Recent Publications

Progress of turn insulation automatic wrapping for CFEDR toroidal field prototype coil

Liming Peng, Jian He, Zhaohui Yan, Wei Wen, Jianjian Xue, Jing Sun, Zhihong Liu, Yu Wu

Three-dimensional assessment of toroidal heat-load distribution on divertor targets in EAST

Wenxue Fu, Dahuan Zhu, Binfu Gao, Rong Yan, Chuannan Xuan, Yang Wang, Yang Lei, Bin Zhang, Mehdi Firdaouss, Pengfei Zi, et al.

Although actively cooled W/Cu monoblock targets are designed for high steady-state heat exhaust, local overheating and damage have been observed on these targets in EAST. These observations indicate that, beyond the nominal heat-removal capability, the practical thermal margin can be affected by engineering alignment, target geometry and plasma operating conditions, which modify the local surface-normal heat flux through magnetic incidence and magnetic shadowing. In this work, the toroidal heat-load distribution on EAST divertor targets is analysed by combining infrared thermography, finite-element heat-flux inversion and three-dimensional field-line tracing using PFCFlux. The analysis focuses on the effects of toroidal-field ripple, ripple-coupled cassette misalignment and divertor target geometry. The 16-fold toroidal-field ripple produces a 2π/16 modulation of the peak heat flux on the present upper outer target, with a peak fluctuation amplitude of approximately 17.75%. Under a peak heat-flux constraint of Qsafe = 10 MW m-2, the allowable average heat flux decreases from 4.28 MW m-2 without ripple to 3.94 MW m-2 with ripple. When ripple and relative cassette misalignment are considered together, it is further reduced to 3.11, 2.79 and 2.27 MW m-2 for Delta = 0.6, 1.0 and 3.0 mm, respectively. Comparison with the lower divertor shows that improved toroidal continuity reduces ripple-only peak amplification. Using the lower outer horizontal target as a reference, the new upper horizontal target reaches an allowable average heat flux of 4.70 MW m-2 under ripple and Δ = 1 mm misalignment. These results show that magnetic ripple, assembly tolerance and toroidal geometric continuity should be considered together in divertor thermal design.

Application of low-Z materials for enhancing H-mode plasma performance and pulse duration in EAST with full metal wall

G Z Zuo, Zhe Wang, Zhen Sun, Yun Zhu, Haotian Qiu, Zhongdi Lu, Yanzhen Xu, Y.H. Guan, Jingsheng Yuan, W Xu, et al.

Wall conditioning plays a key role in controlling impurity accumulation and fuel recycling for achieving long pulse, high-performance plasmas in fusion device. In this work, the effects of real-time wall conditioning using low-Z materials—boron (B) and lithium (Li) powders injection—are systematically investigated and compared in the EAST tokamak equipped with a full-metal wall. Continuous boron injection effectively suppresses high-Z impurity accumulation and maintains a low effective charge (Zeff), reducing the core W concentration by up to ~ 30%, and enabling reproducible 105-s H-mode discharges. Lithium injection also significantly improves impurity and fuel recycling control, supporting a record-breaking 1066-second H-mode plasma under combined lithiation using a 20 g pre-deposited Li coating and 1 g real-time powder injection. A statistical comparison of lithium- and boron-conditioned discharges shows that lithium powder conditioning provides about 20% higher energy confinement than B conditioning. This confinement improvement is accompanied by systematically lower neutral pressure (pn) and reduced Zeff at comparable plasma conditions, indicating more effective control of particle recycling and impurity content under lithium conditioning. These results demonstrate the effectiveness of low-Z material-based wall conditioning in improving plasma confinement and extending discharge duration, offering important implications for ITER and future fusion devices.

SOLPS-ITER simulation analysis on the synergistic effect of boron and neon in detached plasma on EAST

Lei Peng, Zhen Sun, Kedong Li, G Z Zuo, Jizhong Sun, Jinqin Ye, Qianhui Mao, Jun Ding, Haidong Li

