Posted on 02/05/2025 4:54:44 AM PST by Red Badger
For decades, fusion researchers struggled with neutron isotropy, a key indicator of scalable plasma stability. Zap Energy’s latest results show its FuZE device avoids the pitfalls of past Z pinch failures, generating isotropic neutrons that confirm thermal fusion is occurring.
A Major Milestone for Zap’s Fusion Technology
In physics, “isotropy” refers to a system where properties remain the same in all directions. In fusion research, neutron energy isotropy is a key measurement that assesses how evenly neutrons are emitted from a device. This uniformity is crucial — when fusion plasmas are isotropic, they indicate a stable, thermal plasma that can be scaled up for greater energy production. In contrast, anisotropic plasmas, which emit neutrons unevenly, suggest instability and may not support sustainable fusion.
A recent Zap Energy study, published in Nuclear Fusion, presents the most compelling evidence yet that its sheared-flow-stabilized Z-pinch method produces stable, thermal fusion. The research, conducted on the FuZE device, marks a significant milestone in proving that Zap’s approach can be scaled to higher energy outputs, strengthening confidence in the performance potential of the next-generation FuZE-Q device.
“Essentially, this measurement indicates that the plasma is in a thermodynamic equilibrium,” explains Uri Shumlak, Zap’s Chief Scientist and Co-Founder. “That means we can double the size of the plasma and expect the same sort of equilibrium to exist.”
Inside a Zap core, hydrogen nuclei are fused into helium, a process that kicks out a neutron at high energies. These neutrons carry 80% of the energy that comes from the fusion reaction, so, in general, the more neutrons, the better.
However, not all kinds of fusion reactions are created equal. Thermal fusion is Zap’s goal — when nuclei are fused together by the extreme heat and pressure inside its plasmas. Thermal fusion produces energetic neutrons that scale exponentially (at around 10 to the eleventh power) as the amount of current conducting through the plasma is dialed up to reach the levels necessary for fusion to yield net energy.
Less desirable is what’s known as beam-target fusion, which happens when a hydrogen nucleus is accelerated to high velocity and strikes a stationary nucleus. Unlike in thermal fusion, beam-target fusion indicates the plasma is out of equilibrium, and therefore doesn’t scale as strongly, making a working energy source much more difficult.
Thermal fusion produces neutrons with isotropic velocities, or with the same energy in all directions, while beam-target fusion produces them anisotropically, or such that neutrons in certain directions have higher energies. So, comparing measurements of the neutron energy at different locations is a simple way to see how much of the fusion in the FuZE device is non-thermal.
“If we saw neutrons primarily from a beam-target source, it would mean that our machine wouldn’t be scalable. We couldn’t get to net energy production,” says Rachel Ryan, a senior scientist at Zap and lead author of the new research.
To test the neutron isotropy in FuZE, Zap scientists and engineers ran a series of tests using neutron detectors placed around the device. Measuring 433 plasma shots generated with the same machine settings, the neutrons were found to be almost totally isotropic.
Neutron Detector Fusion Test Prep
Zap researcher Rachel Ryan prepares a neutron detector prior to fusion tests. Credit: Zap Energy
A Meaningful Measurement, in More Ways Than One
Besides being a key benchmark for physics progress, neutron isotropy holds extra historical significance for Zap’s fusion approach.
The Z pinch is one of fusion’s oldest approaches and dates back to the 1950s. When scientists working on the Zero Energy Thermonuclear Assembly (ZETA) device in the United Kingdom began using magnetic fields to “pinch” a plasma strongly enough to create fusion, they thought they had succeeded. But that success didn’t come in the way they had hoped. Their device turned out to be creating almost entirely beam-target fusion through the creation of instabilities in the magnetic field. That meant they could never generate net-energy-gain fusion. What had been a hopeful moment for the physics community turned out to be a disappointment and a PR disaster.
And while isotropy became a particular black mark for pinch-based approaches, all fusion technologies risk measuring false positives from beam-target neutrons. For example, a device known as a dense plasma focus (DPF) has also been largely dismissed as a practical path to a fusion power plant. Though they are similar in some ways to Zap’s devices and are considered an effective means of generating neutrons, DPF neutrons come primarily from beam-target interactions.
A Step Toward Scalable Fusion Power
In the shadow of those experiments, Zap is extra conscious of the story its neutrons tell. The company first measured thermal fusion in 2018 and these new tests, done with higher sensitivity and at higher energies, are the latest confirmation that sheared flows can postpone the instabilities that doomed previous Z pinch efforts. Scalable thermal Z-pinch fusion, without requiring any external magnets for confinement, remains promising.
The paper represents a major physics consideration, Shumlak says. “This is why we put so much effort into making these precise measurements,” he says.
Preparing for the Future
Since joining Zap in 2023, Ryan has played the lead role in planning and carrying out neutron measurements at Zap, building on work previously done by collaborators and co-authors from Lawrence Livermore National Lab. Next up for the team is running the same set of tests at higher energies on Zap’s FuZE-Q device. Initial results look promising.
“As we continue to scale up, it’s important for us to keep taking this measurement and keep checking whether beam-target fusion is contributing to our yields,” Ryan says.
