Overview of Recent Experimental Results on EAST in Support of ITER New Research Plan X. Gong1* with J. Huang1, B. Zhang1, X. Zhang1, H. Xu1, M. Wang1, J. Qian1, R. Ding1, A. Loarte2, R. Pitts2, T. Wauters2, L. Zeng3, A. Ekedahl4, D. Moreau4, X. Zou4, S. Liu5, W. Liu1, L. Xu1, P. Li1, K.D. Li1, G.L. Xu1, M. Li1, M. Jia1, G. Zuo1, Y. Yu1, F. Ding1, M. Xu1, X. Wu1, B. Guo1, D. Yao1, B. Xiao1, Y. Sun1, Q. Ren1, Q. Zang1, G. Li1, H. Liu1, G. Xu1, J. Hu1, K. Lu1, Y. Song1, B. Wan1, J. Li1 and the EAST team1 1Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, China 2ITER Organization, Saint Paul Les Durance, France 3Tsinghua University, Beijing, China 4CEA, IRFM, F-13108 Saint Paul-lez-Durance, France 5Donghua University, Shanghai, China Presented at the 30th IAEA Fusion Energy Conference Chengdu, China October 13-18, 2025 *E-mail: [email protected] Acknowledgement Open Test Bench Collaborating institutions include: Fusion for Energy (F4E), EUROfusion, York University, Plasma Research Laboratory, General Atomics (GA), Princeton Plasma Physics Laboratory (PPPL), MIT Plasma Science & Fusion Center (PSFC), Lawrence Livermore National Laboratory (LLNL), Queensland University of Technology (QUT), The Culham Centre for Fusion Energy of the United Kingdom Atomic Energy Authority (CCFE), Joint Institute for Nuclear Research (JINR), The Nuclear Research Center "KURCHATOV INSTITUTE" (NRC KI), Lappeenranta university of technology, Finland, University of Saskatchewan, French Alternative Energies and Atomic Energy Commission (CEA), The Institute of Plasma Physics of the Italian National Research Council (IFP-CNR), Max-Planck Institute of Plasma Physics (IPP), Forschungszentrum Juelich GmbH (FZJ), National Institute for Fusion Science (NIFS), National Fusion Research Institute of Korea (NFRI), Thailand Institute of Nuclear Technology (TINT), Pusan National University, Air Liquide, Institute of Plasma Research (IPR), Denmark Technical University, University of Twente, General Fusion, Academy of Sciences of the Czech Republic, National Institutes for Quantum and Radiological Science and Technology (QST), National Council for Scientific and Technological Development (CNPq), iThemba LABS, National Agency for Atomic Energy (ENEA). Great Progresses on EAST Benefit from Broad Domestic and Wide International Collaborations! Outline ❑ Breakthrough on Long-Pulse Operation ❑ Solutions to key issues of LPO ❑ Physics understanding in H-mode SSO ❑ Joint ITER/EAST experiments ❑ Future plan and summary Long-Pulse Initiative: Achieve Integrated SS High Performance Plasma and Study Related Physics and Fusion Engineering EAST is the first fully superconducting Tokamak in the world, oriented to support the ITER new research plan and the BEST project both of scientifically and technically. • Prof. Wan Yuanxi at 21st IAEA FEC Oct. 2006, Chengdu • ~ 20 Years, ~160,000 Shots Strategies for Establishing Scientific-Based Solutions for Steady-State Operation to Support Future Fusion Devices S1: Enhance H&CD efficiency and relevant fundamental physics understanding and key diagnostics S2: Demonstrate long-pulse (≥400s) H-mode plasmas and develop fully non-inductive high-β scenarios S3: Extend EAST operation regime to demonstrate high fusion performance plasmas and deliver relevant physics for ITER and CFEDR Supporting: ITER, BEST, CFEDR Significant Progress of Long-pulse H-mode Plasma on EAST • Integrated solutions of high-performance LPO – High confinement and bootstrap current fraction – High RF current drive at high density – Core-edge integration • On time scale of particle and heat balance – Particle recycling and W regulation – ELM mitigation and active control – Divertor target power