中国物理B ›› 2023, Vol. 32 ›› Issue (7): 75208-075208.doi: 10.1088/1674-1056/acc1d7

所属专题： SPECIAL TOPIC — Plasma disruption

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Drift surface solver for runaway electron current dominant equilibria during the current quench

Lu Yuan(袁露) and Di Hu(胡地)†   

  1. School of Physics, Beihang University, Beijing 100191, China
  • 收稿日期:2022-12-30 修回日期:2023-02-17 接受日期:2023-03-07 出版日期:2023-06-15 发布日期:2023-06-28
  • 通讯作者: Di Hu E-mail:hudi2@buaa.edu.cn
  • 基金资助:
    Project supported by the National MCF Energy Research and Development Program of China (Grant No. 2019YFE03010001) and the National Natural Science Foundation of China (Grant No. 11905004).

Drift surface solver for runaway electron current dominant equilibria during the current quench

Lu Yuan(袁露) and Di Hu(胡地)†   

  1. School of Physics, Beihang University, Beijing 100191, China
  • Received:2022-12-30 Revised:2023-02-17 Accepted:2023-03-07 Online:2023-06-15 Published:2023-06-28
  • Contact: Di Hu E-mail:hudi2@buaa.edu.cn
  • Supported by:
    Project supported by the National MCF Energy Research and Development Program of China (Grant No. 2019YFE03010001) and the National Natural Science Foundation of China (Grant No. 11905004).

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摘要： Runaway electron current generated during the current quench phase of tokamak disruptions could result in severe damage to future high performance devices. To control and mitigate such runaway electron current, it is important to accurately describe the runaway electron current dominated equilibrium, based on which further stability analysis could be carried out. In this paper, we derive a Grad-Shafranov-like equation solving for the axisymmetric drift surfaces of the runaway electrons instead of the magnetic flux surfaces for the simple case that all runaway electrons share the same parallel momentum. This new equilibrium equation is then numerically solved with simple rectangular wall with ITER-like and MAST-like geometry parameters. The deviation between the drift surfaces and the flux surfaces is readily obtained, and runaway electrons are found to be well confined even in regions with open field lines. The change of the runaway electron parallel momentum is found to result in a horizontal current center displacement without any changes in the total current or the external field. The runaway current density profile is found to affect the susceptibility of such displacement, with flatter profiles result in more displacement by the same momentum change. With up-down asymmetry in the external poloidal field, such displacement is accompanied by a vertical displacement of runaway electron current. It is found that this effect is more pronounced in smaller, compact device and weaker poloidal field cases. The above results demonstrate the dynamics of current center displacement caused by the momentum space change in the runaway electrons, and pave a way for more sophisticated runaway current equilibrium theory in the future with more realistic consideration on the runaway electron momentum distribution. This new equilibrium theory also provides foundation for future stability analysis of the runaway electron current.

关键词: tokamak, disruption, runaway electrons, equilibrium

Abstract: Runaway electron current generated during the current quench phase of tokamak disruptions could result in severe damage to future high performance devices. To control and mitigate such runaway electron current, it is important to accurately describe the runaway electron current dominated equilibrium, based on which further stability analysis could be carried out. In this paper, we derive a Grad-Shafranov-like equation solving for the axisymmetric drift surfaces of the runaway electrons instead of the magnetic flux surfaces for the simple case that all runaway electrons share the same parallel momentum. This new equilibrium equation is then numerically solved with simple rectangular wall with ITER-like and MAST-like geometry parameters. The deviation between the drift surfaces and the flux surfaces is readily obtained, and runaway electrons are found to be well confined even in regions with open field lines. The change of the runaway electron parallel momentum is found to result in a horizontal current center displacement without any changes in the total current or the external field. The runaway current density profile is found to affect the susceptibility of such displacement, with flatter profiles result in more displacement by the same momentum change. With up-down asymmetry in the external poloidal field, such displacement is accompanied by a vertical displacement of runaway electron current. It is found that this effect is more pronounced in smaller, compact device and weaker poloidal field cases. The above results demonstrate the dynamics of current center displacement caused by the momentum space change in the runaway electrons, and pave a way for more sophisticated runaway current equilibrium theory in the future with more realistic consideration on the runaway electron momentum distribution. This new equilibrium theory also provides foundation for future stability analysis of the runaway electron current.

Key words: tokamak, disruption, runaway electrons, equilibrium

中图分类号:  (Tokamaks, spherical tokamaks)

  • 52.55.Fa
52.55.-s (Magnetic confinement and equilibrium) 52.25.Xz (Magnetized plasmas) 52.65.Cc (Particle orbit and trajectory)