EAST experiments have demonstrated that combined neon (Ne) and boron (B) injection overcomes the narrow operational window of pure neon seeding, and compensates for the insufficient radiative capacity of B alone, establishing a stable ELM-suppressed H-mode with a partially detached outer divertor and good confinement (H₉₈ ~1) [Sun et al 2026 Nucl. Fusion 66 044002]. To reveal the underlying physical mechanisms, SOLPS-ITER simulations of Ne-B co-injection are performed under EAST conditions. Three mechanisms are identified. First, B and Ne form a poloidal radiation synergy: Ne radiates efficiently at Te ~20-27 eV near the X-point, while B fills the radiative gap below ~17 eV in the divertor region, together extending the energy dissipation zone from the X-point to the target and enabling deep energy detachment. Second, the B-enhanced D⁺-D charge exchange in the near-SOL amplifies momentum loss and substantially reduces the target particle flux. Third, the reduced Ne seeding rate through compensating B radiation is the dominant lever for lowering core radiation and Zeff, because core impurity content is governed by Ne, with its density exceeding that of B by nearly two orders of magnitude regardless of injection rate. Additionally, the deeper detachment state further promotes B deposition on the divertor target, reinforcing wall conditioning. These mechanisms provide a generalizable physics framework for mixed low-Z/high-Z impurity injection strategies on ITER and future fusion devices.

Simulation study of Li-pellet-triggered ELMs in EAST towards understanding small-ELM behavior of HFS Li-pellet injection

Mao Li, Zhen Sun, Huayi Chang, Yue Zhang, Dayu Zhou, T Y Xia, Jizhong Sun

Motivated by recent EAST experiments showing that Li pellet injection from the high-field side triggers much smaller ELMs than outer-midplane (OMP) injection, a BOUT++ three-field MHD model coupled with impurity effects has been employed to investigate how the poloidal injection angle affects the triggering and subsequent evolution of ELMs. To this end, two scenarios are considered, in which Li pellets are injected near the upper X-point from the low-field side (LFS-UP) and the high-field side (HFS-UP), respectively. The OMP simulation data obtained within the numerical framework established in our previous study are also included for comparison. The simulations show that the ELM-triggering threshold decreases as the poloidal injection angle shifts from the OMP toward the HFS; the trend is associated with the easier excitation of a low-n mode capable of reaching the amplitude required for ELM triggering. The subsequent ELM evolution also depends on the poloidal injection angle. In the LFS-UP scenario, the ELM undergoes phases of linear growth, fast crash, turbulent transport, and saturation, similar to that in the OMP scenario. In contrast, in the HFS-UP scenario, the nonlinear dominant mode is suppressed shortly after ELM onset by the stronger stabilizing effect of the pedestal E×B flow shear, leading to a negligible fast crash phase. Meanwhile, the inward spreading of the pressure perturbation is constrained near the pedestal top. The rapid mode suppression, together with the restricted inward spreading of the pressure perturbation, prevents the ELM from developing into a large crash. Accordingly, the HFS-UP scenario exhibits a parameter window for small pellets in which the triggered ELM causes a pedestal energy loss of about 0.1% or less. The present results provide a plausible physical explanation for the EAST observations.

Quantitative validation of SMBI deposition profiles on EAST using experimentally constrained simulations

Yangdi Yu, Tianyang Xia, Jie Zhang, Jia Huang, Huimin Qi, Dazheng Li, Yanlong Li, Xiaoxue He, Xiaowei Mao, Hang Yu, et al.

Quantitative comparison between SMBI fueling simulations and experiments has long been hampered by the poor constraint on the effective source. Here, the particle increment per pulse is extracted experimentally and used to calibrate the simulation source. For EAST shot 71438, the density evolution from microwave reflectometry is analyzed for nine SMBI pulse groups. The SMBI-induced density increase is isolated from the background by comparing the rising and falling phases around each pulse group. Its radial profile peaks in the mid-pedestal region for every pulse group. Volume integration of this increment provides the experimental reference. The simulations use a multi-fluid model in the BOUT++ framework in which two transport operators are recast into conservative flux form, with the particle balance residual reduced to about 2% of the injected amount, and the perpendicular transport coefficients are constructed from the discrete radial flux balance, with the unphysical changes of the initial density and temperature profiles in source-free evolution reduced by an order of magnitude. For three cases sharing the same nominal molecular flux, the simulated deposition peak agrees with the experimental one in the relative pedestal coordinate. The simulated conversion of the injected particles at the end of the injection is slightly lower than the value inferred from the experiment, while the fraction retained at the end of the pulse is higher. The perturbation thus decays more slowly in the simulation, which we attribute to fast loss channels not represented in the model, such as parallel losses to the scrape-off layer. The edge electron temperature stays on the high-temperature plateau of the dissociation and ionization rate coefficients throughout the pulse, and the inward shift of the deposition with edge cooling reported earlier does not occur under the present conditions.

