Nuclear Fusion Power Without Regular Tokamaks Or Stellarators

When it comes to nuclear fusion, the most well-known reactor type today is no doubt the tokamak, due to its relatively straight-forward concept of plasma containment. That’s not to say that there aren’t other ways to accomplish nuclear fusion in a way that could conceivably be used in a commercial power plant in the near future.

As we covered previously, another fairly well-known type of fusion reactor is the stellarator, which much like the tokamak, has been around since the 1950s. There are other reactor types from that era, like the Z-pinch, but they seem to have all fallen into obscurity. That is not to say that research on Z-pinch reactors has ceased, or that other reactor concepts — some involving massive lasers — haven’t been investigated or even built since then.

In this article we’ll take a look at a range of nuclear fusion reactor types that definitely deserve a bit more time in the limelight.

Inertial Confinement Fusion

Target assembly at the NIF in 2010, with the target pellet mounted in the cryogenic positioning device.

Inertial Confinement Fusion (ICF) relies on the rapid transfer of energy into a fuel target — usually a fuel pellet. This causes the outer layer of the pellet to rapidly expand, causing a shock wave to travel inwards, into the target. If done properly, this causes compression of the fuel (usually deuterium and tritium) at sufficient levels to start a fusion reaction that travels outwards from the center.

The use of ICF ranges from fusion weapons research to generating electricity. France’s Laser Mégajoule (LMJ) is an example of the former, whereas the US’s National Ignition Facility (NIF) is the world’s most prominent example of the latter, though it has also been used for materials science and weapons research.

Both LMJ and NIF use lasers to transfer energy to the fuel pellets, which in the case of NIF involves 192 main laser amplifier beamlines that amplify the initial low-power (1 billionth of a joule) laser pulse to the target of about 4 million joules, with each beam traveling 1.5 km before hitting the target.

At this point in time, there are a number of ICF facilities operating around the world, though some newer ones like the EU’s HiPER ICF project never got off the ground. Interest in ICF seems to be waning on account of its economic viability as an energy source remaining questionable. This is mostly due to the cost of the fuel pellets and surrounding infrastructure. Unless ways can be found to sharply reduce these costs, it seems unlikely that ICF reactors will be used for anything other than materials science and weapons research.

Magnetic Confinement Fusion

Although tokamaks and stellarators are also Magnetic Confinement Fusion (MCF) reactor designs, they are not the only type of MCF reactor. The Z-pinch reactor design is another type of MCF reactor, using the Lorentz forces through the plasma instead of surrounding the plasma with (super-conducting) magnets. The main advantage of the latter approach is that it allows for continuous operation, something which is a fairly unique property in fusion reactor designs, which most commonly use a pulse-based design.

Whereas ITER is considered to be a bog-standard tokamak design, along with China’s HL-2M and upcoming CFETR tokamaks, more exotic configurations are also being worked on. One of the most prominent being the ARC design. The acronym stands for ‘Affordable, robust, compact’, one can tell where its focus lies. While ITER and CFETR are massive tokamaks with a large internal volume, ARC aims to use ReBCO — rare-earth barium copper oxide — high-temperature superconducting magnets.

The inside of the National Spherical Torus Experiment’s vacuum chamber.

Theoretically, this should allow ARC to generate a stronger magnetic field than current tokamaks, doubling the magnetic force on the plasma, while allowing it to be much more compact and sheeting the requirement the same level of cryogenics as low-temperature superconducting magnets. It is also suggested that the use of ReBCO would allow for enough flexibility to allow the tokamak to be ‘folded open’ when not in use, to allow for easy maintenance. At this point, however, ARC is a purely theoretical design by MIT and PSFC. It’s possible that a demonstration reactor (SPARC) could be constructed in the future.

Spherical tokamaks (STs) are another interesting topic of current research. The principle here is simple: instead of forcing the plasma into a tokamak’s typical toroidal (‘doughnut’) shape, it is allowed to take on a spherical shape as much as possible, with only a minimal ‘hole’ in the center for the central magnets. This should make a reactor less expensive and easier to manage. A currently active ST is the National Spherical Torus Experiment, (NSTX) constructed by Princeton Plasma Physics Laboratory along with Oak Ridge National Laboratory, Columbia University and University of Washington.

