Overview of Recent DIII-D Experimental Results

DIII-D research advances scientific understanding for ITER and future tokamak fusion reactors. Applied resonant magnetic perturbations (RMPs) increase confinement and stabilize peeling ELMs in a newly identified “pump in” regime. Experiments in H plasmas find a critical D fraction is required to maintain RMP ELM suppression. Multimodal plasma response to applied 3D fields explains heat and particle flux structures at the divertor. The benefits of divertor closure disappear in the deeply detached state. High q_min steady state scenarios benefit from broadening the energetic particle profile in a high bootstrap fraction, noninductive plasma. Transport studies quantify the particle pinch and diffusion in the pedestal after edge localized modes (ELMs); others show micro-tearing modes can dominate electron heat transport in ELMy H-mode pedestals. Multi-Z impurity studies show that the ion thermal gradient instability and the ∇n trapped electron mode dictate transport, with a radially varying Z dependence. Radial core transport events seen at reduced mean E_rxB shear flow may explain confinement degradation in high-collisionality H-modes. Experiments and theory show that fast ions drive β-induced Alfven eigenmodes, while the newly identified low-frequency Alfven mode is driven by T_e. Explorations of a negative triangularity (NT) reactor concept show that fast ions from counter-/co-current neutral beam injection de/stabilizes sawtooth crashes, and that a low-n MHD mode triggers NT ELMs at a critical pressure gradient.