exhaust Total injected energy up to 3.05GJ Demonstrate expertise in engineering and technical issues for LPO Recent Advancement and Breakthrough in Long Pulse H-mode Operation with W-Divertor on EAST An exciting milestone in achieving a 1066.7 second steady-state high confinement plasma on January 20th, 2025 EAST Made an Important Advance by Achieving a Record H-mode Plasma over 1066-second – Bt ~ 2.5T / LSN, H98y2 ~ 1.35, ne/nG ~ 0.6, fBS ~ 50%, Te0 ~ 10keV, Einj ~ 3.05GJ Diagnostics & Profiles: - Total current: 305 kA - Bootstrap current: 155 kA - Lower Hybrid (LH) current: 105 kA - Electron Cyclotron (EC) current: 45 kA - Te(keV, TS), Te(keV, ECE), Te(keV, fit), ne(10^19/m^3), q-profile across normalized radius rho EAST Made an Important Advance by Achieving a Record H-mode Plasma over 1066-second – Bt ~ 2.5T / LSN, H98y2 ~ 1.35, ne/nG ~ 0.6, fBS ~ 50%, Te0 ~ 10keV, Einj ~ 3.05GJ • PLHCD = 1.1 MW, PECRH = 1.9 MW, βP = 2.0 with e-ITB, fBS ~ 50%, Tdiv ~ 600-800°C • A flux loop feedback control to sustain zero loop voltage, guaranteeing a fully non-inductive plasma with an electron density at 60% of the Greenwald limit. • A grassy ELM regime with OSP on the horizontal target, facilitating efficient RF power coupling and reducing W sputtering/erosion. • Low Z materials wall coating and real-time powder injections to improve particle control capability. Outline ❑ Breakthrough on Long-Pulse Operation ■ Solutions to key issues of LPO (Highlighted) ❑ Physics understanding in H-mode SSO ❑ Joint ITER/EAST experiments ❑ Future plan and summary Fully Active Water-cooling Metal-Wall with W-divertors Enable Advances in SSO Research • A new lower water-cooled tungsten divertor installed – 3/4 with the monoblock structure – 1/4 with the flat-type structure • Enhanced particle/heat flux load and removal capability – Increase steady-state heat exhaust to 10-20MW/m2 • Thermal equilibrium achieved quickly at new W-divertor – Actively Cooling Thermal-hydraulic Behaviors: M2 Sector (1/8) Robust Plasma Shape Control and Fully Non-Inductive Current Regime Sustainment via Innovative Loop Voltage Feedback Algorithm • Good accuracy shape control with Gap < 2mm, X-point(R,Z) < 3mm – Magnetic measurement for PF coil current using new fiber optic current sensors – Low drift of integrator with linear drift deduction by timely calibration and algorithm in PCS and nonlinear drift reduction by replacing good integrator modules • Optimization of Flux Loop control by LHW to minimize PF coil current – All PF coil current remained stable and constant to reduce AC loss in superconducting coils Robust Plasma Control Maintain Precise Strike Point Location And Efficient Protection of Divertor Target in Long Pulse Operation • Precise control of strike point with Rx drift < 3 mm • Actively water-cooled divertor target surface: 800°C • Divertor sputtering well controlled, W-sources • Avoid Hot Spot: Time evolution of W44+ concentration maintained low Control of Recycling and Impurity by Real Time Wall Conditioning using Lithium Powder Injection Advancing Long Pulse Operation • Impurity sources at both the divertor and the mid-plane limiter effectively suppressed (W I 400.9 nm, C II 426.7 nm, Li I 413.26 nm, O II 407.59 nm) Time Dependent Modeling of Wall Materials Migration and the Related Effect on Particle Recycling • SOLPS-SDTRIM and SP-DIVIMP integrated modeling framework has been developed for time dependent Li-W material evolution and particle recycling study; • D reflection and reemission rates vary with the surface materials compositions. (See G.L. Xu's Poster in this meeting) Effectively Controlled Fueling Recycling Beyond Wall Saturation Time Scale • Constant density sustained by SMBI