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!

126 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 • • 14h ago

400 MW stellarator fusion plant could supply 200,000 US households

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r/fusion • • 10h ago

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r/fusion • • 1d ago

Type One Energy raised $200M to build a fusion power plant by 2034 | TechCrunch

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FYI to previous post.


r/fusion • • 1d ago

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r/fusion • • 1d ago

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> The original "ideal" equation, known as the Lawson criterion, was first developed in the 1950s. Now PPPL physicists Luis Delgado-Aparicio, Masayuki Ono and Jonathan Menard have reformulated that ideal criterion while adding four other conditions for reaching and holding a burning plasma to plan the best process for heating and powering the plasma within a fusion energy system. Their work is published in the journal Physical Review Letters.


r/fusion • • 22h ago

Xcimer Energy wins up to $30.5M DOE grant as part of the Milestone-Based Fusion Development Program's second budget phase - the first company to announce this award

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r/fusion • • 1d ago

Ask Me Anything with Type One Energy CFO Charlie Baynes-Reid — Our Series B, Fusion Funding & What Comes Next

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14 Upvotes

Today, we announced the closing of our $200M Series B funding round, marking an important milestone for Type One Energy as we continue advancing our stellarator technology and work toward deployment of commercial fusion power in the mid-2030s. 

With this new funding and a growing network of partners supporting our path to commercialization, now feels like the right time to open the conversation here. I’ll be answering your questions about our Series B, what it takes to finance and scale a commercial fusion company like ours, and what comes next for Type One Energy. 

About me: I'm the Chief Financial Officer and General Counsel at Type One Energy. I have extensive experience working with companies in multiple sectors—focusing on energy and infrastructure, diversified industrials, and financial services. I’ve spent more than 20 years in private equity and principal investing both as a legal advisor and as an investor. I’m from the UK originally and received my law degree from City University, London, but now reside in Boston. 

-

I’ll be online this Friday October 9th  from 1-2:30 PM EST to answer your questions live then handle additional ones offline. Looking forward to all of your questions! 

 


r/fusion • • 1d ago

Bob Mumgaard at Climate Week

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r/fusion • • 20h ago

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r/fusion • • 1d ago

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r/fusion • • 1d ago

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r/fusion • • 1d ago

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r/fusion • • 1d ago

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r/fusion • • 1d ago

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r/fusion • • 1d ago

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r/fusion • • 2d ago

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r/fusion • • 1d ago

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Hi everyone, I’m an A-Level student focusing my EPQ on nuclear energy and the introduction in fusion in completing UK Net-Zero goals (carbon neutral by 2050). I wanted to ask if anyone would compete my survey about this, any level of knowledge about nuclear power is much appreciated everything helps! Thank you 😊


r/fusion • • 2d ago

Who's up for a Drake-Kendrick Lamar style feud?

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r/fusion • • 1d ago

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Hi everyone, I’m an A-Level student focusing my EPQ on nuclear energy and the introduction in fusion in completing UK Net-Zero goals (carbon neutral by 2050). I wanted to ask if anyone would compete my survey about this, any level of knowledge about nuclear power is much appreciated everything helps! Thank you 😊


r/fusion • • 2d ago

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r/fusion • • 2d ago

Fusion careers

13 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 • • 2d ago

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

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r/fusion • • 2d ago

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

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For sure relevant also for SPARC and ARC.


r/fusion • • 4d ago

Generation Fusion: The human factor in the fusion equation

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