Formation of Transient Plasmas with Beta and Hall Parameters Simultaneously Greater than Unity*

We report results from the head-on merging of two coaxial-gun-formed pre-magnetized plasma jets. This is an exploratory first step toward forming thermal-pressure-dominated plasmas with tangled magnetic fields [1], which may be of interest as a plasma target for magneto-inertial fusion [2] or as a novel platform for laboratory astrophysics studies. In these experiments, we vary the gun current and magnetic flux linking the electrodes to study those parameters' effects on the resulting plasma collision. A Langmuir probe, magnetic probe array, and visible fast-framing camera are used to diagnose the plasma conditions at the plasma-merging region to experimentally infer both the $\beta$ and Hall parameters (assuming $T_e=T_i$). A second experimental campaign is planned to include measurement of $T_i$. The objective is to achieve a transient plasma state where $\beta$ and the Hall parameter $\omega \tau$ (for both electrons and ions) are simultaneously greater than unity. Using the FLASH code, we study the jet-merging process and the compression of the transient plasma state (at higher densities) by a plasma liner. [1] D. D. Ryutov, Fus. Sci. Tech. 56, 1489 (2009). [2] S. C. Hsu and S. J. Langendorf, J. Fusion Energy 38, 182 (2019). LA-UR-19-26020.