The central solenoid taking shape in the ITER assembly hall.

What’s Sixty Feet Across And Superconducting?

April 22, 2025 by Tyler August 54 Comments

What’s sixty feet (18.29 meters for the rest of the world) across and superconducting? The International Thermonuclear Experimental Reactor (ITER), and probably not much else.

The last parts of the central solenoid assembly have finally made their way to France from the United States, making both a milestone in the slow development of the world’s largest tokamak, and a reminder that despite the current international turmoil, we really can work together, even if we can’t agree on the units to do it in.

A cutaway diagram of the ITER tokamak showing the central solenoid — The central solenoid is in the “doughnut hole” of the tokamak in this cutaway diagram. Image: US ITER.

The central solenoid is 4.13 m across (that’s 13′ 7″ for burger enthusiasts) sits at the hole of the “doughnut” of the toroidal reactor. It is made up of six modules, each weighing 110 t (the weight of 44 Ford F-150 pickup trucks), stacked to a total height of 59 ft (that’s 18 m, if you prefer). Four of the six modules have been installed on-site, and the other two will be in place by the end of this year.

Each module was produced ITER by US, using superconducting material produced by ITER Japan, before being shipped for installation at the main ITER site in France — all to build a reactor based on a design from the Soviet Union. It doesn’t get much more international than this!

This magnet is, well, central to the functioning of a tokamak. Indeed, the presence of a central solenoid is one of the defining features of this type, compared to other toroidal rectors (like the earlier stellarator or spheromak). The central solenoid provides a strong magnetic field (in ITER, 13.1 T) that is key to confining and stabilizing the plasma in a tokamak, and inducing the 15 MA current that keeps the plasma going.

When it is eventually finished (now scheduled for initial operations in 2035) ITER aims to produce 500 MW of thermal power from 50 MW of input heating power via a deuterium-tritium fusion reaction. You can follow all news about the project here.

While a tokamak isn’t likely something you can hack together in your back yard, there’s always the Farnsworth Fusor, which you can even built to fit on your desk.

General Fusion Claims Success With Magnetized Target Fusion

March 27, 2025 by Maya Posch 21 Comments

It’s rarely appreciated just how much more complicated nuclear fusion is than nuclear fission. Whereas the latter involves a process that happens all around us without any human involvement, and where the main challenge is to keep the nuclear chain reaction within safe bounds, nuclear fusion means making atoms do something that goes against their very nature, outside of a star’s interior.

Fusing helium isotopes can be done on Earth fairly readily these days, but doing it in a way that’s repeatable — bombs don’t count — and in a way that makes economical sense is trickier. As covered previously, plasma stability is a problem with the popular approach of tokamak-based magnetic confinement fusion (MCF). Although this core problem has now been largely addressed, and stellarators are mostly unbothered by this particular problem, a Canadian start-up figures that they can do even better, in the form of a nuclear fusion reactors based around the principle of magnetized target fusion (MTF).

Although General Fusion’s piston-based fusion reactor has people mostly very confused, MTF is based on real physics and with GF’s current LM26 prototype having recently achieved first plasma, this seems like an excellent time to ask the question of what MTF is, and whether it can truly compete billion-dollar tokamak-based projects.

Continue reading “General Fusion Claims Success With Magnetized Target Fusion” →

China Claims Commercial Nuclear Fusion By 2050 As Germany Goes Stellarator

March 5, 2025 by Maya Posch 48 Comments

Things are heating up in the world of nuclear fusion research, with most fundamental issues resolved and an increasing rate of announcements being made regarding commercial fusion power. China’s CNNC is one of the most recent voices here, with their statement that they expect to have commercial nuclear fusion plants online by 2050. Although scarce on details, China is one of the leading nations when it comes to nuclear fusion research, with multiple large tokamaks, including the HL-2M and the upcoming CFETR which we covered a few years ago.

Stellaris stellarator. (Credit: Proxima Fusion)

In addition to China’s fusion-related news, a German startup called Proxima Fusion announced their Stellaris commercial fusion plant design concept, with a targeted grid connection by the 2030s. Of note is that this involves a stellarator design, which has the major advantage of inherent plasma stability, dodging the confinement mode and Greenwald density issues that plague tokamaks. The Stellaris design is an evolution of the famous Wendelstein 7-X research stellarator at the Max Planck Institute.

While Wendelstein 7-X was not designed to produce power, it features everything from the complex coiled design and cooled divertors plus demonstrated long-term operation that a commercial reactor would need. This makes it quite likely that the coming decades we’ll be seeing the end spurt for commercial fusion power, with conceivably stellarators being the unlikely winner long before tokamaks cross the finish line.

Can We Ever Achieve Fusion Power?