Time series regression network using exogenous variables for missing effective ion charge reconstruction in EAST tokamak

Kai Jia, Zong Xu, Zhenwei Wu, Wei Gao, Minrui Wang, Ang Ti, Hailin Zhao, Xiaohe Wu, Zhen Zhou, Kaibo Nan, et al.

The effective ion charge (Zeff) is a key parameter for characterizing plasma impurity levels and is important for investigating impurity transport and assessing discharge conditions in tokamaks. However, diagnostic system failures can lead to missing or incomplete Zeff signals. Accurate reconstruction remains challenging because Zeff is related to multiple plasma parameters and exhibits temporal dependencies. In this study, a time series regression network was developed to reconstruct missing Zeff values from exogenous plasma parameters in EAST. The model employed a sequential CNN-BiGRU-Transformer encoder architecture, in which the CNN extracted local temporal features, the BiGRU captured bidirectional temporal information, and the Transformer encoder modelled dependencies across different timescales through multi-head self-attention. The model was trained and validated using a dataset comprising 1566 EAST discharges. The results show that the average similarity between the reconstruction and experimental data is 90.3%, while the average coverage probability is 91.4%, indicating that most reconstruction values fall within the standard deviation error range of the experimental results. Overall, this study presents a feasible offline signal reconstruction method to maintaining the integrity of Zeff signals in EAST and provides a useful reference for reconstructing missing diagnostic data in future fusion devices.

Comparative study of nitrogen and neon seeding impacts on divertor detachment and core confinement in DIII-D high-βp plasmas with ITER-similar shape

Donggui Wu, Lingyi Meng, Liang Wang, Andrea M Garofalo, Xianzu Gong, H Q Wang, Siye Ding, Xiang Jian, Xiaohe Wu, Juan Huang, et al.

Divertor detachment experiments with nitrogen (N2) and neon (Ne) seeding have been performed in DIII-D high-βp scenario at q95~6, and the impacts of impurity seeding on divertor detachment and plasma confinement have been studied. Experimental results demonstrate that both N2 and Ne seeding could effectively reduce the electron temperature at the divertor target (Tet). The reduction in particle flux (jsat) is significantly more pronounced with N2 seeding, indicating a superior capability of N2 to facilitate deep particle detachment compared to Ne under these conditions. SOLPS-ITER simulations corroborate these findings, as the parallel momentum balance analysis reveals that N2 particles are predominantly retained in the divertor region, facilitating strong radiative dissipation near the target with minimal core penetration. In contrast, Ne particles could penetrate upstream, ionize inside the separatrix and lead to higher core radiation. Consequently, the stronger power and momentum loss in the scrape-off layer with N2 seeding is the key to achieve lower Tet and jsat compared to Ne seeding. Furthermore, statistical results suggest that the plasma confinement is maintained with both impurities, as the formation of large-radius internal transport barrier (ITB) compensates for pedestal degradation. Notably, the ITB formed with Ne seeding case is substantially stronger than that with N2 seeding. TGYRO simulations indicate that for Ne seeding case, toroidal rotation shear and the E×B shear play minor roles in ITB formation. Instead, the dominant stabilizing mechanism is identified as the redistribution of the current density and the reduction of magnetic shear at large radius, which is strongly promoted by Ne seeding but only weakly influenced by N2 seeding. These results provide a comprehensive perspective on the impact of N2 and Ne seeding on detachment and plasma confinement sustainment in DIII-D high-βp operations, offering valuable insights into optimizing the core-edge integration in future fusion reactors.

The multiscale nonlinear interactions between kinetic ballooning mode and drift wave turbulence critical for confinement improvement of hybrid fusion plasmas

Xiang Jian, Zhiyong Qiu, Vincent Chan, Jiale Chen, Lei Ye, Guoxu Wang, T Y Xia, Qilong Ren

Nonlinear suppression of short-wavelength drift wave turbulence by long-wavelength kinetic ballooning mode in tokamak fusion plasma is proposed to be the main cause for confinement improvement in the core of hybrid fusion plasmas. Specifically, the ambient ion temperature gradient(ITG) turbulence, which can contribute considerable transport flux if not mitigated, is fully suppressed in the presence of kinetic ballooning mode(KBM). KBM is demonstrated to be robustly unstable from fully electromagnetic gyrokinetic simulations. While its flux is low under low magnetic shear, KBM can generate significant stabilizing zonal flow whose velocity well surpasses the normalized linear growth rate of ITG. This multiscale physics phenomenon is convincingly verified on a representative ASDEX-Upgrade hybrid scenario plasma.