fueling – Wall pumping played a significant role in recycling control – Improved particle exhaust with larger pumping speed and fresh wall condition • More difficult on recycling control in moderate density to adapt to high-Te – Higher Li-powder -> H&CD efficiency decreased -> confinement worse – Lower Li-powder -> H/H+D increased -> uncontrollable density • Modulation of lithium powder by feedback control – Rglobal ~ 0.95 and H/(H+D) ~ 3.5% Outline ❑ Breakthrough on Long-Pulse Operation ❑ Solutions to key issues of LPO ■ Physics understanding in H-mode SSO (Highlighted) ❑ Joint ITER/EAST experiments ❑ Future plan and summary Experiments Show Improved Confinement and Higher Bootstrap Current Fraction when Extending to High-βP Regime • Demonstration of High Confinement, High Density and High fBS towards Steady-state Operation: - High energy confinement and high-βp at high-ne - Zero torque with Self-Regulating e-ITB - Electron heating dominant CD Efficiency - Small ELMs (fELM ~ 1kHz) - Well high-Z impurity control - Compatible Core and Edge Integration • Normalized parameters close to ITER/CFEDR steady state: – βP ~ 4.0, fBS ~ 60%, H98y2 ~ 1.5, Vloop ~ 0, ne/nG ~ 1.0, βN ~ 2.5~4xli – Broader q-profile (weak shear/NCS) and qmin > 2 to avoid NTM Improved Current Drive Efficiency by Adjusting LH Wave Phase • Optimal N|| should be slightly higher than N||acc, lower than which wave accessibility becomes worse, but too large N|| will lead to a decrease in CD efficiency (∝ 1 / N||^2) • For long-pulse H mode with ne0 ~ 3.6×10^19/m^3, optimal N|| is 2.04, corresponding to the phase of 90°. Optimizing EC Power Deposition for Higher Confinement and Enhanced Synergy Effect with LH Wave • The location of EC power deposition depends significantly on the value of magnetic field. • An optimal Bt (corresponding to IT = -11000A) was determined to realize high plasma confinement and synergy effect between EC and LH waves in phase space. (PEC = 1.9 MW) Broad Current Profile by Early EC Heating and off-axis LHCD at High Density Sustained Fully Non-inductive High-βp Scenarios • Lower li obtained by early EC-heating during Ip ramp-up • Current profile becomes broader under more off-axis EC deposition • Broader current profile obtained at high density with more off-axis LHCD – ne ↑ -> ηCD ↓; broad j(r) + negative shear -> confinement ↑ + βP ↑ -> fBS ↑ Model-Predictive Kinetic Control with Data-driven Models Developed on EAST • LHCD, NBI and ICRF were used as actuators for the kinetic control • Simultaneous control of q profile, βp and li was demonstrated for the first time in EAST (Didier Moreau, NF 2024 / CEA IRFM) Saturated m/n=1/1 Kink Mode Sustained High-Te Plasma with Improved Confinement for Long Duration Operation • ETG turbulence is excited when R/LTe is above a threshold (R/LTe > 9) • ETG turbulence can be reduced by m/n=1/1 mode – 1/1 mode can lead negative current – Increase q(0) > 1 to form weak magnetic shear • The self-regulation system to sustain Te-ITB in SS LPO – The interplay among negative current, kink mode, turbulence (X. Zou, ASIPP Seminar, 2024 / CEA IRFM) Compatible Core and Edge Integration by Active Detachment Control for Long Pulse H-mode Control Parameters and Actuators: - Total radiation (Prad, total): LFS and divertor impurity seeding - Divertor particle flux (jsat): Divertor impurity seeding; LFS D2 fueling by SMBI - Div. electron temperature (Tet): Divertor impurity seeding - Div. target temperature (Tt, peak): Divertor impurity seeding - Div. electron temperature + X-point radiation (Tet + Prad, x-point): Divertor impurity seeding; D2 fueling by SMBI Demonstration of Divertor Detachment and ELM-free Long-pulse Discharge Enabled by HFBT-assisted