Investigating Laser Beam Propagation in Strongly Non-Uniform High Energy Density Plasmas: An Experimental and Numerical Study*

In highly inhomogeneous plasmas, strong density gradients can significantly influence the properties of propagating laser light. This presents challenges for electromagnetic (EM) communication during the re-entry of hypersonic vehicles and complicates the use of optical lasers for plasma imaging diagnostics when applied to High Energy Density (HED) Plasmas.

This study explores the impact of plasma turbulence on laser beams using the recently developed X-ray driven plasma platform at the MAGPIE pulsed-power facility [1]. A quasi-one-dimensional turbulent layer is generated through the interaction of counter-streaming spatially modulated plasma flows produced by the ablation of highly transparent meshes driven by the radiation of a Z-pinch wire array. The perturbed plasma region is probed using a combination of laser-based shadowgraphy, interferometry and a newly developed imaging refractometer [2-3]. Moreover, a synthetic diagnostic tool based on a 3-Dimensional Gaussian field with an arbitrary power spectrum has been developed to support the interpretation of the experimental data, helping to evaluate the significance of electron density perturbations on the overall laser beam profile.

Future research will focus on studying the influence of magnetic fields on the turbulent layer and the impact of density perturbations on beam polarisation for the application of Faraday rotation imaging diagnostics to HED turbulent plasmas.

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

[2] J. D. Hare, G. C. Burdiak, S. Merlini, et. al., “An imaging refractometer for density fluctuation measurements in high energy density plasmas”, AIP Review of Scientific Instruments, 2021

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