Generation of non-axisymmetric scrape-off layer perturbations for controlling tokamak edge plasma profiles and stability

Joseph, I.; Cohen, R. H.; Rognlien, T. D.; Ryutov, D. D.

doi:10.1063/1.3702048

Cited by 3 publications

(2 citation statements)

References 36 publications

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“…In addition to the LHW driven SOL current filament, the asymmetric biasing of the divertor target or an electrode might be an alternative method to induce helical SOL current. It has been demonstrated theoretically that the asymmetric helical SOL current induced via biasing can induce sufficient RMPs for the ELM control in ITER [21][22][23]. Experiments using SOL current driven by biased target plates or biased electrodes (EBs) to investigate the effect on boundary plasma or the thermal load of divertor target plates have been carried out in some fusion devices such as NSTX [24,25], JFT-2M [26,27], TORPEX [28,29], MAST [30], COMPASS-D [31,32].…”

Section: Introductionmentioning

confidence: 99%

Impact of the non-axisymmetric SOL current driven by a biased electrode on the diverted J-TEXT plasma

Wang

Ding

et al. 2022

Plasma Phys. Control. Fusion

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It is observed in EAST that the non-axisymmetric helical currents induced by lower hybrid waves (LHW) in the scrape-off layer (SOL) can produce resonant magnetic perturbations (RMPs), hence mitigate edge-localized modes (ELMs) significantly and cause the strike points splitting. In this work, the NA-SOL current driven by an alternative method, i.e. biased electrode, is shown to influence the plasma boundary, especially the strike points, in the divertor configuration on J-TEXT. With positive bias to the electrode, the upper strike points on the divertor target plate is observed to split as captured by the visible camera. Such splitting is usually observed with the RMPs. In addition, the SOL plasma parameters measured by the reciprocating probe, such as floating potential (Vf), electron temperature (Te), and ion saturation current (Is), are significantly altered by applying modulation bias, which is closely related to the SOL current. A SOL current model has been extended from the limiter configuration version to the poloidal divertor configuration, and the magnetic field generated by SOL current and the change of magnetic topological structure of plasma boundary can be simulated. The simulation results shows that the magnetic perturbation generated by the SOL current can induce the lobes near the X-point, which is three-dimensional asymmetric structure, and shows good agreement with the experimental observation. The active control of the boundary magnetic topology indicates that the SOL current is capable of generating strong magnetic perturbations, and hence might be sufficient for the control of ELMs.

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Section: Introductionmentioning

confidence: 99%

Impact of the non-axisymmetric SOL current driven by a biased electrode on the diverted J-TEXT plasma

Wang

Ding

et al. 2022

Plasma Phys. Control. Fusion

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“…Additionally, injected SOL currents may be used to control edge pressure gradients and suppress ELMs [15,16].…”

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confidence: 99%

Suppression of MHD modes with active phase-control of probe-injected currents

et al. 2021

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Active phase-control of probe-injected current is shown to both suppress and amplify long-wavelength rotating magnetohydrodynamic instabilities in the HBT-EP tokamak. Four probes are connected in quadrature and energized to drive non-axisymmetric currents through the edge of the tokamak, creating magnetic perturbations comparable to previously-studied saturated kink modes or resonant magnetic perturbations that are generated by an external control coil array. Measurements of the magnetic perturbations from the probe-injected currents determine a set of current-carrying helical filaments used to model active feedback control of resistive wall modes. These experiments suggest current-injection feedback may be an effective alternative to external control coils for control of RWMs and other long-wavelength kink-like modes at the edge of tokamaks.

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Influence of Li conditioning on Lower Hybrid Current Drive efficiency in H-mode and L- mode plasmas on EAST

Goniche

Peysson

et al. 2017

EPJ Web Conf.

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Abstract. The lower hybrid current drive efficiency on the EAST tokamak is estimated on a large database of low loop voltage discharges (V L <120mV) covering the 2016 campaign starting with lithium-free plasma facing components and ending with strong cumulated deposition of lithium. The efficiency is found to vary in a wide range from 0.6 to 1.2×10 19 A.W -1 .m -2 . No deleterious effect of the density on the efficiency is found between 2.3 and 3.2×10 19 m -3 . The high efficiency occurs after strong lithium evaporation. The low effective charge Z eff and the higher temperature of these discharges, can account for the high efficiency according to the expected scaling with Z eff and . Modelling with a ray-tracing code coupled to a Fokker-Planck solver supports this result, assuming that the fast electron transport is reduced in the zero loop voltage discharge with high efficiency.

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Generation of non-axisymmetric scrape-off layer perturbations for controlling tokamak edge plasma profiles and stability

Cited by 3 publications

References 36 publications

Impact of the non-axisymmetric SOL current driven by a biased electrode on the diverted J-TEXT plasma

Impact of the non-axisymmetric SOL current driven by a biased electrode on the diverted J-TEXT plasma

Suppression of MHD modes with active phase-control of probe-injected currents

Influence of Li conditioning on Lower Hybrid Current Drive efficiency in H-mode and L- mode plasmas on EAST

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