Impurity-Induced Suppression of Core Turbulence and Transport in the DIII-D Tokamak

Turbulence is significantly reduced in a tokamak plasma as a result of neon seeding of an L-mode discharge. Correspondingly, confinement is improved and cross-field ion thermal transport reduced. Fully saturated turbulence in the range 0.1<=k_⊥ρ_s<=0.6 is measured at ρ = 0.7 and exhibits a factor of 5 reduction in total power after neon injection, with almost complete suppression for k_⊥ρ_s>0.35. These observations are consistent with a reduction in the calculated linear growth rate for k_⊥ρ_s>0.5 and an increase in the measured E×B flow shearing rate.