Transition from Te-ITB sustainment with saturated m/n=1/1 activity to q=3/2 rational-surface-mediated collapse in EAST

Yan Chao, Liqing Xu, Chaowei Mai, Yanmin Duan, Shiyao Lin, Kangning Geng, Haipeng Quan, Weixi Cao, Tonghui Shi, Tianfu Zhou, et al.

A collapse of an electron internal transport barrier (Te-ITB) followed by a major disruption, is observed in electron-heating-dominant H-mode plasmas with a core-peaked Te profile on EAST tokamak. Before the collapse, the Te-ITB coexists stably with a long-lived saturated m/n=1/1 mode, where m and n denote the poloidal and toroidal mode numbers, respectively. During this phase, the dominant electron-temperature information-transfer pathway identified by the transfer entropy (TE) analysis remains in the core region, consistent with barrier sustainment. In the pre-collapse phase, nonlinear coupling among core m/n=1/1 modes, secondary destabilization of the saturated m/n=1/1 mode and enhanced core impurity radiation are observed. The dominant TE response then shifts toward the q = 3/2 rational surface, while the inward-directed coupling is weakened. Although an m/n = 2/1 mode already exists before the collapse, it remains relatively passive until the heat perturbation propagates outward. The m/n = 3/2 mode emerges closest in time to the Te-ITB collapse and may participate in the final barrier degradation, which is followed by rapid outward thermal-perturbation propagation, fast-electron redistribution, enhanced impurity radiation, and finally a major disruption. These observations suggest that Te-ITB collapse is associated with the reorganization of electron-temperature information-transfer pathways and local rational-surface coupling, rather than with static magnetic-island topology alone.

Cross‑device and cross‑modal arc detection: Transfer learning between EAST visible and WEST infrared diagnostics

zhongfang Guan, Erwan Grelier, Bin Zhang, Sébastien Vives, Baoguo Wang, Victor Moncada, Leo Dubus, Jinping Qian, Kedong Li, Jian Liu, et al.

This work presents an engineering-oriented data processing and model training pipeline for EAST visible and WEST infrared data, enabling a systematic study of cross-device and cross-modal electric arc detection. A lightweight convolutional neural network is adopted as a cross-device arc detection model, and joint training and transfer learning experiments are conducted on EAST visible (VIS) and WEST infrared (IR) data. Single‑modality baselines are first trained on EAST and WEST, then evaluated zero‑shot on the opposite device, followed by a comparison of frozen‑backbone and fine‑tuned transfer for VIS→IR and IR→VIS. The results show that models trained from scratch on each diagnostic channel already achieve high precision and recall for arc detection, whereas direct zero-shot cross-modal transfer drives the arc recall on the opposite domain almost to zero. In contrast, starting from the single-modality baselines and modestly fine tuning higher convolutional layers and the classification head on the target domain can significantly restore-cross device, cross-modal detection performance, with positive class precision and recall approaching or even surpassing the single-domain baselines. Class activation map analysis further indicates that, under fine-tuned and joint training configurations, the models consistently focus on the antenna, the arc, and its surrounding scattering region, supporting physically meaningful explanations and suggesting that cross-device, cross-modal training can capture arc related structures that generalize across devices while providing a lightweight, scalable route to reusing imaging-based diagnostic knowledge with reduced annotation and retuning effort.

First observation of anisotropic distribution evolution of hydrogen fast ions heated by ICRF in EAST

Yang Liu, Ming Xu, Huishan Cai, Zhanhong Lin, Yihai Liao, Wei Zhang, Hailin Zhao, Jiayi Zhang, Jianjun Zhu, Ye Li, et al.

The continuous energy and pitch-angle distribution of hydrogen fast ions generated by ion cyclotron range of frequencies (ICRF) minority heating is measured in EAST using an imaging neutral particle analyzer (INPA). The measured two-dimensional fast-ion distribution exhibits a triangular structure: as energy increases, the pitch-angle distribution becomes progressively narrower, with its peak located around 0.4<|v_∥/v|<0.5. This behavior is consistent with resonance localization theory, which associates the pitch-angle peak with trapped orbits whose turning points are close to the ion cyclotron resonance layer. Through diagnostic response correction, the reconstructed spectrum shows a progressive enhancement of the high-energy minority-ion tail with rising ICRF power. A clear anisotropic evolution of the fast-ion distribution is also observed between discharges with different electron-temperature profiles. In the discharge with higher core electron temperature, the signal enhancement appears mainly for fast ions at energies above 100 keV and |v_∥/v|≥0.5, together with a broader measured pitch-angle distribution. This behavior is interpreted as the combined result of collisional pitch-angle scattering, fast-ion accumulation, and finite-orbit-width effects. The enhanced signal region corresponds to wide-orbit fast ions whose inner orbit legs extend to the hotter inner plasma region, making them more sensitive to changes in the electron-temperature profile. These results demonstrate the capability of INPA to resolve the anisotropic evolution of ICRF-heated fast ions and provide experimental insight into the optimization of ICRF heating schemes in EAST and future fusion devices.

