage between the injector and spheromak regions. Spheromaks with currents up to 29 kA have been produced. (author)