MIT-designed project achieves major advance toward fusion power

On September 5th, for the first time, a large high-temperature superconducting electromagnet was ramped up to a field strength of 20 tesla, the most powerful magnetic field of its kind ever created on Earth. That successful demonstration helps resolve the greatest uncertainty in the quest to build the world’s first fusion power plant that can produce more power than it consumes, according to the project’s leaders at MIT and startup company Commonwealth Fusion Systems (CFS).

This large-bore, full-scale high-temperature superconducting magnet designed and built by Commonwealth Fusion Systems and MIT’s Plasma Science and Fusion Center (PSFC) has demonstrated a record-breaking 20 tesla magnetic field. It is the strongest fusion magnet in the world. (Credit: Gretchen Ertl, CFS/MIT-PSFC, 2021)
This large-bore, full-scale high-temperature superconducting magnet designed and built by Commonwealth Fusion Systems and MIT’s Plasma Science and Fusion Center (PSFC) has demonstrated a record-breaking 20 tesla magnetic field. It is the strongest fusion magnet in the world.
(Credit: Gretchen Ertl, CFS/MIT-PSFC, 2021)

That advance paves the way for the long-sought creation of practical and inexpensive power plants.

David Chandler for MIT News Office:

“Fusion in a lot of ways is the ultimate clean energy source,” says Maria Zuber, MIT’s vice president for research and E. A. Griswold Professor of Geophysics. “The amount of power that is available is really game-changing.” The fuel used to create fusion energy comes from water, and “the Earth is full of water — it’s a nearly unlimited resource. We just have to figure out how to utilize it.”

Developing the new magnet is seen as the greatest technological hurdle to making that happen; its successful operation now opens the door to demonstrating fusion in a lab on Earth, which has been pursued for decades with limited progress. With the magnet technology now successfully demonstrated, the MIT-CFS collaboration is on track to build the world’s first fusion device that can create and confine a plasma that produces more energy than it consumes. That demonstration device, called SPARC, is targeted for completion in 2025.

[Dennis] Whyte, who is the Hitachi America Professor of Engineering, says this week’s demonstration represents a major milestone, addressing the biggest questions remaining about the feasibility of the SPARC design. “It’s really a watershed moment, I believe, in fusion science and technology,” he says.

To capture the sun’s power source here on Earth, what’s needed is a way of capturing and containing something that hot — 100,000,000 degrees or more — by suspending it in a way that prevents it from coming into contact with anything solid.

That’s done through intense magnetic fields, which form a kind of invisible bottle to contain the hot swirling soup of protons and electrons, called a plasma. Because the particles have an electric charge, they are strongly controlled by the magnetic fields, and the most widely used configuration for containing them is a donut-shaped device called a tokamak. Most of these devices have produced their magnetic fields using conventional electromagnets made of copper, but the latest and largest version under construction in France, called ITER, uses what are known as low-temperature superconductors.

The major innovation in the MIT-CFS fusion design is the use of high-temperature superconductors, which enable a much stronger magnetic field in a smaller space. This design was made possible by a new kind of superconducting material that became commercially available a few years ago. The idea initially arose as a class project in a nuclear engineering class taught by Whyte. The idea seemed so promising that it continued to be developed over the next few iterations of that class, leading to the ARC power plant design concept in early 2015. SPARC, designed to be about half the size of ARC, is a testbed to prove the concept before construction of the full-size, power-producing plant.

“It’s a big moment,” says Bob Mumgaard, CEO of CFS. “We now have a platform that is both scientifically very well-advanced, because of the decades of research on these machines, and also commercially very interesting. What it does is allow us to build devices faster, smaller, and at less cost,” he says of the successful magnet demonstration…

The next step will be building SPARC, a smaller-scale version of the planned ARC power plant. The successful operation of SPARC will demonstrate that a full-scale commercial fusion power plant is practical, clearing the way for rapid design and construction of that pioneering device can then proceed full speed.

Zuber says that “I now am genuinely optimistic that SPARC can achieve net positive energy, based on the demonstrated performance of the magnets. The next step is to scale up, to build an actual power plant. There are still many challenges ahead, not the least of which is developing a design that allows for reliable, sustained operation. And realizing that the goal here is commercialization, another major challenge will be economic. How do you design these power plants so it will be cost effective to build and deploy them?”

