中国物理B ›› 2023, Vol. 32 ›› Issue (7): 75212-075212.doi: 10.1088/1674-1056/acd369

所属专题： SPECIAL TOPIC — Plasma disruption

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Stability impacts from the current and pressure profile modifications within finite sized island

Yuxiang Sun(孙宇翔) 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:2023-05-05 接受日期:2023-05-09 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).

Stability impacts from the current and pressure profile modifications within finite sized island

Yuxiang Sun(孙宇翔) and Di Hu(胡地)†   

  1. School of Physics, Beihang University, Beijing 100191, China
  • Received:2022-12-30 Revised:2023-05-05 Accepted:2023-05-09 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： The stability (or instability) of finite sized magnetic island could play a significant role in disruption avoidance or disruption mitigation dynamics. Especially, various current and pressure profile modifications, such as the current drive and heating caused by electron cyclotron wave, or the radiative cooling and current expulsion caused by the shattered pellet injection could be applied within the island to modify its stability, thus changing the ensuing dynamics. In this study, we calculate the mode structure modification caused by such profile changes within the island using the perturbed equilibrium approach, thus obtain the change of stability criterion $\varDelta$' and assess the corresponding quasi-linear island stability. The positive helical current perturbation is found to always stabilize the island, while the negative one is found to do the opposite, in agreement with previous results. The pressure bump or hole within the island has a more complicated stability impact. In the small island regime, its contribution is monotonic, with pressure bump that tends to stabilize the island while pressure hole destabilizes it. This effect is relatively weak, though, due to the cancellation of the pressure term's odd parity contribution in the second derivatives of the mode structure. In the large island regime, such cancellation is broken due to the island asymmetry, and the pressure contribution to stability is manifested, which is non-monotonic. The stability analysis in this paper helps to more accurately clarify the expected island response in the presence of profile modifications caused by disruption avoidance or mitigation systems.

关键词: tokamak, magnetic island, tearing mode, magneto-hydrodynamic (MHD) instability

Abstract: The stability (or instability) of finite sized magnetic island could play a significant role in disruption avoidance or disruption mitigation dynamics. Especially, various current and pressure profile modifications, such as the current drive and heating caused by electron cyclotron wave, or the radiative cooling and current expulsion caused by the shattered pellet injection could be applied within the island to modify its stability, thus changing the ensuing dynamics. In this study, we calculate the mode structure modification caused by such profile changes within the island using the perturbed equilibrium approach, thus obtain the change of stability criterion $\varDelta$' and assess the corresponding quasi-linear island stability. The positive helical current perturbation is found to always stabilize the island, while the negative one is found to do the opposite, in agreement with previous results. The pressure bump or hole within the island has a more complicated stability impact. In the small island regime, its contribution is monotonic, with pressure bump that tends to stabilize the island while pressure hole destabilizes it. This effect is relatively weak, though, due to the cancellation of the pressure term's odd parity contribution in the second derivatives of the mode structure. In the large island regime, such cancellation is broken due to the island asymmetry, and the pressure contribution to stability is manifested, which is non-monotonic. The stability analysis in this paper helps to more accurately clarify the expected island response in the presence of profile modifications caused by disruption avoidance or mitigation systems.

Key words: tokamak, magnetic island, tearing mode, magneto-hydrodynamic (MHD) instability

中图分类号:  (Tokamaks, spherical tokamaks)

  • 52.55.Fa
52.55.-s (Magnetic confinement and equilibrium) 52.35.Py (Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.))