Stationary high-performance grassy ELM regime in EAST

Yang, Qingquan; Xu, Guosheng; Niu, Y.; Wang, Yifeng; Lin, Xin; Yang, Yong; Hu, G.H.; Zhang, Ling; Duan, Yanmin; Xu, Jichan; Wang, Liang; Chen, Ran; Lan, H.; Chen, Liang; Lu, Zhiying; Ding, Genfan; Meng, Lingyi; Gong, Xianzu; Wan, Baonian

doi:10.1088/1741-4326/ab8e0f

Cited by 25 publications

(29 citation statements)

References 46 publications

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“…It is worth pointing out that studies of the grassy ELM regime in DIII-D and EAST plasmas have identified similar operational spaces for this regime (Wang et al 2021c;Yang et al 2020). DIII-D results suggest that grassy ELMs are obtained with q 95 ≥ 5.9 and P ≥ 1.7 , while EAST results indicate q 95 ≥ 5.2 and P ≥ 1.2 .…”

Section: Edge Solution: Detached Divertor and Small/no Elmsmentioning

confidence: 86%

Progress in the development and understanding of a high poloidal-beta tokamak operating scenario for an attractive fusion pilot plant

Ding

Garofalo

2022

Rev. Mod. Plasma Phys.

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The high poloidal-beta ($$\beta _{\textrm{P}}$$ β P ) regime was first proposed as a high bootstrap current scenario for a steady-state fusion pilot plant (FPP) in the 1990s (Kikuchi in Nucl Fusion 30:265, 1990). Since then, there have been many theoretical, modeling, and experimental research activities on this topic. A joint DIII-D/EAST research team began exploring the high-$$\beta _{\textrm{P}}$$ β P regime in 2013, focusing on addressing the needs of attractive FPP design by taking advantage of the extensive diagnostic set and sophisticated plasma control system on DIII-D and the well-developed integrated modeling capability at General Atomics. The ultimate goal is to demonstrate such a scenario on EAST with truly long pulse and metal wall compatibility. This paper summarizes the highlights of the research results on DIII-D by the joint team in the past decade. Experimental evidence and modeling analysis show the high-$$\beta _{\textrm{P}}$$ β P scenario has great advantages in addressing key needs for an attractive FPP design, such as high-energy confinement quality at low rotation, excellent core-edge integration, high line-averaged density above the Greenwald limit, low disruption risk, and high bootstrap current fraction for steady-state operation. This provides a relatively safe and economical option to base an FPP design on that will lead to commercial fusion energy.

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Section: Edge Solution: Detached Divertor and Small/no Elmsmentioning

confidence: 86%

Progress in the development and understanding of a high poloidal-beta tokamak operating scenario for an attractive fusion pilot plant

Ding

Garofalo

2022

Rev. Mod. Plasma Phys.

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“…Future works will focus on the numerical β p scan to address these effects. The high β p effects are highlighted in recent EAST experiments, especially for the double transport barrier control and the onset of the grassy ELM regime [35][36][37]. Additional current drive, magnetic geometry control, or other control methods are used in those high β p experiments, the ELM behaviors are different from the one here and need to be studied separately in the future.…”

Section: Summary and Discussionmentioning

confidence: 97%

Study on filament width of type-I ELM in EAST using VUV imaging system and simulation

Ming

Tang²,

Shi³

et al. 2022

Nucl. Fusion

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The poloidal width of the filaments induced by the Type-I edge localized mode has power dependence in EAST. The poloidal widths of the filaments observed by the high-speed vacuum ultraviolet (VUV) imaging system are proportional to the heating power and the ELM size. To understand this power dependence, the BOUT++ nonlinear simulations have been performed with the reconstructed equilibriums from the experimental measurements in this paper. The synthetic filament structures from BOUT++ nonlinear simulation match the experimental observations by the VUV imaging system. The BOUT++ nonlinear simulations also reproduce the power dependence of the filament widths and the ELM size. The filament width and the ELM size are inversely proportional to the toroidal mode number. The low-n mode has a broader radial and poloidal structure, which causes the larger filament width and ELM size. In the high input power case, the mode spectrum shifts to low-n, a result of increasing peeling drive. Besides, we found the β_p in a higher input power case leads to a broader pedestal, expanding the radial mode structure of the Peeling-Ballooning mode.

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“…Later, the grassy ELM was also observed in JET and AUG with a higher internal inductance li > 1.1 [7][8][9]. In the EAST 2016 campaign, discharges with grassy ELM were successfully achieved with good energy confinement, strong tungsten impurity exhaust capability, and good compatibility with low rotation [2,10]. Through analysis of DIII-D experimental data, researchers found two types of grassy ELM discharges: discharge with low input power and resonant magnetic perturbation (RMP), and discharge with high input power and without RMP [11,12].…”

Section: Introductionmentioning

confidence: 99%

Edge-localized-mode simulation in CFETR steady-state scenario

Tang

Li³

2021

Nucl. Fusion

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The EPED1 model and self-consistent core-pedestal coupling in integrated modeling are used to design the pedestal structure of the China Fusion Engineering Testing Reactor (CFETR) steady-state scenario. The key parameters, such as β p and q 95, are based on the grassy edge-localized-mode (ELM) experimental database. In this work, we use the BOUT++ six-field two-fluid code to simulate the onset of the ELM in the CFETR steady-state scenario. The ELM size is around 0.2% in nonlinear simulations, which is in the experimental range of the grassy ELM discharges, 0.1%–1% observed in multiple tokamak devices. Linear and nonlinear simulations show that the dominant high-n ballooning modes peak around n = 40. Compared to type-I ELM crashing dynamics, grassy ELM crashing has a smaller initial crash and is then followed by three phases of turbulence spreading, which are dominated by multi-modes, a high-n mode of n = 45 and low-n mode of n = 5, respectively. In contras to type-I ELM, the perturbation of the high-n mode has a narrow width around ψ = 0.95, and magnetic island formation and reconnection occur only beyond ψ = 0.95, leading to a small initial crash. Mode–mode interaction in the multi-mode coexistence stage stops the growth of individual modes and reduces the transport of particles and heat, and these are the two reasons why the ELM size is small. In–out asymmetry of transient heat flux with a ratio of E out/E in = 3.5 is found during grassy ELM crash. The rise and delay times of the heat flux match the calculation from the free-streaming model. To evaluate the erosion of the divertor target, the energy fluence at the outer divertor target is calculated, which is 0.029 MJ m−2, 5.5 times smaller than the tungsten melting limit 0.16 MJ m−2. The calculated energy fluency still follows the experimental scaling law from type-I ELM experiments. The fluctuation eddies in the toroidal direction show a filament structure at the outer mid-plane. Parallel heat flux patterns with a toroidal mode number n = 10 are found at the outer divertor with an amplitude of 680 MW m−2.

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Stationary high-performance grassy ELM regime in EAST

Cited by 25 publications

References 46 publications

Progress in the development and understanding of a high poloidal-beta tokamak operating scenario for an attractive fusion pilot plant

Progress in the development and understanding of a high poloidal-beta tokamak operating scenario for an attractive fusion pilot plant

Study on filament width of type-I ELM in EAST using VUV imaging system and simulation

Edge-localized-mode simulation in CFETR steady-state scenario

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