Zap Energy unveils an innovative method for quantifying fusion energy gain


Zap Energy Fusion


Zap Energy, in an article published on Fusion science and technology, defined its methodology for measuring and calculating the net energy gain, or Q, in shear-flow-stabilized Z-pinch fusion plasmas. This marks a significant step towards demonstrating energy gain in fusion power development. Credit: Zap Energy

A new paper outlines scientific methods for measuring and calculating Q in a shear-flow-stabilized Z pinch.

Zap Energy has outlined its unique approach to measuring the net energy gain, known as Q, in fusion power development, according to a newly released study. The company’s Z-pinch fusion plasmas differ significantly from other fusion technologies, boasting[{” attribute=””>plasma that is 100,000 times denser and lasting several microseconds longer.


In the race to develop fusion energy, each unique approach requires its own specialized techniques to determine net energy gain, an equation balancing energy in and out thats known by the letter Q.

A new paper, published today (June 5) in the journal Fusion Science and Technology, establishes the companys method of measuring and calculating Q in Zaps sheared-flow-stabilized Z-pinch fusion plasmas. The publication will be an important part of Zap demonstrating energy gain on the way to building a commercial fusion system.


The way we generate fusion-grade plasmas in our devices is different from other fusion technologies so this paper helps lay the groundwork for quantifying our progress, says Uri Shumlak, Zap Energy cofounder, Chief Science Officer and lead author on the paper.
Hot enough, thick enough, long enough the three variables of temperature, density and time are collectively known in smelting as the triple product. And while there are several ways to create fusion, all of them need to triple product for net energy gains. Credit: Zap Energy


A distinctive approach

Like other fusion devices, Zap Energy plans to fuse hydrogen nuclei within material called plasma that must be superheated to temperatures hotter than the sun. Plasma properties can be measured to determine Q, or net energy gain, in part by calculating their triple product: how hot and how dense a plasma is, and how long it lasts.

The triple product is useful when comparing different fusion concepts, such as looking at how shear flow-stabilized Z-pinch devices differ from more traditional fusion devices, such as the tokamak or other fusion approaches, and can also be used as a simplified proxy for q.

Flow stabilized Z-Pinch plasma


Zap Energy creates fusion in a plasma filament less than two feet long. The inset image is a high-speed camera photo of a plasma in the Zaps device. Credit: Zap Energy

In the case of Zaps, its distinctive Z-pinch plasmas are about 100,000 times denser than those of tokamaks and last many microseconds. A pulsed system is being designed to create plasmas repeatedly.

Zaps plasmas flow in a line with material at different distances from the innermost part of the line moving at different speeds from its outer edges. This creates what is called shear flow stabilization, which keeps the plasma long enough for sustained fusion reactions to occur. The stabilization of the shear flow allows the Zap to confine plasmas without external magnets, but also leads to the need for uniquely suited measurements and analyses.


Measure Q

To calculate the triple product, Zap measures the temperature of the plasma, its density and the velocity of the flow to determine the duration of the plasma confinement. The corresponding calculation of Q is the ratio of fusion (output) power to input power and compares closely with the method used to measure gain in other magnetic confinement approaches, such as the tokamak. Inertial confinement approaches, such as last year’s demonstration of Q>1 by Lawrence Livermore National Laboratory’s National Ignition Facility, produce short-lived plasmas and define Q as the ratio of fusion energy to fusion energy. input.

Zap Energy FuZE-Q device

Zap Energy is improving the performance of fusion plasma within its FuZE-Q device. Credit: Zap Energy


The main difference between power and energy is that power is energy per unit time. Because Zaps plasmas are limited for times that fall between traditional magnetic and inertial fusion approaches, choosing to compute Q based on power is an important distinction.

The publication of these technical details is very important. You can’t just drop a thermometer into a fusion plasma to see what’s going on, so we instead use a combination of direct and indirect observations that help paint a picture of conditions, says Ben Levitt, vice president of research and development at Zap Energy. This paper gives us a chance to make sure other physicists agree that our methodology conforms to what has been established over the years in the fusion community and outlines how we intend to report our results in the near future.

Z-pinch shades

The document includes a number of specific details of Zaps’ merger approach. One of the most important is to account for the input power required to drive the stabilizing plasma flow.


The paper also notes that for high-performance pinches, an energetic product of fusion reactions called alpha particles is likely to become trapped and increase the fusion gain by offsetting some of the required input power.

Zap plans to correlate observations of plasma conditions with measurements of emitted neutrons. Since neutrons are a primary product of fusion reactions, scientists would expect them to increase when fusion conditions are right and decrease when they are not.


Zap got the first plasmas on its fourth generation device, FuZE-Q, last May. R&D campaigns are now underway using FuZE-Q. The Zap team will analyze results from both FuZE-Q and its predecessor FuZE as they move towards demonstrating the first shear-flow-stabilized Z-pinch plasmas capable of Q>1.

Reference: Fusion Gain and Triple Product for Shear Flow Stabilized Z Pinch Jun 5, 2023, Fusion science and technology.
DOI: 10.1080/15361055.2023.2198049

Zap Energy is building a low-cost, compact and scalable fusion energy platform that confines and compresses plasma without the need for expensive and complex magnetic coils. Zap’s shear-flow stabilized Z-pinch technology provides compelling casting economics and requires orders of magnitude less capital than conventional approaches. Zap Energy has over one hundred team members at two facilities near Seattle and is backed by leading financial and strategic investors.


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