Turbulence behaviour during electron heated reversed shear discharges in JET

Low-frequency/long-wavelength density turbulence is found to be reduced within the volume enclosed by an electron thermal internal transport barrier generated with lower hybrid microwave heating in the JET tokamak. The turbulence reduction coincides with a region (typically r/a < 0.4) of negative, or reversed magnetic shear s and reduced electron thermal diffusion chi(e). In the tokamak edge region (r/a > 0.8), the turbulence amplitude is also reduced coinciding with large positive magnetic shear s > 1. Estimates of the core turbulence wavelengths (lambda(perpendicular to) > 0.1 m) are not in agreement with expectations from electron temperature gradient instabilities.