Transport, islands, flow and distribution functions

The production of magnetic islands at different resonant surfaces due to toroidicity is inhibited by velocity shear between the surfaces unless the perturbing field exceeds a critical value. Detailed experiments supported by theory show that plasma rotation is crucial in determining whether magnetic islands are formed at rational surfaces due to applied resonant (or error) fields. The energy confinement decreases and the sawtooth activity ceases when the plasma rotation changes in association with that magnetic turbulence associated with island overlap can have a serious impact on confinement in some circumstances. However detailed studies of the Bremsstrahlung spectra on a number of devices, when compared with a 3D Fokker-Planck code, indicate that the energy dependence of the radial diffusivity for magnetic turbulence is weak and does not though more detailed spatial information is needed to ascertain if the plasma is composed of 'annular rings' of magnetic turbulence. (author)