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Chin. Phys. B, 2026, Vol. 35(4): 045203    DOI: 10.1088/1674-1056/ae37f5
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES Prev   Next  

Interpretable logistic regression for predicting 1/1 kink-driven regular complete sawtooth phenomenon in EAST tokamak plasmas

Haipeng Quan(全海鹏)1,2,†, Liqing Xu(徐立清)2, Chaowei Mai(麦晁玮)3, Yan Chao(晁燕)2,‡, Yuhang Wang(王宇航)4, and EAST Team2
1 School of Computer Science and Engineering, Anhui University of Science and Technology, Huainan 232001, China;
2 Plasma Institute, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China;
3 Guangdong Ocean University, School of Electronics and Information Engineering, Zhanjiang 524088, China;
4 School of Physical Science and Information Technology, Anhui University, Hefei 230601, China
Abstract  Sawtooth phenomena are a central topic in tokamak fusion research; nevertheless, different sawtooth classes differ markedly in underlying physics, statistical abundance and diagnostic definition. This paper focuses exclusively on regular complete sawtooth — ideal, 1/1 internal-kink-driven events with full magnetic reconnection — which are the most frequent, unambiguously identifiable and theoretically best characterized (hereafter, all references to "sawtooth" denote this specific class). Compound crashes, partial-reconnection events and fast-ion-induced giant sawtooth are deliberately excluded because of their limited data volume and still-contested classification criteria, the inclusion of which would introduce intolerable label noise and theoretical ambiguity. To this aim, we propose a machine-learning-based temporal binary-classification framework that converts multi-diagnostic, high-resolution signals into precise labels distinguishing "oscillation" from "quiet" windows for this specific category, thereby supplying critical timing information for active control. A large-scale database covering 124 discharges and hundreds of millions of samples was constructed, and three representative algorithms — logistic regression, decision tree and random forest — were trained and compared. Among them, logistic regression achieved the best and most robust performance, reaching 95 % accuracy on an independent test set and significantly outperforming the other models. Furthermore, shapley additive explanations (SHAP) was innovatively employed to quantify the contribution magnitude and direction of key physical features to the onset of regular 1/1 sawtooth, substantially enhancing model interpretability and physical fidelity. The study provides an efficient and robust predictor for the active intervals of ordinary 1/1 sawtooth; the uncovered correlations between physical drivers and sawtooth behavior lay a solid foundation for deepening the understanding of regular sawtooth evolution and for optimizing control strategies, thereby holding significant promise for improving the operational stability of fusion plasmas.
Keywords:  sawtooth prediction      logistic regression      SHAP      interpretative model  
Received:  20 October 2025      Revised:  12 January 2026      Accepted manuscript online:  14 January 2026
PACS:  52.35.Py (Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.))  
  52.55.Fa (Tokamaks, spherical tokamaks)  
  52.30.-q (Plasma dynamics and flow)  
  07.05.Mh (Neural networks, fuzzy logic, artificial intelligence)  
Fund: Project supported by the National Key R&D Program of China (Grant No. 2022YFE03010003) and the National Natural Science Foundation of China (Grant No. 12275309).
Corresponding Authors:  Haipeng Quan, Yan Chao     E-mail:  haipeng.quan@ipp.ac.cn;chaoyan@ipp.ac.cn

Cite this article: 

Haipeng Quan(全海鹏), Liqing Xu(徐立清), Chaowei Mai(麦晁玮), Yan Chao(晁燕), Yuhang Wang(王宇航), and EAST Team Interpretable logistic regression for predicting 1/1 kink-driven regular complete sawtooth phenomenon in EAST tokamak plasmas 2026 Chin. Phys. B 35 045203

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