Part 1 of 2 Parts
     China’s “artificial sun” reactor has broken its own world record for maintaining super-hot plasma. This marks another milestone in the long road towards near-limitless clean energy.
     The Experimental Advanced Superconducting Tokamak (EAST) nuclear fusion reactor maintained a steady, highly confined loop of plasma for one thousand sixty-six seconds (eighteen minutes) on January 20th, 2025. This more than doubled its previous best of four hundred seconds. (seven minutes).
     Nuclear fusion reactors are nicknamed “artificial suns” because they generate energy in a way that is similar to the Sun by fusing two light atoms into a single heavy atom via heat and pressure. The Sun has a lot more pressure than Earth’s fusion reactors, so scientists compensate by using temperatures that are many times hotter than the Sun
     Nuclear fusion offers the potential of a huge power source without greenhouse gas emissions or much nuclear waste. However, scientists have been working on this technology for more than seventy years, and it is probably not progressing fast enough to be a practical solution to the climate crisis. Researchers expect us to have commercial fusion power plants within decades, but it could take much longer.
     EAST’s new record won’t immediately usher in what is dubbed the “Holy Grail” of clean power. However, it is a step towards a possible future where commercial fusion power plants generate electricity.
     EAST is a magnetic confinement reactor, or tokamak, which is designed to keep the plasma continuously burning for prolonged periods. Fusion reactors like this have never achieved ignition, which is the point at which nuclear fusion creates its own energy and sustains its own reaction. However, the new record is a step towards maintaining prolonged, confined plasma loops that future commercial fusion reactors will need to generate electricity.
     Song Yunta is the Director of the Institute of Plasma Physics responsible for the fusion project at the Chinese Academy of Sciences. He said, “A fusion device must achieve stable operation at high efficiency for thousands of seconds to enable the self-sustaining circulation of plasma, which is critical for the continuous power generation of future fusion plants.”
     EAST is one of a growing number of nuclear fusion reactors worldwide, but they all currently use far more energy than they produce. In 2022, the U.S. National Ignition Facility’s fusion reactor briefly achieved ignition in its core using a different experimental method to EAST. It relied on quick bursts of energy, but the reactor as a whole still used more energy than it consumed.
     Tokamaks like EAST are the most common research nuclear fusion reactors. EAST heats up plasma and traps it inside a donut-shaped reactor chamber with powerful magnetic fields. For the latest Chinese EAST record, researchers made several upgrades to the reactor, including doubling the power of its heating system.
     The data gathered by EAST will support the development of other fusion reactors, both in China and internationally. China is part of the International Thermonuclear Experimental Reactor (ITER) program. This project involves dozens of countries, including the U.S., U.K. Japan, South Korea and Russia.
     The ITER reactor, which is being built in southern France, contains the world’s most powerful magnet and will be operational in 2039 at the earliest. ITER is an experimental tool designed to create sustained fusion for research purposes, but it could pave the way for commercial fusion power plants. Song said, “We hope to expand international collaboration via EAST and bring fusion energy into practical use for humanity.”

Experimental Advanced Superconducting Tokamak

Please read Part 2 next

     Researchers at the SLAC National Accelerator Laboratory have achieved a significant milestone in laser-plasma accelerator (LPA) technology. They have created fast, bright proton beams by using the power of a simple steam of water. This breakthrough addresses some long-standing challenges and moves LPA technology closer to real-world applications.
     Siegfried Glenzer is the director of the High Energy Density Science division at the SLAC National Accelerator Laboratory. He said, “These exciting results pave the way for new applications of relativistic high-power lasers for applications in medicine, accelerator research, and inertial fusion.”  

     Traditional particle accelerators, such as synchrotrons, use electromagnets to generate these proton beams. However, the massive size of the magnets limits their use in many settings.

     LPAs offer a compact and cost-effective alternative. However, they also face several challenges. The researchers explained that “One challenge arises from the high-intensity laser, which destroys the targets after each pulse, requiring a new target for every shot. Another issue is the beam divergence – proton beams produced by LPAs typically spread out like a floodlight rather than maintaining a narrow focus.”
     The new breakthrough at SLAC aims to resolve these issues. This advance was made possible by replacing a solid target with a thin stream of water. The researchers commented that “Instead of using a traditional solid target, they introduced a thin sheet of water – a self-regenerating stream that replenishes after each shot.”
     This self-regenerating water sheet not only eliminates the need to replace the target after each laser pulse but also unexpectedly enhances the proton beam’s characteristics. When the high-intensity laser struck the sheet of water, the resulting evaporated water formed into a vapor cloud that interacted with the proton beam. This interaction generated magnetic fields, which focused the proton beam. This result of this interaction resulted in a significantly brighter and more tightly aligned proton beam.
     Compared to experiments utilizing solid targets, the water sheet reduced beam divergence by one order of magnitude and increased efficiency by two orders of magnitude. The resulting proton beam exhibited great stability as it operated consistently at five pulses per second for hundreds of laser shots.
     Griffin Glenn is a Stanford University PhD student and the second author of the report on the experiment. He said, “This effect was completely unexpected. This work has shifted the whole paradigm.”
     The proton beam delivered the equivalent of 40 Gray with each shot, which is a standard radiation dosage used in proton therapies. This is an result never before achieved with LPAs at this repetition rate. This was accomplished using a readily available low-energy laser system. The use of a common laser system marked a significant step towards practical applications.
     Glenn added, “Finally, we are no longer totally reliant on simulations. We can now drive the physics from an experimental point of view, testing different laser intensities, target densities, and environmental pressures.”
     Researchers at the Lawrence Berkeley National Laboratory (Berkeley Lab) had already achieved a significant milestone in laser-plasma acceleration. They successfully accelerated electrons to an energy of ten billion electronvolts within twelve inches.

SLAC National Accelerator Laboratory