Numerical Simulations of Collisionless Shock Formation in Merging Plasma Jet Experiments

In upcoming experiments at the Plasma Liner Experiment (PLX) facility at Los Alamos National Laboratory, two high Mach number plasma jets, composed of gases such as H and Ar, will be collided. We describe numerical simulations using particle-in-cell (PIC) and hybrid-PIC methods using the code Lsp. Using expected experimental plasma conditions ($n \sim 10^{14}-10^{17}$ cm$^{-3}$), large scale transport simulations demonstrate that the jets are essentially collisionless at the merge point. In smaller-scale 1D and 2D simulations we show that collisionless shocks are generated by the merging jets when immersed in applied magnetic fields ($B \sim 0.1-1$ T). Unmagnetized collisionless shocks are not found in simulations at the expected jet velocities ($\sim 10-100$ km/s). Considerably higher velocities are required to see this effect. The orientation of the magnetic fields and the axial and transverse gradients of the jets are shown to have a strong effect on the nature of the interaction.