Assessment of Impurity Content and Radiated Power in LHI discharges on the \textsc{Pegasus} ST

Local Helicity Injection (LHI) is routinely used in the \textsc{Pegasus} ST to produce high-performance discharges with $I_{p} \le 0.24$ MA, $n_{e} \approx 10^{19}$ m$^{\mathrm{-3\thinspace }}$and $T_{e} \approx 100$ eV. Recent experiments show that the impedance of the plasma is independent of the helicity drive as $I_{p} $ scales linearly with $V_{LHI} $. One possible explanation of this behavior would be that $Z_{eff} $ and the plasma resistivity increases with $I_{p} $. To examine this possibility an assessment of radiated power and impurity concentration is being done in \textsc{Pegasus} using a tangential bolometer array, VB spectroscopy and a SPRED VUV spectrometer. Discrete line radiation from N and O are at least 10$\times $ higher during LHI than Ohmic. A broadband spectrum at $\lambda \le 35$ nm is observed during LHI but absent during Ohmic discharges. Radiated power increases rapidly with $V_{LHI} $, suggesting an increase in $Z_{eff}_{\mathrm{\thinspace }}$as $I_{p} $ increases. Initial observations suggest Bremsstrahlung radiation measurements are infeasible during LHI but may be measured during an Ohmic phase in an LHI-Ohmic handoff scenario. To quantify estimates of impurity content, a new multichannel diode bolometer array with full coverage across the plasma is being developed.