• Comment: This is a much better article than the one I reviewed back in Mid-March. It seems to demonstrate notability now, and many other issues have also been resolved. I'd actually be likely to accept it now, but there are still some improvements I'd like to see before moving it to mainspace. The mechanism of operation in #Shear Flow Stabilisation seems to be a bit overly technical in its wording, and could do with some expansion to help to explain how the process works to someone less familiar with nuclear fusion technologies.
  This is slightly off topic, but might I also recommend that once this one is satisfactorily complete, the attention given here could be directed to the Z-pinch article? That has got some substantial issues with insufficient inline citations and such, and some of the sources used in this article may be able to be used to greatly enhance that article.

• Comment: @WikiHelper2221: Can you please move some of the content on Z-pinch in general and the technology used to the main Z-pinch article, as this is an article on Zap Energy, and the detail here on the technology overall should be as brief as possible, basically just stating what it is, and linking to it. The majority of the content here doesn't pertain specifically to Zap Energy, and would be better off in the main Z-pinch article. Mako001 (C)  (T)  🇺🇦 12:26, 17 May 2022 (UTC)

• Comment: I think Reuters and IEEE Spectrum meet the bar for NCORP. Maury Markowitz (talk) 19:21, 6 May 2022 (UTC)

• Comment: Can you give at least two sources that meet WP:NCORP? Nomadicghumakkad (talk) 14:54, 19 March 2022 (UTC)

Zap Energy is an American company that is aiming to generate fusion power through use of a sheared-flow stabilized Z-pinch. The company is based in Seattle, Washington with offices in Everett and Mukilteo, Washington.^[1] It was co-founded by President Benj Conway, Chief Technology Officer Brian A. Nelson and Chief Science Officer Uri Shumlak.^[2]

The pinch effect is one of the earliest methods of fusion power to be explored. It relies on the fact that a current flowing in a conductor will produce an inward-directed force, squeezing the conductor. In the case of a fusion device, the conductor is a plasma of the fusion fuel itself. The current is either induced using an external magnet, or directly applied using electrodes in the reaction chamber. The device is almost trivially simple, and led many researchers around the world to attempt to build pinch systems.

In early experiments, pinch systems were found to be unstable and the plasma was quickly forced into the walls of the reaction chamber, cooling it off so that fusion would not occur. This led to the development of the stabilized pinch machines, with the canonical example being the UK's ZETA. At first it appeared these designs were free from the instabilities of the earlier devices. However, further investigation showed that new "microinstabilities" were just as effective at destroying confinement as the earlier, larger, instabilities had been. With no obvious solution to these new class of problems, major research on the classic pinch devices ended by the early 1960s.

The idea of using the flow of the plasma as an additional stabilizing force developed in the 1990s. In this concept, the pinch is developed such that the plasma flows at different speeds as one moves out from the center of the plasma column, with the outer layers being about ten times as fast as the center.^[3] As the magnetic field created by the pinch current is a function of both the density and speed of the charges, this causes the resulting pinch field to be non-linear across the plasma column. This surpasses the growth rate of the kink, sausage and interchange instability. The exact conditions that need to be reached to stabilize the pinch is still an open area of research.^[4][5]

Zap Energy can trace its' technical origins to the work of Dr. Uri Schumlak at the University of Washington starting in 1995. The university built three experimental machines to test the flowing pinch:

• ZAP (1999-2014)^[8][9],
• ZAP-HD (2014-2017)
• FUZE device (2017-2021)

Since then the company has built other machines^[10]. Because shots on the flowing pinch were much smaller in volume than in a Tokamak and much longer than an ICF implosion, the Schumlak lab had to develop custom tools to measure their plasmas^[11].

Zap created their first fusion reaction in 2018 ^[12] but in November of 2021, Livermore National Laboratory provided an independent and more precise measurement of neutron production inside the flowing pinch, proving that the machine can do fusion with deuterium^[13]. The effort was led by ARPA-E, where the agency organized fusion teams to support private fusion companies.

