Effect of B-Field Dependent Particle Drifts on ELM Behavior in the DIII-D Boundary Plasma

ELM effects in the DIII-D pedestal and boundary plasmas were measured with multiple fast diagnostics in matched, lower single null, ELMing H-mode discharges with the ion Bx(gradient)B drift toward and away from the divertor. Data show a strong dependence of the delay in inner vs. outer divertor ELM Dalpha emission on drift direction, and a weaker drift dependence of the inner vs. outer delay of the total radiated power, in addition to the strong density dependence seen in previous work [1]. Time dependent modeling of the boundary plasma during an ELM was done with the UEDGE code including a six-species fluid carbon model and the effect of B-field induced particle drifts [2]. The ELM perturbation was modeled as an instantaneous, outer midplane peaked, increase of diffusion coefficients from the top of the pedestal to the outer SOL. The simulations show delays in the ELM perturbation at the inner vs. outer divertor targets that are similar to the measured delays