Current Drive Scaling of Local Helicity Injection in the \textsc{Pegasus} Toroidal Experiment

Local Helicity Injection (LHI) is a non-solenoidal startup technique that utilizes electron current injectors at the plasma edge to initiate a tokamak-like discharge. In order to determine the scalability of LHI to MA-class facilities, it is necessary to identify the key parameters that dictate LHI performance$.$ Injection on the high-field-side (HFS) allows for the creation of discharges driven purely by helicity injection. Ohmic and stochastic confinement scalings predict a favorable non-linear relationship between $I_{p} $ and drive voltage $V_{LHI} $. Recent experiments have indicated a linear current drive scaling suggesting a constant impedance. This scaling has been observed over different levels of $B_{T} $ and MHD activity. Thomson measurements at low $B_{T} $ indicate hollow $T_{e} $ profiles that increase in $\left\langle {T_{e} } \right\rangle $ and decrease in $\left\langle \eta \right\rangle $ as the input power is increased. Despite this decrease in $\left\langle \eta \right\rangle $, the current drive scaling remains linear. At higher levels of $B_{T} $, peaked $T_{e} $ profiles ($T_{e,0} \sim 100\;$ eV) and higher $I_{p} $ are observed for the same amount of $V_{LHI} .$ These results have been compared to the first Thomson documentation of Ohmic discharges in \textsc{Pegasus} which feature $T_{e} \le 250$ eV. Calculation of neoclassical resistivity and plasma impedance from equilibrium reconstructions and Thomson data suggest this scaling result may be attributed to an increase in $Z_{eff} .$