China unveils HL-4 tokamak: World’s first HTS burning fusion facility
Short summary
China is building the HL-4 tokamak in Shanghai to demonstrate that high-temperature superconducting magnets can sustain continuous fusion reactions. The reactor uses a 25-tesla magnetic field to trap plasma and will serve as a validation step before moving to a commercial demonstration reactor.
- HL-4 will be the first tokamak with high-temperature superconducting magnets capable of steady-state burning operation, solving the overheating problem that limits current reactors like HL-3 to pulsed operation
- The 25-tesla magnetic field shrinks the reactor's physical size while enabling study of plasma behavior at previously unreachable conditions
- The project is explicitly positioned as an engineering validation platform, not a commercial reactor—success here leads to a demonstration reactor phase before any commercial deployment
Full summary
China's building the HL-4 tokamak in Shanghai to tackle a real problem with existing fusion reactors: they can't run continuously. The machine uses a donut-shaped magnetic field to trap superheated plasma, mimicking the sun's fusion process. Previous models like HL-3 relied on copper coils that overheat too quickly, forcing the reactor to shut down. HL-4 swaps those for high-temperature superconducting magnets generating 25 tesla—strong enough to keep plasma trapped in a much smaller package. This isn't China's first rodeo; the Southwestern Institute of Physics has been developing the Huanliu series since the 1980s, so HL-4 represents decades of incremental progress.
The real engineering challenge is making those superconducting magnets work reliably under the extreme conditions inside a fusion reactor. Teams are already doing preliminary work on-site, and the R&D team moves into a 500-meter factory in Shanghai next year for full-scale magnet manufacturing and testing. China's also layering in AI-driven control systems to manage reactor performance, which hints at the complexity involved. The stronger magnetic field unlocks plasma behavior studies that weren't possible before, giving physicists access to conditions they've only theorized about.
Scientists treating HL-4 as a validation step rather than the end goal. The immediate win is proving high-temperature superconducting magnets can handle fusion's demands. Once that's locked down, China plans to build a demonstration reactor to show the tech works commercially, then move to actual power-generation reactors. It's a deliberate sequence: validate the science, demonstrate commercial viability, then scale to production.