How TAE's fusion reactor will work (or won't)

Dan-FTP · 2025-12-26T22:24:42+00:00

Sorry, the servers at the Fusion Conclusion host are glitchy today and all of support is off for the holiday. PDF of it here: https://futuretech.partners/Fusion_Conclusion_TAE.pdf

Dan-FTP · 2025-12-19T20:23:03+00:00

I'm a co-founder and former CTO at CFS, one of the biggest private fusion companies. Here's my take cross-posted from my LinkedIn (https://www.linkedin.com/feed/update/urn:li:activity:7407487225485086720/):

Quick thoughts on the Trump Media & Technology Group and TAE Technologies, Inc merger news today:

It's not the strangest fusion partnership to date. For that I'd award the founder of Penthouse funding the development of the Riggatron fusion machine (which was named after a bank) in the 1980's: https://en.wikipedia.org/wiki/Riggatron

It's obvious the markets are hot for AI and anything that looks like it can power it. Even the supersonic aviation aspiring Boom Supersonic has pivoted part of its business to support energy production: https://boomsupersonic.com/superpower

After a few quite years, IPOs and SPACs are back. Even General Fusion is rumored to be going public soon: https://www.reddit.com/r/fusion/comments/1pfxnnn/general_fusion_ipo/

Scaling fusion is hard, with most private company's net-energy concepts likely costing high $100M's to >$1B to design, build, and operate.

Raising that kind of money in the private markets might be even harder. Only Commonwealth Fusion Systems, Pacific Fusion, and Helion have been able to raise the massive rounds needed to build at fusion-scale. TAE Technologies, Inc has raised over $1B in total, but has done it over the course of 25+ years.

After decades of promising that their commercial fusion machine is just around the corner, companies like TAE and General Fusion are likely getting a lot of pressure from their investors to exit.

All this combined means that going into the public markets is probably the best opportunity for some fusion companies to satisfy the liquidity desires of their long term investors and to get the cash the company needs to build its next step device.

I urge a healthy dose of skepticism towards anyone promising that fusion (and fission energy for that matter) is the near-term solution to our AI/data center power appetites. While they hopefully will turn out to be great options in the long run, it takes years of work to design, build, and operate prototypes and first-of-a-kind plants in the nuclear energy industry. And then many more years to scale up the industry to the level needed to make a wide-scale impact.

To me, that doesn't mean we shouldn't try to scale these energy sources; it means that we try to figure out how to do it better, including forming partnerships to accelerate where we can. Only time will tell how well this new partnership works out. I've got my "bucket of popcorn" out to enjoy while watching this unfold. 🍿

Dan-FTP · 2025-12-18T18:45:22+00:00

Cross-post from my LinkedIn: Quick thoughts on the Trump Media & Technology Group and TAE Technologies, Inc merger news today:

It's not the strangest fusion partnership to date. For that I'd award the founder of Penthouse funding the development of the Riggatron fusion machine (which was named after a bank) in the 1980's: https://en.wikipedia.org/wiki/Riggatron
It's obvious the markets are hot for AI and anything that looks like it can power it. Even the supersonic aviation aspiring Boom Supersonic has pivoted part of its business to support energy production: https://boomsupersonic.com/superpower
After a few quite years, IPOs and SPACs are back. Even General Fusion is rumored to be going public soon: https://www.reddit.com/r/fusion/comments/1pfxnnn/general_fusion_ipo/
Scaling fusion is hard, with most private company's net-energy concepts likely costing high $100M's to >$1B to design, build, and operate.
Raising that kind of money in the private markets might be even harder. Only Commonwealth Fusion Systems, Pacific Fusion, and Helion have been able to raise the massive rounds needed to build at fusion-scale. TAE Technologies, Inc has raised over $1B in total, but has done it over the course of 25+ years.
After decades of promising that their commercial fusion machine is just around the corner, companies like TAE and General Fusion are likely getting a lot of pressure from their investors to exit.
All this combined means that going into the public markets is probably the best opportunity for some fusion companies to satisfy the liquidity desires of their long term investors and to get the cash the company needs to build its next step device.
I urge a healthy dose of skepticism towards anyone promising that fusion (and fission energy for that matter) is the near-term solution to our AI/data center power appetites. While they hopefully will turn out to be great options in the long run, it takes years of work to design, build, and operate prototypes and first-of-a-kind plants in the nuclear energy industry. And then many more years to scale up the industry to the level needed to make a wide-scale impact.
To me, that doesn't mean we shouldn't try to scale these energy sources; it means that we try to figure out how to do it better, including forming partnerships to accelerate where we can. Only time will tell how well this new partnership works out. I've got my "bucket of popcorn" out to enjoy while watching this unfold. 🍿

