Cooling our cryogenic system down to its very low operating temperature of 8 kelvin is a big moment for our SPARC fusion demonstration machine. It shows how deeply we’re now into the work of building, commissioning, and running the industrial hardware needed to operate SPARC. We’re steadily checking the check boxes on the SPARC to-do list. Fusion works by heating and confining a very energetic cloud of charged particles called a plasma. In our case, we do that with very strong magnets that must be cooled to very low temperatures. The plasma is exotic, but the cooling system is ordinary technology you’ll see at liquified natural gas plants and other industrial sites. But it takes skill and expertise to run cryogenics, and that’s what we’ve shown with this 8 kelvin achievement. We’ve already begun applying this knowledge to designing a very similar cryogenic system for our ARC power plant. Check out our video and blog post to learn more about this core technology and how CFS is working in parallel on both the core SPARC equipment at the heart of the facility and the support equipment like the cryo system surrounding it. Congrats to the team that put in long hours to install all the cryogenic system’s pumps, compressors, pipes, and valves and get it working smoothly. This gets us ready to check off one of the big check boxes on SPARC’s path to Q>1, aka net fusion energy.

Even though fusion is hard, we’re really confident SPARC will hit its first big goal of Q>1. That milestone means that the amount of fusion energy we get out of the plasma (our very hot fusion fuel) will exceed the heating energy we put in to make the fusion happen. So far, only one machine in the world has done that, but we expect SPARC will be the second. Check our blog post about this to understand why we’re confident and why achieving Q>1 is important. To reach Q>1, you don’t just need good science. You also need a team with the skills to engineer, manufacture, build, and operate a fusion machine. @CFS_energy has exactly that. And we put this all together with commercialization in mind: SPARC demonstrates most of the core technology we need for our ARC power plant.

Dennis Whyte (@MIT_Fusion) is taking over as CEO of the UK Atomic Energy Authority (@UKAEAofficial), and I’m excited to see a longtime friend and collaborator in this new leadership role. I worked for years with Dennis at @MIT's Plasma Science and Fusion Center — where Dennis was Director, I was a grad student getting my PhD, and @CFS_energy has its origins — and now I look forward to his arrival in the UK. CFS has had a joint R&D partnership with UKAEA for four years, including efforts like the LIBRTI program for fusion fuel production. Dennis is a giant in the fusion world, an author on nearly 400 peer-reviewed papers including several involving the SPARC fusion machine we’re building right now at CFS headquarters. The UKAEA is lucky to have him. Dennis helped build and maintain a strong PSFC program, and now he’ll have a chance to do the same for UKAEA. His taking this job shows how a well coordinated effort with a strong vision, significant financial and government support, and leading-edge new facilities can attract top talent. Bringing his skill to UKAEA directly strengthens the country’s ability to benefit from fusion energy’s advantages — clean, safe, dispatchable electricity. One of UKAEA’s most important fusion projects, the Joint European Torus (JET) tokamak, produced important research and operational expertise. It’s also the tokamak that came closest to producing net fusion energy (Q>1), with a Q of 0.67. JET has entered decommissioning now, but there’s more work to be done in fusion. I’m looking forward to seeing how Dennis can help UKAEA push fusion forward now that the world’s attention is focusing not just on experimental projects but commercial fusion technology, supply chains, and the first power plants heading toward the grid. #FusionEnergy

Neither of these entities is anywhere close to accomplishing what’s needed in their respective domains to warrant working together. reuters.com/business/energy/…

News today: Commonwealth Fusion Systems has raised an additional $1 billion — the largest amount since our $1.8 billion investment in 2021. That brings our total capital raise since the start of the company to $4 billion — about 30% of what all fusion companies have raised together, according to the latest @Fusion_Industry Association figures. This new funding cements our position as the global leader in fusion, a maturing company that’s able to attract a maturing investor set: pension funds, sovereign wealth funds, infrastructure investors, and industrial corporate partners. The reason we’re able to win their confidence is they see the full range of what we do. There’s the bedrock of our science. There’s our execution ability, evident when they come to Devens, Massachusetts, and see our SPARC fusion demonstration machine is now about 80% done. And there’s our progress in delivering our first ARC power plant, including our application to PJM Interconnection, the largest wholesale electricity market in the United States. This new funding puts us in a position to move at scale and as quickly as we need to deliver fusion energy. We’ll be able to apply what we’ve already learned from SPARC, to build at-scale prototypes of other technology we need, retool our supply chain, expand our manufacturing, prepare the site for our first ARC power plant, and start contracting power for the next plants. It’s like we’re standing on two feet, shifting our weight gradually from the SPARC foot to the ARC foot. That’s very exciting: once we turn on SPARC, we’ll be able to take off on the next step to ARC.