After an upgrade between 2012 and 2015, NSTX was renamed to ‘NSTX-U’, for ‘Upgrade’. This version was stopped in 2016 due to issues with its poloidal coils, which required dismantling of a significant part of the reactor to diagnose and fix the issue. Reactivation of NSTX-U is not planned until the end of 2020. With some luck we’ll be seeing more of this reactor soon.

An interesting proposition by some scientists involved in STs is to replace the central magnet column with a design inspired by the Z-pinch reactor, using Lorentz forces to provide the magnetic field in the center instead of a physical column. This would allow for an ST to form a virtually perfect sphere of plasma.

One of the two yin-yang mirrors arrives at LLNL.

Finally, Lockheed Martin’s Compact Fusion Reactor (CFR) has received a lot of attention since they announced it in 2014, conveniently omitting that a lot of work was still left to be done on the design. This MCF design is interesting because it appears to revive the concept of a magnetic mirror, a fusion design that many had thought to have been left behind in history after the Mirror Fusion Test Facility was shut down in the 1980s. Time will tell whether the demise of magnetic mirror reactors was truly exaggerated.

Worthy of mention is the Field-Reversed Configuration (FRC). Although not as prominently present in power generation research, FRC has the interesting property that by trapping plasma on closed magnetic field lines, it can manipulate this plasma to be accelerated in one direction, which would make it useful for spacecraft propulsion. It’s one of various possible new propulsion designs under consideration.

Here’s to All the Other Designs

Implosion of a fusion microcapsule on the NOVA laser system.

Although the goal of this article wasn’t to provide an exhaustive list of current fusion power reactors, it should at least give a solid overview of the big players on the field at this point in time. There are countless smaller players out there as well, often start-ups testing out a new idea or concept using some funding money. Some of those designs may prove to work well as a neutron source, while an occasional concept may make it past the prototyping stage and show enough promise to be considered for something more.

The most exciting thing about nuclear fusion research is perhaps that nothing is set in stone. Much like the plasma inside a tokamak, it constantly changes shape and direction. Once it was thought that the stabilized Z-pinch reactor design was going to work, only for that to fall apart. Then there are the magnetic mirror, stellarator, tokamak (spherical or toroidal), and ICF configurations. Nobody can tell which of these approaches will turn out to be the golden ticket towards the one design that will end up getting commercialized.

This knowledge, along with the promise of the immense pay-off if one cracks this one, has led to a modern day gold rush. Who will figure out the first commercial scale fusion power reactor? The first compact and cheap fusion reactor? The first fusion battery that will run a smartphone for a decade? The first fusion powered spaceship?

With the tokamak design seemingly reaching its zenith with ITER and CFETR, we might end up with another ZETA moment in another decade or two with plasma physics throwing an unexpected spanner in the wheels, or we will have 2 GW commercial fusion reactors churning out cheap, clean power by the 2030s. Nobody knows for sure. That’s both exciting and terrifying, which is exactly the kind of situation that draws in those who are in for a bit of adventure.

Here’s to keeping that bright star of fusion research burning.


[Featured image: The preamplifiers of the National Ignition Facility in 2012. (CC-BY 3.0, Damien Jemison/LLNL)]

120 thoughts on “Nuclear Fusion Power Without Regular Tokamaks Or Stellarators

    1. Your statement very much applies to the paperwork and politics around Fusion research. The actual reactors are in theory quite safe, as long as you don’t hug them during operation. The experimental reactors are generally very safe as they’re all low powered and off most of the time for maintenance.

      1. What urban myth would that be?
        I remember sitting in high school in the 80’s reading issues of various science magazines talking about how we would have fusion power by the early 2000’s. I remember reading articles in the early 2000’s talking about how we would have fusion power by 2020. Here it is 2020 and scientists are now saying that fusion power is 10 – 20 years away.
        Please explain where any stupid urban myth comes into this.

          1. At least in my country (USA), almost all fusion research is paid for by taxpayers, of which I am one of them.

            The total cost per year is less than the subsidies given to oil companies, so I’m okay with it.

      1. And how do you get it in the night?

        I know: Not at all.

        It is not guaranteed, not even during the day.
        And this pumped storage station in the graphics is nice. They only have one drawback: There are not enough of them and not enough place where you could build enough of them.

