Pedestal fueling variation in a closed divertor configuration at DIII-D

The role of particle fueling on the pedestal was examined in a closed divertor geometry at DIII-D. By varying fueling schemes between gas puff and pellet injection, the particle source location was increased in the core relative to the edge. Discharges with particle injection rates from 5 to 40 Torr L s^-1 in combination with either neutral beam heating (which contributes to central fueling) or electron cyclotron heating (no fueling) were compared. The different fueling schemes, which are expected to vary the particle source profile, were shown to impact the density pedestal structure, which in turn affects stability and plasma performance. Equilibria and profiles are generated using CAKE (an automatic kinetic equilibria generating tool), and transport properties and heating schemes are investigated with TRANSP. Pellet injection is shown to significantly increase the pedestal top density and flatten the maximum electron temperature gradient, whereas increased gas puff shifts the density profile radially outwards.