Design and installation of divertor biased target system on the HL-2A TOKAMAK

Cui, Butian; Ji, X.Q.; Sun, Tengfei; Liang, S.Y.; Zhang, J.Z.; Wang, A.; He, M.Y.

doi:10.1016/j.fusengdes.2021.112963

Cited by 5 publications

(6 citation statements)

References 19 publications

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“…Here, the spectrum and amplitude of B-RMP can be tuned for a specific purpose, through varying the biased electric voltage (from −210 V to +130 V) and the biasing configuration of four plates. For example, when the #1 and #4 plates are biased with positive electric voltage with respect to the grounded vacuum vessel and the others are grounded, the n = 1, 2, 3, 4 components are dominant [57]. n is the toroidal mode number.…”

Section: Configuration Of Divertor Biased Target Platesmentioning

confidence: 99%

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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: Configuration Of Divertor Biased Target Platesmentioning

confidence: 99%

“…The effective area of one plate is about 2 cm ×6 cm = 12 cm 2 , for which the sheath theory is still valid based on the experiment observations. More detailed hardware information about the biased target plates are presented in reference [57].…”

Section: Configuration Of Divertor Biased Target Platesmentioning

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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“…It has also been demonstrated theoretically that the asymmetric helical SOL current induced via biasing can induce sufficient resonant magnetic perturbations for the edge localized mode (ELM) control in ITER [8]. Accordingly, the researchers in the HL-2A team designed a divertor biased target system to investigate the physics of ELM control by biasing [9]. In some small and medium devices, the EB is widely used to control turbulence transport and magnetohydrodynamics (MHD) instabilities and thus to improve plasma confinement.…”

Section: Introductionmentioning

confidence: 99%

Effects of negative and positive bias voltages on turbulence characteristics in J-TEXT tokamak

Zhang¹,

Liu²,

Xu³

et al. 2022

Plasma Phys. Control. Fusion

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The effects of positive and negative bias voltages on the turbulence characteristics in edge plasmas of J-TEXT are studied using Langmuir probe arrays. The experimental results illustrate that the turbulent particle transport fluxes are suppressed in both positive and negative bias cases, while the suppression mechanisms are quite different. For the positive bias (+300 V), the long-range correlation (LRC) structures with frequencies of about 10 ~ 30 kHz are generated, which are beneficial for the turbulent transport suppression. In the -300 V bias case, no LRCs appear, while a strong mean flow shear exists which can reduce the amplitudes of potential and density fluctuations and thus decreases the turbulent transport.

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“…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. In the future, experiments on the suppression of ELMs by SOL currents will be carried out on HL-2A.…”

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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Design and installation of divertor biased target system on the HL-2A TOKAMAK

Cited by 5 publications

References 19 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

Effects of negative and positive bias voltages on turbulence characteristics in J-TEXT tokamak

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

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