Particle Exhaust – PEC ~ 2.5MW + PLHCD ~ 1.9MW = 2.2 PL-H – βP ~ 1.55, βN ~ 1.36, q0 ~ 1, κ ~ 1.6, δl ~ 0.66 – LSN with dRsep ~ -2 cm and dRout ~ 5.9 cm – nel ~ 61%nGW, Te0 ~ 4.7 keV, Ti0 ~ 1.1 keV, frad = Prad / Pinj = 29% • 50-second long pulses operated without ELMs throughout the whole discharge. • After nitrogen impurity injection, Te and Tsurface of the divertor target plate decreased significantly, entering a partially detached state. • A high-freq. turbulence mode of ~600 kHz existed in the steep gradient region of pedestal, assisting in particle removal and preventing impurity core accumulation and ELM bursts. (See G.S. Xu's Oral in this conference) First ELM Suppression by Helical Current with LHW Modulation • Achieved first ELM suppression with LHW modulation on EAST. – Developed physical model of helical current filaments. – Sheared turbulence structures observed during LHW-on phase. Parameters: PECRH = 1.4-2 MW, PNBI = 1.5-2.5 MW, PLHW = 1.2-2 MW, n_e_bar = 4.0-5.5×10^19 m^-3, q95 = 4.6-6.2 (Collaboration with Jülich; See S.C. Liu's Oral in this conference) Divertor Detachment Achieved in 3-D Magnetic Geometry by RMP Being Applied for ELM Control • With rigidly rotated n=2 RMP field, spiral pattern of particle and heat fluxes clearly observed on divertor • Detachment achieved on both original and splitting strike lines • Core W concentration and radiation reduced during RMP application and the detachment state (Sheng, et al., Nuclear Fusion 65 (2024) 016009; See M.N. Jia's Poster in this meeting) Density Windows for ELM Suppression with n = 4 RMPs • ELM suppression is primarily associated with peeling response and resonant component • Peeling dominant at low density and ballooning dominant at high density (See X.M. Wu's Poster in this meeting) Development of High Ion Temperature Scenarios • Bt = 2.5T / LSN / Ip = 0.5MA / nel ~ 1.6x10^19/m^3 • Fishbone & Ion-ITB, Ti(0) > 9.0keV / Te(0) ~ 3.5keV • Total store energy ~ 217kJ, thermal energy ~ 51% • The neutron yield ~ 2.5x10^14 (With Ar Impurity Puffing) Multi-scale Instabilities in High Ion Temperature Discharges • Ti0 ~ 9 keV, βpi ~ 2.2 • Modes: LLM, FB, BAE • FB: broaden radial location and n=2 component • Ion scale turbulence (f = [200-1000]kHz) suppression in FB phase (See L.Q. Xu's Poster in this meeting) Outline ❑ Breakthrough on Long-Pulse Operation ❑ Solutions to key issues of LPO ❑ Physics understanding in H-mode SSO ■ Joint ITER/EAST experiments (Highlighted) ❑ Future plan and summary Dedicated EAST Mini-Campaign was Performed in Support of ITER New Research Plan • EAST experiments with full W-limiter and W-divertors – Boronization studies (T. Wauters) – H-mode operation with W wall (A. Loarte) – W Limiter start-up experiments (R.A. Pitts) • Hardware: W-Limiter on EAST, New Tungsten Lower Divertor (Monoblock and Flat-type) (See J. Huang's Oral in this conference) Demonstration of Long Pulse H-mode Plasmas on Full Metal Wall in Support of ITER New Research Plan • Stationary ~100s H-mode plasmas achieved with Boronization – q95 ~ 6.0, ne ~ 4.3 / H98y,2 ~ 1.1, PEC ~ 3.0MW, PLH ~ 2.2MW • Optimization of the H&CD coupling – Separatrix W-limiter gap ~6cm and using gas puffing • Well controlled high Z impurity – Small ELMs and high density reduced W-sputtering – Avoid impurity accumulation by on-axis ECH Development of High-β Steady-state Operation Scenarios with W-Divertor in ITER-relevant Configuration towards High-Q • High-β plasmas by RF heating at high Bt ~ 2.5T – PLHW ~ 2.7MW, PEC ~ 2.0MW, PIC ~ 4.0MW – nGr ~ 0.7, βP ~ 2.1 / βN ~ 1.85, H98y2 ~ 1.25, q95 ~ 6.0 – Boronization wall • Broader current profile via ICRF heating • Joint Experiments & Activities for ITPA IOS-3.2 (See