Power-law scaling of plasma pressure on laser-ablated tin microdroplets

TL;DR

This study investigates how plasma pressure scales with laser energy in ablated tin microdroplets, revealing a power-law relationship supported by experiments and simulations, and explores the theoretical basis of this scaling.

Contribution

It provides the first detailed measurement of plasma propulsion velocity over a wide laser energy range and compares it with radiation-hydrodynamic simulations, highlighting the role of radiative losses.

Findings

Propulsion velocity follows a power-law dependence on laser energy.

Simulations agree with experimental data above a threshold energy.

Radiative losses significantly influence the pressure scaling.

Abstract

The measurement of the propulsion of metallic microdroplets exposed to nanosecond laser pulses provides an elegant method for probing the ablation pressure in dense laser-produced plasma. We present the measurements of the propulsion velocity over three decades in the driving Nd:YAG laser pulse energy, and observe a near-perfect power law dependence. Simulations performed with the RALEF-2D radiation-hydrodynamic code are shown to be in good agreement with the power law above a specific threshold energy. The simulations highlight the importance of radiative losses which significantly modify the power of the pressure scaling. Having found a good agreement between the experiment and the simulations, we investigate the analytic origins of the obtained power law and conclude that none of the available analytic theories is directly applicable for explaining our power exponent.