Investigating the generation of intrinsic rotation via turbulence-driven Reynolds Stress

Understanding the generation of intrinsic rotation in fusion plasmas is essential to ensure stable operation and good confinement. The mechanism of intrinsic rotation generation via turbulence-driven Reynolds Stress is investigated at DIII-D using 2D BES and UF-CHERS fluctuation measurements. Beam Emission Spectroscopy (BES) measures long wavelength (k_⊥ρ_s<1) density fluctuations, which can be used to calculate turbulence characteristics and a 2D velocity field (ṽ_r, ṽ_Θ). Ultra-Fast Charge Exchange Recombination Spectroscopy (UF-CHERS) measures ion temperature and toroidal velocity fluctuations (ṽ_Φ). Multi-field correlation analysis shows that density and toroidal velocity exhibit correlated broadband fluctuations in the local turbulence. Poloidal〈ṽ_rṽ_Θ〉and toroidal〈ṽ_rṽ_Φ〉Reynolds Stress are calculated with the measured velocity fluctuations. An additional experiment will be conducted at DIII-D to perform a scan of with ECRH and vary via plasma current, which enables studies of their effects on the dominant instabilities, turbulence characteristics, turbulent momentum transport, Reynolds Stress, and generation of intrinsic rotation.