Electron Heating Studies of Helicity Injection Plasmas on the Pegasus-III Experiment*

DC helicity injection (HI) shows promise as a non-solenoidal method of plasma initiation for fusion power. To explore HI's effectiveness, detailed investigations of the electron heat transport and confinement are ongoing. The Multi-Point Thomson Scattering (MPTS) system on the Pegasus-III experiment was used to capture electron temperature (T_e) profiles in HI plasmas. T_e profiles have shown HI plasmas created by local HI (LHI) tend to start peaked at around 60 eV and become hollow over the duration of a discharge with core T_e near 20 eV and edge T_e around 50–60 eV. This T_e evolution, combined with AXUV measurements, suggests plasma material interaction is causing significant radiative power loss. Experiments to investigate the effects helicity input and electrode voltage have on T_e are underway to find ways to burn through this radiation limit and create plasmas with peaked electron temperature profiles through the whole LHI discharge. Future studies will compare these profiles with ones from transient coaxial HI (T-CHI) plasmas. The novel T-CHI system design aims to limit the impurities that similarly limited sustained CHI plasmas, presenting an opportunity to examine HI plasmas and their capabilities with fewer contaminants.