Effect of Scrape-Off-Layer Current on Reconstructed Tokamak Equilibrium

Abstract

Methods are described that extend fields from reconstructed equilibria to include scrape-off-layer current through extrapolated parametrized and experimental fits. The extrapolation includes both the effects of the toroidal-field and pressure gradients which produce scrape-off-layer current after recomputation of the Grad-Shafranov solution. To quantify the degree that inclusion of scrape-off-layer current modifies the equilibrium, the $\chi$-squared goodness-of-fit parameter is calculated for cases with and without scrape-off-layer current. The change in $\chi$-squared is found to be minor when scrape-off-layer current is included however flux surfaces are shifted by up to 3 cm. The impact on edge modes of these scrape-off-layer modifications is also found to be small and the importance of these methods to nonlinear computation is discussed.

14 pages

References in corpus (2)

• The Impact of Collisionality, FLR and Parallel Closure Effects on Instabilities in the Tomakak Pedestal: Numerical Studies with the NIMROD code
• NIMROD Modeling of Quiescent H-mode: Reconstruction Considerations and Saturation Mechanism

Cited by in corpus (1)

• MHD modeling of a DIII-D low-torque QH-mode discharge and comparison to observations