COMMONWEALTH FUSION SYSTEMS
For the last 100 years, humanity has been working on a collective project: creating an artificial star.
If it is successful, it would rank among the most monumental technological achievements in human history. Generating a virtually limitless supply of low-cost entirely green energy, its impact would be felt around the world and beyond: from climate change to space exploration.
This project is to make a fusion energy machine.
Fusion energy is produced when two small atoms combine to make one larger one. Unlike nuclear fission, which releases energy when a large atom breaks up into smaller ones, fusion is safe and easily controlled, with negligible byproducts, no risk of meltdowns or combustion, and almost no waste. It is, after all, how the sun generates its power.
Since the 1930s, scientists around the world have been working to develop a fusion machine that could generate more energy than it takes to power it. For almost 100 years, they have inched incrementally forward, but each step of progress reveals the true complexity of the problem.
Commonwealth Fusion Systems (CFS) may have finally shortened the timeline. Unlocking a significant breakthrough in magnet technology, CFS has brought us to the precipice of a commercial-scale fusion power plant.
Once deployed, it would produce a nearly limitless grid-ready and consistent source of carbon-free energy; its fuel (deuterium and tritium, which we can derive from lithium in the oceans) are plentiful enough that they could power the world for somewhere between 30 million and ten billion years before running out.
The potential benefits are staggering. In the near term, it could aid in averting an impending climate catastrophe. The medium and long term implications range from water desalination to universal food security to interstellar space travel.
As continued breakthroughs deliver us to the precipice of achieving net energy fusion, these scenarios, once the stuff of science fiction, appear closer than ever before.
Last year, Helena participated in a record-breaking investment in CFS, with investors and media around the globe recognizing both the urgency and the impact of fusion energy.
What is Fusion?
For a fusion reaction to occur, two nuclei must combine to make a larger nucleus. This is difficult because the positively charged nuclei are repelled by electromagnetic force. In order for them to merge, they must therefore be moving with enough energy to overcome that repulsion and collide. (Even then, a fusion reaction is not guaranteed). The energy generated in fusion comes from the difference in mass between the initial atoms and the new atom.
This process requires both extreme heat and extreme pressure. For context, solar fusion occurs in the sun’s core, where the temperature is roughly 15 million degrees Celsius. Its pressure is 100 billion times than on Earth. The sun’s core temperature transforms hydrogen gas into plasma (where negatively charged electrons are shorn from positively charged nuclei) and accelerates the nuclei, increasing their energy. At the same time, the sun’s pressure and gravitational pull keep the plasma ‘confined’, increasing the likelihood of collisions occurring.
For a human-built fusion device to be successful, it must create an environment in which temperature, plasma density (pressure), and confinement time are all astrally high, despite the fact that these variables are fundamentally at odds with each other. The higher the temperature, the harder it is to maintain pressure and keep it contained.
And it must do so without expending more energy that it generates. (The ratio of energy generated to energy injected per second is “Q.” The proverbial white whale of current fusion technology is a device that breaks even, a device for which Q = 1.)
Designing A Fusion Device
Fusion is one of nature’s most elegant and essential reactions. But artificially creating it has been one of humanity’s most insurmountable technological pursuits. It has also been one of its most collaborative.
The modern understanding of fusion dates back to 1920, when British astrophysicist Arthur Eddington theorized that the sun drew its power from the fusion of hydrogen into helium.
Eighteen years later, in a clandestine experiment at the National Advisory Committee for Aeronautics’ Langley Memorial Aeronautical Laboratory, physicists Arthur Kantrowitz and Eastman Jacobs became the first to try to actually build a fusion device. The experiment was a failure – no reaction occurred – but it set the stage for the next ninety years of advances in the field.
In 1950, Soviet physicists Andrei Sakharov and Igor Tamm began working on a new design called a tokamak. It resembled a large donut, and it used two magnetic fields to keep the plasma confined and compressed. Since then, many scientists have pursued advancements in fusion through the optimization of tokamak technology.
Tokamaks are not the only way to approach fusion. The National Ignition Facility (NIF), for example, the current record holder for energy gain, uses inertial confinement. While magnetic confinement holds the plasma in place for (relatively) long periods of time in extreme temperatures, inertial confinement holds it there for very short periods, but it uses plasma that is incredibly dense in pressures that are similar to the sun’s. TAE Technologies uses a combination of hydrogen and boron instead of deuterium and tritium, Helion Energy uses compressed plasmas of deuterium and helium and Lockheed Martin uses magnetic mirrors.
CFS: Magnetic Confinement Fusion
Commonwealth Fusion Systems has its roots in the Alcator C-Mod tokamak at MIT’s Plasma Science and Fusion Center (PSFC). The structure of the Alcator is not dissimilar to other tokamaks.
