Effects of a coherent mode on the redistribution of divertor particle flux in HL-2A H-mode plasmas

Wu, Na; Cheng, J.; Yan, Lei; Huang, Z.H.; Xu, Jianqiang; Wang, W C; Ke, Rui; Yang, Z.C.; Ji, X.Q.; Liu, L; He, Xiaoxue; Jiang, M.; Wen, Jie; Miao, X G; Zhong, Weizhi; Yu, Liming; Gao, Jinming; Dong, Y.B.; Shi, Z.B.; Liu, Y; Yang, Q. W.; Dong, J. Q.; Xu, M.

doi:10.1088/1361-6587/abf672

“…The spectrum of the CM for shot #77730 is shown in figure 1(h). Figure 1(i) represents the time evolution of the ELM size and In order to obtain a clear relationship between the ELM size and the CM intensity, the statistical analysis [16,40] is performed in the EAST experiments. The statistical results of the discharges are shown in figure 2, and one symbol represents one single ELM.…”

Section: The Experiments and Analysismentioning

confidence: 99%

The simulation of ELMs mitigation by pedestal coherent mode in EAST using BOUT++

Li¹,

Xia²,

Zou³

et al. 2022

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A general phenomenon that the edge localized modes (ELMs) can be effectively mitigated with the enhanced coherent modes (CMs) has been observed on EAST. For this phenomenon, the experimental statistical analysis and electromagnetic (EM) simulations have been performed. There is a threshold value of the CM intensity in the experiments, which plays a key role in ELMs mitigation. Through the ELITE and conventional BOUT++ analysis, we found that when the insignificant ELM and enhanced CM co-exist, the pedestal is located in unstable P-B region and the ELM is relatively large. The simulation results only using the experimental profiles without considering other factors cannot reproduce the no significant ELM experiment. The CM enhances the edge turbulence, which can control ELMs. Therefore, the effects of CM are considered to explain the ELM mitigation. Modifying the three-field reduced model in BOUT++, an imposed perturbation is added as the CM. The simulation results indicate that: without the CM, the ELM size belongs to the relative large ELM region; after considering the CM, the ELM is mitigated and the energy loss is reduced by about 44.5%. Analysis shows that the CM enhances the three-wave nonlinear interactions in the pedestal and reduces the phase coherence time (PCT) between the pressure and potential, which lead the perturbation to tend to be ‘multiple-mode’ coupling. The competition of free energy between the multiple modes leads to the lack of obvious filament structures and the decreased energy loss. The above reveals that there is a competitive relationship between turbulence and ELMs, and the CM-enhanced turbulence can effectively reduce ELM energy loss. In addition, through the parameter scanning, there is a threshold of the amplitude A, which is consistent with the statistical results in the experiments.

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“…In HL-2A, a low frequency turbulence less than 50 kHz in the vicinity of separatrix is considered to be able to enlarge the heat flux width by the enhanced outward cross-field transport [23]. And it is also found in HL-2A that a pedestal CM can result in about 30% increase of the divertor particle flux on the outer divertor target, which indicates that the CM changes the distribution of the divertor particle flux [24].…”

Section: Introductionmentioning

confidence: 99%

Impact of coherent mode on divertor particle and heat flux in a type I ELMy H mode plasma on EAST tokamak

Long

¹

,

Zhang²,

Ming³

et al. 2022

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The paper investigates the effect of pedestal turbulence, i.e. coherent mode (CM), on the divertor total particle flux, the particle flux distribution and heat flux distribution, and their decay lengths in the scrape-off layer (SOL) region on EAST tokamak. The experimental evidence indicates the coherence between the pedestal CM and the divertor particle flux fluctuation, which implies that the pedestal CM can affect the divertor plasma behavior. The increase of the particle flux decay length ( λ j s ) correlates with the density radial decay length (λ n,SOL) in the SOL region where the λ n,SOL is largely affected by the change of pedestal CM amplitude. A quantitative statistical analysis shows that the divertor total particle flux and λ j s in the SOL region increase with increasing amplitude of the electron density fluctuation and the electron temperature fluctuation induced by the pedestal CM. The temporal decay process of the total particle flux is interrupted by the appearance of CM at the pedestal. Meanwhile, the spatial distributions of the divertor particle flux and heat flux are enhanced when the pedestal CM appears, which are observed in both the upper single null and lower single null configurations.

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“…Figure 6 The above experimental results demonstrate that the newly designed divertor probe system runs well and can provide the high spatiotemporal divertor parameters on HL-2A tokamak. Up to now, this system has contributed a large amount of experimental data for studying the distribution of ELM induced heat flux [27], the decay length of divertor heat flux [28] and divertor detachment.…”

Section: Resultsmentioning

confidence: 99%

“…The experimental results represent that this newly designed divertor probe system could provide reliable experimental data for the HL-2A experiment. They have been beneficial for studying the detached divertor physics, the scaling law of the decay lengths Type-I ELM power loads and ELM mitigation [27,28]. In near future, this divertor probe system will make greater contribution to HL-2A physical study, e.g.…”

Section: Discussionmentioning

confidence: 99%

Upgrade of an integrated Langmuir probe system on the closed divertor target plates in the HL-2A tokamak

Huang¹,

Cheng²,

Wu³

et al. 2022

Plasma Sci. Technol.

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A newly designed divertor Langmuir probe diagnostic system has been installed in a rare closed divertor of the HL-2A tokamak and steadily operated for the study of divertor physics involved edge-localized mode (ELM) mitigation, detachment and redistribution of heat flux, etc. Two sets of probe arrays including 274 probe tips were placed at two ports (approximately 180° separated toroidally), and the spatial and temporal resolutions of this measurement system could reach 6 mm and 1 s, respectively. A novel design of the ceramic isolation ring can ensure reliable electrical insulation property between the graphite tip and the copper substrate plate where plasma impurities and the dust are deposited into the gaps for a long experimental time. Meanwhile, the condition monitoring and mode conversion between single and triple probe of the probe system could be conveniently implemented via a remote control station. The preliminary experimental result shows that the divertor Langmuir probe system is capable of measuring the high spatiotemporal parameters involved the plasma density, electron temperature, particle flux as well as heat flux during the ELMy H-mode discharges.

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Effects of a coherent mode on the redistribution of divertor particle flux in HL-2A H-mode plasmas

Cited by 5 publications

References 41 publications

The simulation of ELMs mitigation by pedestal coherent mode in EAST using BOUT++

The simulation of ELMs mitigation by pedestal coherent mode in EAST using BOUT++

Impact of coherent mode on divertor particle and heat flux in a type I ELMy H mode plasma on EAST tokamak

Upgrade of an integrated Langmuir probe system on the closed divertor target plates in the HL-2A tokamak

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