Influence of Isotope Mass on Core Turbulence and Transport Properties in Dimensionally Matched H-Mode Plasmas on DIII-D

Long-wavelength turbulence characteristics are found to differ significantly in dimensionally similar low-rotation hydrogen and deuterium ELM’ing H-mode plasmas, which may partially explain the large differences in transport. Spatiotemporal measurements of long-wavelength ion gyroscale density fluctuations are obtained with 2D Beam Emission Spectroscopy over ρ=0.4-0.8. The NBI and ECH-heated H and D discharges exhibited the “isotope effect” with confinement time about 80% higher in the deuterium (D) compared to hydrogen (H), though electron heating degraded D plasmas more significantly than H plasmas. H plasmas are observed to have lower integrated turbulence amplitude over 60-300 kHz: ñ/n|_D~1.5*ñ/n|_H. The measured turbulence radial correlation lengths, however, are larger in the H-plasma (~2.5 cm) compared to D (~1.5 cm), while the H and D poloidal correlation functions were significantly different: the D poloidal correlation function exhibited a unimodal broadband structure, while the H poloidal correlation function exhibited two distinct counter-propagating modes. Comparisons with gyrokinetic simulations will be performed to identify the underlying mechanisms for the isotope dependence of turbulence and transport.