Abstract
For long pulse operation of fusion reactors, it is important to reduce sputter-erosion and power loading of the divertor target by means of plasma detachment. It has been reported that the small-angle-slot (SAS) divertor employed by the DIII-D tokamak can initiate detachment at a relatively low upstream plasma density as it can effectively dissipate heat by concentrating neutrals near the target. Motivated by these findings in DIII-D, we investigated the effects of a SAS-like divertor in KSTAR using SOLPS-ITER simulations without drifts. One remarkable feature revealed by our simulation study is that even a very shallow SAS can lead to a considerably lower heat load on the divertor target than the original flat, open divertor of KSTAR. Deuterium neutrals are concentrated along the divertor separatrix line in the shallow SAS, while deuterium density in the open divertor peaks in the far-scrape-off layer. Furthermore it was found that the neutral density and temperature-drop induced by SAS are both fairly incentive to the depth of the slot. The highest heat dissipation was obtained for a SAS depth of 10.3 cm.
Highlights
Advanced tokamaks and future reactors require long-pulse operation, which inevitably entails new divertor designs that can significantly reduce the heat flux and temperature at the divertor targets
Motivated by these findings in DIII-D, we investigated the effects of a SAS-like divertor in KSTAR using SOLPS-ITER simulations without drifts
One remarkable feature revealed by our simulation study is that even a very shallow SAS can lead to a considerably lower heat load on the divertor target than the original flat, open divertor of KSTAR
Summary
Advanced tokamaks and future reactors require long-pulse operation, which inevitably entails new divertor designs that can significantly reduce the heat flux and temperature at the divertor targets. The general conclusion of these studies is that the higher the closure is, the higher the neutral particle density at the divertor target is, and detachment can be obtained at lower upstream densities. The high correlation between neutral particle density and electron temperature at divertor targets has been reported in several studies (see [22] and references in [23]) Based on these results and additional studies [21–24], DIIID installed a small angle slot (SAS) divertor [25, 26], to obtain more efficient heat dissipation than with conventional divertor shapes. Through numerical simulations using the SOLPS-ITER package [27–31] (but without particle drifts), we examined SASlike divertors in the KSTAR tokamak geometry to identify the factors that dominate the volumetric heat loss near the target (see reference [32, 33] for general characteristics of KSTAR).
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