Filamentary plasma eruptions and their control on the route to fusion energy

Ham, Christopher; Kirk, A.; Pamela, S.; Wilson, H. R.

doi:10.1038/s42254-019-0144-1

Cited by 34 publications

(25 citation statements)

References 88 publications

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“…In particular, the filament dynamics were compared to experimental observations revealing good qualitative agreement regarding structure and dynamics (figure 41). The general role of filaments in ELM dynamics and ELM energy losses was also addressed in reference [195]. The ELM energy losses, and divertor heat flux profiles were found to agree reasonably well in spite of using a reduced MHD model in this low aspectratio configuration and neglecting diamagnetic drift effects.…”

Section: Natural Elmsmentioning

confidence: 86%

“…After the first confirmation of the generic features of full non-linear ELM dynamics using the JOREK code, extensive studies of ELMs physics in existing tokamaks (JET, ASDEX Upgrade, KSTAR, DIII-D, MAST) were performed with the aim of further validation and improvement of JOREK physical models for more confident predictive modelling for nextstep machines and in particular ITER. Such extensive studies have also enabled the JOREK code to contribute to general ELM physics issues like the role of filamentary structures in ELM and ELM control [195]. In the following, we briefly describe some examples and main results.…”

Section: Natural Elmsmentioning

confidence: 99%

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The JOREK non-linear extended MHD code and applications to large-scale instabilities and their control in magnetically confined fusion plasmas

et al. 2021

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JOREK is a massively parallel fully implicit non-linear extended magneto-hydrodynamic (MHD) code for realistic tokamak X-point plasmas. It has become a widely used versatile simulation code for studying large-scale plasma instabilities and their control and is continuously developed in an international community with strong involvements in the European fusion research programme and ITER organization. This article gives a comprehensive overview of the physics models implemented, numerical methods applied for solving the equations and physics studies performed with the code. A dedicated section highlights some of the verification work done for the code. A hierarchy of different physics models is available including a free boundary and resistive wall extension and hybrid kinetic-fluid models. The code allows for flux-surface aligned iso-parametric finite element grids in single and double X-point plasmas which can be extended to the true physical walls and uses a robust fully implicit time stepping. Particular focus is laid on plasma edge and scrape-off layer (SOL) physics as well as disruption related phenomena. Among the key results obtained with JOREK regarding plasma edge and SOL, are deep insights into the dynamics of edge localized modes (ELMs), ELM cycles, and ELM control by resonant magnetic perturbations, pellet injection, as well as by vertical magnetic kicks. Also ELM free regimes, detachment physics, the generation and transport of impurities during an ELM, and electrostatic turbulence in the pedestal region are investigated. Regarding disruptions, the focus is on the dynamics of the thermal quench (TQ) and current quench triggered by massive gas injection and shattered pellet injection, runaway electron (RE) dynamics as well as the RE interaction with MHD modes, and vertical displacement events. Also the seeding and suppression of tearing modes (TMs), the dynamics of naturally occurring TQs triggered by locked modes, and radiative collapses are being studied.

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Section: Natural Elmsmentioning

confidence: 86%

Section: Natural Elmsmentioning

confidence: 99%

The JOREK non-linear extended MHD code and applications to large-scale instabilities and their control in magnetically confined fusion plasmas

et al. 2021

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“…is the leading material to handle the plasma exhaust challenge in ITER and future fusion devices [1,2]. However, the explosive heat and particle outburst during edge-localized modes (ELMs), which are magnetohydrodynamic instabilities occurring at the edge of H-mode plasmas [3,4], degrade the structural integrity of the tungsten plasma-facing components (PFCs) and introduce tungsten impurities into the plasma [5][6][7][8][9][10]. Understanding such extreme plasma surface interactions is critical in determining the operational limits of PFCs and instrumental for the operation of future fusion devices, therefore motivating extensive experimental and numerical work in recent years.…”

Section: Introductionmentioning

confidence: 99%

Power deposition behavior of high-density transient hydrogen plasma on tungsten in Magnum-PSI

Li¹,

Morgan²,

Berg-Stolp³

et al. 2021

Plasma Phys. Control. Fusion

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The lifetime of plasma-facing components (PFCs) will have a strong influence on the efficiency and viability of future fusion power plants. However, the PFCs suffer from thermal stresses and physical sputtering induced by edge-localized modes (ELMs). ELMs in future fusion devices are expected to occur with a high plasma density compared to current day devices such that coupling of recycling neutrals and plasma ions will be strong. Because of the scale hierarchy of future fusion devices compared to the present ones, the influence of this coupling is difficult to predict. Here, we investigate the ELM-like hydrogen plasma induced heat loads on tungsten in the linear device Magnum-PSI, producing ∼1 ms plasma pulses with electron densities up to 3.5 × 10 21 m −3 . A combination of time-resolved Thomson scattering and coherent Thomson scattering was used to acquire plasma parameters in front of the target. Moreover, a fast infrared camera coupled to finite element thermal analyses allowed to determine the deposited heat loads on the target. We found a significant inconsistency between the plasma power calculated with a conventional collisionless sheath model and the absorbed power by the target. Moreover, plasma stagnation upstream and plasma cooling downstream were observed during the pulses. The observations are explained based on ionization and elastic collisions between the recycling neutrals and plasma ions. The results highlight the impact of plasma-neutral interaction on the power deposition behavior of ELM-like hydrogen plasma on tungsten.

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“…These types include violent, low-frequency Type-I ELMs, or more intermittent, burst-like Type-III ELMs, as well as a mixed regime [8,9,10]. While two-fold stability analysis of peelingballooning modes explains linear stability of ELMs [11,12], the actual ELM crash is a nonlinear magnetohydrodynamic phenomenon and an area of active research interest [13,3,14,15,12].…”

Section: Introductionmentioning

confidence: 99%

Machine-Learning enabled analysis of ELM filament dynamics in KSTAR

Jacobus¹,

Choi²,

Kube³

2022

Preprint

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The emergence and dynamics of filamentary structures associated with edge-localized modes (ELMs) inside tokamak plasmas during high-confinement mode is regularly studied using Electron Cyclotron Emission Imaging (ECEI) diagnostic systems. Such diagnostics allow us to infer electron temperature variations, often across a poloidal cross-section. Previously, detailed analysis of these filamentary dynamics and classification of the precursors to edge-localized crashes has been done manually. We present a machine-learning-based model, capable of automatically identifying the position, spatial extend, and amplitude of ELM filaments. The model is a deep convolutional neural network that has been trained and optimized on an extensive set of manually labeled ECEI data from the KSTAR tokamak. Once trained, the model achieves a 93.7% precision and allows us to robustly identify plasma filaments in unseen ECEI data. The trained model is used to characterize ELM filament dynamics in a single H-mode plasma discharge. We identify quasi-periodic oscillations of the filaments size, total heat content, and radial velocity. The detailed dynamics of these quantities appear strongly correlated with each other and appear qualitatively different during the pre-crash and ELM crash phases.

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Filamentary plasma eruptions and their control on the route to fusion energy

Cited by 34 publications

References 88 publications

The JOREK non-linear extended MHD code and applications to large-scale instabilities and their control in magnetically confined fusion plasmas

The JOREK non-linear extended MHD code and applications to large-scale instabilities and their control in magnetically confined fusion plasmas

Power deposition behavior of high-density transient hydrogen plasma on tungsten in Magnum-PSI

Machine-Learning enabled analysis of ELM filament dynamics in KSTAR

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