Electron Thermal Transport and Multi-scale Turbulence in Low Collisionality H-mode Plasmas

Electron thermal transport and the role of local ITG/TEM/ETG-scale core turbulence are investigated in high temperature DIII-D H-mode/QH-mode plasmas at ITER-relevant electron to ion temperature ratio ($0.5\leq T_e/T_i \leq 1.2$) and collisionality ($\nu_e^*\sim 0.05$). The $T_e/T_i$ ratio is varied using central ECH ($P_{ECH}\leq 2.7\,$MW). Experimentally determined H-mode electron transport fluxes and turbulence wavenumber spectra are directly contrasted with nonlinear gyrokinetic (GYRO) simulations results. The effects of $E\times B$ shear on core ITG/TEM-scale turbulence are studied at low and high rotation, with the latter leading to reduced electron thermal transport across the entire minor radius. GYRO simulations indicate that a significant portion of the remaining H-mode electron heat flux results directly from short-scale TEM/ETG turbulence.