Divertor footprint modeling due to RMP in HL-2A and role of plasma response

Abstract

The divertor heat flux footprint is modeled for the HL-2A discharge, in the presence of the resonant magnetic perturbation (RMP) applied to control the edge-localized mode. Both the magnetic field lines and the guiding-center drift orbits of test thermal ions are traced, based on the computed plasma response to the RMP. Toroidal modeling identifies a reason—a vertical shift of the plasma separatrix—for the observed upper shift of the heat flux footprint during the initial phase of the RMP application in the experiment. While both the field-line tracing and particle orbit tracing replicate the experimental observation reasonably well, the latter approach is found to produce results that better align with the measured heat flux peaking along the divertor leg. A sensitivity investigation of the simulated footprint location and width against the assumed plasma response models—the conventional fluid model, the fluid model with strong parallel sound wave damping (SWD), and magnetohydrodynamic-kinetic hybrid mode—reveals that the fluid model with SWD yields the best agreement with the experiment, due to the fact that this model produces a stronger field response inside the plasma. These toroidal modeling results, while helping explain and interpret the experimental observations in HL-2A, provide physics insight to guide divertor footprint control via RMP in the future high-performance experiments in devices such as HL-3.

Keywords

• RMP
• divertor footprint
• plasma response model
• HL-2A