Ion Temperature Measurements in the \textsc{Pegasus} Toroidal~Experiment

Ion temperature measurements are being made on the \textsc{Pegasus}~Toroidal~Experiment in OH and helicity-injection driven plasmas using thermal Doppler broadening of emission spectra. The system consists of a 0.75 meter~monochromator~with UV sensitive optics, an image intensifier, and a high speed imaging system that can achieve a 5 kHz frame rate.~Presently the system achieves a spectral resolution of 0.21 {\AA}, and collects light over a single radial chord. Of particular interest is the ion temperature evolution during non-solenoidal startup using point source helicity injection. Turbulent magnetic reconnection during helicity injection is expected to provide strong ion heating, as seen in lab and astrophysical plasmas. Indeed, $\left\langle {T_i } \right\rangle $ is measured to be $\sim $ 0.5 keV while $\left\langle {T_e } \right\rangle $ is estimated to be $\le 0.1$ keV from passive impurity spectroscopy. Presently the system is used to compare the $T_i $ evolution of plasmas produced through helicity injection, OH drive, and hybrid current drive scenarios. Future upgrades will provide plasma rotation measurements using multiple tangential views in \textsc{Pegasus}.