Development of Non-Solenoidal Tokamak Startup on the \textsc{Urania} Experiment

Initiation of plasma current without a central solenoid is a critical scientific goal for the spherical tokamak (ST). Following several campaigns on the \textsc{Pegasus} Toroidal Experiment using local helicity injection (LHI), which achieved $I_{p} >0.2$ MA without use of an Ohmic solenoid, the facility is being shut down to upgrade into the Unified Reduced $A$ Non-Inductive Assessment (\textsc{Urania}) experiment. This enhancement to the \textsc{Pegasus} facility will remove the central solenoid entirely, increase the toroidal field a factor of 4, up to 0.6 T, and investigate a variety of non-inductive startup techniques, including LHI, transient and sustained coaxial helicity injection (T- and S-CHI), poloidal field induction, and EBW radiofrequency heating and possibly current drive. A next-generation LHI system is being designed and built for \textsc{Urania}. Unlike the previous circular plasma-cathode electron sources used for LHI, this injector has a curved-slot arc channel of 1 cm width and 16 cm in length that is mounted off of a re-entrant port. This geometry allows for large $A_{inj} $ for helicity input, while keeping $w_{inj} $ low for a high Taylor limit, and matches the plasma edge curvature. A prototype of this design is currently in fabrication for initial testing with $I_{inj} $ from 8--16 kA, and $V_{inj} $ up to 1 kV.