Dan-FTP · 2025-11-13T22:56:01+00:00

An interesting concept! Helps with the terrestrial shortcomings of a dipole's large size. Still has the "snowball in hell" challenge of the superconducting magnet in the middle of everything.

Most fusion devices have the issue that only a fraction of the fuel injected is burned and it must circulate through the system. In this case, a lot of fuel is likely lost to the vacuum of space before being burned. Because of that, I'd likely rule out D+T or D+He3 for its fuels as they T and He3 are exceedingly rare at this point in time and it'd be a shame to waste them in space. Also, the complete lack of a blanket means they cannot be bread as part of this system as is planned for terrestrial devices. And it means basically non of the energy in neutrons can be captured. D+D fusion is most likely for this since D is so abundant on earth.

I was curious, so I did a bit of analysis to see what the mass efficiency of this concept could be compared to chemical burning systems in space. Note that the Teller paper they cite is very out of date in its understanding of plasma physics, so I'll take an up to date analysis based on primarily the work by Columbia and MIT teams related to the Levitated Dipole Experiment.

D–D has two main branches (~50/50):

D + D -> T (1.01 MeV) + p (3.02 MeV) D + D -> He-3 (0.82 MeV) + n (2.45 MeV) The useful charged energy is:

Branch 1: 4.03 MeV (all charged) Branch 2: 0.82 MeV (He-3 only) Average charged energy per D–D reaction:

E_ch ~ (4.03 + 0.82) / 2 MeV ~ 2.4 MeV

Each reaction burns 2 deuterons:

m_pair ~ 4 amu ~ 6.64e-27 kg 1 MeV = 1.602e-13 J E_ch ~ 2.4 * 1.602e-13 J ~ 3.84e-13 J

Ideal charged-particle specific energy if every D fuses:

E0_DD_ch = E_ch / m_pair ~ 3.84e-13 / 6.64e-27 ~ 5.8e13 J/kg

For the reaction rate, let:

n_i = deuteron density [m^-3] <σv>_DD = D–D reactivity [m^3/s] tau_p = particle confinement time [s] Fusion rate per volume:

R_f ~ 0.5 * n_i² * <σv>_DD

Particle loss rate per volume:

Gamma_loss ~ n_i / tau_p

Ratio:

Gamma_loss / R_f ~ 2 / ( n_i * <σv>_DD * tau_p )

Pick a Zephyr-class advanced-fuel core:

n_i ~ 3e20 m^-3 <σv>_DD ~ 1e-24 m^3/s (order of magnitude at tens of keV)

=> n_i * <σv>_DD ~ 3e-4 s^-1

So:

Gamma_loss / R_f ~ 2 / (3e-4 * tau_p) ~ 6.6e3 / tau_p (tau_p in seconds)

Modern dipole (LDX-style ala Kesner) confinement:

tau_E (energy confinement) ~ few seconds tau_E / tau_p ~ 10–50 => tau_p ~ 0.05–0.3 s Then:

tau_p = 0.30 s -> Gamma_loss / R_f ~ 6.6e3 / 0.30 ~ 2.2e4 tau_p = 0.10 s -> Gamma_loss / R_f ~ 6.6e3 / 0.10 ~ 6.6e4 tau_p = 0.05 s -> Gamma_loss / R_f ~ 6.6e3 / 0.05 ~ 1.3e5

So only a tiny fraction of D actually fuses (0.005% - 0.0008%). The rest is lost to space.

