Divertor dissipation in the DIII-D V-shaped slot divertor with strong external heating

Experiments in the DIII-D V-shaped slot divertor confirms the essential roles of target shaping, B_T and I_p on divertor dissipation with strong external heating (P_NBI~9MW). For ion B×▽B drift into the divertor, upstream density at detachment onset (T_e < 10eV) is lower by 7-12% with the outer strike point at the inner slanted baffle instead of the slot V-end. SOLPS-ITER was able to quantitatively reproduce the measured trends, indicating that the enhanced E×B drift flows lead to better dissipation and a double-peak T_e profile. Upstream density required for complete detachment remains nearly the same, regardless of the strike point position and heating power. The detachment threshold increases almost linearly, by ~35%, when I_p increases from 1MA to 1.25MA, independent of the strike point position. Reversing the B_T(ion B×▽B drift out of the divertor) shows clear benefits of lower detachment threshold, consistent with previous SAS experiments. However, the degree of detachment is less profound with target T_e still around 5eV. In-slot impurity injection of N₂ significantly reduced (~25%) the detachment threshold, accompanied by ~ 15% less confinement degradation, in both B_T directions, and in addition can aid complete detachment with ion B×▽B drift out of the divertor.