Revisiting the liquid conductor model of the linear pinch: an experimental study on the pinch instability

The linear pinch (a.k.a. Z-pinch) has been of interest as a plasma compression method to achieve fusion since the mid-20th century. This linear configuration, however, has been shown through theory and experiments to be unstable with respect to both axisymmetric and azimuthal modes of instability. Although much work has focused on these instabilities, particularly for dense plasmas, few experimental studies exist that provide experimental validation of theoretical models of the instability. The present study revisits an experimental method developed in the late 1950s in which a conducting liquid jet is subjected to an electric discharge as an analog model of the plasma instabilities of a Z-pinch. An experiment has been developed that produces a liquid metal (Bi₅₈Sn₄₂) jet and conducts current along its length in a configuration analogous to a typical Z-pinch. Analysis of the high-speed imagery of the instabilities allows us to observe the instability qualitatively and quantify its growth rates for a range of electric currents and liquid jet configurations. The experimental results are compared to different theoretical approaches used to predict growth rates, giving insight into the important physical mechanisms driving the instability.