Photo: A D-shaped toroidal field (TF) magnet, welded into its stainless steel case and surrounded by the team who helped manufacture it, rests in a testing chamber at the Commonwealth Fusion Systems magnet factory.
Right now, Commonwealth Fusion Systems (CFS) is building a fusion demonstration machine called SPARC and designing its successor, a power plant called ARC. And at a major physics conference this week, CFS and our collaborators from labs and universities will detail how research on the first machine leads directly to progress on the second.
Hundreds of fusion scientists from around the world swarm to the American Physical Society’s Division of Plasma Physics (APS-DPP) annual meeting to hear about research into this very complex science. That research has taken on new importance as fusion has moved out of the lab and into companies like CFS commercializing it.
A plasma is the superhot cloud of electrically charged particles at the heart of every fusion machine. The interaction of the electrical fields and magnetic fields in and around a plasma makes it challenging to manage, but we’ve learned a lot through decades of experimentation. At CFS, our research aims to use and extend that knowledge so we can harness fusion’s energy and bring this clean, safe new form of power to the electricity grid.
We’ve already shared plenty about what’ll keep SPARC ticking, including seven research papers about SPARC in 2020 that lay out the physics basis underpinning the machine. Now, through first-principles research, large-scale prototype tests, computer simulations, and other approaches, we and collaborating researchers are making the detailed physics predictions needed to get SPARC running the best it can. At APS-DPP, we and our collaborators are sharing our research through 62 presentations.
That research clears our path to demonstrating net fusion energy with SPARC, a threshold known in scientific circles as Q>1. Crossing that threshold — SPARC’s first big goal — means we’ll show the machine produces more power out than it takes to sustain the fusion process. Reaching Q>1 is a crucial moment to proving our technology.
But SPARC has other jobs, too. At APS-DPP, we’re also discussing some of the physics underpinnings of ARC and how we’ll put SPARC knowledge to use with ARC.
“What we’re going to accomplish on SPARC is testing our models and our understanding in a physics environment indicative of ARC,” said Phil Snyder, Vice President of Plasma Physics at CFS.
Open research makes you smarter
Why should a private company with plenty of competitors share this information publicly? Because that’s the best way to handle the challenges and complexities of plasma physics.
“We’re benefiting from the collective expertise of the broader plasma physics community,” Snyder said. We invite new ideas from the community, not just through informal conversations at conferences, but with research partnerships at universities, the Department of Energy’s National Laboratories, and international research institutes.
And isolating yourself from that conversation and collaboration poses real risks to your chances for progress.
“You can delude yourself — being off in a corner thinking you’ve solved every issue — but there could be dozens of other problems you aren’t aware of,” Snyder said. “By being open to scrutiny, we learn about the potential risks we’re facing, and the community’s knowledge helps us to solve key problems.”
SPARC paves the way for ARC
Both our fusion machines are called tokamaks, a donut shaped construction that uses strong magnets to confine and control a plasma. Among the SPARC and ARC subjects that CFS and our collaborators will discuss at APS-DPP:
- Disruptions: It’s tricky to handle moments when the plasma escapes confinement in the tokamak. Our research shows that ARC will behave similarly to SPARC when it comes to these disruptions, which means SPARC can guide us for this aspect of ARC. “That was a real positive thing to see come out of the analysis,” said Jon Hillesheim, a CFS Principal Scientist focused on ARC physics and another APS-DPP presenter.
- Stability: SPARC and ARC both will have relatively low plasma pressure given their very high magnetic field, making it easier to avoid instabilities that crop up. “At very high plasma pressures, plasma wants to kink and tear the magnetic field,” Hillesheim said.
- Exhaust: Managing the hot power exhaust from a plasma is another tokamak challenge, and more generally a challenge for any fusion machine. SPARC is designed to prove out advanced technology in the divertor region of the tokamak that handles that exhaust, and ARC’s heat loads are actually significantly lower and easier to manage. “I’m impressed by the cutting-edge exhaust solutions for SPARC and ARC,” Snyder said.
CFS is now deep into ARC design work. About every two months, we produce an updated design that seeks to optimize factors like physical performance and manufacturing cost.
“We have a strategy to put ARC on the grid in the early 2030s. That strategy runs through SPARC,” Hillesheim said. “Getting the data from SPARC will be essential to answer a lot of the questions and close the gaps for ARC.”
SPARC® and ARC™ are trademarks of Commonwealth Fusion Systems®.
