Effect of runaway electrons on tearing mode stability: with or without favorable curvature stabilization

Li, L.; Liu, Yueqiang; Wang, Y.F.; Guo, Lucun; Zhong, Fangchuan

doi:10.1088/1741-4326/ac19fa

Cited by 4 publications

(3 citation statements)

References 44 publications

(99 reference statements)

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“…Detailed derivation of this hybrid formulation and implementation into the MARS-F code have been reported in reference [28]. Below we list the final combined equations for stability analysis of resistive MHD instabilities, assuming vanishing plasma equilibrium flow…”

Section: Fluid Mhd-re Hybrid Modelmentioning

confidence: 99%

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Interaction between runaway electrons and internal kink in a post-disruption plasma

Liu¹,

Li²,

Kim³

et al. 2021

Nucl. Fusion

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Direct interactions between the n = 1 (n is the toroidal mode number) resistive internal kink instability and relativistic runaway electrons (REs) in a post thermal quench toroidal plasma are numerically investigated. A recently developed hybrid model, where the runaway current is treated as a fluid component, is adopted to study how REs affect the internal kink stability and the associated eigenmode structure. The RE-modified internal kink perturbation is in turn superposed with the equilibrium field, in order to study the effects of 3D fields on the drift orbits of REs and consequently on the RE confinement and loss. Results are compared with that assuming the single fluid model for the runaway beam. It is found that REs destabilize the resistive internal kink mode, leading to a better recovery (compared to the standard single fluid model) of the mode growth rate scaling of γ ∼ S −1/3 at lower values of Lundquist number S. Furthermore, REs significantly modify the internal kink eigenfunction inside or near the q = 1 surface. In particular, a new narrow layer forms within the resistive layer, where a strong peaking of the perturbed parallel current develops. The RE contribution is also found to substantially enhance the coupling among poloidal harmonics, in particular between m = 1 and its nearest sidebands. All these changes to the perturbation structure consequently affect the RE drift orbits in the presence of the internal kink instability. Compared to the fluid model, 3D perturbations computed with the more consistent hybrid model lead to less loss of relativistic electrons in the RE beam, when the perturbation level reaches that of the equilibrium field. At lower (but still large) perturbation amplitude (∼10% of the equilibrium field), the internal kink mode has little effect on the RE loss. REs launched within the q = 1 surface always stay confined within the plasma, independent of the field perturbation amplitude (up to the level of the equilibrium field), the beam model adopted (fluid versus hybrid), or the particle traveling direction. On the other hand, the individual drift orbit trajectory is qualitatively sensitive to these factors.

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Section: Fluid Mhd-re Hybrid Modelmentioning

confidence: 99%

“…A fluid-like hybrid model for the RE current has recently been developed and implemented in the MARS-F code [27], and applied to study the tearing mode instability [28]. In this work, we apply the same model to investigate the RE effect on the resistive internal kink, for a toroidal RE beam plasma with conventional aspect ratio.…”

Section: Introductionmentioning

confidence: 99%

Interaction between runaway electrons and internal kink in a post-disruption plasma

Liu¹,

Li²,

Kim³

et al. 2021

Nucl. Fusion

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“…Therefore, generally speaking, a MHD-RE hybrid model is needed, in order to properly describe the stability of such a runaway beam plasma. Such models have recently been developed [31,[44][45][46][47]. In this study, we nevertheless adopt the fluid model, which shows a reasonably good agreement with experiments in DIII-D, in terms of both the instability time scale and the resulting RE loss properties [15,16,31].…”