MacDailyNews Take: Obviously, this is a huge scientific and engineering milestone on the road to what, if perfected, would be a massive game-changer for the entire world: Virtually unlimited, cheap, clean power.

Doc Brown empties the contents of the McFly family's trash can into his Mr. Fusion to refuel his DeLorean. (Still from Back to the Future, 1985)
Doc Brown empties the contents of the McFly family’s trash can into his Mr. Fusion to refuel his DeLorean time machine. (Still from Back to the Future, 1985)


  1. “On September 5th, for the first time, a large high-temperature superconducting electromagnet was ramped up to a field strength of 20 tesla, the most powerful magnetic field of its kind ever created on Earth” and Poof SPARC disappeared into a wormhole.

    1. Ah, no. What disappeared into that Wormhole was Fusioncynic, formerly known as Snapplecynsix. That’s why we haven’t heard from him. He didn’t perish from COVID, he perished from terminally haughty snobbery.

  2. Yea, yea, yea. Commercially viable fusion reactors are 25 years away. It’s been that way since 1955! If the initial prediction had been correct we’d have had commercial fusion for the past 40 years.

    Having created a reasonable 20 Tesla field coil is a long, long way from having a reactor. Hell, we’ve been able to build those kinds of fields for over 20 years. Maybe not as compact, and maybe not having such a low power requirement, but they’ve existed.

    Even with the right field strengths things often screw up once the plasma starts moving around. Kinked field lines that self extinguish the process is just one of many things that can still kill the functionality even once you have a system with the appropriate fields in a non plasma rich environment.

    Hell, a team at Lockheed a few years back was doing press releases (under Lockheed’s name and supported by Lockheed) that they had fusion designs and very early prototypes that would support fusion reactors the size of 18-wheeler trucks — and they’d have commercially viable version by today (late 2021). That didn’t come to pass either.

    Wake me up when they have a positive energy coefficient averaged over the course of a month of full operation. Then, and only then, will commercial fusion be a real thing.

    1. Isn’t the point that the new magnets use less power resulting in a more consistent net positive power output? I would think that is the important difference here that makes fusion reaction systems feasible than the systems of the past. Why pump more energy into a system that produces less unless there is some other benefit produced?

      1. Yes, the video seems to indicate so. In the past, it was a bit of joke when talking about fusion plasma experiments when needed more energy to produce less energy. But it was OK in order to establish the theory in a lab condition. It’s OK in experimentation but I did not think it has been solved (yet). It is largely because these experiments tried to produce high temperature/energy plasma by ultra strong electromagnetic field. Unless, some other method to produce sustainable and controllable fusion reaction is discovered, we may still in a dreaming stage. Just a flash fusion reaction in experimental container seems too far from taking it out as an energy source. But what do I know…

  3. I agree that fusion reactor is too far away. Those 2 persons in the video do not seem to understand how fusion reactor works and what the current problems are. They never talked about the core issues of fusion reactor, except sprinkling of terminology such as plasma etc. One is still talking about the comparison with renewable energy etc. Among others, the single biggest problem is how to sustain the plasma for long enough to use it in any form. It used to be a millisecond level. As far as I know, the latest development was something like a couple of hundred million celsius for 20 seconds or so achieved by China, which is astonishing. Then it has to be contained in a material that won’t melt. It uses the fusion of hydrogen, the lightest material on earth. Today’s nuclear reactors use “fission” of heavy material (Uranium 235 and Plutonium 244 etc). Fusion and fission are different but similar energy creation (google “mass defect”). First bomb dropped in Japan was a Plutonium one. Then, thermonuclear (Hydrogen fusion) bomb was developed. As far as I know H2 bomb has never been dropped dropped on any human being!?
    So, the energy sustainability is the thing of concern and I do not believe it would be achieved in the next 50yrs at least. Then the next problem is how to convert the enormous heat energy to usable electrical power. I suppose it should still use some kind of boiler and steam turbine generator (no direct conversion from plasma, not yet). Many countries are competing to accomplish “something”. France is running top now followed by the US, Russia (Tokamak), Japan and China etc. Tell you what… It makes far more sense that Apple gets involved in and spend money on something like fusion reactors (in any branch of tech) than Apple funnicar. Bill Gates is pursuing mini reactor concept (fission reactor).

