Publication Type
Journal
Journal Name
Physical Review Letters
Publication Date
Page Number
065002
Volume
116
Issue
6
Abstract
High spatial resolution Doppler backscattering measurements in JET have enabled new insights into the development of the edge E-r. We observe fine-scale spatial structures in the edge E-r well with a wave number k(r rho i) approximate to 0.4-0.8, consistent with stationary zonal flows, the characteristics of which vary with density. The zonal flow amplitude and wavelength both decrease with local collisionality, such that the zonal flow E x B shear increases. Above the minimum of the L-H transition power threshold dependence on density, the zonal flows are present during L mode and disappear following the H-mode transition, while below the minimum they are reduced below measurable amplitude during L mode, before the L-H transition.
