Foundational Stronger Magnet Made by Commonwealth Fusion Systems

Commonwealth Fusion Systems and MIT’s Plasma Science and Fusion Center (PSFC) have demonstrated a magnet with a record-breaking 20 Tesla magnetic field. This is the core technology that they planned to create. They now have to mass produce it at ten times lower cost and assemble it into a net energy gain system by 2025. They have $200 million in funding from Bill Gates and many other funds and investors. The 20 Tesla magnets will make the Commonwealth Fusion reactor 40 times smaller than the ITER tokamak reactor which will use 11-tesla magnets.

The 20 Tesla magnets will be used in SPARC, which is on track to begin construction in 2021 and demonstrate net energy gain from fusion for the first time in history by 2025. SPARC will pave the way for the first commercially viable fusion power plant called ARC.

A 19 Tesla field is powerful enough to life 403 Boeing 747s. It has 166 miles of superconducting tape.

Commonwealth Fusion is trying to make a compact Tokomak with more powerful superconducting magnets. They wanted a commercial tokamak by 2033 but the current target is 2035 for a commercial tokamak. MIT spunout a tokamak fusion project into Commonwealth Fusion systems. They want to apply modular designs to high-temperature superconductors. They want to get to stronger magnets that will shrink the size and cost of the potential nuclear fusion reactor. Improved magnets would improve any nuclear fusion design that involves confinement of plasma. There is less science risk to this MIT approach but more technological risk. They are trying to accelerate the commercial use of high-temperature superconducting magnets and trying to contain their costs. Cost for superconducting magnets for past fusion projects have been $20 per watt but other applications have seen costs of $1.4 to $1.8 per watt.

They want to mass produce superconducting magnets that are 2X the field strength of past strong magnets while bringing the cost per watt down.

The list of items below that Commonwealth fusion is targeting is from 2018.

There are 16 subsegments stacked for each magnet and 18 magnets are needed for the demo net gain system.

Commonwealth Fusion has more detailed project plans and peer-reviewed papers indicate the science is sound.

SPARC will use new high temperature superconducting (HTS) magnets to enable a similar performance as ITER but built more than 10 times smaller and on a significantly faster timeline.

The papers also predict that SPARC will very likely achieve a burning plasma for the first time on earth, meaning the fusion process will be dominantly self-heating. This is a major multi-decade goal of the world’s scientific community. In 2020, Commonwealth Fusion Systems (CFS) had a series of seven papers published and peer reviewed in a special edition of the Journal of Plasma Physics validating CFS’ approach to commercial fusion energy.

NOTE: Two years ago Tokamak Energy reported progress on a 20 Tesla magnet.The Commonwealth Fusion System 20 Tesla magnet is more complete for a fusion project. There are also more powerful magnets at the National Magnet lab. There is a 32 Tesla superconducting magnet. 42 Tesla hybrid magnet and 100 Tesla pulse magnet. Those magnets are for lab work and would be suitable for the Tokamak project.

SOURCES – Commonwealth Fusion Systems, Journal of Plasma Physics
Written By Brian Wang,

18 thoughts on “Foundational Stronger Magnet Made by Commonwealth Fusion Systems”

  1. I have a question, it says in the article, "The papers also predict that SPARC will very likely achieve a burning plasma for the first time on earth." BUT there have been several hydrogen bombs detonated by the US, USSR and China. How is it that those brief, violent fusion reactions do not count?

  2. An alternative to lithium metal is something like FLiBe. The beryllium is a good neutron reflector with a low neutron absorption crossection; it is not just dead weight. This makes it a good moderator for neutrons. It is used as a neutron reflector for fast neutrons in some atomic bombs and as a "modulator" between the primary and secondary device in thermonuclear weapons; where it prevents neutrons from heating the secondary prematurely before the "sparkplug" fission device in the secondary goes (you don't want heating until the secondary is compressed sufficiently).

