title: Experimental evidence of turbulent transport regulation by zonal flows.
abstract: The regulation of turbulent transport by zonal flows is studied experimentally on a flux surface of the stellarator experiment TJ-K. Data of 128 Langmuir probes at different toroidal and poloidal positions on a single flux surface enable us to measure simultaneously the zonal flow activity and the turbulent transport in great detail. A reduction of turbulent transport by 30% during the zonal flow phase is found. It is shown that the reduction process is initiated by a modification in the cross phase between density and electric field followed by a reduction in the fluctuation levels, which sustain low transport levels on larger time scales than the zonal flow lifetime.
authors.affiliation: Institut für Plasmaforschung, Universität Stuttgart, Pfaffenwaldring 31, 70569 Stuttgart, Germany and Max-Planck-Institut für Plasmaphysik, EURATOM-Assoziation, Boltzmannstr. 2, 85748 Garching, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Birkenmeier
authors.affiliation: Institut für Plasmaforschung, Universität Stuttgart, Pfaffenwaldring 31, 70569 Stuttgart, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Ramisch
authors.affiliation: Institut für Plasmaforschung, Universität Stuttgart, Pfaffenwaldring 31, 70569 Stuttgart, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Schmid
authors.affiliation: Institut für Plasmaforschung, Universität Stuttgart, Pfaffenwaldring 31, 70569 Stuttgart, Germany and Max-Planck-Institut für Plasmaphysik, EURATOM-Assoziation, Boltzmannstr. 2, 85748 Garching, Germany.
authors.forename: U
authors.initials: U
authors.lastname: Stroth