Turbulence and Transport Dependence on rho* and Isotope Mass in H-Mode Plasmas on DIII-D

Normalized long-wavelength (k_⊥ρi<1) density fluctuation amplitudes are found to scale approximately linearly with the normalized local ion gyroradius, ñ⁄n~ρ* in ITER-like ELM’ing H-mode plasmas on DIII-D; ρ_I was systematically varied both via a ρ* scan in deuterium as well as by changing isotope mass in matched hydrogen and deuterium plasmas. Interestingly, confinement is found to increase at smaller ρ* as ρ* is varied within a single ion species (deuterium), consistent with gyro-Bohm predictions. However, when ρ* is reduced by changing isotope mass (D->H), confinement degrades, counter to simple gyro-Bohm predictions, potentially indicating that the dimensionless electron-to-ion mass ratio is important to confinement scaling. Comprehensive measurements of the spatiotemporal turbulence properties, obtained with 2D Beam Emission Spectroscopy, are compared as the local ion gyroradius is altered via magnetic field and/or isotope variation. The turbulence radial correlation length is found to scale with ρ_I in the deuterium ρ* scan, but not in the isotope scan. These turbulence measurements and analysis will be compared with linear and nonlinear gyrokinetic simulations to help resolve the conundrum of ρ* scaling of confinement and the isotope effect.