The FuZE-3 device is Zap's first system equipped with a third electrode, separating the forces responsible for plasma acceleration and compression. The company presented details of these initial tests at the American Physical Society's Division of Plasma Physics meeting in Long Beach, California.
"There are some big changes in FuZE-3 compared to Zap's previous systems and it's great to see it perform this well so quickly out of the gate," said Colin Adams, Head of Experimental Physics.
Fusion energy generation depends on extremely hot and dense plasma. High pressure combines temperature and particle density and is critical for producing energy through fusion reactions. Fusion devices either pursue maximum pressure or prolonged confinement time; Zap's sheared-flow-stabilized Z-pinch approach aims for both.
FuZE-3's highest electron pressure measurement to date is 830 MPa. Since plasma consists of electrons and ions, and their temperatures are expected to be comparable, total plasma pressure is estimated at 1.6 GPa. This pressure is roughly ten thousand times atmospheric pressure and ten times that at the Mariana Trench's deepest point.
Plasma pressures were maintained for about one microsecond and measured using optical Thomson scattering. Recent test campaigns have documented repeated shots showing electron densities between 3 and 5 x 10^24 per cubic meter and electron temperatures exceeding 1 keV, equivalent to 21 million degrees Fahrenheit.
"This was a major effort by the team that was successful because of a tightly coupled cycle of theoretical predictions, computational modeling, rapid build and test engineering, experimental validation, and measurement expertise," said Ben Levitt, Vice President of R and D. "With a smaller system we have the benefit of being able to move quickly, and achieving these results in systems that are a fraction of the size and cost of fusion devices of comparable performance is a big part of what makes this such a significant accomplishment."
The FuZE-3 is Zap's third-generation device and fifth in its series of sheared-flow-stabilized Z-pinch experiments. FuZE, the initial device, surpassed 1 keV in temperature and is now retired. FuZE-Q - the most powerful in plasma production and neutron yield - continues in parallel operation with FuZE-3.
FuZE-3 was specifically designed to reach new levels of triple product, a fusion metric that multiplies density, temperature, and confinement time. Innovations include three electrodes and dual capacitor banks.
Previous Zap experiments used systems with one electrical pulse and two electrodes, requiring one source of power to both accelerate and compress the plasma. Adams said, "The capability to independently control plasma acceleration and compression gives us a new dial to tune the physics and increase the plasma density. The two-electrode systems have been effective at heating, but lacked the compression targeted in our theoretical models."
Despite these very high pressures, Zap's method is a form of quasi-steady-state magnetic confinement, distinct from inertial fusion techniques pursued by devices using powerful lasers or rapid compression. Ongoing control of plasma acceleration and compression remains key for their fusion approach.
FuZE-3 results are still preliminary, and further scientific campaigns continue as the team plans for publication in academic journals. "We're really just getting started with FuZE-3," said Levitt. "It was built and commissioned just recently, we're generating lots of high-quality shots with high repeatability, and we have plenty of headroom to continue making rapid progress in fusion performance. We'll be integrating lessons from FuZE-3 into our next generation systems as we continue advancing toward commercial fusion."
Zap Energy expects to launch another next generation FuZE device this winter alongside power plant engineering and the Century demonstration platform.
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