Advances in understanding and utilising ELM control in JET

Chapman, I. T.; Luna, de la E; Lang, P. T.; Liang, Y.; Alper, B.; Denner, P.; Frigione, D.; Garzotti, L.; Ham, Christopher; Huijsmans, Gta Guido; Jachmich, S.; Kocsis, G.; Lennholm, M.; Lupelli, I.; Rimini, F.; Sips, A.

doi:10.1088/0741-3335/58/1/014017

Cited by 7 publications

(5 citation statements)

References 46 publications

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“…It can clearly be seen that the application of RMPs destabilizes the infinite n ballooning mode. This is in agreement with results found on both MAST and JET plasmas [4,26].…”

Section: Infinite N Stabilitysupporting

confidence: 93%

Non-axisymmetric ideal equilibrium and stability of ITER plasmas with rotating RMPs

et al. 2016

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The magnetic perturbations produced by the resonant magnetic perturbation (RMP) coils will be rotated in ITER so that the spiral patterns due to strike point splitting which are locked to the RMP also rotate. This is to ensure even power deposition on the divertor plates. VMEC equilibria are calculated for different phases of the RMP rotation. It is demonstrated that the off harmonics rotate in the opposite direction to the main harmonic. This is an important topic for future research to control and optimize ITER appropriately. High confinement mode (H-mode) is favourable for the economics of a potential fusion power plant and its use is planned in ITER. However, the high pressure gradient at the edge of the plasma can trigger periodic eruptions called edge localized modes (ELMs). ELMs have the potential to shorten the life of the divertor in ITER (Loarte et al 2003 Plasma Phys. Control. Fusion 45 1549) and so methods for mitigating or suppressing ELMs in ITER will be important. Non-axisymmetric RMP coils will be installed in ITER for ELM control. Sampling theory is used to show that there will be significant a n c o i l s − n r m p harmonic sideband. There are nine coils toroidally in ITER so n c o i l s = 9 . This results in a significant n = 6 component to the n r m p = 3 applied field and a significant n = 5 component to the n r m p = 4 applied field. Although the vacuum field has similar amplitudes of these harmonics the plasma response to the various harmonics dictates the final equilibrium. Magnetic perturbations with toroidal mode number n = 3 and n = 4 are applied to a 15 MA, q 95 ≈ 3 burning ITER plasma. We use a three-dimensional ideal magnetohydrodynamic model (VMEC) to calculate ITER equilibria with applied RMPs and to determine growth rates of infinite n ballooning modes (COBRA). The n r m p = 4 case shows little change in ballooning mode growth rate as the RMP is rotated, however there is a change with rotation for the n r m p = 3 case.

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“…It can clearly be seen that the application of RMPs destabilizes the infinite n ballooning mode. This is in agreement with results found on both MAST and JET plasmas [4,26].…”

Section: Infinite N Stabilitysupporting

confidence: 93%

Non-axisymmetric ideal equilibrium and stability of ITER plasmas with rotating RMPs

et al. 2016

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“…The application of a fast and controlled vertical plasma motion (known as vertical kicks in JET) for frequency control of ELMs has been successfully demonstrated on several tokamaks [39][40][41][42]. This method on JET relies on the vertical stabilization control system to drive the fast vertical plasma motion.…”

Section: Methodsmentioning

confidence: 99%

Pedestal particle balance studies in JET-ILW H-mode plasmas

Horváth

Lomanowski

Karhunen

et al. 2023

Plasma Phys. Control. Fusion

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JET-ILW type I ELMy H-modes at 2.5MA/2.8T with constant NBI heating (23 MW) and gas fuelling rate were performed, utilising ELM pacing by vertical kicks and plasma shaping (triangularity, δ) as tools to disentangle the eﬀects of ELMs, inter-ELM transport and edge stability on the pedestal particle balance. In agreement with previous studies, the pedestal conﬁnement improves with increasing δ, mostly due to a signiﬁcant increase in pedestal density while the ELM frequency (fELM) is decreased. Improved pedestal conﬁnement with increasing δ was observed even when the pedestal MHD stability was degraded artiﬁcially by vertical kicks, implying that increased triangularity may favourably aﬀect the inter-ELM pedestal recovery. The workﬂow developed to quantify the pedestal particle balance uses high time-resolution proﬁle reﬂectometry to characterise the inter-ELM evolution of the plasma particle content (dN/dt), the NEO drift-kinetic solver to evaluate the neoclassical ﬂuxes and interpretative EDGE2D-EIRENE simulations to estimate the edge particle source. The edge particle source is then constrained by deuterium Balmer-α line intensity measurements in the main chamber, which are, however, strongly aﬀected by reﬂections from the metal walls. The reﬂections are accounted for by the CHERAB code taking the divertor emission (the brightest light source in the torus) distribution from imaging spectroscopy measurements as input. Our analysis shows that in the second half of the ELM cycle, the volume-integrated particle source is larger than dN/dt, indicating that transport plays a key role in the inter-ELM pedestal recovery.

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“…The kick-triggered ELM model proposed here has been further tested in recent experiments carried out in JET-ILW where vertical kicks, large enough to trigger ELMs in H-mode plasmas with β = 1.8 MW) [48]. These observations can be explained by taking into account the strong influence the enhanced Shafranov shift associated to the increase in core pressure has on the edge stability [48]. This effect has already been observed in DIII-D [49] and MAST [50].…”

Section: Edge Mhd Modellingmentioning

confidence: 99%

Understanding the physics of ELM pacing via vertical kicks in JET in view of ITER

Luna¹,

Chapman

Rimini

et al. 2015

Nucl. Fusion

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Experiments on JET, with both the previous carbon wall (JET-C) and the new Be/W wall (JET-ILW), have demonstrated the efficacy of using a fast vertical plasma motion (known as vertical kicks in JET) for active ELM control. In this paper we report on a series of experiments that have been recently conducted in JET-ILW with the goal of further improving the physics understanding of the processes governing the triggering of ELMs via vertical kicks. This is a necessary step to confidently extrapolate this ELM control method to ITER. Experiments have shown that ELMs can be reliably triggered provided a minimum vertical plasma displacement and velocity is imposed. The magnitude of the minimum displacement depends on the plasma parameters, being smaller for higher pedestal temperatures and lower collisionalities, which is encouraging in view of ITER. Modelling and stability analysis suggest that a localized current density induced by the vertical plasma movement close to the separatrix plays a major role in the ELM triggering mechanism, which is consistent with the experimental observations. The implications of these results for the extrapolation of this ELM control scheme to ITER are discussed.

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Advances in understanding and utilising ELM control in JET

Cited by 7 publications

References 46 publications

Non-axisymmetric ideal equilibrium and stability of ITER plasmas with rotating RMPs

Non-axisymmetric ideal equilibrium and stability of ITER plasmas with rotating RMPs

Pedestal particle balance studies in JET-ILW H-mode plasmas

Understanding the physics of ELM pacing via vertical kicks in JET in view of ITER

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