    1. Your sentiments mirror mine completely. As for a comment posted below, I believe that your life and mine and all humans are relevant to the establishment of fusion power simply because we, and our offspring, are the instigators and potential beneficiaries of a successful outcome of the research. From my andromorphic viewpoint all scientific endeavors, assuming they are not employed for evil purposes, are ultimately the realizations of the noble dream for a better life for all of us. I will never live to see the advent of fusion power being too damned old, and it is possible that no human may survive global warming so it may all be irrelevant anyway. Ironic it is that we have a fusion reactor that currently supplies us with all our power, and, we know how to harass it. Solar energy I have lived to see! Thank the Lord for our G2 yellow dwarf that keeps us warm. Maybe humanity ought to stick with what it already has in so wonderful abundance. Of course we should continue to try to imitate the sun, but if we fail it will not be a disaster.

      1. Sometimes the Earth is warm for ages and cold for ages, climate change will self regulate like it always has. If the Earth warms because of us then starvation will kill all, but a few of us, so in this way the population will never be too overwhelming or the Earth too hot or cold. There is always a disaster to balance the success of a species and it may be warming, fusion disaster, a meteor or war. The thing to remember is that it WILL happen and we will go from many to few, so accept the part you can control with grace and stop worrying so much.

    1. Either they’re geniuses or they’ve no idea what they’re fucking doing. I thought you needed something on the order of a nuclear explosion to compress Deuterium into fusion. Or at least some ludicrous number of amps in a plasma. This bloke reckons he can do it with steam powered pistons. Just seems like something very important is missing somewhere.

  1. Intriguing. Actually I have my bets on ReBCO.
    The even better thing: when someone works out room temperature superconductivity the coils can be swapped out.
    A possible fix is to fabricate them from inert elements with the right isotopic enrichment and rely on neutron activation to form the magic material, plus it makes good use of them pesky neutrons.

  2. Where’s muon-catalyzed fusion? The muon replaces the electron in the atom, but due to their higher mass, they shrink the diameter of the orbital, to draw tritium to deuterium nuclei. It catalyzes the fusion reaction at non-sun temperatures. After fusion, the muon catalyst is expelled to fuse another set of nuclei. It will catalyze ~100 reactions before disintegration. Generating muons today costs more energy than the reaction produces (like all these technologies), but they also rain from the sky, as cosmic rays, for free, as you’ve covered in articles about muon tomography.

    1. From wikipedia : “The muon flux at the Earth’s surface is such that a single muon passes through an area the size of a human hand per second”, so if you manage to capture a muon per second, that’s 100 fusion per second => maybe something lile 1500 MeV => 2.4×10^-10 watts

    2. Muons take too much energy to generate vs the amount you can get out. By lots, and then some more lots.

      It does work though and can be used to generate a low flux of 14MeV neutrons from fusion. Built the space to house it at UKAEA’s Culham site.

  3. Y’all need RW’s patent gamma scalpel, it’s a subatomic hotknife for welding or slicing and dicing. Get it on Tindie as soon as commercial availability of like a 2N3055 with a 2×10^23 Hz switching rate occurs so I can actually build it.

  4. “we will have 2 GW commercial fusion reactors churning out cheap, clean power by the 2030s.”

    I’ve become quite convinced that will never happen (certainly not in that timescale). A lot of the supposed advantages of fusion are contradicted by physical requirements of the D-T reaction. They will not be cheap, or completely clean (will require costly decommissioning) and will not reduce issues of nuclear proliferation. A truly cheap and clean fusion reactor may never be achievable. I suspect these reactors will become white elephants for rich countries, but not of commercial value.

    For the background on my view, see https://thebulletin.org/2017/04/fusion-reactors-not-what-theyre-cracked-up-to-be/. I haven’t seen any convincing rebuttals of Daniel Jassby, only “don’t worry we will figure it out”.

    It’s no means certain that all technologies can progress to commercial reality. Apart from “where’s my flying car?”, Concorde illustrates a technology that is technically possible, but not commercially viable.

