Experimental investigation of two staged coaxial plasma gun acceleration dynamics.

In this experiment, we investigate the effect of adding a second acceleration stage on the performance of a coaxial plasma gun (CPG). CPGs are of interest in applications such as magneto-inertial fusion, spheromak formation, and space propulsion, due to the generation of high velocity plasma jet using the Lorentz force (J x B). While increasing the energy of the pulse system to power the CPG and varying electrode geometry can enhance the jet acceleration, there are inherent limitations such as restrike and blowby instabilities. Parallel plate plasma guns tested with multiple stages have shown higher jet acceleration. However, a staged geometry is more difficult in a CPG due to the central electrode.

We have developed a two stage CPG operating at 40 J, with the second stage driven by its own pulsed power system. Velocity measurements of the plasma jet are performed using fast photodiodes and high-speed imaging. Jet density is characterized using triple Langmuir probes, and the magnetic field is mapped with a B-dot probe. This poster investigates the impact of RLC circuit characteristics, inter stage timing delays, and spatial separation between the first and second stages on the behavior of the plasma jet. We analyze how these factors influence jet acceleration, plasma density, and magnetic field evolution providing insights into optimizing multi-stage CPG performance.