Update on Zap Energy Compact Z-Pinch Nuclear Fusion

Zap Energy, the University of Washington, and Lawrence Livermore National Laboratory are advancing the shear-flow stabilized Z-pinch concept and assessing its potential for scaling to fusion conditions and a practical path to a compact, low-cost fusion reactor. The Z-pinch is a geometrically simple and elegant approach to fusion, utilizing an electric current to simultaneously magnetically confine, compress, and heat a cylinder of plasma. However, the traditional Z-pinch is known to be plagued by instabilities that prevent attainment of conditions required for net fusion energy output. Sheared axial flows have been shown to stabilize disruptive Z-pinch instabilities at modest plasma conditions. Through experimental and computational studies, the team has successfully scaled this concept over the past four years from 50 kA to over 300 thousand amps of pinch current with a final goal in the present device of over 400 thousand amps.

The primary goal for Zap Energy’s next step device is to achieve 600 kA of plasma current where plasma density and temperature are predicted to approach conditions of scientific breakeven, i.e. fusion power would exceed power input to the pinch were it fueled with a 50-50 mix of deuterium-tritium.

Zap Energy is the most compact solution to Fusion Energy and does not use complex and costly magnetic coils. They surpassed ARPA-E Alpha Milestones in August 2018. Their reactor is consistently producing neutrons and they received $6.8 million ARPA-E OPEN funding. Nextbigfuture had Zap Energy coverage five months ago.

Zap Energy has progressed from 200,000 amps to over 300,000 amps.

Written By Brian Wang, Nextbigfuture.com

19 thoughts on “Update on Zap Energy Compact Z-Pinch Nuclear Fusion”

  1. Not needed. If you can fuse He3, then you can also fuse D+D which produces He3 in one branch (and a T in the other that will decay to more He3). So you could produce the fuel on Earth (and even make a little energy in the process).

  2. We have pretty good understanding of neutron shielding by now. Prof Uri Shumlak of UW and ZAP actually released a paper outlining possible fusion drives based on the SFS Z- Pinch. He seems to favor D+He3 over PB11.
    The good news is that once you have reactors that can fuse D+D, you can produce He3 on Earth.

  3. This one does not use Z-pinch targets like Sandia’s machine. Tritium production should be easier with this design than with donut shaped tokamaks.

  4. An ambitious idea like the Z-pinch rocket producing TW of power you would probably want to look at directly mining He3; that kind of rocket would make the gas giants easily reachable.  So assuming the H + B11 reaction doesn’t work for a rocket drive (disappointing if true) because of the side reactions, then He3 is the next contender.

  5. John Slough’s Fusion rocket design uses the D + T reaction surrounded by a Lithium blanket to absorb the Neutrons and generate more Tritium. Very much a 1.0 version fusion rocket design doable with current technology. That would get us to Mars/Asteroid belt/outer planets. Then we can get more ambitious. 


    Power output 33MW 5000 sec. SI. Obviously designed to be lifted to orbit with current rocket tech. Sure as the BFR becomes available we can consider larger upgrades producing more power.

  6. Need to slow neutrons before anything can really absorb them. Absorption in 10B is about 1/4000 as probable at 14MeV as it is at room temperature.

  7. Generally they rely on stronger magnets further away. Not impossible, mind you, but the test reactors omit a lot of things between the magnets and the plasma that an actual power reactor would need.

    The Polywell reactor actually had the coils INSIDE the plasma. But they were planning an aneutronic reactor.

  8. That is something that has bothered me about most schemes for fusion reactors.

    Most plausible reactions put out much of the energy as high energy neutrons (or gamma rays) which must be absorbed in a blanket of (probably) molten metal or salt both to provide a hot end for a heat engine & to protect delicate equipment from being damaged by the neutrons.

    I don’t see how any of the magnetic confinement fusion schemes can do the confinement from outside the neutron shield. With the inertial confinement schemes maybe the lasers can be directed through thin pipes in the neutron shield.

