Impulse-driven transport of liquid metal from z-pinch electrodes and implications for fusion fuel contamination

TL;DR

This study investigates how magnetic forces in z-pinch devices cause liquid metal jets and droplets, assessing the risk of core contamination in fusion reactors using various liquid metal materials.

Contribution

It provides detailed experimental observations of liquid metal ejection dynamics under magnetic pressures relevant to z-pinch fusion devices.

Findings

Liquid metal jets reach velocities up to 5.3 m/s.

Droplet ejection velocities range from -3.1 to +18.9 m/s.

Implications for core contamination depend on droplet behavior and material properties.

Abstract

The Liquid Electrode eXperiment is a surrogate environment to study the dynamic behavior of liquid metal plasma facing components relevant to a z-pinch device. Current pulses with amplitudes between 50 and 200 kA produce magnetic fields up to 30 T at the surface of a wire 1.5 to 2.5 mm in radius, mounted with one end submerged in a pool of liquid metal. The resulting forces generate a fast-moving annular jet surrounding the wire, preceded in some cases by small ejected droplets of varying sizes. High-speed videography records the motion of the liquid metal free surface upon exposure to magnetic pressures between 0.5 and 10 MPa. The vertical velocity of the resulting jets ranged from 0.6 to 5.3 m/s with consistent radial expansion. The velocities of the ejecta ranged from -3.1 to +18.9 m/s in the vertical direction and from -14.3 to +6.3 m/s in the radial direction. We investigate the likelihood and severity of z-pinch core contamination for repetitively-pulsed plasmas in the context of the observed droplets for liquid metal plasma facing component candidate materials: lithium, gallium, silver, tin, lead, FLiBe, and FLiNaK.