Observation and analysis of thermonuclear neutron production in a sheared-flow-stabilized Z-pinch

Sustained neutron production has been demonstrated on the Fusion Z-pinch Experiment (FuZE), a sheared-flow-stabilized Z-pinch device. Measurements indicate that neutron production is primarily the result of thermonuclear processes. FuZE produces 0.3 cm radius by 50 cm long Z-pinches using D2/H2 or D2/He fill gas mixtures, with up to 20% D2. The plasma columns are magnetically compressed by a 200 kA plasma current, resulting in 1 - 2 keV ion temperatures and >10¹⁷ cm^-3 densities, during a 20 μs quiescent period when magnetic fluctuations are diminished. The Z-pinch plasmas are stabilized by an embedded radially-sheared axial flow, a method proposed in Shumlak and Hartman PRL 1995 and demonstrated experimentally in other sheared flow stabilized Z-pinch devices, ZaP and ZaP-HD. Within the quiescent period, sustained neutron production is observed for a duration of approximately 5 μs, hundreds of times longer than the 20 ns instability growth time for a static Z-pinch at FuZE plasma parameters. The measured neutron yield is >10⁵ neutrons/pulse, agreeing with predictions from D-D fusion reaction rates. The number of observed counts scales with the square of the deuterium concentration, suggesting a thermonuclear fusion process.