Impurity transport with strong and weak internal thermal barriers in JET optimized shear plasmas

Results of particle transport analysis are presented for both low and high charge impurity species in JET optimized shear plasmas. The impurity content in the plasma centre is sensitive to the strength of the internal transport barrier. In a strong transport barrier plasma, the diffusion coefficient in the centre is about an order of magnitude lower than that in plasmas with weak transport barriers. Impurity transport is close to the neoclassical transport prediction in the centre of the plasma, whereas it is much higher than the neoclassical theoretical value in the plasma edge. A convection term in the vicinity of the transport barrier was required in order to account for the measurements. These data support theories of turbulence suppression by the E x B shearing rate.