Target plate conditions during stochastic boundary operation on DIII-D

Abstract

A major concern for large tokamaks like ITER is the presence of edge localized modes (ELMs) that repeatedly send large bursts of particles and heat into the divertor plates. Operation with resonant magnetic perturbations (RMP) at the boundary of DIII-D has suppressed ELMs for values of q95∼3.7. At the target plate, the conditions during ELM-suppressed operation for both high and low collisionality are observed by a set of radially distributed Langmuir probes. At high collisionality (νe∗∼1), the target plate particle flux and temperature drop by >30% during ELM suppression. At low collisionality (νe∗∼0.1), the core density, target plate density, and target plate particle flux drop but the plate electron temperature increases after the ELMs are suppressed. The ELM-suppressed target plate heat flux is nearly the same as the heat flux between ELMs but the (5× higher) transient heat flux peaks due to ELMs are eliminated.