Experimental Study of Magnetic Field Effects on Cylindrically Convergent Plasma Flows*

In this talk, we present initial measurements of cylindrically converging plasma flows (n_e~ 10¹⁸ cm^-3, v_r ~ 20 kms^-1) in the presence of dynamically significant magnetic fields (B ~ 1 T). To understand the effect of magnetic fields, we also show equivalent experiments in a purely hydrodynamic regime.

All experiments presented in this talk were performed on the MAGPIE pulsed power generator at Imperial College (1.4 MA peak current, 240 ns rise time). The flows were produced via plasma ablation from additively manufactured targets driven by soft X-rays produced by a Z-pinch, assuring smooth and uniform plasma¹. Diagnostics deployed during the experiments included laser interferometry, Thomson scattering, and fast-frame imaging.

The initial diameter of the converging plasma flow was ~ 10 mm, significantly larger than the resistive diffusion length that is expected to be ~ 1 mm for these plasmas. As such, these experiments can be used to study amplification of B fields via flux compression², resistive diffusion effects, and potentially modification of hydrodynamic instability growth in the presence of B fields³.

[1] J.W.D. Halliday, Phys. Plasmas 29, 042107 (2022)

[2] J.R. Davies, Phys. Plasmas 24, 062701 (2017)

[3] C. A. Walsh, HEDP 101103 (2024)