Performance assessment of long-legged tightly-baffled divertor geometries in the ARC reactor concept
Author(s)Labombard, Brian; Kuang, A. Q.; Golfinopoulos, Theodore; Terry, J.L.; Whyte, D.G.
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Extremely intense power exhaust channels are projected for tokamak-based fusion power reactors; a means to handle them remains to be demonstrated. Advanced divertor configurations have been proposed as potential solutions. Recent modelling of tightly baffled, long-legged divertor geometries for the divertor test tokamak concept, ADX, has shown that these concepts may access passively stable, fully detached regimes over a broad range of parameters. The question remains as to how such divertors may perform in a reactor setting. To explore this, numerical simulations are performed with UEDGE for the longlegged divertor geometry proposed for the ARC pilot plant conceptual design-a device with projected heat flux power width (λq∥) of 0.4 mm and power exhaust of 93 MW-first for a simplified Super-X divertor configuration (SXD) and then for the actual X-point target divertor (XPTD) being proposed. It is found that the SXD, combined with 0.5% fixed-fraction neon impurity concentration, can produce passively stable, detached divertor regimes for power exhausts in the range of 80-108 MW-fully accommodating ARC's power exhaust. The XPTD configuration is found to reduce the strike-point temperature by a factor of ∼10 compared to the SXD for small separations (∼1.4λ [subscript]q [subcript]∥) between main and divertor X-point magnetic flux surfaces. Even greater potential reductions are identified for reducing separations to ∼1λ [subscript]q [subscript]∥ or less. The power handling response is found to be insensitive to the level of cross-field convective or diffusive transport assumed in the divertor leg. By raising the separatrix density by a factor of 1.5, stable fully detached divertor solutions are obtained that fully accommodate the ARC exhaust power without impurity seeding. To our knowledge, this is the first time an impurity-free divertor power handling scenario has been obtained in edge modelling for a tokamak fusion power reactor with λ [subscript]q [subcript]∥ of 0.4 mm. ©2019
DepartmentMassachusetts Institute of Technology. Plasma Science and Fusion Center
Wigram, M.R.K., et al., "Performance assessment of long-legged tightly-baffled divertor geometries in the ARC reactor concept." Nuclear fusion 59, 10 (2019): no. 106052 doi: 10.1088/1741-4326/AB394F ©2019
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