Physics of Plasmas
American Institute of Physics Inc.
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 χ-squared goodness-of-fit parameter is calculated for cases with and without scrape-off-layer current. The change in χ-squared is found to be minor when scrape-off-layer current is included; however, flux surfaces are shifted by up to cm3 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.
King, J.R., Kruger, S.E., Groebner, R.J., Hanson, J.D., Hebert, J.D., Held, E.D., Jepson, J.R. Effect of scrape-off-layer current on reconstructed tokamak equilibrium (2017) Physics of Plasmas, 24 (1), art. no. 012504, .