Magnetised reverse shock structures formed by colliding plasma flows

We describe experiments fielded on the MAGPIE pulsed-power generator (1.4 MA, 240 ns rise time) designed to study radiative shocks and instabilities in the laboratory, with applications to astrophysical phenomena such as accretion shocks. These experiments use the x-ray pulse emitted from a wire array z-pinch to drive plasma ablation from two parallel targets. This results in two counter-propagating, supersonic plasma flows which form a dense layer of shocked, stagnated plasma where they collide. The ablated plasma propagates in the ambient magnetic field supported by the current flowing through the z-pinch.

By altering the position and orientation of the targets, the magnitude and direction of the magnetic field relative to plasma flow can be changed to independently investigate its contribution to the shape and stability of the shock structures formed. Effects such as radiative cooling are explored by changing target material.

Previous work characterising ablation from a single planar target [1] has shown that the plasma flow is uniform. Changing the shape of the target surface allows us to impose the same shape upon the resulting plasma flow – for example a sinusoidal perturbation on the target surface results in a corresponding perturbation in the plasma. This gives us the potential to seed density perturbations into the stagnation layer and then explore whether these perturbations are suppressed or become unstable.

[1] Halliday, JWD et al. 2022, 'Investigating radiatively driven, magnetized plasmas with a university scale pulsed-power generator', Physics of Plasmas, 29. DOI: 10.1063/5.0084550