J. Huang's Oral in this conference) Outline ❑ Breakthrough on Long-Pulse H-mode Operation ❑ Solutions to key issues of LPO ❑ Physics understanding in H-mode SSO ❑ Joint ITER/EAST experiments ■ Future plan and summary (Highlighted) Integration of High-fusion Performance and Long Pulse Operation is the Fusion Energy "Grand Challenge" The Integration Challenge: Reduction of fusion performance by 2-3 orders of magnitude when increasing duration from ~1 s to 1000 s (Xavier Litaudon, NF 2024 / IAEA FEC 2025). • Scientific gaps for the development of LPO combined with high-fusion performance: – Machine/engineering limits: operate at higher power compatible with power handling capacity; Sustain a fully detached/semi-detached regime for LPO compatible with core performance; ... etc. – Plasma physics limits: MHD stability; core/pedestal confinement; RF H&CD efficiency at high density; plasma radiation with W; ... etc. Major Upgrade of EAST to Extend Operation Regime to Close the Gaps towards ITER and BEST EAST Upgrade Strategies: • Enlarged plasma volume in LFS for plasma current up to 1.0 MA • Increased plasma radius a ~ 0.4-0.55m and cross section R/a ~ 4.3 -> 3.6 • Enhanced the coils current limitation for PF&IC • Upper divertor re-designed for BEST-like cooling structure with 12MW/m2 power handling capability • Total available injected power will be increased from 12 MW to 18 MW Hardware Enhancements Propel EAST Forward to Bridge Gaps to ITER and BEST in Steady State Operation Studies • New BEST-like Divertor -> Enhance power handling capability • 3-strap ICRF antenna -> Decrease electric field • New two Gyrotrons dual freq. -> Flexible j(r) control • 4.6GHz/4MW LHW: PAM -> Improve long-distance coupling Summary • Significant progress has been made in long-pulse SSO on EAST – Demonstration of high performance long pulse H-mode plasmas with a reactor-like metal wall, low momentum input, and electron dominated heating scheme – A series of solutions to mitigate the challenges faced by long pulse H-mode plasmas are recently addressed • Advances on the key issues essential for long pulse SSO, providing supports to ITER and BEST steady state operation – Improved confinement with high bootstrap current, and interaction with MHD and turbulence – Active controls of wall conditioning, fueling recycling, plasma wall interaction and W accumulation • Dedicated set of joint ITER-EAST experiments have been performed in support of the ITER new researcher plan • Near-term plan with upgrade of inner components and augmented H&CD systems – Demonstrate SSO with extended fusion performance at 12-18 MW power injection Contributions to 30th IAEA FEC from EAST Team: - OV2-3 (OV) Xianzu Gong: Overview of recent experimental results on EAST in support of ITER new research plan - EX3-2 (Orals) Juan Huang: Development Of Steady-State Operation Scenarios With Full Tungsten Limiter/Divertor In ITER-Relevant Configuration On EAST - EX3-3 (Orals) Guosheng Xu: Long-Pulse Elm-Free H-Mode Regime With Feedback-Controlled Detachment Under Boronized Metal Wall In EAST - EX5-1 (Orals) Shaocheng Liu: First Edge-Localized Mode Suppression With Lower Hybrid Waves On The EAST Tokamak - EX4-2 (Orals) Long Zeng: Thermal Quench Dynamics And Heat Flux Distribution During Massive-Impurity-Injection Triggered Disruption In EAST - 2676 (Posters) Shengyu Shi: Tungsten (W) Impurity Reduction By ICRH In A High Power And High Performance H-Mode Discharge On EAST - 3233 (Posters) Manni Jia: Divertor Flux Control By RMP Elm Suppression And Radiative Divertor Operation In EAST H-Mode With Tungsten Plasma Facing Components In Support Of ITER New Research Plan - 2925 (Posters) Zhen Sun: Simultaneous ELM Suppression And