June 29, 2024 by Jenny List 51 Comments

Fusion power has long held the promise of delivering near-endless energy without as many unfortunate side effects as nuclear fission. But despite huge investment and some fascinating science, the old adage about practical power generation being 20 years away seems just as true as ever. But is that really the case? [Brian Potter] has written a review article for Construction Physics, which takes us through the decades of fusion research.

For a start, it’s fascinating to learn about the many historical fusion process, the magnetic pinch, the stelarator, and finally the basis of many modern reactors, the tokamak. He demonstrates that we’ve made an impressive amount of progress, but at the same time warns against misleading comparisons. There’s a graph comparing fusion progress with Moore’s Law that he debunks, but he ends on a positive note. Who knows, we might not need a Mr. Fusion to arrive from the future after all!

Fusion reactors are surprisingly easy to make, assuming you don’t mind putting far more energy in than you’d ever receive in return. We’ve featured more than one Farnsworth fusor over the years.

Nuclear Fusion R&D In 2024: Getting Down To The Gritty Details

May 22, 2024 by Maya Posch 42 Comments

To those who have kept tabs on nuclear fusion research the past decades beyond the articles and soundbites in news outlets, it’s probably clear just how much progress has been made, and how many challenges still remain. Yet since not that many people are into plasma physics, every measure of progress, such as most recently by the South Korean KSTAR (Korea Superconducting Tokamak Advanced Research) tokamak, is met generally by dismissive statements about nuclear fusion always being a certain number of decades away. Looking beyond this in coverage such as the article by Science Alert about this achievement by KSTAR we can however see quite a few of these remaining challenges being touched upon.

Recently KSTAR managed to generate 100 million degrees C plasma and maintain this for 48 seconds, a significant boost over its previous record from 2021 of 30 seconds, partially due to the new divertors that were installed. These divertors are essential for removing impurities from the plasma, yet much like the inner wall of the reactor vessel, these plasma-facing materials (PFM) bear the brunt of the super-hot plasma and any plasma instabilities, as well as the constant neutron flux from the fusion products. KSTAR now features tungsten divertors, which has become a popular material choice for this component.

Researching the optimal PFMs, as well as plasma containment modes and methods to suppress plasma instabilities are just some of the challenges that form the road still ahead before commercial fusion can commence.

Continue reading “Nuclear Fusion R&D In 2024: Getting Down To The Gritty Details” →

You Got Fusion In My Coal Plant!

February 24, 2024 by Navarre Bartz 48 Comments

While coal was predominant in the past for energy generation, plants are shutting down worldwide to improve air quality and because they aren’t cost-competitive. It’s possible that idle infrastructure could be put to good use with fusion instead.

While we’ve yet to see a fusion reactor capable of generating electricity, Type One Energy, the Tennessee Valley Authority, and Oak Ridge National Lab have announced they’re evaluating the recently-closed Bull Run Fossil Plant in Oak Ridge, Tennessee as a site for a nuclear fusion reactor. One of the main advantages for siting any new generation source on top of an old one is the ability to reuse the existing transmission infrastructure to get any generated power to the grid.

Don’t get too excited as it sounds like this is yet another prototype reactor that will be the proof-of-concept before construction of a reactor that can produce commercial power for the grid. While ambitious, the amount of investment by government entities like the Department of Energy and the state of Tennessee (>$55 million) seems to indicate they aren’t just blowing smoke.

If any of this seems familiar, you might be thinking of the Department of Energy’s report on placing advanced fission reactors on old coal sites. A little fuzzy on the difference between a stellarator and a tokamak? Checkout this explainer on some of the different ways to (non-explosively) do fusion on Earth.

NIF’s Laser Fusion Experiment’s Energy Gain Passes Peer Review

February 9, 2024 by Maya Posch 53 Comments

Back in December of 2022, a team of researchers at the USA’s National Ignition Facility (NIF) announced that they had exceeded ‘scientific breakeven’ with their laser-based inertial confinement fusion (ICF) system. Their work has now been peer-reviewed and passed scrutiny, confirming that the energy put into fusing a small amount of deuterium-tritium fuel resulted in a net gain (Q) of 1.5.

Laser Bay 2, one of NIF's two laser bays — Laser Bay 2 at the NIF.

The key take-away here of course remains that ICF is not a viable method of producing energy, as we detailed back in 2021 when we covered the 1.3 MJ yield announcement, and again in 2022 following the subject of this now completed peer review. The sheer amount of energy required to produce the laser energy targeting the fuel capsule and loss therein, as well as the energy required to manufacture each of these fuel capsules (Hohlraum) and sustaining a cycle make it a highly impractical proposition for anything except weapons research.

Despite this, it’s good to see that the NIF’s ICF research is bearing fruit, even if for energy production we should look towards magnetic confinement fusion (MCF), which includes the many tokamaks active today like Japan’s JT-60SE, as well as stellarators like Germany’s Wendelstein 7-X and other efforts to make MCF a major clean-energy source for the future.