Research Progress on EAST L-H Transition Mechanism

Important progress has been made on the research exploring the low-to-high confinement mode transition (L-H transition) mechanism based on EAST H-mode plasma discharge. A quasiperiodic Er oscillation at a frequency of <4?kHz, much lower than the geodesic-acoustic-mode frequency, with a modulation in edge turbulence preceding has been observed for the first time in the EAST tokamak. The result was published in "Physical Review Letters" in an article "First Evidence of the Role of Zonal Flows for the L-H Transition at Marginal Input Power in the EAST Tokamak" in mid-September

　  EAST edge-tokamak research group used two reciprocating probes separated in toroidal direction, observed a quasi-periodic small-amplitude limit cycle oscillation at a frequency of f<4kHz and its modulation on edge turbulence preceding and following the low-to-high(L-H) mode transition on EAST.

　  These new findings not only shed light on the underlying physics mechanism for the L-H transition, but also have significant implications for ITER operations close to the L-H transition threshold power. More researches will be experimentized to test whether it can obtain H-mode with the critical input power. (Yang Ying Reports)

　  Links: http://prl.aps.org/abstract/PRL/v107/i12/e125001