Study of power width scaling in scrape-off layer with 2D electrostatic turbulence code based on EAST L-mode discharges

Liu, X.; Nielsen, A. H.; Rasmussen, Jens Juul; Naulin, V.; Olsen, J.; Xia, Tianyang; Wang, L.; Deng, G. Z.; Wu, Xuwen; Liu, Y.; Wang, Y. M.; Li, Y. Y.; Zang, Qing; Xu, G. S.; Li, J.

doi:10.1063/1.5083063

Cited by 6 publications

(7 citation statements)

References 35 publications

(96 reference statements)

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“…The major finding is the strong negative scaling of λ q on the plasma current I p [11][12][13][14][15][16][17][18], which is in reasonable agreement with Goldston's heuristic drift-based model in both trend and magnitude [19]. Transport and turbulence simulation studies over λ q have also been widely carried out and obtained similar results to the experiments [20][21][22][23][24][25][26][27][28][29][30][31][32]. The more pessimistic of these results are definitely not good news for future tokamaks like ITER and China fusion engineering test reactor (CFETR).…”

Section: Introductionsupporting

confidence: 64%

Simulation of divertor heat flux width on EAST by BOUT++ transport code

Deng

et al. 2020

Nucl. Fusion

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The BOUT++ edge plasma transport code is applied to study the effects of neutral recycling, drifts and heating scheme on edge plasma profiles and the divertor heat flux width of two discharges of the experimental advanced superconducting tokamak (EAST) steady-state H-mode plasmas heated by low hybrid wave (LHW) and neutral beam (NB), respectively. Neutral recycling seems to have played an important role in the plasma density profile. The edge plasma density drops dramatically for the case w/o neutral recycling, while it can be sustained for the case w/ neutral recycling. Drifts are found to have significant influences on edge plasma profiles. Both the amplitude and width of the divertor heat flux are found to have increased a lot due to drifts. The simulated heat flux width w/ drifts for the two discharges shows reasonable agreement with the experiments. However, the width from the simulation and experiment for the LHW heated discharge is much larger than that of the NB heated discharge. Comparison with Goldston’s drift-based model and more detailed analysis on the heat flux contributions from drifts versus turbulence show that drifts are the dominant factor in edge plasma transport for both LHW and NB heated discharges, while turbulence may have played a more important role in determining the heat flux width in LHW heated discharges than that in NB heated discharges. This may account for the larger heat flux width in the LHW heated discharge. The magnetic topology and the equilibrium change by the LHW power may also be a potential reason for the larger heat flux width in the LHW heated discharges, which still needs more evidence and studies to support it. Additional SOLPS simulation w/o drifts for the two discharges show reasonable agreement with the counterpart from the BOUT++ simulation, suggesting the two are both suitable codes for EAST edge plasma simulation.

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Section: Introductionsupporting

confidence: 64%

Simulation of divertor heat flux width on EAST by BOUT++ transport code

Deng

et al. 2020

Nucl. Fusion

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“…With an increase in the LHW power ratio"λ q increases significantly, which may be related to the extra heat and particle flux channels created by the LHW-induced magnetic topology changes [41]. Some of the simulation work related to λ q in EAST has also been carried out by edge-plasma modeling programs, such as SOLPS, HESEL, and BOUT++ [22][23][24][25][26][27][28][29]. Similar results have been obtained from the simulations, which show that I p (or equivalently the poloidal magnetic field B p ) plays an important role in determining the heat flux width.…”

Section: Introductionmentioning

confidence: 99%

Effects of radial transport on divertor power and particle flux widths under different operational regimes in EAST