The Design and Experimental Investigation of Metal Wire Explosion-Type DC Circuit Breaker in Magnetic Confinement Fusion System

Zhenhan Li, Hua Li, Xiaohua Bao, Ge Gao

Cleaning rate and uniformity of simultaneous cleaning of two face-to-face mirrors using RF plasma

Yuxian Wen, Rong Yan, Chuannan Xuan, Lei Mu, Yuming Liu, Yuhao Pan, Zhaohui Wang, Baoguo Wang, Shuyue Sun, Rui Ding, et al.

Soft H-L back transitions induced by RMP coils in high q95 plasmas on EAST

Linming Shao, Hui-Hui Wang, Shouxin Wang, Zichao Lin, R Chen, Shuai Gu, Wenbo Hua, Pan Li, Yichao Li, zhiguo li, et al.

Soft H-mode to L-mode (H-L) back transitions, combined with simultaneous particle and heat pumping via n=2 resonant magnetic perturbations (RMPs), have been achieved in EAST plasmas at low safety factor (q95=3.5-4.0) without reducing auxiliary heating power [Shao L M, et al., 2024 PPCF 66 035018]. For the termination control of ITER, which is also equipped with RMP coils, this process inevitably drives the plasma toward a high q95,where the established n =2 RMP is unlikely to produce a soft H-L back transition, because the edge-resonant surface at such high q95 requires a high poloidal mode number m, and the n=2 RMP field is strongly attenuated at such high m and couples only weakly to the edge. However, an n =1 RMP can restore edge coupling, enabling reliable particle and heat pump-out without radiative collapse or current-profile MHD risks on EAST. Within an operating window constrained by impurity and NBI conditions, both the n=1 and n=2 RMPs exhibit a reproducible energy confinement time threshold at the H-L transition τ^{H-L}_{e}∼ 49 ms, which can serve as a control trigger.

A data-driven model for stable long-horizon autoregressive prediction of plasma current and control-oriented boundary evolution in EAST

Minglong Wang, Chenguang Wan, Yuehang Wang, Jia Huang, Zhi Yu, Jingjing Lu, Xiaojuan Liu, Zhisong Qu, Weidong Chen, Teng Wang, et al.

Accurate long-horizon prediction of tokamak plasma current, position, and boundary evolution is essential for magnetic control, rapid controller development, and reinforcement-learning-based optimization. However, high-fidelity physics-based simulators are often computationally prohibitive when large numbers of simulations are required for controller tuning and large-scale optimization. In this work, we develop a fast, data-driven model for the Experimental Advanced Superconducting Tokamak (EAST) to predict plasma current, position, and shape evolution over horizons of up to 1 s, with an inference time of 0.1 s on a single NVIDIA H800 GPU. Evaluated on a temporally separated test set comprising 5907 discharges, the model demonstrates strong generalization to evolving operating conditions and maintains stable agreement with experimental measurements during long-horizon autoregressive rollouts. The mean geometric error of the plasma centroid and the control-oriented boundary representation is 2.4 cm, indicating reliable centimeter-level accuracy for control-oriented prediction of plasma position and shape evolution. The proposed framework provides a practical, high-throughput alternative to first-principles simulators, enabling efficient control algorithm prototyping, large-scale scenario exploration, and future data-driven optimization for tokamak plasma control. This study focuses on the post-shaping phase of EAST discharges, where sustained plasma current and control-oriented boundary regulation are most critical.

Parametric effects and rate-limiting mechanism analysis of tritium extraction process in permeator against vacuum

Zuocong Liu, Qingjun Zhu, Qiankun Shao, Songlin Liu

Effect of pedestal current on the density window for ELM suppression using n = 4 RMP in EAST

Xuemin Wu, Youwen Sun, Qun Ma, Shuai Gu, Manni Jia, Yueqiang Liu, Yifeng Wang, Cheng Ye, Pengcheng Xie, Alberto Loarte, et al.

