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

Brooks, J. W.; Bialek, J.; Hansen, Chris; Levesque, J.P.; Mauel, M. E.; Navratil, G.A.; Saperstein, A.; Stewart, I. G.

doi:10.1088/1741-4326/ac1544

Cited by 2 publications

(2 citation statements)

References 42 publications

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“…The toroidally asymmetric gas puffing is also proposed to drive the SOL current, based on the thermo-electric potential difference [18,19] between the two targets on the inner and outer divertor. The driven current in the SOL region not only affects the plasma transport in the pedestal region, but also impacts the magneto-hydrodynamic (MHD) instabilities, such as the ELM, resistive wall mode (RWM), and tearing mode [20][21][22]. The SOL current can also affect the transport in the SOL region which results in the extension of SOL layer width.…”

Section: Introductionmentioning

confidence: 99%

Toroidal modeling of 3D perturbations generated by current filaments in scrape-off layer in tokamak with biased divertor targets

et al. 2022

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The divertor biasing technique offers a promising alternative to control the edge localized mode (ELM) as well as the divertor heat load in tokamaks, as compared to the resonant magnetic perturbation (RMP) generated by magnetic coils. The linear resistive MHD code MARS-F [Liu et al. Phys. Plasmas 7, 3681 (2000)] is employed to study the plasma response to the $n=2$ ($n$ is the toroidal mode number) field perturbation in HL-2A, produced by the divertor biasing current filaments flowing in the scrape-off layer (SOL) region. The response field due to biasing currents is compared with the RMP field utilized for ELM control in HL-2A. The strength of the radial resonant field perturbation, produced by the biasing currents of 100 A level, is found to be comparable with RMP generated by several kA of ELM control coil currents for the reference plasma. The plasma normal displacement near the X-point and {the associated neoclassical toroidal viscosity torque are} also computed to be similar between these two techniques. The modeling results thus strongly suggest that the biasing technique can be applied to control ELMs. Moreover, the biasing currents produce field perturbations, including the plasma response, that are localized more near the plasma edge (compared to the RMP counterpart), thus reducing the chance of mode locking associated with core perturbations. Particle orbit tracing also reveals that the biasing current produced magnetic perturbation tends to widen the heat deposition region and induce the strike point splitting of the ion saturation flow on the outer divertor surface, consistent with experimental observations in HL-2A. These toroidal modeling results confirm the possibility of ELM control and plasma exhaust solution by the divertor biasing technique.

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Section: Introductionmentioning

confidence: 99%

Toroidal modeling of 3D perturbations generated by current filaments in scrape-off layer in tokamak with biased divertor targets

et al. 2022

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“…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]. More recently, the interaction between SOL current driven by EB and MHD mode has also been studied on HBT-EP [33,34]. The biased target plate is designed to be mounted on the HL-2A tokamak [35], and it has been demonstrated numerically that the SOL current driven by the target plate can change the magnetic topology.…”

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

Cited by 2 publications

References 42 publications

Toroidal modeling of 3D perturbations generated by current filaments in scrape-off layer in tokamak with biased divertor targets

Toroidal modeling of 3D perturbations generated by current filaments in scrape-off layer in tokamak with biased divertor targets

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

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