Reduced-model turbulence (nSOLT) simulations comparing three fueling scenarios: neutral puffing (SOL), divertor recycling (edge) and injection from the core

The 2D scrape-off-layer turbulence code (nSOLT) includes 1D Boltzmann neutral-plasma interactions [1], a model of divertor recycling (introduced here), and a fixed source of plasma concentrated at the core-side boundary. 1) Neutral injection in the far-SOL is accomplished by specifying the density of Franck-Condon distributed neutrals, n$_{\mathrm{puff}}$, streaming in from the boundary. 2) Divertor recycling is modeled by injecting a fraction of the particle parallel flux in the SOL back into the edge region as a source of plasma, while 3) the fixed source fuels the edge plasma from the core-side boundary, as in neutral beam injection. For machine parameters (B, R, L$_{\mathrm{//}})$ anticipated at MAST-U, and for a deuterium plasma, turbulent equilibria are obtained that share the same plasma fueling rate for each of the three fueling methods, with only one of the sources ``on'' in each case. Equilibrium plasma and neutral (deuterium) profiles, fueling efficiencies, SOL transparencies, heat flux widths and confinement times are compared. Skewness, cross-phase and spectral measurements of the turbulent fluctuations are presented. [1] D.A. Russell, J.R. Myra and D.P. Stotler, Phys. Plasmas \textbf{26}, 022304 (2019).