Turbulence Decorrelation via Controlled $E$x$B$ Shear in High-Performance Plasmas

Multi-scale spatiotemporal turbulence properties are significantly altered as toroidal rotation and resulting ExB shearing rate profile are systematically varied in advanced-inductive H-mode plasmas on DIII-D ($\beta_N\approx$2.7, $q_{95}$=5.1). Density, electron and ion temperature profiles and dimensionless parameters ($\beta_N$, $q_{95}$, $\nu^*$, $\rho^*$, and $T_e$/$T_i$) are maintained nearly fixed during the rotation scan. Low-wavenumber turbulence ($k_\bot\rho_S < 1$), measured with Beam Emission Spectroscopy, exhibits increased decorrelation rates (reduced eddy lifetime) as the ExB shear rises across the radial zone of maximum shearing rate (0.55$ < \rho < 0.75$), while the fluctuation amplitude undergoes little change. The poloidal wavenumber is reduced at higher shear, indicating a change in the wavenumber spectrum: eddies elongate in the direction orthogonal to shear and field. At both low and high shear, the 2D turbulence correlation function exhibits a tilted structure, consistent with flow shear. At mid-radius ($\rho\sim$0.5), low-k density fluctuations show localized amplitude reduction, consistent with linear GYRO growth rates and $\omega _{ExB}$ shearing rates. Intermediate and high wavenumber fluctuations measured with Doppler Back-Scattering ($k_\bot\rho_S\sim$2.5-3.5) at $\rho$=0.7 and Phase Contrast Imaging ($k_\bot\rho_S > 5$) exhibit decreasing amplitude at higher rotation. The energy confinement time increases from 105 ms to 150 ms as the toroidal Mach number (M=$v_{TOR/vth,i}$) increases to ${M_o} \approx$ 0.5, while transport decreases. TGLF calculations match the $T_i$ profile with modest discrepancies in the $T_e$ and $n_e$ profiles. These results clarify the complex mechanisms by which ExB shear affects turbulence.