    A former unclear changenieer

    1. Plutonium 239 not 244 (virtually has to be an odd number — in theory you can make even numbers “fissionable” but for “fissile” elements you need that odd number. You can look up in the CRC the fissile cross section for thermal neutrons. Another good one is Uranium 233, but tat’s extreamely rar The best way to get to U-233 is to start with Thorium, but the “standard” way to kick strt a Throrium reactor is to start with a P-239 seed reaction.e.

      We built 3 bomb near the end of WWII. Two uranium 235 and one Plutonium 239. They went: Trinity, Hiroshima, Nagasaki. Then we threatened to drop another if Japan did not surrender, but we didn’t have another at the time to drop. It was a bluff that worked.

      There were extremely few above ground thermonuclea(fission) r devices detonated. One interesting thing to note is that the early thermonuclear devices used a transuranic fission devise at its core to get things triggered. Trigger sets of the fission device whiu sets off the fission device.

      There is a lot more energy released in the fusion of any variant of Hydrog into heavier but still very light elementsen than in is the split of any transuranic. A lot.

      Other things people forget is that there are a lot of free neutrons zipping out of t fusionhe reaction when fusion is going on. Not all the neutrons are captured in the production of the heavier elements from the initial And, those free neutrons from a fusion reactor are VERY energetic. hydrogen. Those free neutrons damage the and anything else in their pathscontainment vessel. Also there’s a lot of gamma. That also damages everything.

      These things are not (and may never be) as simple as a TRIGA reactor (Training, Research, Industry, General Atomics). College kids often run those. All that nastiness is house/containedd in room temperature light water baths. With the temnearly ps and densities required for fusion, this level of “teaching reactor” will likely not come to pass for well over 100 years — if ever.

      1. Good, thanks. I used to work in San Jose, Calif. but am now retarded, oops, retired and with machine gun typing without much thoughts in fuzzy head, I am vulnerable to errors.
        Re neutron, yes, there are a lot of free neutrons but in actual nuclear power plant, it was never an issue. Reactor pressure vessel (RPV) still stands even with injuries from neutron or gamma-ray bombardment and many are extending it’s life to 60 years. In fusion reactors, because of splitting atoms (fission) by neutral particles (hence neutron) , nuclear fission is very controllable (essentially control the absorption of neutrons). I described the issue with plasma heat, that cannot be contained as of today even for short seconds but extracting them for actual work is the engineering part, passing science stage (I do not think we are there yet). The sun produces enormous energy essentially by H2 fusion simply because the mass is so huge that hydrogen at core is literally crushed and fused together, the heat of which propagates up to the surface. I wish fission reactors will be materialized soon but I am not so optimistic on actual implementation (engineering) of the thing but who knows. Fission bomb was relatively easy task since Enrico Fermi theory. All it has to do is to instantly attach two fiissionable bulks by TNT, i.e., uncontrolled and instant chain reaction. It took so many more years to control the fission in actually energy/heat containing vessel. By definition (material it uses and energy density etc), it will probably save the global energy issue with the least contamination, but knowing how the engineering/implementation stage is so difficult in any industrial project, I am not too optimistic. Getting back to the line on Apple cars, I repeat, I want to believe there are more Apple can do for somewhat more bleeding edge technology particularly at device level and perhaps some kind of software to control plasma etc. Apple car does not attract my fantasy 🙂
        Don’t want to bore other people either…. It just that those videos bugged me.

      2. Utter nonsense. You need to do your homework and come back. First of all, there was a 4th nuclear weapon ready and on hand that you obviously never read about. They never used it. Hit the books and learn. Also, the US was in a position to produce 10 or 12 by the end of 1945 to use in the invasion of mainland Japan to kill every living thing on the beaches this time … soldiers, babies, women, dogs, bugs, birds … all of it, thankfully. No more island-to-island bloodbaths. But who cares. We had nearly 300 B-29s and upwards to 10,000 B-17s, B-24s, B-25s, B-26s and Lancaster bombers available to bring over from Europe and to continue the conventional air campaign that burned up 75% of Japan’s cities anyway, God bless LeMay. More people died in the bombing of that shithole Tokyo in April of 1945 than any other single battle or event in the history of mankind. All bombers now could be based within range of all of Japan because we took Okinawa with the blood of American Marines. All escorted by P-51s, P-shooters,now that had drop tanks. There was no bluff, but, that is what the woke teachers teach today in woke schools.