    1. Don’t know where you’re getting that proliferation thing from – breeding Pu is best done in fission machines, as now. The high energy neutrons from fusion would NOT be anywhere near as good for that. They would, however, tend to destroy the fusion reactor materials, and create various isotopes well enough to create waste problems. Even DD neutrons, as 2.5 or so MeV, would be a problem.
      For those who don’t have the info – breeding U238 wants neutrons around 25 eV or so, neither fast nor slow. U238 has some capture resonances around there, and that’s why fission neutrons need to be moderated to keep a chain reaction going – if not slowed below the U238 capture energies, the 238 just eats them all before they can cause fission in the U235.

      Note that high energy neutrons would be especially damaging to the new rebco magnets.
      And if you put the magnets further away, behind a moderator, you lose the benefit of those magnets. The MIT presentation arm-waves and dodges that one.

      DT fusion makes ~ 16 megavolt energy neutrons.
      DD makes around 2.5 megavolt ones.
      Speed that high have a low absorption cross section in materials – you have to slow them down first, in general. (no simplification is going to be perfect here)
      Neutrons that come to a stop in a material decay into hydrogen. Hydrogen embrittlement is a thing. Fast ones that hit nuclei (don’t have to be captured) disrupt the lattices of materials – see “Wigner energy” in say, widipedia. It’s thought to have been a possible cause of the Windscale reactor fire in Britain.

      So, huge fluxes of neutrons are the problem, generally speaking, and there are more per output watt in fusion than fission with any reasonably practical fuels. The reactions commonly referred to as aneutronic are NOT, only less so, and take many times the activation energy as the hydrogen isotope ones, so are further out of reach at present, and wouldn’t solve it if they were feasible.

      Yes, I do work in this field. It’s a fun problem in that no one has cracked it yet, so it never gets boring, like an easy one would. I think we ALL wish someone would, we all hope it’s us, but really – as long as someone gets it, we’re going to be fine with it.

      Most of the cost of electricity is in things other than the fuel, though if you stick in the externalized costs of pollution, this is less true. I’m off the grid myself – solar photovoltaics, but even that needs the occasional backup generation.

      1. not to mention that the main barrier to weapons-grade fissile material is the isotopic separation…U235 needs a lot of enrichment, Pu239 requires handling highly active material. Both are costly and hard to hide.

        1. What makes you suspect it’s snake oil? Their results have been published in peer reviewed scientific journals, and the fusion approach they use (Dense Plasma Focus) has/is being worked on by multiple groups, so the work is reproducible.

  5. LPP, Pinch fusion, hold the temperature record, and ultimately that is the one thing that controls if atoms will overcome repulsive forces and undergo fusion. They also have a device that is remarkably compact and aneutronic, the energy comes out as a particle beam whose energy can be directly converted to electrical power with a coil, the other part of their output is just x-rays and they can feed a form of multilayered photovoltaic cell. Other than that no radiation or radioactive waste, no erosion of the reactor wall from neutrons etc. They have aimed very high so that they can burn boron and if they get there the result will make all other technologies completely redundant. I have yet to see a write-up explaining why they can’t do what they are planning either, other than it is very hard, and despite having a tiny and under-funded team they have actually being getting the sorts of incremental results that indicate that they are on a trajectory toward success.

      1. Haynes Manual?

        We’re lucky the aliens didn’t leave one in there!
        Or we would have gone up in a (very big) bang long ago.
        (I used to have a Chilton’s and a Haynes manuals for my Suzuki Sidekick. It’s a crying shame that Haynes bought out Chilton’s)

    1. according to bob lazar the fuel source they ran on (a stable isotope of element 115 unknown to classical science) was mined from certain stars. so we will never be able to mine it terrestrially. it’s a concept of industrial globalism taken to extremes, comparable to asking a bronze age farmer where to buy some uranium.

  6. I wish that more attention and effort would be spent on Fusor type fusion reactors. These are cheap, small, and well established and have the added benefit of generating electricity directly. They could even provide desktop sized power. The problem is the fusion is self-destructive to the device. It is simply an engineering problem needing to be solved. A few university projects are working on it, and my favorite idea to overcome the problem has been proposed by that great YouTube chemist Robert Murray Smith.

  7. Because I’m a pedant but also because it brings up an interesting point.

    Ask the general population the following question:
    Which of the following have you heard of:
    The Sun
    Hydrogen Bombs
    Tokamaks
    Stellarators

    I’m willing to bet that the most commonly given answers will be in the order listed with the last two near tied.

