Quantitative Comparisons of DIII–D Turbulence Measurements to Gyro-Kinetic and Gyro-Fluid Turbulence Simulations

Experimental turbulence and transport characteristics in DIII–D plasmas have been compared with similar quantities calculated from gyro-kinetic and gyro-fluid turbulence simulations. Turbulent radial correlation lengths ∆r from DIII–D L–mode plasmas scale as 5 to 10 ρs (ρs = ion gyro-radius evaluated using the electron temperature) and are independent of the poloidal magnetic field. Comparisons to a global gyrokinetic code (UCAN) show similar behavior (i.e. magnitude, radial scaling, lack of Bθ dependence) when zonal flows are included. Experimental ∆r from quiescent double barrier (QDB) plasmas show both a reduction below this L–mode scaling, consistent with reduced core transport, as well as similarities with UCAN simulations of ∆r. Gyro-fluid flux tube simulations (GRYFFIN) of L–mode discharges have likewise been performed and comparisons show similarities between measured and simulated poloidal wave number spectrum while the simulated ion thermal transport and density fluctuation levels are larger than experiment by factors of ~1.5 and ~4 respectively.