When turned on, the gas in the chamber is heated using both radio waves and current conducted through oscillating magnetic fields, and the magnets keep the plasma both confined and hot.
One of the greatest challenges in fusion is that, even when the conditions for collisions are perfect, a reaction does not always occur. Therefore any successful fusion device needs to generate as many collisions as possible without expending energy than the fusion reaction will produce. (In other words, it must achieve a Q value greater than 1.)
The Alcator C-Mod tokamak set numerous records – including the highest volume average plasma pressure in a magnetic confinement device. In 2016, the device was placed into “safe shutdown.” To achieve the next echelon of development, the scientists at PSFC understood that the power output of a tokamak like Alcator C-Mod increases exponentially with an increase in magnet strength. What they needed, therefore, were stronger magnets.
In a moment of atomic serendipity, exciting technological developments in high temperature superconductors (HTC) emerged right around the time when the Alcator C-Mod was being retired.
Superconductors are so-named because they provide no resistance to the flow of electrical current. This allows them to create very high currents and very strong magnetic fields. Most tokamaks (including ITER), if they use superconductors at all, use low temperature superconductors (LTS). LTS must be extraordinarily cold –and must remain extraordinarily cold – to allow current to pass through without resistance. HTS, on the other hand, are much more fusion friendly: they are non-resistive at higher temperatures, so they are potentially cheaper, smaller, and easier to operate; and they work across a larger temperature range.
The big development, though, wasn’t the existence of HTS; it was that manufacturers were able to make them into long, flexible tapes. A team at PSFC correctly predicted that, with this new superconductive tape, they could wind and coil it in such a way to drastically increase the strengths of their magnets. The team saw this as the key to developing commercial fusion energy for the world. So in 2018, they raised $18 million to form Commonwealth Fusion Systems.
In late August 2021, less than four years after it was founded, the CFS team wound 165 miles of HTS tape into 256 coils (16 layers of magnets, each with 16 coils) to make one supermagnet. They then placed the supermagnet into the “hole” of a vacuum chamber designed to replicate a tokamak, pumped helium into the chamber, and, once the magnet had been cooled enough, began charging it.
On September 5, the magnet surpassed 20 Tesla. (For reference, MRI machines, which have been known to magnetically pull into their mouths the occasional chair, have a strength of 1.5T.) Not only was this the strongest magnet of its kind ever created, but it was more than 50% more powerful than the projected magnetic field strength of ITER, a $25 billion, 500 acre fusion device.
What's Next
Creating a 20T magnetic field test was the first phase in CFS’s three phase plan to make commercial fusion energy a reality. The next phase is to employ those magnets in a demonstration tokamak called SPARC. SPARC – a pilot device, designed to prove that producing net positive fusion power (Q>1) is possible – is scheduled to be functional by 2025. Though any Q value greater than 1 would be an unprecedented success, the CFS team has higher ambitions: in September 2020, they published a series of papers in the Journal of Plasma Physics in September 2020 detailing the mechanics of yielding higher values.
Once SPARC has demonstrated the feasibility of its device, CFS will move onto the final phase: bringing fusion energy to the power grid. To do this, CFS will use the SPARC design to construct commercial-scale ARC power plants. These plants will generate energy through their fusion devices (larger, more advanced versions of SPARC), then convert that energy into electricity that could be deployed immediately to the electrical grid.
The plan is well under way. In late 2021, Helena joined investors including Breakthrough Energy in a more than $1.8 billion financing, the largest private investment in nuclear fusion to date. Helping lead Helena’s investment process was Member Will Jack, who, before attending MIT, worked at the Princeton Plasma Physics Laboratory on its lithium tokamak experiment and in high school developed particle accelerators capable of carrying our nuclear fusion reactions.
Last year, CFS broke ground on a new, $300 million, 47 acre campus in Devens, Massachusetts. It will feature a 150,000 square foot research facility for the ongoing development of SPARC, as well as a 165,000 manufacturing facility to mass produce magnets for the future construction of ARC power plants.
CFS plans to bring the first ARC online in the 2030’s and scale their production to become humanity’s default source of clean baseload energy.
Deuterium and tritium fill a donut-shaped main chamber, which is confined by three sets of magnets: Torroidal field coils wrap around the donut, winding through the ‘donut hole’ and around the outer edge; poloidal field coils halo the top and bottom of the donut; and a central solenoid drops vertically into the ‘donut hole’.
The fusion power a tokamak produces is proportional to the strength of its magnetic field to the power of four – i.e., if you were to double the magnetic field strength, the tokamak would produce 16 times the fusion power. Given that incremental improvements in magnetic field strength result in significant improvements in fusion power output, breakthroughs in magnet technology could enable appreciably more powerful and smaller tokamaks.
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