Vortex dynamics governing oscillations in a high-pressure xenon laser-sustained plasma

Abstract

This study demonstrates that the intrinsic oscillation of the laser-sustained plasma (LSP) flow field originates from the periodic and coherent evolution of vortex rings (VRs) attached to the outer boundary of the main thermal plume. The complete formation and shedding process of vortical structures was clearly captured through high-speed schlieren imaging. In parallel, a multiphysics model coupling laser transport, heat transfer, and fluid dynamics successfully reproduces the periodic oscillation of the LSP plume. Dynamic mode decomposition and circulation analysis quantitatively confirm these vortical structures take the form of VRs and play the dominant role in the formation evolution of the oscillatory convective flow in the LSP source. Further hydrodynamic analysis reveals that the VR formation and plume oscillation are driven by baroclinic torque and buoyancy-induced vorticity, together with velocity shear that rolls up vorticity near the plume base, from where the oscillatory flow originates. This work establishes an integrated framework combining experiment and simulation to offer new physical insights into the instability mechanisms governing LSP as an advanced broadband radiation source.