Divertor Detachment Combined Boron Powder And Ne Gas Injection In EAST - 3145 (Posters) Cong Li: Endoscope Laser-Induced Breakdown Spectroscopy (Libs) For In Situ Elemental Distribution Diagnosis On The Surface Of Divertor In EAST - 2923 (Posters) Pengjun Sun: Experimental And Numerical Study Of Broad Wavenumber Turbulence And Transport In Ion Internal Transport Barrier Plasmas On EAST - 3226 (Posters) Pan Li: Turbulence And Transport Dependence On Temperature Ratio With Te/Ti 1-1.5 In EAST H-Mode Plasma - 3342 (Posters) Jiayi Zhang: The Establishment Of The Synthetic Diagnostic Modeling Specifically For The Imaging Neutral Particle Analyzer On The EAST - 2701 (Posters) Weiye Xu: Design Of The Electron Cyclotron Heating Expansion System On EAST - 2889 (Posters) Shouxin Wang: Particle Transport Of Ohmic Discharges With Different Plasma Current In EAST Tokamak - 2895 (Posters) Yongliang Li: Improvement Of Plasma Performance By Edge ECRH Power Deposition In EAST - 2968 (Posters) Gongshun Li: Impact Of The Temperature Ratio On Turbulence And Impurity Transport In The EAST Plasma Core - 2673 (Posters) Francesco Orsitto: Physics Basis Of Discrepancies Between Temperature Measurements By ECE And Thomson Scattering In High Performance Plasmas On JET, EAST And DIII-D - 2894 (Posters) Ming Xu: Experimental Study Of EPM Instability In The EAST Off-Axis Region With Elevated Safety Factor (Q)Value - 2981 (Posters) Youwen Sun: Lower Density Limit For Accessing To Elm Suppression Using N=4 RMP In EAST - 3006 (Posters) Wei Shen: Investigation Of Double Frequency Fishbone In EAST With Neutral Beam Injection - 3147 (Posters) Miaohui Li: Progress Of Lower Hybrid Current Drive Experiment Towards Long-Pulse Operation On EAST - 3207 (Posters) Yifeng Wang: Natural Small Elms Achieved At Low Pedestal Collisionality (<1) In A Metal Wall Environment On EAST - 3307 (Posters) Zixin Zhang: Impact Of Neutral Particles On Beam-Ion Losses In EAST Tokamak - 3358 (Posters) Andong Xu: Analysis Of Fast Ion Distributions Using Neutron Emission Spectroscopy In NBI-ICRF Synergistic Heating Plasma On EAST - 2672 (Posters) Ilya Senichenkov: Modelling of H-Mode EAST Edge Plasma With Impurity Seeding By SOLPS-ITER 3.2.0 On Wide Grid - 2879 (Posters) Liqing Xu: Investigating Of Multi-Scale Instabilities In EAST Ion Temperature Central Peak Discharge - 2893 (Posters) Zihao Gao: Simulations Of RMP Configurations For Tungsten Impurity Control In EAST Tokamak - 2967 (Posters) Huihui Wang: Overview Of Error Field Scaling Studies In EAST And Implications For ITER - 3162 (Posters) Jiaxing Liu: Validation Of Plasma -Wall Self-Organization Theory By High Density Limits Achieved On EAST - 3276 (Posters) Yunhu Jia: Plasma Instability Events Detection And Disruption Prediction In EAST Tokamak Via Heterogeneous-Feature Multi-Task Learning - 3309 (Posters) Guoliang Xu: Modeling Of Wall Material Evolution And The Impact On Edge Particle Recycling For Long Pulse Discharges In EAST - 2920 (Posters) Zhengshuyan Wang: Sawtooth Crashes Prediction Using A Convolutional Neural Network On EAST - 3123 (Posters) Ling Zhang: Progress Of Core-Edge Integrated Tungsten Transport Study In EAST With ITER-Like Tungsten Divertors Using Advanced Impurity Diagnostics - 3161 (Posters) Zhihao Zhao: Investigation Of Transient Transport Dynamics Induced By Compact Torus Injection In The EAST Tokamak - 3297 (Posters) Yahao Wu: Experimental Research On The Penetration Behavior Of Compact Toroid Fueling On EAST - 2883 (Posters) Guizhong Zuo: Application Of Low-Z Materials For Enhancing H Mode Plasma Performance And Pulse Duration In EAST With Full Metal Wall - 2878 (Posters) Binfu Gao: Modeling Of Heat Flux On The Main Limiter In EAST