Except for some remaining plywood stairs and dust, the complex appeared to be nearly completed. There’s a huge wall of glass on the front of the building—a feature intended to show that the company is open with the community about the goings-on inside, as my tour guide, chief marketing officer Joe Paluska, put it.
Four main buildings surround the central tokamak hall. These house support equipment needed to cool down the magnets, heat up the plasma, and measure conditions in the reactor. Most of these big, industrial systems that support SPARC are close to being ready to turn on or are actively being installed, explained Alex Creely, director of tokamak operations, in a call after my tour.
When it was finally time to see the tokamak hall that will house SPARC, we had to take a winding route to get there. A maze of concrete walls funneled us to the entrance, and I lost track of my left and right turns. Called the labyrinth, this is a safety feature, designed to keep stray neutrons from escaping the hall once the reactor is operating. (Neutrons are a form of radiation, and enough exposure can be dangerous to humans.)
Finally, we stepped into a cavernous space. From our elevated vantage point on a metal walkway, we peered down into a room with gleaming white floors and equipment scattered around the perimeter. At the center was a hole, covered with a tarp and surrounded by bright-yellow railings. That empty slot is where the star of the show, SPARC, will eventually be installed.
COMMONWEALTH FUSION SYSTEMS
While there’s still very little tokamak in the tokamak hall right now, Commonwealth has an ambitious timeline planned: The goal is to have SPARC running and the first plasma in the reactor by 2026. The company plans to demonstrate that it can produce more energy in the reactor than is needed to power it (a milestone known as Q>1 in the fusion world) by 2027.
When we published our 2022 story on Commonwealth, the plan was to flip on the reactor and reach the Q>1 milestone by 2025, so the timeline has slipped. It’s not uncommon for big projects in virtually every industry to take longer than expected. But there’s an especially long and fraught history of promises and missed milestones in fusion.
Commonwealth has certainly made progress over the past few years, and it’s getting easier to imagine the company actually turning on a reactor and meeting the milestones the field has been working toward for decades. But there’s still a tokamak-shaped hole in suburban Massachusetts waiting to be filled.
Related reading
Read our 2022 feature on Commonwealth Fusion Systems and its path to commercializing fusion energy here.