Deng

Liu

et al. 2021

Nucl. Fusion

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A study of the effects of radial transport on the outer divertor particle and power flux widths (λ js and λ q ) is carried out using plasmas under different operational regimes in the Experimental Advanced Superconducting Tokamak (EAST). In the EAST experiments, the λ js values measured during the grassy intra- and inter-ELM phases are similar, and the averaged value of λ js during grassy ELMy discharges is found to be smaller than that of the intra-ELM phase of type-I ELMy discharges but larger than that of the inter-ELM phase of type-I ELMy discharges. Simulations of scans of the radial particle and heat transport coefficients, D and χ e, performed using the BOUT++ transport code show that both λ q and λ js increase with D and χ e, especially when D or χ e is larger than a threshold value, indicating that background turbulence starts to matter in the determination of λ q and λ js when D or χ e surpasses the threshold value. A comparison between the simulation of the D scan and the experimental results shows that the different values of λ js obtained under different plasma operational regimes are probably due to the different intensities of background turbulence, which is beyond the scope of Goldston’s heuristic drift-based model as reported by Goldston et al (2012 Nucl. Fusion 52 013009), since their model was derived by assuming that turbulent transport does not exceed a certain level. The ratio of λ js to λ q is greatly affected by the radial transport; however, simulations carried out using Scrape-off Layer Plasma Simulation (SOLPS) show that divertor geometry and plasma density have big influences on λ js , and thus could also affect the ratio of λ js to λ q .

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“…[18] Simulation work based on EAST L-mode discharges also shows that the SOL power width is influenced by the edge electron temperature through both parallel and radial heat transport, and λ q scaling yields λ q ∝ T −1.03 e,LCFS , where T e,LCFS is the electron temperature at the last closed flux surface (LCFS). [12] Unfortunately, T e,LCFS is not measured in EAST experiments yet. In the experiments with P total = 3.2 MW, n el ≈ 2 × 10 19 m −3 , T e,LCFS should be much higher than that in the Ohmic discharges or the shots with only 1-MW source auxiliary power.…”

Section: Discussion On the Decay Lengthmentioning

confidence: 99%

“…The underlying mechanism may be that higher edge T e can narrow the λ js , λ q , consistent with the simulation results. [12]…”

Section: Discussionmentioning

confidence: 99%

“…[9] And the decay lengths of divertor particle flux and heat flux, λ js , λ q , will be discussed and compared with previous work. [10][11][12] This paper is organized as follows: Section 2 describes the experimental setup and introduces the relevant diagnostics; Section 3 presents the experimental results and discussion. Summary is given in Section 4.…”

Section: Introductionmentioning

confidence: 99%

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Study on divertor plasma behavior through sweeping strike point in new lower divertor on EAST

Tao¹,

Xu²,

Meng³

et al. 2022

Chinese Phys. B

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A series of L-mode discharges have been conducted in the new ‘corner slot’ divertor on the Experimental Advanced Superconducting Tokamak (EAST) to study the divertor plasma behavior through sweeping strike point. The plasma control system controls the strike point sweeping from the horizontal target to the vertical target through poloidal field coils, with keeping the main plasma stability. The surface temperature of the divertor target cools down as the strike point moves away, indicating that sweeping strike point mitigates the heat load. To avoid the negative effect of probe tip damage, a method based on sweeping strike point is used to get the normalized profile and study the decay length of particle and heat flux on the divertor target λ js , λ q .In the discharges with high radio-frequency (RF) heating power, electron temperature T e is lower and λ js is larger when the strike point locates on the horizontal target compared to the vertical target, probably due to the corner effect. In the Ohmic discharges, λ js , λ q are much larger compared to the discharges with high RF heating power, which may be attributed to lower edge T e .

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Study of power width scaling in scrape-off layer with 2D electrostatic turbulence code based on EAST L-mode discharges

Abstract: Toward integrated multi-scale pedestal simulations including edge-localized-mode dynamics, evolution of edge-localized-mode cycles, and continuous fluctuations

Cited by 6 publications

References 35 publications

Simulation of divertor heat flux width on EAST by BOUT++ transport code

Simulation of divertor heat flux width on EAST by BOUT++ transport code

Effects of radial transport on divertor power and particle flux widths under different operational regimes in EAST

Study on divertor plasma behavior through sweeping strike point in new lower divertor on EAST

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