Core tungsten effects and transport in DIII-D high poloidal beta (b_p) scenario with the SAS-VW divertor

Core tungsten (W) effects and transport are for the first time analyzed in DIII-D high poloidal beta (b_P) scenario with a Small Angle Slot V-shaped W-coating (SAS-VW) upper divertor. It is found that high b_P (>2) plasma performance is not degraded by this W divertor in the lower density regime (line average electron density n_e<6×10¹⁹m^-3) without internal transport barriers (ITBs) although the W concentration is larger than 10^-4 from Soft-X Ray (SXR) inversion and from the Survey Low Resolution Extended Domain (SPRED) Spectrometer diagnostic. The ratio of total radiation inside the separatrix diagnosed by bolometry to NBI power is about 30%. In addition, the central (r<0.3) W profile is also peaked with a peaking factor of 4 modeled by TGLF and NEO. Hence it seems that the high b_P scenario is resilient to core impurity content and can tolerate more W than other scenarios [1]. In the high-density regime (Greenwald fraction of the line-averaged density f_Gr>1) with large radius ITBs, it is found that there is strong W screening generated by the near-zero density gradient (rather than via T_i screening) in the core region around 0.5<r<0.9, which decreases the core radiation significantly. Furthermore, by reducing the pedestal height in the density channel and reducing core toroidal rotation to optimize the high b_P scenario [2], it is possible to realize full radius (central, core and pedestal) W control in the high b_P scenario with ITBs.