Commonwealth Fusion Systems (CFS) has completed and delivered our first cutting-edge, superstrong magnet — a culmination of years of work to develop and manufacture the foundational technology to bring fusion energy to the grid.
In December, we shipped the 24-ton steel-clad magnet across the CFS campus in Devens, Massachusetts, from our factory to our SPARC facility. It’s now perched on an assembly stand where it’ll become part of SPARC, the machine we’re building to demonstrate the core technology of a fusion power plant.
Although it’s only the first of 18 D-shaped toroidal field (TF) magnets we need for SPARC, it’s a big deal. It shows the maturity not just of this key technology but also of our company: We’ve progressed from ideas to prototypes to initial manufacturing to full production.
“We didn’t just make a single magnet. We made a whole manufacturing facility that can make many, many magnets,” said CFS Chief Science Officer and Co-founder Brandon Sorbom. “We learned how to set up a factory and run it at speed. Full steam ahead!”
That operational excellence is crucial to CFS’ long-term plans. Just as we ramped up magnet manufacturing, we ultimately plan to ramp up our ARC power plant business from the first in Chesterfield County, Virginia, to hundreds more power plants to supply fusion’s clean, effectively limitless electricity.
Meet our new fusion magnet
SPARC and ARC are a type of fusion machine called a tokamak that uses magnets to bottle up and control its fusion fuel, a superhot cloud of charged particles called a plasma. Heating that plasma to about 100 million degrees Celsius makes its particles energetic enough to fuse together and release energy that can be harnessed as electricity.
Key to the CFS tokamak approach is a breakthrough material, high-temperature superconductors (HTS). These carry high electrical currents with no losses at all and can better withstand the strong magnetic fields inside the tokamak.
Crucially, HTS lets us create smaller, stronger magnets than was possible with last-generation superconductors. And making tokamaks more compact means fusion power becomes more affordable.
SPARC and ARC feature three types of HTS magnets: toroidal field (TF), poloidal field (PF), and central solenoid (CS). We build our TF magnets with NINT technology — short for its non-insulated, non-twisted construction — that houses many layers of HTS tape within a spiral groove in a flat steel plate. We call these plates pancakes, and a stack of 16 pancakes forms a single TF magnet.
“Basically, NINT allows us to build stronger, smaller magnets faster,” Sorbom said.
NINT magnet advantages
The NINT pathway is open to us because SPARC’s TF magnets will run with a steady electrical current.
Many fusion electromagnets carry electrical current inside superconductors bundled into cables that are electrically insulated, meaning that the electricity follows a single, simple path. That’s necessary in ”pulsed” magnets with rising and falling electrical current.
But with steady current, we don’t need electrical insulation between the turns of a magnet. When the magnet is cooled down and then charged up, the electricity naturally flows along the superconducting pathway and ignores the surrounding metal with its relatively high resistance. It’s like the difference between skiing on fast snow instead of concrete.
The “NT” part of NINT refers to the superconducting tape being non-twisted. Again, the steady current makes this simpler approach possible: the TF magnets don’t require the helical twist that’s electromagnetically helpful for the superconducting cables in pulsed magnets.
Making a magnet factory, not just a magnet
It wasn’t simple to develop our NINT magnets. It started back at MIT, where CFS has its roots, and proceeded through our TFMC prototype test in 2021.
Saehan Lenzen, Director of NINT Magnet Production, has seen the company grow during her four years at CFS. We’ve refined magnet making into an operation that runs smoothly from HTS tape insertion at the beginning of the process to magnet testing and welding into a steel case at the end.
“The company now is vastly different. When I joined, we were really scrappy, doing a lot of design and development,” she said. “Now we’re a full-blown production company. The skillset and the systems and the quality controls you need are really different. We have 17 more magnets to deliver, and we’re going to apply all those lessons learned.”
SPARC® and ARC™ are trademarks of Commonwealth Fusion Systems®.
