Electron density and ion temperature measurements of HIT-SI3 and HIT-SIU spheromak plasmas

The HIT-SI3 and subsequent HIT-SIU devices study application of steady inductive helicity injection, using multiple injectors driven with frequencies in the 10's of kHz, to form and sustain spheromak plasmas. The final run campaign of the HIT-SI3 experiment at the University of Washington produced discharges with record performance, including toroidal plasma current exceeding 100 kA, the first experimental observations of peaked plasma density profiles during sustainment as measured by a new multi-chord interferometer, and impurity ion temperatures up to 40 eV. Comparisons to initial results from the new HIT-SIU experiment, which provides additional control over the applied mode spectrum and plasma density, will be presented.