Zap Energy strives for magnetic confinement fusion power—with no magnets

The Z-pinch concept: Z-pinch fusion features a thin line of plasma that carries an electrical current to generate its own magnetic field and “pinch” the plasma, compressing and heating it to the point that fusion can occur. Like other magnetic confinement fusion approaches, Z-pinch fusion strives for containment and must control plasma instabilities that can erupt within nanoseconds.

Zap Energy is building on a long history of Z-pinch fusion experiments around the world and approaching useful energy production by using sheared-flow stabilization (SFS) to suppress instabilities and sustain a plasma. SFS works by applying variable current to produce an axial plasma flow that varies by radius, with faster velocities farther from the center of the plasma column. The concept doesn’t require magnetic coils or external heating systems—just the source to drive the electrical current.

“Z-pinch has long been an appealing way to achieve nuclear fusion, but for many years researchers considered Z-pinch’s plasma instabilities to be an insurmountable challenge,” says Uri Shumlak, Zap Energy’s chief science officer and a University of Washington professor of aeronautics and astronautics. “We’ve shown through both simulation and experiment that sheared flows can stabilize fusion plasmas, and that the stability should extend to a commercially viable scale. The Zap Energy team has made rapid progress since this technology moved out of the lab, especially with recent team and investment growth.”

FuZE-Q: The first plasmas in FuZE-Q follow work to extend the lifetime of stabilized plasmas achieved in its predecessor, FuZE—a machine that could supply up to 500 kiloamps (kA) of current. FuZE-Q, with a new power bank being installed later this year, is expected to be able to deliver over 650 kA of current—the current that models predict will be required to achieve a net energy gain, or, Q=1.

“FuZE-Q is the fourth generation of Z-pinch device that we’ve built and is undoubtedly the most ambitious,” notes Brian Nelson, Zap Energy’s chief technology officer and a research professor emeritus at University of Washington. “We designed it to be versatile, resilient, and tunable in lots of ways that will be critical as we ramp to higher currents, temperatures, and densities.”

Power vision: Zap Energy’s fusion power concept would inject deuterium-tritium gas to form a plasma that accelerates down a coaxial accelerator before assembling into a single Z-pinch plasma column on the axis. Fusion neutrons produced in the Z-pinch would be captured in a liquid lithium-lead blanket, which serves as return electrode, heat-transfer fluid, tritium breeding ground, and a biological shield.

Zap Energy sees potential for factory-built modular power plants that could support multiple fusion cores, each rated at about 50 MWe. At the annual ARPA-E Fusion Review Meeting in April, the company described its plan for cylindrical modules 3 meters in height and diameter and capable of producing about 200 MWt from 10-Hz pulsed operation.

‍A stealth technology? In a recent ARPA-E video, “Just A Little Z-Pinch: Zap Energy's Game-Changing Approach to Fusion Power,” Scott Hsu, who is leaving his previous role as an ARPA-E program director to become a Department of Energy senior advisor and lead fusion coordinator in the Office of the Under Secretary for Science and Innovation, said, “I think we're at an inflection point where redoubling our efforts will really get us to the finish line on the timescale that matters. Zap has one of the very most interesting fusion core concepts out there. If they're successful it might just be the most compact fusion core out there. I don't want to belittle the challenges remaining, but I think that if these challenges can be solved, this team and this idea are very promising. This could be ARPA-E's Internet or ARPA-E’s stealth technology . . . and I think that's really what we're all looking for.”

Collaboration: Zap Energy’s FuZE-Q is supported by an ARPA-E BETHE award of $1 million for work from July 2020 through June 2023 that will let the company upgrade the FuZE-Q to allow independent control of the plasma formation and acceleration stages. Zap Energy previously received funding for the SFS Z-pinch approach from ARPA-E’s ALPHA and OPEN 2018 programs, demonstrating a factor of 50 increase in three to four years in the key scientific metric of the fusion triple product: density, temperature, and confinement time.

ARPA-E has also secured assistance from national laboratories. A team from Lawrence Livermore National Laboratory helped Zap Energy prove the existence of neutrons produced through thermonuclear reactions from a sheared-flow stabilized Z-pinch device, while Los Alamos National Laboratory has enabled fast imaging, spectroscopy, X-ray measurements, and neutron measurements.

University startup: The conceptual basis for Zap Energy’s technology was developed at the University of Washington with collaborators from LLNL. Shumlak and Nelson cofounded Zap Energy in 2017 with entrepreneur and investor Benj Conway, and the company now has over 60 employees based in Seattle, Everett, and Mukilteo, Wash.

Zap Energy investors include Lowercarbon Capital, Breakthrough Energy Ventures, Addition, Chevron Technology Ventures, DCVC, Energy Impact Partners (EIP), Shell Ventures, and Valor Equity Partners.