TY - JOUR

T1 - Observation of a new turbulence-driven limit-cycle state in H-modes with lower hybrid current drive and lithium-wall conditioning in the EAST superconducting tokamak

A1 - Wang,H.Q.

A1 - Xu,G.S.

A1 - Guo,H.Y.

A1 - Wan,B.N.

A1 - Naulin,Volker

A1 - Ding,S.Y.

A1 - Yan,Ning

A1 - Zhang,W.

A1 - Wang,L.

A1 - Liu,S.C.

A1 - Chen,R.

A1 - Shao,L.M.

A1 - Xiong,H.

A1 - Liu,P.

A1 - Jiang,M.

A1 - Luo,G.-N.

AU - Wang,H.Q.

AU - Xu,G.S.

AU - Guo,H.Y.

AU - Wan,B.N.

AU - Naulin,Volker

AU - Ding,S.Y.

AU - Yan,Ning

AU - Zhang,W.

AU - Wang,L.

AU - Liu,S.C.

AU - Chen,R.

AU - Shao,L.M.

AU - Xiong,H.

AU - Liu,P.

AU - Jiang,M.

AU - Luo,G.-N.

PB - Institute of Physics Publishing

PY - 2012

Y1 - 2012

N2 - The first high confinement H-mode plasma has been obtained in the Experimental Advanced Superconducting Tokamak (EAST) with about 1 MW lower hybrid current drive after wall conditioning by lithium evaporation and real-time injection of Li powder. Following the L–H transition, a small-amplitude, low-frequency oscillation, termed a limit-cycle state, appears at the edge during the quiescent phase with good energy and particle confinement. Detailed measurements by edge Langmuir probes show modulation interaction and strong three-wave coupling between the low-frequency oscillations and high-frequency-broadband (80–500 kHz) turbulences that emerge after the L–H transition or in the inter-ELM phase. The potential fluctuations at the plasma edge are correlated with the limit-cycle oscillations, and the fluctuations in the floating potential signals at different toroidal, poloidal and radial locations are strongly correlated with each other, with nearly no phase differences poloidally and toroidally, and finite phase difference radially, thus providing strong evidence for zonal flows. The growth, saturation and disappearance of the zonal flows are strongly correlated with those of the high-frequency turbulence. And the measurements demonstrate that the energy gain of zonal flows is of the same order as the energy loss of turbulence. This strongly suggests the interactions between zonal flows and high-frequency turbulences at the pedestal during the limit-cycle state.

AB - The first high confinement H-mode plasma has been obtained in the Experimental Advanced Superconducting Tokamak (EAST) with about 1 MW lower hybrid current drive after wall conditioning by lithium evaporation and real-time injection of Li powder. Following the L–H transition, a small-amplitude, low-frequency oscillation, termed a limit-cycle state, appears at the edge during the quiescent phase with good energy and particle confinement. Detailed measurements by edge Langmuir probes show modulation interaction and strong three-wave coupling between the low-frequency oscillations and high-frequency-broadband (80–500 kHz) turbulences that emerge after the L–H transition or in the inter-ELM phase. The potential fluctuations at the plasma edge are correlated with the limit-cycle oscillations, and the fluctuations in the floating potential signals at different toroidal, poloidal and radial locations are strongly correlated with each other, with nearly no phase differences poloidally and toroidally, and finite phase difference radially, thus providing strong evidence for zonal flows. The growth, saturation and disappearance of the zonal flows are strongly correlated with those of the high-frequency turbulence. And the measurements demonstrate that the energy gain of zonal flows is of the same order as the energy loss of turbulence. This strongly suggests the interactions between zonal flows and high-frequency turbulences at the pedestal during the limit-cycle state.

U2 - 10.1088/0029-5515/52/12/123011

DO - 10.1088/0029-5515/52/12/123011

JO - Nuclear Fusion

JF - Nuclear Fusion

SN - 0029-5515

IS - 12

VL - 52

SP - 123011

ER -