“Each second of operation at these extreme conditions requires years of effort from thousands of scientists and engineers,” said Professor Luo Guangnan of the Chinese Academy of Sciences. In January 2025, China’s Experimental Advanced Superconducting Tokamak (EAST) did something long regarded as a daunting benchmark in fusion research: sustaining a high-confinement plasma for 1,066 seconds nearly 18 minutes at temperatures close to 70 million degrees Celsius. This milestone, says the Institute of Plasma Physics of the Chinese Academy of Sciences, is not just a technical success; it is a success of the world’s endeavor to achieve sustainable, carbon-free energy.
The EAST device, which is also known as the “artificial sun,” is the globe’s first superconducting tokamak. Its non-circular cross-sectional geometry, water-cooled plasma-facing components, and suite of real-time diagnostics have all been designed to allow steady-state plasma operation modes. These allow EAST to operate as an open, versatile testbed for fusion researchers worldwide, and as a valuable contributor to international cooperative efforts such as ITER.
Technical Advance: The Super I-mode Regime
Making this latest milestone remarkable is not only the length, but also the level of plasma confinement. The EAST researchers demonstrated a new operating regime known as Super I-mode, in which there is coexisting ITB at the core of plasma and an optimal energy confinement mode (I-mode) at the edge. This regime avoids the unwanted edge-localized modes (ELMs) that plague high-confinement H-mode plasmas, which offer high energy confinement coupled with stability on unprecedented timescales. The energy confinement enhancement factor (H98) in Super I-mode, according to the Science Advances paper, was as high as 1.2, 20% over the H-mode scaling law.
This was achieved through a series of engineering upgrades. The power source, formerly equivalent to 70,000 home microwave ovens, was doubled and yet provided operational stability. The plasma parameters were controlled and regulated through more than 80 diagnostic tools, real-time feedback control, and high-performance plasma control systems (PCS), keeping impurities low and the plasma immobile throughout the entire discharge. Notably, lithium powder injection was used to quell impurities and control recycling, and the actively cooled tungsten divertor sustained maximum heat fluxes of less than 3 MW/m² far below the system’s 10 MW/m² design.
Superconducting Magnet Technology and Advanced Materials
The secret to the success of EAST cannot be detached from the use of superconducting magnet technology. These are superconducting magnets cooled cryogenically and are the ones used to generate the strong magnetic fields required to confine the plasma for long durations without the resistive losses which would be caused by copper coils. The stability and reliability of these magnets are paramount to controlling plasma shape and current profiles on long timescales, an endeavor that grows greater each second it is in operation.
Of comparable significance is the development of high-performance materials for plasma-facing elements. Tungsten, chosen because of its melting point and low sputtering yield, is the material used to fabricate the divertor and first wall armor. Yet even tungsten, scientists at MIT report, is in danger of neutron bombardment and helium accumulation, causing embrittlement and cracking. To solve this, teams are turning to synthetic composite materials and nanoscale fillers such as iron silicates that can capture helium and shield grain boundaries, extending component lifetimes by orders of magnitude.
Wall conditioning technologies are advancing rapidly as well. Boron powder injection has been proven at the Princeton Plasma Physics Laboratory to prevent tungsten surfaces from contamination by impurities, purifying the plasma. Such techniques, used in EAST and other leading tokamaks, are being engineered for application in ITER and commercial reactors in the future.
Global Context: EAST, ITER, and the US Fusion Landscape
EAST’s achievement is otherwise compared with other recent fusion milestones. In 2022, the US National Ignition Facility (NIF) generated news for net energy gain, but only for an instant fraction of a second using inertial confinement. To put this in perspective, EAST’s 1,066-second plasma reflects the engineering maturity required to run steadily, a prerequisite to produce useful power.
France’s ITER, the largest fusion experiment in the world, is designed to produce 500 MW of fusion energy for at least 300 seconds, initiating first plasma operations in 2035. EAST’s long-pulse operation has immediate implications for ITER’s design, including heat and particle flux control, impurity control, and incorporation of advanced diagnostics and algorithms for control. “Successful long-pulse tokamak operation requires a high degree of integration and control to ensure that neither physics processes nor technological limitations limit the pulse duration,” said Alberto Loarte, head of the ITER Science Division.
The US fusion effort, however, also faces its own challenges. While private companies such as Commonwealth Fusion Systems and Helion Energy are making rapid progress with high-temperature superconducting magnets and small reactors, the federal grants remain tilted towards conventional research rather than commercialization.
Persistence Problems: Plasma Gain and Plasma Stability
Despite the huge progress, the underlying problem remains: net energy gain. The long-pulse tests in EAST, though technologically sophisticated, still burn more energy than they produce. The “ignition” threshold at which fusion reactions become self-sustaining still evades scientists. To be economically viable, reactors must not only hold plasma for thousands of seconds but also possess the energy gained to be greater than the energy input to heat and contain.
Plasma stability is another tough hurdle. Magnetohydrodynamic (MHD) instabilities like tearing modes can destabilize plasma and make discharges cut short. Recent work at the DIII-D National Fusion Facility in the US has demonstrated that artificial intelligence and reinforcement learning algorithms can predict and kill the instabilities in real time, and this could be a good path to even more secure plasma control in future reactors.
International Cooperation and the Future Ahead
China’s achievement is not only a triumph for China, but also an addition to the entire fusion family. As a key participant in ITER, China shares operational experience and technical expertise, accelerating global progress. The integration of superconducting technology, advanced materials, and real-time control systems is shaping the road map for next-generation devices, some of which include China’s CFETR and Europe’s DEMO project.
As the international race for fusion power accelerates, the scientific, technical, and geopolitical stakes are higher than ever. The road from record-setting plasma pulses to commercial fusion remains long and arduous, but with each milestone such as EAST’s 1,066-second record lighting the path ahead.