  9. IF you can get the He3-He3 reaction to go you can get the D-D reaction to go & the result of the latter reaction is
    D + D -> T + p
    D + D -> He3 + n
    So given fusion reactors that do work with these reactions, you can use the D-D reaction in stationary power plants with a heavy blanket of neutron absorbing material heating up to run a heat engine. Then the He3 can be used for your torch drive. The T can also be used in stationary power plants or stored to decay to He3 for use in the torch drives.
    So, no He3 mining on the moon or gas giants.

  10. In theory, you can confine neutrons magnetically; As they have a magnetic dipole moment, they’re attracted to areas of high magnetic field by virtue of the gradient. Takes one heck of a magnetic gradient to pull it off, though; I doubt you could contain 14MeV neutrons short of conditions on a magstar.

    Obviously in this circumstance you’re going to require some kind of outer jacket with an extreme neutron cross section. Boron 10 has a fantastically high cross section, and the products of capture aren’t themselves radioactive. Then you’d use the heat to boil water, as usual.

  11. Like most fusion concepts, this one is a bit of a stretch if the goal is competitively priced energy production. Z-pinch targets at Sandia’s Z machine consist of cylindrical arrays of fine wires. They would not be cheap even if you mass produced thousands of them. How do you replace the targets fast enough to achieve a high enough rep rate to produce significant energy? Then there’s the usual problem of breeding and extracting tritium. I suspect that will be a lot more difficult and expensive than the proponents of this idea imagine.

  12. I do not believe in mining lunar helium-3. Such ideas are entertained by people who do not understand the material inputs for digs involving megatons of material to be processed annualy. It is clearly a failure of imagination, as gas planets are the obvious source of helium-3. Content of helium-3 increases from Jupiter to Neptune. Jupiter is too hard due to radiation, gravity. Saturn has less radiation, but still gravity is problematic. Uranus is overall second best, Neptune is best, but timing and logistics move Uranus above Neptune. There you go, the best reason in the galaxy for a meaningful development of long-range robotic ships, refineries and infrastructure. It would take decades, which is another problem for humans: they do not care much about anything that is decades away, good or bad. Perhaps Chinese do, so there is hope.

  13. Thanks for the information; I assume the Helium 3 would have to come from the atmospheres of the gas giants like Jupiter/Saturn/Uranus, etc.  Not enough likely recoverable from lunar regolith; I believe the concentrations are on the order of 12-13ppb.  Even without the Neutron flux problem the radiant energy generated by the fusion would have to be protected against not just the neutrons.  Seem to recall energies discussed as being well into the Terawatt range for the rocket applications; plasma at millions of degrees would emit a lot of EM radiation.

  14. Argue with the article

    from page 10
    The high density avails the more attractive fusion reactions that generate fewer neutrons, like D–He3, or are completely aneutronic, such as p–B11 . The reaction with the highest cross-section is D–T, but
    it produces one neutron per reaction that must be shielded. The D–He3reaction does not produce any neutrons, but two Dions can react and produce a neutron. Shielding against neutrons significantly increases
    the required mass of the spacecraft.

  15. With D-T fuel, the energy output is almost entirely in 14MeV neutrons flying out in all directions. That is not a torch, that is a neutron bomb. D-D fuel generates less intense neutron flux, but it is still a neutron bomb. In order to make “Epstein drive”, pure aneutronic helium-3 fuel is required. Not even p-B11 fuel will be safe, as it still generates point-something percent fraction of output in neutron flux. If reactor in “Tachi” was in the gigawatt range, even 0.1% of output in neutrons would generate a megawatt of power that is still a neutron bomb. So, no torch ships until helium-3 fuel.

  16. More than energy… the Shear Flow Stabilized Z-Pinch Fusion concept can provide almost Epstein Drive (from Expanse TV show) space thrust capabilities… in other words… TORCHSHIPS.

    10 million Isp and 1 million N of thrust.

    Is that good enough for you guys?

Comments are closed.