Structure and stability of shock-bounded layers in counter-streaming supersonic plasma flow experiments*

Shock-bounded layers formed at the collision of supersonic plasma flows produce mixing sites which can be strongly influenced by radiative cooling effects and magnetic field, leading to instabilities and turbulence [1-3]. Our experimental study the structure of shock-bounded layers at the MAGPIE pulsed power facility, employing supersonic plasma flows from X-ray ablated solid targets [4].

Two parallel planar silicon targets exposed to radiation from a wire array Z-pinch results in counter-propagating, supersonic plasma flows which uniformly propagate along an ambient magnetic field, forming a shocked dense layer of stagnated plasma at the collision plane. Laser probing and optical self-emission images were used to determine properties of the shocked layer, revealing overall consistency with a 1-D shock model for a value of γ ≤ 1.2. In the case of magnetic field perpendicular to the flow propagation direction, a shocked layer does not form; instead, enhancement of density is observed at the edges of the two plasma plumes, resembling magnetohydrodynamic shocks.

Finally, to explore the stability of the shocked-bounded layers, these results are compared with similar experiments performed using 3D printed meshes allowing the production of spatially modulated colliding plasma flows. This comparison aims to explore unstable regimes of shocked-bounded layers under different magnetic field configurations and radiative cooling effects.

[1] R. N. Markwick, et al., “Cooling and instabilities in colliding flows”, MNRAS, 2021

[2] V. I. Sotnikov, et. al., “Collision of expanding plasma clouds: Mixing, flow morphology, and instabilities”, AIP Physics of Plasma, 2020

[3] S. Merlini, et. al., “Radiative cooling effects on reverse shocks formed by magnetized supersonic plasma flows”, AIP Physics of Plasma, 2023

[4] J. Halliday, et. al., “Investigating radiatively driven, magnetized plasmas with a university scale pulsed-power generator”, AIP Physics of Plasmas, 2022