Predictive modeling of a slot divertor in high triangularity double null magnetic topology using SOLPS-ITER

Simulations of double null divertor detachment reveal up/down power flow asymmetry due to the impact of divertor closure on the convected heat fraction in each divertor. Here, an assumed upper V-shaped divertor and a lower open divertor in DIII-D are investigated numerically using the SOLPS-ITER code [1] to predict closed divertor conditions and to study particle and heat balance. The simulations employ a symmetric double null magnetic topology with high triangularity ($/delta = 0.87$) to be used in DIII-D’s initiative for increased volume and plasma shaping. Boundary input power is 4 MW and upstream electron density is scanned around a nominal value of $10^{19}$ m$^{-3}$. Both conducted and convected heat fluxes flow toward the lower horizontal target. For the upper slot divertor, conducted heat flows into the slot as expected; however, convected heat flows out of the slot and is carried mainly by electrons. This heat flux reversal causes an asymmetry in the power entering the upper slot and lower divertors. A similar heat flux reversal is observed at the entrance to the slot divertor in single null simulations [2].

[1] X. Bonnin et al., Plasma Fusion Res. 11, 1403102 (2016).

[2] R. Maurizio et al., this conference.