Century: Zap Energy’s 100-kW-Scale Repetitive Sheared-Flow-Stabilized Z-Pinch System with Liquid Metal Cooling

From the source

1. The sheared-flow-stabilized Z pinch relies on plasma self-organization, in the sense that plasma dynamics play a critical role in confinement. Using plasma axial current for confinement and compression eliminates the need for external confinement or heating technologies. The prototypical plasma planned for power plants is compact in length at about half a metre, thin in the radial dimension at about 0.15 mm, and high in density at about 10²⁶ per cubic metre, and is driven directly and efficiently by an electrical power supply without external magnets, auxiliary heating, or inefficient conversion of the drive energy to other intermediate forms.Abstract; Sec. I, Introduction

2. Recent sheared-flow-stabilized Z-pinch experiments in the FuZE and FuZE-Q devices have demonstrated deuterium-deuterium fusion neutron production rates of 5 times 10⁷ neutrons per microsecond with simultaneous electron temperatures of 3 keV.Sec. I, Introduction, citing Levitt et al., Phys. Rev. Lett. 132, 155101 (2024)

3. Century is the first integrated engineering test of high average-power repetitive Z-pinch plasmas operating in a vacuum chamber protected and cooled by liquid metal — effectively a miniature mock-up of a future fusion power plant core. Its design point is 100 kW of average plasma drive power delivered as Z-pinch arcs at about 0.1 Hz, roughly one percent of the nominal plant figures of about 10 MW at 10 Hz; but the roughly half-metre pinch region already matches the anticipated plant dimension. Construction began in June 2023 and phase one commissioning started in June 2024.Sec. I; Sec. II, Century

4. The driver and the liquid metal system are the substance of the engineering. The second-generation driver is five identical containerized pulse forming network modules, each sourcing 100 kA for 0.5 MA in full operation, with pulses of about 100 microseconds at 0.1 to 0.3 Hz; spark gaps and ignitrons are ruled out by their limited lifetimes at this repetition rate, so high-power semiconductor thyristors do the switching, in a Blumlein topology feeding a three-to-one transformer, charged at up to about 120 kW so that a three-second charge is followed by a shot of about one gigawatt. The wall is molten bismuth — about seven litres, seventy kilograms — pumped by an alternating-current electromagnetic conduction pump at over five gallons per minute, cascading over a weir at around 400 degrees Celsius, and the loop ran one hundred hours continuously under vacuum with negligible erosion of the coated surfaces.Sec. III; Sec. V

5. Three successful continuous runs of 1,080 shots at 0.1 Hz — three hours each — took place between June and October 2024, with hydrogen plasmas and circulating liquid metal throughout. Run 3 showed high shot-to-shot reproducibility with delivered energies grouped tightly around 14 kJ and an average delivered power of about 1.4 kW; even at a fraction of full driver capability the current reached about 125 kA with a corresponding peak power of about 150 MW. The vacuum system cleared the injected hydrogen and recovered to about 10⁻⁴ Torr in the ten seconds between shots, and the bismuth temperature rose from 374 to 401 degrees Celsius on plasma heating alone.Sec. VII, Century commissioning runs; Figs. 14, 15, 17

6. Electrode erosion is the named limit and the named next measurement. Heat and plasma fluxes could hold the operational life of a basic solid cathode to roughly a day in a power plant. Measured on the SiMPL test device, a tungsten-copper nose cone lost about 860 mg over 50 shots delivering about 2,500 coulombs, an erosion rate of 0.34 mg per coulomb — the same order as literature rates for 80 A copper vacuum arcs, which may mean the pinch arc erodes gently or may mean significant current leaves the inner electrode elsewhere; a nose cone current sensor is under development to resolve the ambiguity. In Century itself, liquid metal coating of the tip produced a clear qualitative reduction in pitting of the stainless steel substrate. Next: raise average power from about 1.4 kW toward the full 100 kW design point behind the larger FCLBi-03 heat exchanger, then the successor platform Millenium at 1,000 kW input power.Sec. IV; Sec. VI; Sec. VII, Fig. 19; Sec. VIII, Summary

The way in

How to cite it

Matthew C. Thompson, Vidya Nalajala, Brian C. Kelleher, J. Steven Brantley, Clemente J. Parga, Alex H. Cheung, Matt Aubuchon, Brian A. Nelson, Micki Acks, Skyler Ashrun, Steven Bagdy, Allan Basile, Brianne J. Beers, Clyde Joshua Beers, Kenneth Blackwell, Haley Blanck, Felipe Caliari, Hannah Carlson, Michael Christenson, Thomas Connolly, Steven Cortez, Justin Costa-Greger, Christopher Dion, Sean Gagnon, Harpreet Grover, Corwin Hansen, Kaleb W. Hatfield, Santtu Joni Eemeli Huotilainen, Steve Jurovich, Scott Korlann, Brad Maynard, Santhosh Kumar Muniyal Krishna, Marcus E. Parry, Wyatt Pauley, Bill Pedler, Tyler Rhodes, David Sanabria Diaz, Whitney Schoenthal, Tim Schwartz, Geoff Staines, James Stuber, Zofia Toth, Nathan Tripp, Bruce Wakefield, Ben Watson, Chen Ying, Cassidy Zehner (2025) Century: Zap Energy’s 100-kW-Scale Repetitive Sheared-Flow-Stabilized Z-Pinch System with Liquid Metal Cooling doi:10.1080/15361055.2025.2532331

Where it sits in the curriculum

• Fusion machines: pinches, focus devices and inertial drivers