Zap Energy was founded in 2017 as a spin-off from the FuZE (Fusion Z-pinch Experiment) research team at the University of Washington and collaborations with researchers from Lawrence Livermore National Laboratory.^[15] The Zap reactor is a pulsed power system with no external magnets.^[16] Z-pinch was one of the earliest approaches to fusion power, most notably through the United Kingdom's ZETA reactor experiments in the 1950s, but was considered unworkable due to instabilities that form in the plasma. Shumlak and Nelson's contribution was showing the instabilities could be controlled through sheared axial flows, where the plasma moves at different velocities across the radius of the plasma.^[17][18]

The company aims to scale their reactor to maintain plasma stability at increasingly higher energy levels, with the goal of achieving scientific breakeven and eventual commercial profitability.^[19][20][21]

From 2015 to 2020, a series of U.S. Department of Energy grants enabled the team to test their sheared-flow stabilized Z-pinch reactor at progressively higher energy levels.^{[22][23][24][25]}

In July 2020, Zap Energy raised $6.5 million in Series A funding.^[26] In May 2021 they received $27.5 million in Series B funding from Addition, Energy Impact Partners, Chevron Technology Ventures, GA Capital, Fourth Realm, and LowerCarbon Capital.^{[27] [28][29]} Chevron's financing was the first investment in fusion energy by a major U.S. oil company^[30][31] but not the first investment by an oil firm into fusion. The Italian oil company ENI invested 50 million in Commonwealth Fusion Systems in 2018^[32].

Since 1999, the flowing pinch has been tested in a series (ZAP, ZAP-HD, FuZe, etc) of similar experimental devices. The machine is a ~2 meter long metal tube with a cathode running halfway down the middle. A voltage is applied between the central cathode and the grounded wall. Fusion fuel is puffed in the back of the machine, which ionizes due to Paschen breakdown creating a plasma ^[33]. This plasma sweeps forward and assembles into a flowing pinch in the gap between the cathode and the wall. The University of Washington has outfitted these machines with several tools to measure the performance of the flowing pinch:

• Ion Spectroscopy is used to measure the temperature of the plasma and in the flowing pinches' case it measures the emissions from Carbon-III impurities inside the plasma^[34].
• Fast Cameras are used to get overall photos and video of the pinch performance. In 2019, the team was used a 5 million frame per second camera made by Kirana in the UK.
• Interferometry is used to measure the density of the plasma across the flowing pinch. The tool passes a test laser beam through the plasma and compares it to a reference beam to measure the plasma density ^[35]. But, this tool is limited because it can only measure densities along the narrow path where the laser travels (known as a Chord).
• Magnetic Field Probes line the surface of the tube to measure the field generated by the flowing pinch current ^[36]

Zap Energy has argued that the rate of fusion in a flowing pinch scales as the pinch current to the 11th power^[37][38][39] and that because of this, all that is needed to generate net power from a flowing pinch is higher current.

However, this scaling model is based on adiabatic plasmas and that model fails to capture all real-world behavior. Critics have pointed out that when the flowing pinch goes to higher currents, it could introduce drift instabilities and shockwaves that could tear the plasma apart.^[40] In the case of drift waves, the (+) ions and (-) electrons would move at different speeds because of their mass differences, and this would rip the plasma apart. Shockwaves could also form during the assembly process of the pinch, when the plasma sweeps together at high speeds, the two plasma waves could form a shockwave at higher speeds.

Supporters have argued that all that is needed to reach net power is ~650 kiloamps of current through the flowing pinch; as of 2022 the company was testing with currents between 300 to 400 kiloamps.^[41]

• Fusion Power
• Z-Pinch
• History of nuclear fusion
• List of fusion power technologies

• official website

Category:Energy companies of the United States Category:Nuclear technology companies of the United States Category:Companies based in Seattle, Washington Category:Nuclear fusion