        1. … correction. Almost 3,000 B-29 Superfortreses. Would mean, with the other bombers brought over from Europe, 1,000-bomber raids on Japan at the rate of 5 or 6 a week, given the naval logistics to provide bombs, napalm (than you Harvard), fuel and spare parts. Japan got off easy.

        2. Terrible talking not appropriate or Apple related discussions like MDN. Now that a fusion/MIT story suddenly popped up for some unknown reason (MDN team member?), discussion went off the track. Talking about off base info, I wanted to shut my mouth as many people jumped in (WWII survivors?) with their own opinions. Some are outright wrong (bluff story for example), which is not good as this is a public forum. But one thing. A 3rd (or whatever number) bomb was supposed to be assembled in Tinian where B-29 was waiting. It’s a very famous story (documented and publicized by USN) that a heavy cruiser named Indianapolis was carrying highly enriched Uranium to be assembled into a bomb. Unfortunately, it was torpedoed by a Japanese sub just before reaching Tinian and sunk. The Captain was court marshalled as he did not zig zag as the cruiser approached the island. His name was reinstated much later. I have too much time in my hands. Good night…

      3. Building a TRIGA reactor is not so simple, either.
        Oh, the physics and mechanics aren’t so bad, but the regulation and costs kill it. Don’t even ask General Atomics to build one for you; they will laugh in your face.
        Heck, upgrading a TRIGA reactor to something that isn’t totally obsolete (so student can continue to run them) is a major issue.

        Now as for Universities and “students” running fusion reactors, last time I checked, most of the fusion projects were being done at Universities or on collaboration with Universities. And, yes, “students” (granted, advanced grad students) are working on those projects.

    2. “Fusion and fission are different but similar energy creation (google “mass defect”).”

      Fission of U produces about 200MeV of energy per event. Fusion of Tritium and Hydrogen produces only about 18MeV per event. Fission produces roughly ten times more energy per event than does fusion. Hydrogen was added to bombs to produce more neutrons, not to produce more energy.

      Even if they produce 5% net energy that means 95% is coming from other sources, like solar panels. These will produce vast amounts of waste heat and consume vast amounts of materials for construction until the efficiency is very high. I will never see this in my lifetime.

      1. “Fusion and fission are different but similar energy creation (google “mass defect”).”

        It was meant to explain where an how nuclear energy comes from, not an explanation of energy level, but energy creation “process” or more accurately “form” of energy.. Fission extract energy, equivalent to mass defect (sort of hidden energy in atoms) by splitting heavy elements while fusion process extracts the same hidden energy by fusing atoms of light elements. But as I said, fusion may be demonstrated in lab condition but to actually use it, it has to use some kind of coolant, be it water, Helium, Sodium or other gases to produce high temp./pres. medium to run generators on a sustained basis. That fusion was “demonstrated” in lab by way of electromagnetic field only means fusion was artificially created, There may be other more appropriate method created in the future which could be totally different from electromagnetic method but may be more appropriate method to transport heat energy generated could be built to actually run generator for sustained period (like 10 continuous time at a time with 2 months maint. shutdown etc.
        Apple might be more respected if it contributed to some key inventions related to fusion reactors. Or, perhaps it’s more appropriate for Elon Mask’s job 🙂

  4. Don’t know enough about fusion reactions to know if it possible but isn’t some light produced? I wonder if a photovoltaic component to the system could be possible to collect that portion of energy in addition to the heat energy collected in some other way. Too bad the ‘unobtanium’ mentioned in “The Core” couldn’t be used. 🙂

  5. Use Thorium, oh but wait you can’t easily built a bomb out of it which is why it was put on the back burner. The USA had a Thorium reactor in Tennessee for over 20 years at Oak Ridge and it worked and the size can fit in 4,000 sq ft room.

  6. We should be happy it isn’t Apple doing this. Given their recent advocacy of making warrant-less searches of user data, if they had their hands on this it might at the last minute get re-purposed as an energy weapon to silence complaints.

  7. As is virtually all millennial ‘science’, it is purely hypothetical. Could care less. This is what happens when you l;et math and algorithms think for you. Venture capitalists are free to continue to throw their money away.

    1. Geez you’re small minded. Of course future iPhones will need miniature fusion reactors as a power source. You’re not one of those dim witted cynics, are you, with the lazy thinking?

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