Section: Mhd Instabilities During Disruptionmentioning

confidence: 72%

Toroidal modeling of runaway electron loss due to 3D fields in ITER

Liu¹,

Aleynikova²,

Paz-Soldan³

et al. 2022

Nucl. Fusion

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Mitigation of runaway electrons (REs) by three-dimensional (3-D) magnetic field perturbations is numerically investigated for the ITER 15 MA baseline D-T scenario, utilizing the MARS-F code [Liu et al Phys. Plasmas 7 3681] with a drift orbit test particle tracing module. Considered are two types of 3-D fields: the n=3 (n is the toroidal mode number) resonant magnetic perturbation (RMP) utilized for the purpose of controlling the edge localized modes in ITER, and perturbations generated by the n=1 magneto-hydrodynamic (MHD) instabilities in a post-disruption plasma. The RMP field, applied to a pre-disruption plasma, is found to be moderately effective in mitigating the RE seeds in ITER when vacuum field model is assumed. Up to ~40% loss fraction is possible at 90 kA-turn coil current. The mitigation efficiency is however substantially reduced, down to less than 5%, when the plasma response is taken into account. This is due to strong screening of the resonant magnetic field components by the plasma response resulting in much less field line stochasticity. On the other hand, the MARS-F modeling, based on the DINA-simulated post-disruption equilibria, shows that the n=1 resistive kink instabilities develop in these plasmas, as the edge safety factor qa evolves and drops below integer numbers. RE mitigation by these MHD instabilities is sensitive to the eigenmode structure. The best mitigation is achieved as qa drops below 3, when a global kink instability occurs that encompasses both internal and external components. This global instability is found to be capable of mitigating over 80% MeV-level passing RE orbits at a field perturbation |delta B|/B0 that is comparable to that observed in DIII-D experiments, and full mitigation if the perturbation amplitude is doubled. The ``wetted" area on the ITER limiting surface, due to MHD instability induced RE loss, generally increases with the perturbation amplitude (together with increasing loss fraction). At the highest perturbation level assumed in this study, the wetted area reaches ~60% of the total limiting surface area. The lost RE orbits mainly strike the outer divertor region of the limiting surface, with some fraction also hitting a wide area along the inboard side of the surface.

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Diffusion–convection model of runaway electrons due to large magnetohydrodynamic perturbations in post-thermal quench plasmas

Liu,

Aleynikova,

Hollmann

et al. 2023

Physics of Plasmas

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Systematic test particle tracing simulations for runaway electrons (REs) are performed for six post-thermal quench equilibria from DIII-D and ITER, where large scale, kink-like n = 1 (n is the toroidal mode number) magnetohydrodynamic (MHD) instabilities are found. The modeled particle guiding center orbits allow extraction of the effective diffusion–convection coefficients of REs in the presence of large three-dimensional (3D) perturbations up to 10% of the equilibrium toroidal field. With a fixed spatial distribution of the field perturbation, the RE transport coefficients along the plasma radial coordinate track reasonably well with the surface-averaged perturbation level. A substantial variation in the value of the transport coefficients—by three orders of magnitude in most cases, however, occurs with varying launching location of REs along the plasma radius. Large 3D perturbations almost always lead to comparable diffusion and convection processes, meaning that diffusion alone is insufficient to describe the particle motion. At lower (but still high) level of perturbation, the RE convection is found to be dominant over diffusion. A similar observation is made when the perturbation is too strong. In the presence of large perturbation, the dependence of the RE transport on the particle energy is sensitive to the spatial distribution of the perturbation. Based on numerically obtained RE transport coefficients, an analytic fitting model is proposed to quantify the particle diffusion and convection processes due to large MHD events in post-thermal quench plasmas. The model is shown to reasonably well reproduce the direct test particle tracing results for the RE loss fraction and can, thus, be useful for incorporating into other kinetic RE codes in order to simulate the RE beam evolution in the presence of large 3D perturbations.

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Effect of runaway electrons on tearing mode stability: with or without favorable curvature stabilization

Cited by 4 publications

References 44 publications

Interaction between runaway electrons and internal kink in a post-disruption plasma

Interaction between runaway electrons and internal kink in a post-disruption plasma

Toroidal modeling of runaway electron loss due to 3D fields in ITER

Diffusion–convection model of runaway electrons due to large magnetohydrodynamic perturbations in post-thermal quench plasmas

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