Poloidal inhomogenity of the particle fluctuation induced fluxes near the LCFS at lower hybrid heating and improved confinement transition at the FT-2 tokamak
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Abstract
This paper deals with the new spectral and microturbulence experimental data and their analysis, which show that the radial electric field Er generated at the lower hybrid heating (LHH) in the FT-2 is high enough to form the transport barriers. The ETB is formed when LHH is switched off. The radial fluctuation-induced E × B drift flux densities near LCFS in SOL are measured at two different poloidal angles. For this purpose two Langmuir probes located at low and high field sides of the torus are used. Registration of the poloidal and radial components of the electric field and density fluctuations at the same time during one discharge permits to measure the poloidal asymmetry of the transport reduction mechanism of the radial and poloidal particle fluxes in the SOL. The absolute \(\tilde E_\theta\)θ fluctuation levels show dependence on the sign of Er shear. The modification of the microscale turbulence by the poloidal Er × B rotation shear ωE × B at the L-H transition near LCFS is also studied by X-mode fluctuation reflectometry. The new data were obtained by spatial spectroscopic technique.
Key words
plasma tokamak transport barrier microturbulencePreview
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