SPHEROMAK FORMATION BY STEADY INDUCTIVE HELICITY INJECTION

Steady Inductive Helicity Injection (SIHI) is a novel method for driving current in toroidal magnetized plasmas. The HIT-SI device uses two inductive injectors (with odd toroidal symmetry), oscillating at 5.8 kHz, to form and sustain a steady state spheromak (with even toroidal symmetry) through non-linear relaxation. HIT-SI has formed spheromaks with up to 29 kA of toroidal current, using less than 6 MW of injected power, a much lower power threshold for spheromak production than previously observed. Internal and external magnetic field measurements are well-matched by a theory-based Taylor-state equilibrium model, including the field oscillations driven by the injectors.