Linear calculations of edge current driven kink modes with BOUT++ code

Li, G.; Xu, X. Q.; Snyder, P. B.; Turnbull, A. D.; Xia, Tianyang; H., C.; Xi, Peng

doi:10.1063/1.4898673

Cited by 24 publications

(15 citation statements)

References 37 publications

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“…The artificial vacuum current could have an impact on the instability and lead to disagreement when doing the benchmarking if not treated carefully. One way to deal with the vacuum region is to extend the equilibrium for GATO and ELITE to the whole simulation domain, as was done in [26] for a circular plasma. This is a plausible way to do the benchmarking but it is difficult to extend the method to X-point geometry.…”

Section: Multi-code Benchmarking Of Intermediate-n Modesmentioning

confidence: 99%

Ideal MHD stability and characteristics of edge localized modes on CFETR

Li¹,

Chan²,

Zhu³

et al. 2017

Nucl. Fusion

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Investigation on the equilibrium operation regime, its ideal magnetohydrodynamics (MHD) stability and edge localized modes (ELM) characteristics is performed for the China Fusion Engineering Test Reactor (CFETR). The CFETR operation regime study starts with a baseline scenario (R = 5.7 m, B T = 5 T) derived from multi-code integrated modeling, with key parameters β N , β T , β p varied to build a systematic database. These parameters, under profile and pedestal constraints, provide the foundation for the engineering design. The long wavelength low-n global ideal MHD stability of the CFETR baseline scenario, including the wall stabilization effect, is evaluated by GATO. It is found that the low-n core modes are stable with a wall at r/a = 1.2. An investigation of intermediate wavelength ideal MHD modes (peeling ballooning modes) is also carried out by multi-code benchmarking, including GATO, ELITE, BOUT++ and NIMROD. A good agreement is achieved in predicting edge-localized instabilities. Nonlinear behavior of ELMs for the baseline scenario is simulated using BOUT++. A mix of grassy and type I ELMs is identified. When the size and magnetic field of CFETR are increased (R = 6.6 m, B T = 6 T), collisionality correspondingly increases and the instability is expected to shift to grassy ELMs.

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Section: Multi-code Benchmarking Of Intermediate-n Modesmentioning

confidence: 99%

Ideal MHD stability and characteristics of edge localized modes on CFETR

Li¹,

Chan²,

Zhu³

et al. 2017

Nucl. Fusion

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“…For linear low-n and high-n ideal MHD modes, good agreement has been found between BOUTþþ, ELITE, and GATO results. 16,17 For various densities n 0 with pressure profile fixed, the linear simulations in Fig. 2 show that as the edge density (collisionality) varies, the maximum growth rates of the peeling-ballooning (P-B) modes are almost the same, but the shape of the growth rate spectrum c(n) changes rather dramatically.…”

mentioning

confidence: 94%

“…On the one hand, increasing currents drive peeling instabilities at low n; while at the same time the increasing pedestal current increases the local magnetic shear, which stabilizes high-n ballooning modes. 16 For the fixed pressure 1. (a) The radial equilibrium pressure profiles (dashed curve) and current (solid curve) for a density scan starting from an equilibrium (cbm18 dens6).…”

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confidence: 99%

Impact of the pedestal plasma density on dynamics of edge localized mode crashes and energy loss scaling