Existence of operational window in both edge safety factor and line averaged plasma density for suppression of ELMs using n=4 Resonant Magnetic Perturbations in low input torque plasmas has been observed in EAST experiment, in which q95 and plasma normalized beta (βN) close to that required in ITER high-Q operation. Here, n is toroidal mode number of the magnetic perturbation. In contrast to previous reports from other tokamaks, there is not only an upper density limit but also a lower one for accessing ELM suppression. Modelling results using the MARS-F code show that the RMP with linear plasma response has a peak at an intermediate density and decays as the density increases or decreases, which results in a minimal RMP field penetration threshold at the intermediate density. In this experiment, the observed lower density limit operationally manifests a sensitivity of the q-profile: different densities alter the edge current profile, which change the alignment of the eigenmode structure with the RMP coil configuration, causing a reduction of the resonant field in both low- and high-density cases, and hence making field penetration more difficult. The modelled window of the strongest resonant plasma response in terms of [⟨ne⟩, q95] agrees well with the observed ELM suppression in EAST. Peeling-ballooning modes stability analysis using the ELITE code shows that plasmas gradually approach peeling instability boundary caused by increase of edge bootstrap current as the plasma density decreases, which is consistent with the observation that ELMs come back again in lower density plasmas for fixed q95. These results indicate that linear modelling with full toroidal geometry can well predict the optimized RMP configuration for ELM suppression and reveal the important roles of pedestal plasma current, which need to be carefully considered in the application of high n RMPs for ELM suppression in future ITER.

A composite impurity-pressure index for assessing startup readiness during plasma recovery on EAST

Shuqi Yang, Yaowei Yu, Tao Zhang, Xiang Zhu, G Z Zuo, Xiang Gao

Reliable restart after vessel venting is controlled by the burn-through power balance: the plasma must ionize the residual neutrals, dissociate molecules and raise the electron temperature before ionization, charge-exchange and impurity-radiation losses exhaust the available ohmic or auxiliary power. In practice, however, operators usually do not know whether the wall has recovered until a shot has already been attempted. Six EAST plasma-recovery campaigns from 2023 to 2025 are analysed, and a pre-shot impurity-pressure index is introduced to combine the neutral pressure measured 2–3 s before breakdown with a weighted residual-gas-analyser proxy for nitrogen- and oxygen-bearing species. In this dataset, the index organises discharge duration, stable-shot probability and the loop voltage during the first 50–200 ms more clearly than either pressure or composition alone. Under the standard EAST startup condition used here, stable discharges become much more likely when the index falls to around 1 × 10-7 Pa. In the second 2025 campaign, the shot-by-shot evolution also shows threshold-like burn-through behaviour: the maximum line-averaged electron density in 0–0.2 s stays low at large index values, overshoots in a transition interval, and then settles to a more stable level as the wall recovers. Across campaigns, post-recovery values cluster much more tightly than the recovery paths themselves, indicating that the index characterizes the startup-ready wall state rather than a particular conditioning route. The metric therefore provides a practical pre-shot indicator of whether EAST has recovered sufficiently for reproducible stable startup.

Helium‑3 minority heating with ion cyclotron range of frequencies (ICRF) in the experimental advanced superconducting tokamak

Yongxin Zhu, Wei Zhang, Yevgen Kazakov, Jinhua Wu, Paola Mantica, Gabriele Cassella, Tao Jin, X. J. Zhang, Lunan Liu, Hua Yang, et al.

During the 2025 campaign, helium-3 ( 3 He) minority heating with waves in the ion cyclotron range of frequencies (ICRF) was investigated for the first time on the Experimental Advanced Superconducting Tokamak (EAST). With the lowest available ICRF frequency of f IC = 27 MHz, experiments were conducted at a high toroidal magnetic field of B t = 2.8 T and plasma current I p = 450 kA. To optimize 3 He minority heating, the variation of 3 He concentration was systematically explored. Real-time feedback control of the 3 He concentration was successfully implemented through spectroscopic measurement and closed-loop regulation of the 3 He gas injection, demonstrating the feasibility of the control system functions. The ICRF heating efficiency reached a maximum at a minority concentration of ∼8-9%, with the core electron temperature increasing from approximately 5.0 to 7.0 keV and the ion temperature from approximately 1.3 to 1.9 keV under 2.9 MW of ICRF power. These results are in good agreement with simulations from the two-dimensional full-wave code TORIC. Experiments further indicate that higher plasma density enhances 3He heating efficiency. We also briefly discuss the strategy for future 3 He ICRF experiments on EAST.