At Commonwealth Fusion Systems, we value those with proven experience that applies to our fusion energy mission — which is why I’m happy to welcome Lorence Kim as our new Chief Financial Officer. In that role, he’ll be able to apply to CFS his experience maturing a mission-driven, game-changing company from its deep science roots to commercialization. Lorence has deep experience with strategic advisory work, capital markets, fundraising and venture investing, having led the biotech investment banking effort at Goldman Sachs and co-founded Ascenta Capital. But importantly, he also was CFO for @moderna_tx for six pivotal years of hypergrowth as the company developed its mRNA platform and portfolio of medicines, including its COVID-19 vaccine. His strong financial leadership will help CFS complete the assembly of our SPARC fusion demonstration machine, design our first ARC power plant and plug it into the grid, and eventually scale up to build many fusion power plants around the world. #FusionEnergy

This @eni–@UKAEAofficial work is a healthy sign of where things are headed in commercial fusion: integrated systems that fusion companies can buy as a unit instead of doing the work themselves to find, validate, and connect components. This is a sign of a maturing industry and strengthening supply chain.

Fusion energy has plenty of challenges, but the first is always plasma physics. You have to control superhot fusion fuel in a way that’s agreeable to the laws of the universe. Today, in a set of five peer-reviewed papers, we’re documenting how we’re confident we’ll be able to do that with our ARC fusion power plant. The papers, written by 58 experts from CFS and collaborating universities and research institutions, show the scientific foundation. That starts with calculations and simulations backing up our expectation that an ARC plant will produce 1.1 gigawatts of fusion power that we can convert into 400 megawatts of net electricity for the grid. And the papers address how we’ll tackle fusion challenges like heat exhaust, disruptions, and plasma stability. The bottom line: The science is solid. There are no showstoppers. We begin with decades of tokamak knowledge, extend that with what we’ve learned already from our SPARC demonstration machine, and fine-tune it with what we’ll learn from operating SPARC. Our commercial success is contingent on this successful de-risking of the core science. We published these papers in the Journal of Plasma Physics through the peer-review process. That brings the independent validation of our work that’s crucial to establishing trust in our results. There’s a reason why peer review is the gold standard in the scientific community: It’s the best way to distinguish ideas from reality. In fusion, where the science and engineering are tough, peer-reviewed research helps leaders, investors, customers, and citizens make informed and unbiased decisions about who to trust and where to invest their dollars. Congratulations to all who contributed to these papers, and thank you to the Journal of Plasma Physics from @CambridgeUP for taking on their publication. Today the global fusion community can celebrate a new win in the advancement of the last energy source humanity will ever need.

Happy to see this new $250 million fund from @gigascale Capital designed to let institutional investors become more deeply involved in the startups that’ll build the world’s future infrastructure and other physical technology. This is literally a constructive step forward. Very few people have successfully scaled cutting-edge technology and delivered it to the world. Even fewer can go deep on the novel physics, the operational work, and the people at the same time. @schrep and his team do all of it, and their expertise shines through.

I’m grateful for the opportunity to serve on the President’s Council of Advisors on Science and Technology (PCAST). The United States has long been an innovation powerhouse, helping to tackle some of the world’s most pressing challenges. I look forward to working with other members of the PCAST to ensure the US remains at the forefront of innovation. whitehouse.gov/articles/2026…

In 2024, I introduced a six-milestone framework that the fusion energy industry can use to build trust in fusion energy. This week, we’ve published two blog posts detailing milestones 4 and 5. These are about making the leap from plasma physics into the larger world of fusion power plants. Milestone 4 is a doozy: Q>1, also called net fusion energy. Put simply, it means more energy out of the heart of the machine than in — and so far only one system in the world has been able to do it. This monumental achievement demonstrates the basis of a power plant, so you’ll hear a lot more about Q>1 as the fusion industry matures. Even if you’ve heard of Q>1 before, this post is a chance to read about some of its subtleties. Milestone 5 goes a step further by showing you can generate net electricity suitable for the power grid. That extends beyond the plasma physics skills needed for Q>1 into new domains like plant engineering and energy conversion. Of course you only need this if you have a fusion plasma that can make enough fusion power to overcome its own losses — hence the sequencing of the milestones. I know fusion science and engineering can be confusing, but these milestones are designed to offer a relatively simple guide that investors, journalists, policymakers, and the general public can use to evaluate fusion companies. Ultimately, being able to separate the true progress from shallow marketing hype will build trust in our industry. Check here for posts on milestone 4 and milestone 5 on the path to competitive fusion energy. Milestone 4: blog.cfs.energy/fourth-step-… Milestone 5: blog.cfs.energy/fifth-step-o… #FusionEnergy