Access to and Characterization of Ohmic H-mode Plasmas at Near-Unity Aspect Ratio

The low H-mode transition power threshold at near-unity aspect ratio allows access to H-mode in the \textsc{Pegasus} experiment with only Ohmic heating. Ohmic H-mode plasmas are achieved in both a limited and a new separatrix-limited magnetic configuration. H-mode is attained with high-field-side centerstack fueling, with densities from 1 to \textgreater\ 3x10$^{19}$ m$^{-3}$ and Greenwald fractions $\sim $ 0.2--0.7 for $I_{p} \sim 0.13$ MA. Compared to L-mode plasmas, H-modes show: a doubling of the stored energy; reduced D-$\alpha $ emission; edge current pedestal with characteristic width of $\sim $ 2 cm, with 6 cm for L-mode; reversal of the edge toroidal flow from counter-current to co-current; reduced V-sec consumption due to increased temperatures; and ELM excitation. Operation at A $\sim $1.15 results in strong particle trapping, f$_{T}\sim $ 0.7 -- 0.9, and associated neoclassical effects even at modest plasma temperatures so that P$_{OH}\sim $0.4 MW, which readily surpasses the estimated threshold power of \textless~0.1 MW. Low-field-side fueling appears to degrade access to and quality of the H-mode plasma. Characterization of H-mode access in \textsc{Pegasus} will provide unique data at near-unity A and guide detailed studies of ELM dynamics, as well as provide a critical tool for exploring the extremely high-$\beta_{T}$ regime at A $\sim $ 1.