Measurements and theoretical comparisons of electron turbulence at ASDEX Upgrade*

At ASDEX Upgrade, a Correlation ECE diagnostic with a novel channel comb is used to probe the fundamentals of ion-scale electron heat transport. It measures radial profiles of low-k (k_θ < 0.3) temperature fluctuations_, and radial correlation lengths, L_r(T_e), in unprecedented detail. This diagnostic is augmented by the addition of a reflectometer on the same line of sight to enable measurements of the cross-phase angle between turbulent n_e and T_e fluctuations, α_nT. These measurements are used as quantitative constraints on non-linear ion-scale gyrokinetic simulations, with good overall agreement. α_nT is a good indicator of the balance of Trapped Electron and Ion Temperature Gradient modes and therefore the measurement puts a strong constraint on the simulation in combination with Q_i/Q_e. A validation metric is used to plot trends of agreement between the simulation set and experiment, and a minimum is found close to the experimental inputs. Fluctuating quantities and trends are also compared to TGLF predictions across the ITG/TEM transition.