Design of a compact coaxial magnetized plasma gun for magnetic bubble expansion experiments

Summary form only given. We will discuss the design of a compact coaxial magnetized plasma gun and its associated hardware systems in detail. The plasma gun is used for experimental studies of magnetic bubble expansion into a lower pressure background plasma, as a model for extragalactic radio lobes. The gun is powered by a 120 muF, 10 kV ignitron-switched capacitor bank. High-pressure gas is puffed into an annular gap between inner and outer coaxial electrodes. The applied high voltage ionizes the gas and creates a radial current sheet. The ~100 kA discharge current generates toroidal flux; poloidal flux is provided by using an external bias magnet. The axial JtimesB force ejects plasma out of the gun. If the JtimesB force exceeds the magnetic tension of the poloidal flux by a sufficient amount then a detached magnetized plasma will be formed. Using spatially resolved magnetic probe array measurements and high speed camera, we are studying the evolution of this plasma "bubble" as it interacts with a pre-existing lower pressure background plasma which is provided by helicon source (HelCat). The poster will discuss the plasma bubble formation system including the power system, gas valve control system, bias flux power system, and the magnetic probe diagnostic in detail. Experimental data will also be provided.