Design and experimental demonstration of feedback adaptive RMP ELM controller toward complete long pulse ELM suppression on KSTAR

Shousha, Ricardo; Kim, SangKyeun; Erickson, Keith; Hahn, S.H.; Nelson, A.; Yang, SeongMoo; Park, Jong‐Kyu; Wai, Josiah; Jeon, Y.M.; Lee, J. H.; Jang, Jin; Seo, D. C.; Kolemen, Egemen

doi:10.1063/5.0081928

Cited by 12 publications

(12 citation statements)

References 44 publications

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“…The typical RMP ELM suppression loss precursor of a Dα baseline dip is not observed in shot 169964 prior to the loss of suppression. These precursors are associated with complete island healing enabling a sudden inhalation of scrape-off layer particles by the growing pedestal [46]. From this, it is inferred that the edge island originally opened by the RMP never fully bifurcates away but is smoothly modulated in size during a limit cycle process.…”

Section: Unique Elm Properties With Rmps and Edge Localized Eccdmentioning

confidence: 97%

Access to stable, high pressure tokamak pedestals using local electron cyclotron current drive

Logan,

Lyons,

Knolker

et al. 2023

Nucl. Fusion

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Experiments on the DIII-D tokamak demonstrate that edge localized mode (ELM) stability can be manipulated using localized electron cyclotron current drive (ECCD) in conjunction with resonant magnetic perturbations (RMPs). The injection of counter-plasma-current edge ECCD reduces the RMP amplitude required to suppress ELMs and bifurcates the pedestal into a high-confinement regime with 7 kPA pedestal pressure. This is the first time such a high confinement regime has been accessed through the bifurcation from the ballooning stability branch predicted by existing models. These observations are consistent with modeled ECCD manipulation of magnetic islands induced by the RMPs.

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Section: Unique Elm Properties With Rmps and Edge Localized Eccdmentioning

confidence: 97%

Access to stable, high pressure tokamak pedestals using local electron cyclotron current drive

Logan,

Lyons,

Knolker

et al. 2023

Nucl. Fusion

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“…The adaptive feedback RMP ELM controller [15,38,39] is introduced to compensate for the limitations of the conventional pre-set I RMP control through an interactive I RMP control. The adaptive controller optimizes I RMP based on a built-in real-time ELM crash frequency monitor.…”

Section: Interactive I Rmp Control By Adaptive Feedback Rmp Elm Contr...mentioning

confidence: 99%

“…This iterative adjustment of I RMP can optimize the RMP strength to recover the plasma confinement while maintaining the ELM-crash-suppression phase. More details about the structure and process of the adaptive feedback algorithm can be found in [38,39].…”

Section: Interactive I Rmp Control By Adaptive Feedback Rmp Elm Contr...mentioning

confidence: 99%

“…The pre-emptive RMP onset based on the real-time Machine Learning (ML) classifier [36], which automatically triggers RMP before the first ELM after the L-H transition, can obtain a higher ion temperature at the plasma core region compared to the conventional pre-set RMP onset [37]. The interactive I RMP control by the adaptive feedback RMP ELM controller balances β N enhancement and ELM crash suppression by optimizing I RMP [15,38,39], in contrast to the conventional pre-set I RMP control. The optimization of not only I RMP for the RMP strength but also the RMP spectrum can contribute favorably to plasma confinement.…”

Section: Introductionmentioning

confidence: 99%

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Integrated RMP-based ELM-crash-control process for plasma performance enhancement during ELM crash suppression in KSTAR

et al. 2023

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The integrated resonant magnetic perturbation (RMP)-based ELM-crash-control process aims to enhance the plasma performance during the RMP-driven ELM crash suppression, where the RMP induces an unwanted confinement degradation. In this study, the normalized beta (βN) is introduced as a metric for plasma performance. The integrated process incorporates the latest achievements in the RMP technique to enhance βN efficiently. The integrated process triggers the n = 1 edge-localized RMP (ERMP) at the L-H transition timing using the real-time machine learning (ML) classifier. The pre-emptive RMP onset can reduce the required external heating power for achieving the same βN by over 10 % compared to the conventional RMP onset. During the RMP phase, the adaptive feedback RMP ELM controller, demonstrating its performance in previous experiments, plays a crucial role in maximizing βN during the suppression phase and sustaining the βN-enhanced suppression state by optimizing the RMP strength. The integrated process achieves βN up to ~2.65 during the suppression phase, which is ~10 % higher than the previous KSTAR record but ~6 % lower than the target of the K-DEMO first phase (βN = 2.8), and maintains the suppression phase above the lower limit of target βN (= 2.4) for ~4 s (~60 τE). In addition to βN enhancement, the integrated process demonstrates quicker restoration of the suppression phase and recovery of βN compared to the adaptive control with the n = 1 conventional RMP (CRMP). The post-analysis of the experiment shows the localized effect of the ERMP spectrum in radial and the close relationship between the evolution of βN and the electron temperature.

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“…'snowflake' and 'Super-X' divertors, magnetic configuration with 'negative triangularity'); implementation of liquid metals (e.g. Li) as the material accommodating the heat flux and, potentially, promising a new (zero-recycling) regime of a tokamak operation, the indications of which were observed in experiments; the peculiarities of edge plasma physics in stellarators, etc (see [60][61][62][63][64][65][66][67][68][69][70][71][72][73] and the reference therein, where these topics are discussed in some detail).…”

Section: Discussionmentioning

confidence: 99%

Fascinating physics at the edge of magnetic fusion devices

Krasheninnikov¹

2022

Plasma Phys. Control. Fusion

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Physics of the processes at the edge of magnetic fusion devices is multifaceted and exhibits complex, nonlinear synergistic effects. Even though this region occupies only a small portion of the whole device, it plays a crucial role in overall plasma confinement, heat exhaust, and plasma-wall interactions. The latter affects not only the performance but also the lifetime of plasma-facing components and, therefore remains an outstanding challenge for future fusion reactors. At the edge of fusion devices, researchers are dealing with phenomena including classical and anomalous plasma transport, atomic physics effects, and physics of plasma-facing material under strong irradiation by particle and energy fluxes. Such a diversity of the edge physics makes it particularly attractive for young scientists. By working in this field, they can find endless possibilities to demonstrate their talents and creativity. This short review describes just some of the basic scrape-off layer and divertor plasma phenomena including divertor plasma detachment, intermittent bursts of anomalous cross-field plasma transport, plasma-material interactions, and dust in fusion plasmas, which are of particular interest for fusion reactors.

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Design and experimental demonstration of feedback adaptive RMP ELM controller toward complete long pulse ELM suppression on KSTAR

Cited by 12 publications

References 44 publications

Access to stable, high pressure tokamak pedestals using local electron cyclotron current drive

Access to stable, high pressure tokamak pedestals using local electron cyclotron current drive

Integrated RMP-based ELM-crash-control process for plasma performance enhancement during ELM crash suppression in KSTAR

Fascinating physics at the edge of magnetic fusion devices

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