  3. They were making very good progress until ITER (triple product was making faster-than-moore's law progress towards the region where commercial fusion should be). After ITER they have made little or no progress (theoretical progress understanding and simulating plasma, progress at old fusion power plants such as H-mode etc, but not newer, better tokamaks). ITER is so big it needs to be an international project. When it is finally built and D-T fusion work starts it will have taken more than 50 years from being pitched by the USSR to doing useful experiments. If it is widly successful it tells us very little about the challenges in making a much smaller, much higher B-field tokamak that could actually be commercially viable.

    It's this and Wendelstein 7-x that are the remaining hope for tokamaks and stellarators respectively.

  4. I read the sentence "Humans aren't affected…" and I think "But what about the frog?" and then… Yeah, there's the frog.

    Except my reading of the work is that a changing magnetic field wasn't needed. Just a really strong one. Do you have a better reference?

  5. So we're still trying to make a tokamak?
    I thought we were doing hohlrams and direct electron extraction.
    I'm sorry but it's hard for me to get excited. They've been saying how very close we are to a breakthrough for about 10 years now. It's exhausting trying to hold my smile.

  6. Sure the coils will be big, but they'll mostly be structural steel with less than 1% being the HTS tape material. The core size will be comparable to SMRs in the initial commercial design. In my opinion we should absolutely pursue both.

  7. So we need at least a meter of (liquid) lithium metal between the fusion plasma & the magnet coils to absorb neutrons & breed tritium. This will get very not from the energy of the absorbed neutrons. We need that to be the hot end for a heat engine of some sort to actually get useful work out of this machine.
    This means the coils have to be really big. They better be making a constant magnetic field so it isn't wasting energy inducing currents in the lithium metal.

    The whole thing always sounds Rube Goldbergish to me. Inertial confinement fusion sounds somewhat simpler (though not easy) because all the delicate laser tech can be more easily kept outside the breeder blanket.

    Lets build lots of fission reactors. I don't expect fusion to be solved soon.

  8. For shielding: definitely. 
    For travel: something like M2P2 could be useful within the solar system, but probably not useful for interstellar. 
    For gravity: it seems unlikely. Humans aren’t affected by static magnetic fields. And the changing fields used to levitate a frog probably wouldn’t be good for a human in the long term.

  9. Yes, the first embedded video starts by saying 5 Tesla is enough to lift 32,869 refrigerators. That’s nonsense. If it can lift one fridge, it can lift infinite fridges. Just line them up along an infinite road with 5 T everywhere. It was obviously made by a marketing person who has no idea what the unit “tesla” means.

    The first video mentions that a junkyard magnet is 1 T. So maybe what they meant was that a 5 T magnet OF THE SAME SIZE could lift that many fridges. The number was probably calculated by a competent engineer, and then mangled by the marketing drone that misquoted it.

  10. A really good first wall and breeder blanket / heat exchanger. It's the heat flux that constrains the design much more than the stupendously high temperature. Hence they'll stick to short(!) pulses at first to minimize the heat flux.

  11. Yep, the SPARC design (Smallest Possible, Affordable, Robust, Compact) is just a technology demonstration constrained by cost, supply chains, etc. ARC is the more spherical design, and more drawing board at the moment – although I suspect the spherical design has quite a bit of thought behind it; higher bootstrap currents in the plasma, possibly easier for servicing with jointed coils, likely something to do with neutron flux in the liquid breeder blanket / heat exchange medium as well.

  12. Are there two different designs being showcased here? One design (image) looks quite symmetrical and the other looks like a slightly squashed toroid.

  13. "A 19 Tesla field is powerful enough to life 403 Boeing 747s."

    That's pretty stupid, even if I assume you mean "lift". 0.001 Tesla would be enough to lift 403 Boeing 747s, if applied to enough iron plate. 19 Tesla wouldn't lift 403 Boeing 747 plastic models if applied to a pin.

  14. I suspect that in time we'll discover intensely strong magnetic fields will play a role in interstellar travel, spacecraft shielding, and artificial gravity.


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