Interestingly, the paper also notes that the neutrons became less isotropic and lost uniformity near the end of each shot. The researchers suggest this is likely a phase where the pinch becomes unstable before it breaks down and stops generating fusion entirely. Understanding that phase may give a better understanding of how to keep the instabilities from cutting fusion short and further increase the duration and performance of the plasma.
Reference:
“Time-resolved measurement of neutron energy isotropy in a sheared-flow-stabilized Z pinch”
by R.A. Ryan, P.E. Tsai, A.R. Johansen, A.E. Youmans, D.P. Higginson, J.M. Mitrani, C.S. Adams, D.A. Sutherland, B. Levitt and U. Shumlak, 31 January 2025, Nuclear Fusion.
DOI: 10.1088/1741-4326/ada8bf
Once they get fusion reactors producing electricity then every home will have one!..................
Well, I know a solar farm that might be had for a low low price soon......
Right around the corner... AGAIN!
I could wish that fusion research were done in the name of understanding the physics and not hypotheses (lies might be a better term) about the outcome.
Humans are fortunate to have a giant fusion reactor, already. It is the Sun, and it is far enough away that its radiations don’t cook us. For “free” energy, it may well be the best we can get. I don’t say that fusion research is valueless, but lying about what may come of it probably is.
For my money, it is the gravitational collapse of the Sun which powers its fusion. It may also generate neutrons, or did in an earlier epoch. You probably can’t fake this, or can do so only like a refrigerator operates, on a small scale and against net reversal.
As soon as my perpetual motion stocks kick in I will.
I think you're not understanding the physics. The fusion reactions (D+D and D+T) they're talking about aren't "fed" by neutrons, they produce neutrons -- very energetic ones, in fact. The OP is saying that the neutron production they're seeing is "isotropic" (no directionality), meaning that they have a very homogenous fusion process going on.
The fusion reactions are "fed" by high temperature and pressure. Getting the temperature and pressure high enough, while still getting excess energy out of the fusion reaction, and making the whole thing economically feasible, is the trick. It's not clear that it's even possible.
It's a bit costly. And it requires a lot of tedious research about the climate in your area, your own energy consumption habits, etc. to make sure it's ideal for you (in my case the monthly payment I make on the loan I took out to pay for all of these improvements is less than the cost of the energy I'm not having to buy). But it's a very sweet situation to pull only 20% of the power we need from the grid, including how much power we use to charge the EV for the local driving (last year it was 16K miles just on the home charged miles).
That's mainly because no blankety-blank bureaucrat has figured out a regulation to control how much sunlight hits my property. That's really the only thing that solar has over hydrocarbons (I can't drill my own natural gas or oil, etc.) And so far, Bond villain Bill Gates hasn't figured out a way to block the sun yet.
Thanks for clarifying.
The fusion in the sun's core is a different process than what fusion power experiments (or nuclear bombs) use, which would be even harder to replicate on earth. It generates gamma rays (which are downgraded to light by the time they get to us) but no or few neutrons.
The first step in solar fusion is the fusion of two protons to form a deuterium nucleus and a positron. It's believed that it takes an individual proton, on average and at the conditions in the sun's core, several million years before it successfully completes that reaction. That's why we probably can never replicate that process on earth.
It does seem as if fusion is an industry of process of engineering the “cart” that goes in front of the scientific “horse.”
To be clear, you are saying that the Sun is comprised largely of deuterium?
You state that the Sun’s fusion produces little, or no neutrons, and describe a process creating deuterium (hydrogen with a neutron) which you say is very slow, I believe. Does this mean that deuterium must already exist in the Sun for the fusion that we observe?
Thanks for your explanation!
Sounds like a good project for USAID.
Wait. Never mind.
I joke that solar electricity is “free” energy because it is energy that I have already paid for. ;-)
I find that it differs from electricity that I pay for monthly, in that I don’t mind using it. In fact, I look for ways to fully utilize it - charging lithium battery appliances, for instance.
Instead of electricity that you don’t want to use, you have electricity whose cost is MINIMIZED by consumption! It takes getting used to.
At this rate, my great grandchildren’s great grandchildren might see a semi-working prototype...
They’ve been just about to crack the fusion problem for 50 years. So tomorrow it will be solved?
Maybe their theory is flawed or completely wrong.
Fusion isn’t difficult. You just need massive amounts of gravity........................
Deuterium is produced from protons (hydrogen-1, "protium") in the first step of the fusion process in the sun's core. The deuterium nucleus is very reactive and only lasts a few minutes before it fuses with another proton to produce helium-3. Helium-3 is also very reactive and fuses with another helium-3 to produce helium-4 and two protons. In the conditions that currently exist in the sun's core, helium-4 is non-reactive.
The process to get from 2 protons to deuterium is very slow (on average), but there are a lot of protons in the sun's core, so it's happening all of the time. Still, the sun's power density (power produced per unit volume) is pretty low -- a cubic foot of the sun's core produces on the order of 100 watts of power. Of course, there's a lot of cubic feet in the sun's core.
Because deuterium is so reactive in stellar-core environments, there isn't a lot of it in the universe. "Not a lot in the universe" is still quite a bit. About 1% of the hydrogen on earth is deuterium.
Thank you for that very clear and detailed response! I appreciate the time you took to write it.
You’re welcome!
Two weeks.
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