The sheared-flow Z pinch and the repetition problem

Why the library suggests it

Uri Shumlak's group at the University of Washington, with Lawrence Livermore, report a plasma going quiet for about sixteen microseconds on the FuZE device, with fusion neutrons coming out steadily for five of them at a pinch current near 200 kiloamps — roughly five thousand times as long as the column should have survived. The yield of about 125,000 neutrons a pulse rises with the square of the deuterium fraction and disappears entirely with no deuterium, which is the signature of thermal fusion rather than a stray accelerated beam (Sustained Neutron Production from a Sheared-Flow Stabilized Z Pinch, 2019). The engineering half is Zap Energy's Century: a five-container pulsed-power driver capable of half a million amps firing one shot every ten seconds downward onto a curtain of molten bismuth, with three continuous runs of 1,080 shots each at 14 kilojoules per shot and the liquid metal visibly protecting the cathode tip from erosion (Century: Zap Energy's 100-kW-Scale Repetitive Sheared-Flow-Stabilized Z-Pinch System with Liquid Metal Cooling, 2025).

The experiment or build

The scientific rung is a small sheared-flow pinch with the shear profile measured rather than assumed — the flow profile is the whole mechanism and it is the hardest thing to diagnose. The engineering rung, which is where most of the value now is, is electrode life: run a bench-scale pinch for ten thousand shots and measure the electrodes. The settling measurement is neutron yield per shot held constant across a run of thousands of shots, with electrode mass loss measured before and after. A machine whose yield decays with shot number is a machine whose electrodes are the real experiment.