Stabilization of laser-sustained plasma light sources via near-anode plasma confinement in the gravitational field

Laser-sustained plasma (LSP) offers continuous radiation with high brightness and broad spectral coverage, making it attractive for advanced optical detection. However, the vortices formed around the LSP plume tend to cause periodic energy exchange between the plasma and the surrounding filling gas. This periodic behavior can lead to fluctuations in the radiation flux in LSP light source applications. This paper reveals the mechanism by which the instability of LSP light sources is suppressed under a gravity direction setting through a combination of experimental observations, phase space dynamics analysis and numerical simulations. Specifically, shadowgraphy was employed to visualize the plume oscillation state at different anode-plasma distances along the gravitational direction. It was found that the oscillation frequency gradually decreases as the plasma approaches the anode. The oscillation disappeared when the continuous decrease in distance fell below a certain threshold. Subsequently, the phase space reconstruction of the LSP radiation intensity time series was performed, revealing phase space reconstruction curves for different plume states. The computational fluid dynamics model revealed the distributions of temperature, density, and velocity in oscillatory, critical, and steady states. Simulation calculations showed that under the guiding and stabilizing effect of the anode in proximity to the plasma, the periodic oscillation of the heated ascending gas flow is effectively suppressed by reducing its velocity, thereby eliminating the instability of the LSP light sources. This work not only advances understanding of the internal fluid dynamics of LSP light sources but also provides a reference for the performance optimization of high-stability light sources in optical detection systems.