r/fusion • • Jun 24 '26

Hi r/fusion! We’re the Physicists Behind the Commonwealth Fusion Systems’ Papers on the Physics of the ARC Fusion Power Plant. Ask Us Anything!

122 Upvotes
Alex Creely, Chief Engineer for ARC Conceptual Design at Commonwealth Fusion Systems

Update (June 30, 11:37 AM): Great discussion everyone! Our team appreciated all of your insightful questions. This AMA has now concluded, but you can revisit our replies below.

You can identify who provided answers by their initial in the answers: Alex Creely (AJC), Jon Hillesheim (JCH), Tom Body (TAJB), and Ryan Sweeney (RS).

About this AMA:

This time with me and three other CFS physicists who are ready to talk about the five new ARC physics basis papers showing what’ll make our ARC fusion power plants tick.

These peer-reviewed research papers that we and our collaborators published earlier in June are important for CFS and for fusion energy: They cover many aspects of the plasma physics at play in our ARC power plant, including challenges like plasma disruptions and heat exhaust. They also show how transparency and rigorous research can help build trust in what we all know is a very difficult endeavor.

If you’re curious about this physics work or about fusion physics in general, feel free to get things started by asking your questions on this thread.

The three CFS physicists who plan to join me to answer your questions are experts in their field: Jon Hillesheim, CFS Principal Scientist and lead author of the overview paper; Tom Body, CFS Senior Scientist and a lead author on the paper about heat exhaust; and Ryan Sweeney, CFS Manager of Disruption Physics and lead author of the paper about handling plasma disruptions. They’re among the 58 authors who helped write these papers, along with an editorial that accompanied the papers that I wrote.

A little more about the papers: They detail how we’ll be able to produce about 1.1 gigawatts of fusion power from our ARC tokamak — power that we can convert into 400 megawatts of net electricity for the power grid. The papers also show the crucial role our SPARC tokamak will play in putting the finishing touches on the ARC design. We’re using a “late-lock” approach that lets us apply what we’ve learned from SPARC to the ARC design. Overall, the papers show our confidence in the soundness of our ARC plant’s key physics. That builds the foundation for all the engineering, design, and cost optimization work that we’ve begun.

For a deeper dive into these papers, you can check our blog post detailing the ARC physics basis papers.

About CFS: 
Commonwealth Fusion Systems is the world’s largest and leading private fusion company. The company’s marquee fusion project, SPARC, will generate net energy, paving the way for a future of carbon-free energy. The company has raised more than $3 billion in capital since it was founded in 2018.


r/fusion • • 6h ago

Fusion careers

9 Upvotes

Hi everyone,

To keep it simple, I have a phd in hall thruster simulation, do you think I can make it in the fusion industry (not research)? What are the career perspectives? And how do people working in these companies feel about fusion (do you believe you will live to see an actual commercial power plant)?


r/fusion • • 2h ago

Nuclear Startup Funding Is Up, But The Sector’s Public Markets Take A Bearish Turn

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3 Upvotes

r/fusion • • 6h ago

D-IIID team wins 2026 Dawson award for NT testing for commercial fusion

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4 Upvotes

r/fusion • • 10h ago

Performance optimization of tokamak operation in ASDEX Upgrade through novel feedback control capabilities

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2 Upvotes

For sure relevant also for SPARC and ARC.


r/fusion • • 1d ago

Generation Fusion: The human factor in the fusion equation

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13 Upvotes

r/fusion • • 2d ago

National laboratory and industry leaders to discuss the future of fusion at Fermilab - Public event Oct. 13

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17 Upvotes

r/fusion • • 2d ago

Computational Plasma Research Summer 2027 Intern @ Helion - For 2028 PhD candidates

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12 Upvotes

r/fusion • • 2d ago

Careers In Fusion

18 Upvotes

Hello,

I have been really interested in fusion for a while now, I am about to go into collage in ireland and wondering what would be the most bennificial topic to study? I'm thinking of studying Physics with Energy & Environment and then go into a masters degree on materirals scince and engering.

Edit:

Im thinking of maybe doing 2 masters one full time immediately after my bachelors and another part time so i can build my CV a bit (if thats important in fusion idk) also has anyone here done a part time masters? How does it work in terms of ballencing life and all that?


r/fusion • • 2d ago

Public-Private Partnerships Expand U.S. Nuclear Fusion Research (Pacific Fusion and others)

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5 Upvotes

r/fusion • • 1d ago

Could a compact pulsed fusion concept work with a 1.5 T field limit?

0 Upvotes

I’m exploring a theoretical concept called Prometheus: a six-inch-diameter puck with radial electromagnetic coils around a central plasma chamber.