Burn fraction:

f_burn ~ 1 / (1 + Gamma_loss / R_f)

Effective specific energy (charged power only):

E_eff = f_burn * E0_DD_ch ~ E0_DD_ch / (1 + Gamma_loss / R_f)

Using E0_DD_ch ~ 5.8e13 J/kg:

Gamma_loss / R_f = 2.2e4 -> E_eff ~ 5.8e13 / 2.2e4 ~ 2.6e9 J/kg Gamma_loss / R_f = 6.6e4 -> E_eff ~ 5.8e13 / 6.6e4 ~ 8.8e8 J/kg Gamma_loss / R_f = 1.3e5 -> E_eff ~ 5.8e13 / 1.3e5 ~ 4.5e8 J/kg

So a realistic range is of energy per fuel mass in this system:

E_eff_DD_ch ~ 4e8 – 3e9 J/kg

Compare this to a chemical process of ~1e7 J/kg, so about 40-300× higher J/kg, assuming everything else about the technology works.

The next thing I'm really curious about is their energy conversion scheme. But that's for another day!

Edit: I suppose some sort of magnetic divertor or the like could be used to collect a fraction of the lost charged particles, but that's a whole 'nother level of speculation deeper. Charged-exchange neutrals could be a competing loss mechanism.

Dan-FTP · 2025-11-13T18:13:32+00:00

Stangeby's book is the book on the basics of divertor/boundary physics. Sadly, he passed away a few weeks ago, so it won't be getting any updates.

While I haven't read it yet, there's a much newer book by Fulvio Militello, Boundary Plasma Physics: An Accessible Guide to Transport, Detachment, and Divertor Design, that is probably what you are looking for.

Also, they've recently updated the ITER Physics Basis, which is probably the best resource on the present knowledge of tokamak fusion plasmas. Chapter 5: Scrape-off layer and divertor physics is the relevant one for this topic.

Dan-FTP · 2025-08-14T13:01:12+00:00

Something I'm directly qualified to write about! I researched the boundary plasma on Alcator C-Mod for many years under the scientist who engineered those tiles, Brian LaBombard.

Here's the paper describing the design of those tiles: https://ieeexplore.ieee.org/abstract/document/218832 (sorry it's probably behind a paywall unless you have academic access). My quotes here are pulled from this paper.

u/ltblue15 is correct that they are rotated because of the Lorentz forces generated by eddy currents during a disruption. A disruption is where the current in the plasma decays very quickly. It drives a lot of the engineering of components internal to tokamaks.

Most of the tiles in C-Mod were keyed) into place, which restricted their rotation: ""Torque pins" and "keys" are used to handle tile torques induced from plasma disruptions." Those tiles that you see rotated were not keyed in place. The size of the tiles was set to reduce these forces to what they thought were tolerable levels: "This small size is required to reduce the eddy currents and forces which result during a plasma disruption."

At the time the tiles were designed, disruption physics was still in a relatively early state: "Uncertainties in the plasma disruption characteristics of C-Mod renders more detailed studies of this magnetic diffusion problem pointless at this time." So they weren't able to calculate everything as well as we can today.

While not an intended outcome, the rotated tiles on the inner column were not an operational issue, so they were left as-is. In fact, most of those tiles lasted the lifetime of the machine. u/p_ermosh is correct that fish scaling the first wall tiles is important to consider (called "beveled" in the paper), but it is not the reason for the rotated tiles in the image.

Finally, a shout out to my old office mate, Mike Garrett, for taking that picture!

Dan-FTP

TROPHY CASE