If you want to see the future of energy, take a trip to Devens, Massachusetts. In a corner of the town and surrounded by forest, you will find Commonwealth Fusion Systems (CFS). The CFS campus is comprised of two buildings: the company’s headquarters that includes its 120,000 square foot advanced magnet factory, and the facility that will be home to CFS’s SPARC tokamak machine. The Fusion Report had the opportunity to tour both parts of the site last week, and for those of us who are interested in fusion energy, the visit absolutely didn’t disappoint! CFS was spun out of the Massachusetts Institute of Technology (MIT) Plasma Science and Fusion Center (PSFC) in 2018 by co-founders Bob Mumgaard (CEO); Brandon Sorbom (Chief Science Officer); MIT professors Dennis Whyte and Zach Hartwig; Martin Greenwald, former deputy director of PSFC; and Dan Brunner, who served as Chief Technology Officer. The company has raised more than $2 billion from investors, including Eni, Temasek and Tiger Global Management, making it the largest private fusion company in the world. From those early days in Cambridge, Massachusetts, CFS has grown to more than 1,000 employees. From the start, CFS focused on generating fusion energy that could be delivered economically on the utility grid. To achieve this, CFS continuously examines how to scale technologies in a way that will make fusion power economically viable versus other baseline electricity resources, such as nuclear fission and fossil fuels. The approach to building a fusion machine that could reach Q greater than one (the ratio of the machine’s fusion energy output to the energy put into the fuel) stems from that high-level goal. As Ben Byboth (Director, Business Development and Strategy at CFS) put it, “We aren’t a tokamak company – we are a commercial fusion company.” Two key things make fusion economically viable: i) creating more energy from fusion than is put in to fuel the process; and ii) being able to scale the production of fusion machines so that they can be made at a cost that is economical. In a 1955 research paper, physicist John D. Lawson detailed the conditions — now called the Lawson criteria — that are necessary to produce fusion energy. That idea led to what’s now called the triple product — the temperature of a plasma (expressed in thousands of electron volts, or keV) multiplied by the plasma density and by the plasma confinement time. To date, only one fusion machine, the Lawrence Livermore National Laboratory’s (LLNL) National Ignition Facility (NIF) inertial confinement fusion (ICF) machine, has achieved Q>1 (August 8, 2021). Only two machines under construction today are forecast to exceed Q=1: the International Thermonuclear Experimental Reactor (ITER), which is expected to achieve Q>1 in 2040; and CFS’s SPARC, which is expected to achieve Q>1 in 2027. The second factor critical to the economic viability of fusion energy is the ability to build fusion machines with a total cost of ownership (TCO) that includes construction, fuel, maintenance, and other operational costs that are competitive with that of current electrical power plants. Fusion will need to compete with other energy sources, too, including wind and solar, but it offers some advantages when it comes to 24x7 power availability and site flexibility. Most fusion machines built over the decades largely have been “demonstrators”; their goal is to probe fusion physics rather than to commercialize a power plant design. And costs increased with newer “demonstrator” machines as scientists pushed toward Q>1. For instance, the original budget for ITER was €6 billion ($6.49 billion) in 2007; the official cost projections are now between €18 billion ($19.475 billion) to €22 billion ($23.8 billion), and some estimates place the likely cost between $45 billion and $65 billion, clearly outside a cost which is economically viable. Moreover, ITER is not expected to produce “first plasma” until 2034, and to reach Q>1 until 2040. CFS’s approach employs materials that permit smaller, less expensive designs. SPARC is being used to prototype a design with costs and schedules that will be scaled into production with the company’s later ARC power plant. While ARC is still in design and its costs are not yet known, it should be considerably less than ITER based on its size alone. CFS’s path to commercial fusion includes four major steps: • MIT’s Alcator C-Mod Fusion Machine: Alcator C-Mod was the third model of the Alcator tokamak, which operated between 1991 and 2016 at MIT’s PSFC. The machine had a very high toroidal magnetic field of up to 8 tesla, and achieved a plasma pressure of 2.05 atmospheres in 2016 (a record for tokamaks that stands even today). • High-Temperature Superconducting (HTS) Magnets: One of the areas identified early for innovation was the confinement and drive magnets for production tokamaks. Early tokamaks used low-temperature superconductors, which could only achieve (relatively) limited magnetic fields. CFS decided to pioneer the use of HTS-based magnets for its upcoming machines; the SPARC magnets produce a record-breaking field of 20 tesla. • The SPARC Tokamak: SPARC, currently under construction at the Devens, Massachusetts, campus represents CFS’s proof of concept for a production-grade tokamak. SPARC is a relatively compact tokamak that is 1/40 the volume of ITER. By 2027, SPARC is expected to produce up to 140 MW of fusion heat energy (SPARC will not produce electricity) and Q>1. Later, the company plans to reach Q=11. The goal of SPARC is to demonstrate both net fusion energy and the core technologies required to build production fusion energy machines. • The ARC Tokamak: ARC, which will be CFS’s first commercial machine, is a scale-up of SPARC that will be about 1/6 volume of ITER. ARC will be built at a Dominion Energy-owned site in Chesterfield County, Virginia. By the early 2030s, ARC will be capable of producing 400 MW of net electricity that will go directly onto the utility grid. The footprint of ARC will be similar to that of a “big box” store, making the siting of ARC-based power plants near high-power demand areas (cities, industrial facilities, hyperscale/AI datacenters, etc.) much simpler. Thanks again to CFS for hosting my visit to the Devens, Massachusetts, facility and answering my questions in a very open and transparent manner. For those who regularly follow The Fusion Report, you know how we have spoken about the increased demand for electricity that we (both the US and the world) will undergo over the next 25 years (at least!). There is no doubt in our minds that fusion energy will be critical to providing clean, firm baseline electricity to the grid to meet our increasing demands. For those who have had their doubts whether fusion is “real”, seeing the CFS facility certainly answered the question for me: fusion is real, and closer than you might think!