Outward particle transport by coherent mode in the H-mode pedestal in the Experimental Advanced Superconducting Tokamak (EAST)

Zhang, T; Han, Xiang; Gao, Xiang; Liu, H Q; Shi, Tonghui; Liu, J B; Liu, Y; Kong, Defeng; Liu, Z X; Qu, Hao; Xiang, Haoming; Geng, Kangning; Wang, Y M; Wen, Fei; Zhang, S B; Ling, Bili

doi:10.1088/1361-6587/aa69e8

Cited by 33 publications

(72 citation statements)

References 33 publications

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“…This coherent fluctuation can be observed in all 11 channels of POINT diagnostics and in ECE channels in the pedestal region, indicating that the mode is located in the pedestal region. The toroidal mode number has been determined to be n = 15 by applying a similar method of analysis to that used in figure 3 of [31]. From this analysis, it is confirmed that the coherent fluctuation observed here is just the coherent mode (CM) presented in previous publications [30,31].…”

Section: Resultssupporting

confidence: 68%

“…The toroidal mode number has been determined to be n = 15 by applying a similar method of analysis to that used in figure 3 of [31]. From this analysis, it is confirmed that the coherent fluctuation observed here is just the coherent mode (CM) presented in previous publications [30,31].…”

Section: Resultssupporting

confidence: 68%

“…Higher heating power will lead to a faster recovery for the pedestal pressure, thereby causing a higher ELM frequency [4]. On the other hand, recent studies on turbulence in the pedestal region have shown that pedestal fluctuations could drive radial transport, and influence pedestal evolution [24][25][26][27][28][29][30][31]. Thus, it is possible that pedestal turbulence could affect ELM frequency.…”

Section: Introductionmentioning

confidence: 99%

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Effect of pedestal fluctuation on ELM frequency in the EAST tokamak

et al. 2018

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The dependence of ELM frequency on heating power has been studied on the Experimental Advanced Superconducting Tokamak (EAST). It is found that the ELM frequency (f ELM ) generally increases with the power through separatrix (P sep ), indicating type-I ELM in these plasmas. However, there are two data points, named 'abnormal ELM' in the present paper, which have much lower f ELM than the 'normal ELM', while both types of ELM have similar ELM energy losses. The 'abnormal ELM' occurs at a phase with increased radiation power due to metal impurity influx events. The increased radiation power cannot explain the much lower f ELM for 'abnormal ELM', since the reduction of P sep is weaker than proportional to the observed reduction of the ELM frequency. The 'abnormal ELM' feature can be attributed to the enhanced amplitude of a coherent mode in the pedestal region. Comparing the pedestal evolutions for the two types of ELM with similar separatrix power P sep , it is actually found that the more pronounced pedestal coherent mode in the plasma with 'abnormal ELM' leads to a slower pressure pedestal recovery during the inter-ELM phase. This experimental result implies that the physical mechanism for 'abnormal ELM' is that the more pronounced pedestal fluctuation induces larger outward transport, slows down the pedestal evolution and leads to longer inter-ELM phase, i.e. lower ELM frequency.

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Section: Resultssupporting

confidence: 68%

Section: Resultssupporting

confidence: 68%

Section: Introductionmentioning

confidence: 99%

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Effect of pedestal fluctuation on ELM frequency in the EAST tokamak

et al. 2018

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“…The spectrum is dominated by a coherent mode (CM) after plasma enters the H-mode. This CM is in the pedestal region [11,12] and can be observed in all POINT channels. In order to extract the fluctuation amplitude, the fluctuation component of 10 kHz-35 kHz (δN el6, kHz ) is extracted from the original signal (δN el6 ) by applying a bandpass filter in this frequency range.…”

Section: Modulation Effects On Background Turbulencementioning

confidence: 71%

“…In experiment, it has been found that several turbulence modes in the ELM-free phase or inter-ELM phase are closely related to the pedestal transport [10][11][12][13][14][15][16][17][18][19][20][21][22]. In simulation, gyrokinetic codes found that several types of micro-turbulence, such as the micro-tearing mode (MTM) [23,24] and electron temperature gradient (ETG) mode [25], could be responsible for the pedestal transport.…”

Section: Nuclear Fusionmentioning

confidence: 99%

A low-frequency axisymmetric oscillation in the high-confinement mode pedestal on the EAST tokamak

Xiang¹,

Zhang²,

Ye³

et al. 2019

Nucl. Fusion

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A low-frequency (~1 kHz) oscillation (LFO) in the pedestal region emerged during the ELM-free phase after the L-H transition on the EAST tokamak. Its characteristics were studied. This oscillation has a magnetic component with a toroidal mode number (n) of 0, indicating an axisymmetric mode, while its poloidal magnetic structure demonstrates an m = 1 standing wave with in-out asymmetry. The density fluctuation shows no phase difference radially, indicating that it is not a radial traveling pulse. Before this axisymmetric oscillation, pedestal density fluctuation was dominated by low-frequency (LF) fluctuation with a frequency of less than 400 kHz. During the phase of axisymmetric oscillation, this LF fluctuation was modulated by this axisymmetric oscillation and thus experienced 'suppressed' and 'recovery' phases alternately. As a result, both pedestal density and the particle flux onto the divertor were modulated. During the 'suppressed' phase of the LF fluctuation, a new high-frequency (HF) fluctuation appeared, with a frequency larger than 500 kHz. The result demonstrates complex turbulence behavior in pedestal region.

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