    Interestingly, that order is also the order some would argue ranks engineering feasibility for producing usable amounts of electric power using said reactor.

    But we aren’t getting terrestrial hydrogen bomb power plants any time soon, if ever, for good reasons.

    1. I totally agree, we already have a really excellent fusion generator at our disposal, it is already supplying us with all the energy we need, we just need to use that energy instead of wasting it.

          1. That beam power will be converted into HEAT so unless strictly controlled it will lead to overheating of the climate.
            Ther are more disadvantages : weaponizing the beam, disruption of weather.
            Beaming energy in is also not necessary as more than enough energy can be harvested on the earth surface.

          2. That’s been proposed for many years, and never got beyond the back of the envelope proof of concept stage. Converting it to microwaves, beaming to earth, rectifying it again, all has a lot of losses. Then you have the costs of transporting it up there, and maintaining it. Collecting on earth has advantages, even if you have to store it at night (when power demands are lower anyhow).

          3. You think all the PR that solar-microwave beam power stations got in the 1970s, was actually to soften the public up to the idea of orbiting death rays? IE these “power stations” were meant as weapons first, either to toast your enemy or to fuck with his climate. Then you just blame the “error” on any of the hundreds of things that go wrong with space stuff.

            So the illustrations of families smiling in hovercars etc were just a cover story? The timing is just a bit before Reagan’s Star Wars madness. So perhaps the usual culprits, the military aerospace companies, had been working on another stream of income by putting little Death Stars into the sky, pointing at us. Either they thought it was feasible enough to start bothering the military and politicians for money, or at least fancied $a few hundred million to pay for a feasibility study. And in the meantime keep up the usual public relations. Getting Reagan on board was their big success. After all you don’t think he just thought that stuff up himself?

            Incidentally it’s nothing new, most of the intention behind Sputnik was the Soviets telling the Americans that they can fly stuff right over their heads. The idea of sticking a few nukes on an orbiting platform had been around a few years before Sputnik.

            Their cover story, that they beam power to the ground through microwaves is ludicrous. Water in the atmosphere would absorb a load of the energy, it would wreck weather. It’d be inefficient and dangerous. And it’s advantage is, it’s above the clouds? If there’s a cloud in the way, you can’t beam down the energy anyway cos the cloud is gonna absorb it!

            Even if it were actually more efficient in terms of energy, for the money you could just build 30x as many panels and put them on the ground! That 30x is a complete guess and should probably be more like 30,000x. Space launches are expensive, solar cells just keep getting cheaper.

      1. In contrast to the Tokamak, the Dyson Sphere IS an American invention (invented by Freeman Dyson :)). Although to be honest, it was not completely his idea. (a Brit, Olaf Stapledon, first used the concrete idea in a book of his).

    2. What is lesser known, is that Tokamak is not an American-Indian name for a weapon or something It’s a Russian acronym for ‘тороидальная камера с магнитными катушками’. Literally: toroidal chamber with magnetic coils.

      Russians are in general quite poetic. But the guy who invented this name was clearly an exception. :D

      1. “Then there are the magnetic mirror, stellarator, tokamak (spherical or toroidal)”

        Tokamak’s are by definition toroidal. A spherical design would be ‘сферическая камера с магнитными катушками’. I would use the acronym ‘Sphekamak’ for those.

  8. no polywell love makes jack a dull boy.

    though to be fair they dont do good pr like a lot of the other reactor designers do. but what they are doing is coming up with a design, running a lot of supercomputer simulations on those designs and doing iterative improvements with the end goal of a break even demo reactor.

    1. Pretty sure the “Ancients” did this, and essentially tapped the power of an entire Universe. apart from that whole pesky leakage of exotic particles issue.
      Fun fact: the ZPM design was actually a variant of an Asgard design, as they ran into much the same problems.

  9. If I were to put my money on a dark horse it would be the mirror system,
    and it is to weep that the best entry was cancelled almost the day it was completed, in 1986, due to budget cuts.

    1. A mirror would have to be massive, and the end losses need improving. But yes, I like them too and can’t see a good reason they wouldn’t work if made big enough. Though since it would act as a humongous bar magnet, a second next to it the opposite way around may be required to cancel out the external field a bit.

