Wide Operational Windows of Edge-Localized Mode Suppression by Resonant Magnetic Perturbations in the DIII-D Tokamak

Hu, Qiming; Nazikian, R.; Grierson, B. A.; Logan, N. C.; Orlov, D. M.; Paz-Soldan, C.; Yu, Q.

doi:10.1103/physrevlett.125.045001

Cited by 51 publications

(54 citation statements)

References 45 publications

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“…The broader ion-pedestal also can lead a larger response of T i,ped on RMP strength. Inspired from (Hu et al 2020) 36 , the change of pedestal height (∆T ped ) by ∆I RMP can be described as Eq.1,…”

Section: Resultsmentioning

confidence: 99%

Optimization of 3D controlled ELM-free state with recovered global confinement for tokamak fusion plasmas

Kim¹,

Shousha²,

Hahn³

et al. 2021

Preprint

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Mitigation of deleterious heat flux from edge-localized modes (ELMs) on fusion reactors is often attempted with 3D perturbations of the confining magnetic fields. However, the established technique of resonant magnetic perturbations (RMPs) also degrades plasma performance, complicating implementation on future fusion reactors. In this paper, we introduce an adaptive real-time control scheme as a viable approach to simultaneously achieve both ELM-free states and recovered high-confinement (βN~1.91$ and HN~0.9), demonstrating successful handling of a volatile complex system through adaptive measures. We show that, by exploiting a salient hysteresis process to adaptively minimize the RMP strength, stable ELM suppression can be achieved while actively encouraging confinement recovery. This is made possible by a self-organized transport response in the plasma edge which reinforces the confinement improvement through a widening of the ion pedestal and promotes control stability, in contrast to the deteriorating effect on performance observed in standard RMP experiments. These results establish the real-time approach as an up-and-coming solution towards an optimized ELM-free state, which is an important step for the operation of ITER and reactor-grade tokamak plasmas. Notably, the real-time adaptive control scheme introduced here provides a path towards economic fusion reactors by maximizing the fusion gain while minimizing damage to machine components.

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Section: Resultsmentioning

confidence: 99%

Optimization of 3D controlled ELM-free state with recovered global confinement for tokamak fusion plasmas

Kim¹,

Shousha²,

Hahn³

et al. 2021

Preprint

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show abstract

“…The long-standing mystery of the q 95 width of ELM suppression windows has been effectively resolved based on simulations of resonant field penetration at the pedestal top [24,25]. The TM1 simulations successfully predict that narrow magnetic islands form when resonant field penetration occurs at the top of pedestal, and these islands are easily screened when q 95 moves off resonance, leading to very narrow windows of ELM suppression (typically Δq 95 ∼ 0.1 as shown in figures 6(a) and (b)).…”

Section: Fundamental Plasma Physics Understanding and Model Validatio...mentioning

confidence: 99%

DIII-D research advancing the physics basis for optimizing the tokamak approach to fusion energy

et al. 2022

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DIII-D physics research addresses critical challenges for the operation of ITER and the next generation of fusion energy devices. This is done through a focus on innovations to provide solutions for high performance long pulse operation, coupled with fundamental plasma physics understanding and model validation, to drive scenario development by integrating high performance core and boundary plasmas. Substantial increases in off-axis current drive efficiency from an innovative top launch system for EC power, and in pressure broadening for Alfven eigenmode control from a co-/counter-I p steerable off-axis neutral beam, all improve the prospects for optimization of future long pulse/steady state high performance tokamak operation. Fundamental studies into the modes that drive the evolution of the pedestal pressure profile and electron vs ion heat flux validate predictive models of pedestal recovery after ELMs. Understanding the physics mechanisms of ELM control and density pumpout by 3D magnetic perturbation fields leads to confident predictions for ITER and future devices. Validated modeling of high-Z shattered pellet injection for disruption mitigation, runaway electron dissipation, and techniques for disruption prediction and avoidance including machine learning, give confidence in handling disruptivity for future devices. For the non-nuclear phase of ITER, two actuators are identified to lower the L–H threshold power in hydrogen plasmas. With this physics understanding and suite of capabilities, a high poloidal beta optimized-core scenario with an internal transport barrier that projects nearly to Q = 10 in ITER at ∼8 MA was coupled to a detached divertor, and a near super H-mode optimized-pedestal scenario with co-I p beam injection was coupled to a radiative divertor. The hybrid core scenario was achieved directly, without the need for anomalous current diffusion, using off-axis current drive actuators. Also, a controller to assess proximity to stability limits and regulate β N in the ITER baseline scenario, based on plasma response to probing 3D fields, was demonstrated. Finally, innovative tokamak operation using a negative triangularity shape showed many attractive features for future pilot plant operation.

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“…Issues relating to amplitudes, repetition rates and mode spectra of ELMs remain to be elucidated, at least partly due to numerical limitations of codes operating with realistic conditions. Recent works [10][11][12][13][14][15][16] have tackled the challenge of explaining the mechanism of resonant magnetic perturbation (RMP) control (by mitigation/suppression) of type-I ELMs observed in several experiments [17][18][19][20][21]. The simulations presented in this article were carried out using the Culham Transporter of Ions and Electrons (CUTIE) [8,12,[22][23][24][25] -a two-fluid electromagnetic nonlinear global code.…”

Section: Introductionmentioning

confidence: 99%

Bifurcation behaviour of resonant magnetic perturbation control of edge localized modes in tokamaks: nonlinear simulation results

Thyagaraja

Sen

Chandra

2023

Phil. Trans. R. Soc. A.

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In this article, some novel results of two fluid nonlinear simulations on the control of edge localized modes (ELMs) in tokamaks by resonant magnetic perturbations (RMPs) are presented. Many experiments around the world have demonstrated that RMPs are effective in possibly mitigating or even completely suppressing strong (type I) ELMs that would seriously degrade confinement and could cause other heat-flux problems in both present (e.g. JET) and planned future tokamaks (ITER). Our simulations demonstrate that non-axisymmetric RMPs with toroidal mode numbers n = 2 , 3 , 4 and suitable field-strengths (kAturns) at the plasma wall imply significant bifurcations in their ability to mitigate or even suppress type-I ELMs, qualitatively similar to RMP effects on ELMs reported in experiments. This article is part of a discussion meeting issue ‘H-mode transition and pedestal studies in fusion plasmas’.

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Wide Operational Windows of Edge-Localized Mode Suppression by Resonant Magnetic Perturbations in the DIII-D Tokamak

Cited by 51 publications

References 45 publications

Optimization of 3D controlled ELM-free state with recovered global confinement for tokamak fusion plasmas

Optimization of 3D controlled ELM-free state with recovered global confinement for tokamak fusion plasmas

DIII-D research advancing the physics basis for optimizing the tokamak approach to fusion energy

Bifurcation behaviour of resonant magnetic perturbation control of edge localized modes in tokamaks: nonlinear simulation results

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