2014

Physics of Plasmas

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The latest BOUTþþ studies show an emerging understanding of dynamics of edge localized mode (ELM) crashes and the consistent collisionality scaling of ELM energy losses with the world multitokamak database. A series of BOUTþþ simulations are conducted to investigate the scaling characteristics of the ELM energy losses vs collisionality via a density scan. Linear results demonstrate that as the pedestal collisionality decreases, the growth rate of the peeling-ballooning modes decreases for high n but increases for low n (1 < n < 5), therefore the width of the growth rate spectrum c(n) becomes narrower and the peak growth shifts to lower n. Nonlinear BOUTþþ simulations show a two-stage process of ELM crash evolution of (i) initial bursts of pressure blob and void creation and (ii) inward void propagation. The inward void propagation stirs the top of pedestal plasma and yields an increasing ELM size with decreasing collisionality after a series of microbursts. The pedestal plasma density plays a major role in determining the ELM energy loss through its effect on the edge bootstrap current and ion diamagnetic stabilization. The critical trend emerges as a transition (1) linearly from ballooning-dominated states at high collisionality to peelingdominated states at low collisionality with decreasing density and (2) nonlinearly from turbulence spreading dynamics at high collisionality into avalanche-like dynamics at low collisionality. V C 2014 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4905070]The phenomena of nonlocal transport, such as avalanches or turbulence spreading, are well-known in diverse systems. Examples include, but are not limited to: piles of granular matter, discrete energy dissipating events in earthquakes and solar flares, and turbulent overshoot and penetration in fluid turbulence. Nonlocal dynamics of turbulence, transport, and zonal flows are often observed in plasma turbulence simulations and experiments, such as Edge Localized Modes (ELMs) in tokamaks. ELMs are a common characteristic feature of the tokamak H-mode plasma regime, where the high frequency ELM instability repeats periodically throughout the high confinement mode (H-mode) phase of the discharge. 1 The instability causes quasi-periodic relaxations of the edge pedestal, resulting in a series of hot plasma eruptions on a fast MHD timescale and leading to large energy fluxes to the plasma facing components (PFCs), which will suffer from excessive ablation, fast erosion, or melting. The concern about the survival of PFCs in ITER has sparked intense interest in ELM dynamics and in the parameter scaling of ELM energy loss. Numerous experiments in divertor tokamaks have shown a decrease in the relative type I ELM energy loss with increasing pedestal density (collisionality) over a decade ago. 2 There are attempts to provide an explanation for the dependence of ELM energy loss on collisionality. 3 However, there is as yet no common accepted explanation of the observed scaling neither from analytical theory nor numerical simulations. 4He...

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“…ELITE has been successfully benchmarked against GATO 36 for 4 n 10 and against MISHKA, 37 MARG2D, 38 M3D-C 1 , 39 BOUTþþ, 40 and NIMROD 41 for n ! 5 up to at least 20 but as high as n ¼ 100 for MARG2D.…”

Section: Elitementioning

confidence: 99%

Investigation of peeling-ballooning stability prior to transient outbursts accompanying transitions out of H-mode in DIII-D

et al. 2015

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The H-mode transport barrier allows confinement of roughly twice as much energy as in an L-mode plasma. Termination of H-mode necessarily requires release of this energy, and the timescale of that release is of critical importance for the lifetimes of plasma facing components in next step tokamaks such as ITER. H-L transition sequences in modern tokamaks often begin with a transient outburst which appears to be superficially similar to and has sometimes been referred to as a type-I edge localized mode (ELM). Type-I ELMs have been shown to be consistent with ideal peeling ballooning instability and are characterized by significant (up to $50%) reduction of pedestal height on short ($1 ms) timescales. Knowing whether or not this type of instability is present during H-L back transitions will be important of planning for plasma ramp-down in ITER. This paper presents tests of pre-transition experimental data against ideal peeling-ballooning stability calculations with the ELITE code and supports those results with secondary experiments that together show that the transient associated with the H-L transition is not triggered by the same physics as are type-I ELMs. V C 2015 AIP Publishing LLC. [http://dx.

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Linear calculations of edge current driven kink modes with BOUT++ code

Cited by 24 publications

References 37 publications

Ideal MHD stability and characteristics of edge localized modes on CFETR

Ideal MHD stability and characteristics of edge localized modes on CFETR

Impact of the pedestal plasma density on dynamics of edge localized mode crashes and energy loss scaling

Investigation of peeling-ballooning stability prior to transient outbursts accompanying transitions out of H-mode in DIII-D

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