  10. Im going to be honestly pessimistic. I now think fusion power generation… Is just never going to happen.

    I even recently saw a documentary on iter and while that seems to be the best hope… It’s still decades away from even being fired up. And that’s just another example of the dates constantly being pushed back. But even if it ever works, the best they hope to generate is something like 12% over what they put in. And given the cost of running and fragility of the tech. Really doesn’t seem feasible at all….. Heck the fact it seems to take a life time just to build 1 plant that may or may not work. Doesn’t seem feasible…

    Sadly I think like much other free energy legends. This one is going nowhere…

    I think fusion is a dream and most people who are really behind it and working in it know it’s never going to work. And for decades have been feeding a lie to keep themselves employed.

    I really want to be wrong. But more and more I’m just finding myself unconvinced.

    1. Worse, if they do find a feasible system, it will just be like fusion power plants: years to build, way too expensive and capital-intensive. Distributed PV and storage results in quick payback, and generation nearer the load.

      1. The day the first efficient, low cost fusion technology becomes feasible is the day the idiots who have made fission power so unnecessarily costly will do the same to it, with even less rationale.

        Fusion reactors can’t produce material for nuclear weapons. They can’t explode or melt down because if containment fails *they stop working*. If there is any problem at all, stopping it instantly is simple, merely cut off the fuel input.

        A fusion reactor that works, producing commercially viable levels of electric power, will have so many safeguards – mostly tied to a fuel cutoff – so that if there’s any problem it just quits.

        1. Safeguards is all nice…. but before you have safe guards you have to have a working system… And it just seems that there never will be a working system.
          And yes then theres the commercial pitfalls… even IF fusion happens and we get positive gains. It wont be the cheap abundant energy for all, as the dream sells…

          It would be heavily marked up and wont provide cheaper power for our more electric intensive power needs… Nuclear is the way forward. But they need to develop safer nuclear. Heck smaller localised nuclear plants…

          1. And….Three Mile Island was a catastrophic meltdown!!!! No one was injured. No one was irradiated. Total radiation leakage would only fill the bottom half of a teaspoon. But screaming anti-nukes – in combination with a US government unwilling to set and defend energy policy – shut down the US nuclear industry’s future….and therefore the world’s nuclear future. And here we are. Who knows. With 90+% of stationary energy needs coming from nuclear power, Lithium Ion batteries and some bold people like Musk, we might not be talking about the current climate change crisis. It all comes down to leadership….of which the world has a great shortage.

  11. Aliens be like; “Hey, lets build all these fusion reactors and distribute them across the cosmos. Then, everyone will have free energy. Famine, and war will be eliminated. ”

    Humans be like; “It’s not good enough! We aren’t in control of it!”

  12. I sat next to an oil executive on a plane in the ’80’s and asked him what’s the break-even point for extracting oil, energy out for energy input. He said practically, it’s 3:1. Anything less than that isn’t viable. Of course, advances in extraction technology lower the input energy cost, but overall maybe the equation is a little worse than you think.

    On the other hand, I just looked into “Peak Coal” which I though had already happened – years ago – and it still hasn’t happened!

  13. Fusion reactor is like man in space. It cost a fortune, still have no real outcomes in field of view, but funds literally thousands of scientists and whole industries so cannot be shutdown.

  14. “it should at least give a solid overview of the big players on the field at this point in time”

    How did it miss JET? It’s big and has been working (ish) in an experimenty sort of way for ages. Presently nothing else compares.

    Then there’s MAST, UK’s moderately sized reactor, which is still bigger than many other players. Though it’s present upgrade did require the company I was working for to be evicted to make space. But then I got to build a new and shiny aeronautical lightning test facility for Cobham, and so got the nick name.

    UK also has a version of NIF and has had a long line of laser based experiments. It doesn’t pretend it’s for power research like some others do:
    https://www.awe.co.uk/what-we-do/nuclear-warheads-lifecycle/science/understanding-plasma-physics/orion/

  15. I love that picture of the yin-yang mirror delivery because it’s about the best summation of human progress I’ve ever seen. A giant piece of The Future is being transported using The Past in the form of log rollers.

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