  In the Wendelstein 7-X magnetic confinement experiment, a reduction of
turbulent density fluctuations as well as anomalous impurity diffusion is
associated with a peaking of the plasma density profile. These effects
correlate with improved confinement and appear largely due to a reduction of
anomalous transport as the change in neoclassical transport is small. The
observed decrease of turbulent heat flux with increased density gradients is in
agreement with nonlinear gyrokinetic simulations, and has been attributed to
the unique geometry of W7-X that limits the severity of trapped electron modes.
