Overview of Recent DIII-D Experimental Results

Recent DIII-D experiments leveraged novel actuators, diagnostics and modeling tools to advance the physics basis for ITER and fusion pilot plants. Pressure broadening for AE control from toroidally steerable off-axis NBI and injection of high harmonic FW from a helicon antenna were demonstrated. Feedback control of density and radiated power enabled super H-mode plasmas with 100% radiative fraction. Enhanced divertor dissipation was obtained by injection of low-Z powders. Fast-ion phase space measurements of unprecedented resolution discovered inward transport by AE. Ultrafast active spectroscopy revealed a weak role of T_e/T_i on long-wavelength T_i fluctuations. Fast local magnetic field measurements over an ELM cycle showed complex pedestal current density redistribution. Frequency bands characteristic of H-mode pedestal fluctuations were reproduced with a reduced model for microtearing modes. Advanced polarimetry observed internal n=3 magnetic fluctuations preceding the n=1,2 tearing modes (TM) that limit high-qmin scenarios. By integrating a TM onset model into scenario modeling, TM stable solutions for non-inductive, β_N>4 operation were identified. The magnetic pre-sheath was characterized with micro-engineered divertor targets, validating theoretical models applicable to ITER and pilot plants.