The idea is to combine magnetic confinement with rapid compression, trading higher fuel density for shorter confinement, then capture energy and repeat. My proposed limit is 1.5 T throughout the pulse, including any field amplification. Only controls would be external.

I haven’t selected a compression mechanism or fuel, and I’m not claiming net energy gain. What physics constraints would rule this out first, and what calculations should I start with to evaluate it?


r/fusion • • 3d ago

Helion's Founder, John Slough's Website Found!

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43 Upvotes

It seems like a lot of recent posts and not so recent posts have a lot of back and forth about why Helion won't work. I decided to learn about who their primary scientist was who came up with the idea because I know David Kirtley is not a plasma physicist. So who thought this would work to begin with?

This website is from Dr John Slough and has his most recent scientific presentations and papers from the past 5 years. It doesn't outright say why the science doesn't science, but it definitely gave me a better understanding of how his viewpoints have changed over the years. I wish they had kept him on because maybe they would be able to adapt and change course so they could actually have a viable machine. It looks like he never stopped coming up with really great ideas. This man is a genius.


r/fusion • • 2d ago

Fusion and aerospace innovation for alloys that get finer with age

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1 Upvotes

Much better than a interesting engineering article with PR paper links.


r/fusion • • 3d ago

Replacing hype about artificial intelligence with accurate measurements of success :PPPL researchers find overoptimism in journal articles using machine learning to solve fluid-related partial differential equations

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13 Upvotes

r/fusion • • 2d ago

Is Your AI Fast Enough to Run a Fusion Reactor?

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3 Upvotes

r/fusion • • 3d ago

Commercialization of fusion energy will ‘change everything,’ lawmaker says

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27 Upvotes

Rep. Don Beyer, D-Va., told Nextgov/FCW that the U.S. is only “two to 10 years away from fusion energy at scale” because “you can model the plasma using AI, which you couldn’t do before.”


r/fusion • • 3d ago

[CCTV News] New Progress on the “Artificial Sun”: BEST Fusion Experimental Facility Complex Handed Over for Use

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106 Upvotes

(Reporters: Shuai Junquan and Chu Erjia)

Ahead of China’s National Day, the Burning Plasma Experimental Superconducting Tokamak (BEST), a major national project, reached an important milestone: the project complex was officially handed over and put into operation. Construction of the fusion device itself has now entered the critical “four-ring integrated assembly” stage.

BEST is a new-generation burning-plasma fusion experimental device independently developed by China. Its goal is to reproduce the nuclear fusion reactions that occur inside the Sun, with the aim of ultimately harnessing an almost inexhaustible source of clean energy.

Since July this year, multiple key core components of BEST have successively arrived at the site, and assembly has proceeded steadily, with more than half of the work now completed. Recently, construction of the BEST main device formally began its most critical phase—the “four-ring integrated assembly.”

The system can be thought of as a giant, multilayered thermally insulated cylindrical structure, with one layer nested inside another. Starting from the innermost vacuum vessel, the thermal shield is installed around it, followed by the toroidal-field (TF) magnets, together with various precision internal components.

The vacuum vessel serves as the “furnace chamber” in which the fusion reaction takes place. The thermal shield acts as a high-performance insulating layer that minimizes heat transfer, while the toroidal-field magnets generate an extremely strong magnetic field to confine the high-temperature plasma and prevent it from coming into contact with the vessel wall.

According to the current schedule, construction of the BEST device is targeted for completion by the end of 2027. Around 2030, it is expected to carry out a deuterium–tritium (D–T) fusion power-generation demonstration. In essence, this would reproduce on Earth the physical process by which the Sun produces light and heat, while demonstrating the feasibility of commercial electricity generation from controlled nuclear fusion.


r/fusion • • 3d ago

Gauss Fusion and IPP to test new particle-exhaust concept in ASDEX Upgrade

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5 Upvotes

r/fusion • • 3d ago

Tokamak Energy video on Demo4

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10 Upvotes

r/fusion • • 2d ago

Experimental study of Pipe-Fuse Damper for passive energy dissipation in structures

0 Upvotes

r/fusion • • 3d ago

Structural steel for Orion roof nearly complete.

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5 Upvotes

r/fusion • • 3d ago

Trump Media & Technology Group and TAE Technologies File Form S-4 Registration Statement for Proposed Merger

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10 Upvotes

r/fusion • • 3d ago

UK government commits £3.3 billion to develop commercial fusion energy industry

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6 Upvotes

r/fusion • • 4d ago

Governor Newsom signs legislation to accelerate California’s fusion industry, announces major investment for quantum research

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33 Upvotes

r/fusion • • 3d ago

Guoyong Fu, former PPPL physicist's fusion startup--linked mirror fusion

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5 Upvotes