7th Asia-Pacific Conference on Plasma Physics, 12-17 Nov, 2023 at Port Messe Nagoya

Role of the multiple mode interaction on the excitation of 2/1 tearing mode byresonant magnetic perturbations on J-TEXT

F.Y. Mao1, N.C. Wang1, Q. Zhang1, Z. Huang2, Z.K. Ren1, R. Jia1, Y. He1, Y.B. Li1, C.X. Zhao1, B.
Hu1, X.C. Yao1, Z.R. Hou1, S. Zhou1, D. Li1, Y.H. Ding1, Z.J. Yang1, Z.Y. Chen1 and the J-TEXT
team1
International Joint Research Laboratory of Magnetic Confinement Fusion and Plasma Physics,
State Key Laboratory of Advanced Electromagnetic Engineering and Technology, School ofElectrical and Electronic Engineering, Huazhong University of Science and Technology, Wuhan
430074, People’s Republic of China
2

College of Computer Science, South-Central Minzu University, Wuhan, 430074, People’s
Republic of Chinae-mail (speaker): fy_mao@hust.edu.cn

The excitation of m/n = 2/1 tearing mode (TM) byexternal non-axisymmetric magnetic perturbations,known as field penetration, is a significant concern intokamak research as it leads to confinement degradationand disruption[1]. The threshold for external field exciting
2/1 TM serves as an important reference for error fieldcorrection[2] and edge localized mode suppression[3].
Recent research on J-TEXT has discovered that thethreshold of 2/1 TM excitation is significantly reducedby the interaction of multiple modes.
In experiments with various static resonant magnetic
perturbations (RMPs), the 3/1 and 2/1 TMs were excited
individually and successively, and it was observed thatthe threshold of 2/1 TM excitation was substantiallyreduced with pre-excited 3/1 TM[4]. This phenomenon
suggests that the interaction between 3/1 and 2/1 TMs
has an effect on the field penetration threshold. To better
understand the threshold reduction, the MARS-F code[5,6]was used to investigate the effect of a 3/1 locked tearing
mode on 2/1 plasma response, revealing that the 2/1
plasma response was significantly enhanced with alocked 3/1 TM, which may be the reason for thethreshold reduction in the experiments.
In static RMPs penetration experiments, the 3/1 and
2/1 TMs were born locked, making it difficult to analyze
their behavior separately. As a result, a series of rotating
RMP penetration experiments were carried out using theunique high-frequency RMP system on J-TEXT. In theseexperiments, the helical and radial structure evolutions of
the modes were obtained through magnetic probe arrays
and local ECE measurements, allowing for analysis of

the interaction between 2/1 and 3/1 modes. Additionally,
a 3/1 external kink mode (EKM) was excited by RMP
with qa slightly smaller than 3, and it was discovered thatthe 3/1 EKM also reduced the thresholds of 2/1 TM
excitation[7]. Further details will be presented at theconference.
This work was supported by the National MagneticConfinement Fusion Energy R & D Program of China(Contract Nos. 2019YFE03010004, 2018YFE0309100),and the National Natural Science Foundation of China(Nos. 11905078, 12075096 and 51821005).

References[1] T.C. Hender et al, Nucl. Fusion. 32, 2091 (1992)[2] J.K. Park et al, Nucl. Fusion. 48, 045006 (2008)[3] Q.M. Hu et al, Phys. Rev. Lett. 125, 045001 (2020)[4] F.Y. Mao et al, Plasma Sci. Technol. 24, 124002(2022)[5] Y.Q. Liu et al, Phys. Plasmas. 17, 122502 (2010)[6] L. Li et al, Nucl. Fusion. 57, 126027 (2017)[7] Q. Zhang et al, “Reduction of the external resonant
magnetic perturbation threshold for 2/1 locked mode
excitation by the pre-excited mode on J-TEXT”,
submitted to Plasma Phys. Control. Fusion (2023)