Sawtooth control in JET with ITER relevant low field side resonance ion cyclotron resonance heating and ITER-like wall

Graves, J. P.; Lennholm, M.; Chapman, I. T.; Lerche, E.; Reich, M.; Alper, B.; Bobkov, V.; Dümont, R.; Faustin, J. M.; Jacquet, P.; Jaulmes, F.; Johnson, T.; Keeling, D.; Liu, Yueqiang; Nicolas, T; Tholerus, Emmi; Blackman, T.; Carvalho, I.; Coelho, R.; Eester, D. Van; Felton, R.; Goniche, M.; Kiptily, V.; Monakhov, I.; Nave, M. F. F.; Thun, C. Perez von; Sabot, R.; Sozzi, C.; Tsalas, M.

doi:10.1088/0741-3335/57/1/014033

Cited by 22 publications

(32 citation statements)

References 24 publications

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“…A need for control of the sawtooth instability is also anticipated in ITER, in order to avoid long period sawteeth with large amplitude crashes that could trigger an NTM instability [23], and several schemes using ECCD or ICRF heating have been proposed [24]. Recent JET experiments have shown that the sawtooth period can be controlled with low field side ICRF heating (as will be available in ITER) near the q=1 surface [25], and that sawtooth pacing can be achieved with modulated central ion cyclotron heating [26], a method that is less sensitive to the deposition location. Further work is needed to validate ICRF sawtooth control in ITER-relevant H-mode discharges.…”

Section: Plasma Configuration Controlmentioning

confidence: 99%

Progress in disruption prevention for ITER

Strait¹,

Barr²,

Baruzzo³

et al. 2019

Nucl. Fusion

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Key plasma physics and real-time control elements needed for robustly stable operation of high fusion power discharges in ITER have been demonstrated in US fusion research. Optimization of the current density profile has enabled passively stable operation without n " 1 tearing modes in discharges simulating ITER's baseline scenario with zero external torque. Stable rampdown of the discharge has been achieved with ITER-like scaled current ramp rates, while maintaining an X-point configuration. Significant advances have been made toward real-time prediction of disruptions: machine learning techniques for prediction of disruptions have achieved 90% accuracy in offline analysis, and direct probing of ideal and resistive plasma stability using 3D magnetic perturbations has shown a rising plasma response before the onset of a tearing mode. Active stability control contributes to prevention of disruptions, including direct stabilization of resistive-wall kink modes in high-β discharges, forced rotation of magnetic islands to prevent wall locking, and localized heating/current drive to shrink the islands. These elements are being integrated into stable operating scenarios and a new event-handling system for off-normal events in order to develop the physics basis and techniques for robust control in ITER.

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Section: Plasma Configuration Controlmentioning

confidence: 99%

Progress in disruption prevention for ITER

Strait¹,

Barr²,

Baruzzo³

et al. 2019

Nucl. Fusion

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“…In this perspective of avoiding dangerous NTMs and reducing the adverse effects of heavy impurities, ICRH control of the sawtooth cycle is very promising. Different methods for sawtooth pacing with ICRH have been recently tested in JET-ILW [10,11]. ICRH is believed to act on the pressure and distribution function of energetic ions in the plasma, which have a stabilizing effect on sawteeth.…”

Section: Icrh Modulation For Sawteeth Pacingmentioning

confidence: 99%

On the Use of Transfer Entropy to Investigate the Time Horizon of Causal Influences between Signals

Murari

Lungaroni

Peluso

et al. 2018

Entropy

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Understanding the details of the correlation between time series is an essential step on the route to assessing the causal relation between systems. Traditional statistical indicators, such as the Pearson correlation coefficient and the mutual information, have some significant limitations. More recently, transfer entropy has been proposed as a powerful tool to understand the flow of information between signals. In this paper, the comparative advantages of transfer entropy, for determining the time horizon of causal influence, are illustrated with the help of synthetic data. The technique has been specifically revised for the analysis of synchronization experiments. The investigation of experimental data from thermonuclear plasma diagnostics proves the potential and limitations of the developed approach.

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“…We now investigate the effect of α CD on the possibility to control sawteeth with current or power deposition. Since the sawtooth period varies as we change α CD (see figure 4), we define the relative modification of the sawtooth period ∆T ST of the sawtooth period, defined as (29) where T N o RF sawtooth is the sawtooth period in the absence of current deposition (J RF = 0), and is a function of α CD . In figure 17, ∆T ST is plotted as a function of the deposition radial location for a given value of the current (I RF /I P = 1%), for different values of α CD .…”

Section: Role Of the Current Source Terms On The Dynamics Of Sawteethmentioning

confidence: 99%

“…Two main methods have been explored. In the first one, the population of fast particles in the core plasma is controlled using either NBI [28] or ICRH [29], thus modifying the stability of the internal kink mode and ultimately the sawtooth period. The second method relies on the use of external current-drive or heating in order to change the the current profile near the q = 1 surface, either by using external current-drive [30,31,32,33,34], or by modifying the temperature profile through localized heating so as to change the plasma resistivity and therefore the inductive current profile.…”

Section: Introductionmentioning

confidence: 99%

Non-linear MHD simulations of sawteeth and their control by current and power depositions

Février¹,

Nicolas²,

Maget³

et al. 2018

Nucl. Fusion

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Sawteeth in tokamak plasmas correspond to periodic relaxations of the temperature and density in the central region of the plasma, caused by the internal kink mode. They are a key player in core confinement and impurity transport in the central region of a tokamak discharge, and can trigger secondary instabilities. Being able to control their dynamics is therefore important. In this article, we explore by means of MHD simulations the control of sawteeth, relying on Electron Cyclotron Resonant Heating (ECRH) or Electron Cyclotron Current Drive (ECCD) deposition in the vicinity of the q = 1 surface. To do so, simulations with the full-MHD code XTOR-2F [1], which features power and current source terms mimicking the effects of ECCD and ECRH, are performed. Simulations show that deposition of current inside the inversion radius leads to an increase of the sawtooth frequency whereas deposition near or outside the inversion radius leads to a decrease of the sawtooth period. The modification of the sawtooth shape in presence of additional heating or current drive is also investigated. Finally, we briefly explore possible scenarios for the triggering of magnetic islands, and show that controlling the sawteeth can indeed help to prevent the triggering of tearing instabilities.

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Sawtooth control in JET with ITER relevant low field side resonance ion cyclotron resonance heating and ITER-like wall

Cited by 22 publications

References 24 publications

Progress in disruption prevention for ITER

Progress in disruption prevention for ITER

On the Use of Transfer Entropy to Investigate the Time Horizon of Causal Influences between Signals

Non-linear MHD simulations of sawteeth and their control by current and power depositions

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