Direct Visualization of Laser-Driven Focusing Shock Waves

TL;DR

This paper presents a novel method for real-time visualization and measurement of laser-driven focusing shock waves, demonstrating significant pressure increases and supersonic speeds at shock convergence in liquids.

Contribution

The study introduces a direct visualization technique for laser-driven focusing shock waves, combining experimental and numerical methods to analyze shock dynamics and pressure amplification.

Findings

Shock waves reach Mach 6 at convergence in water.

Pressure at focus exceeds 30 GPa.

Method enables real-time observation of shock focusing phenomena.

Abstract

Cylindrically or spherically focusing shock waves have been of keen interest for the past several decades. In addition to fundamental study of materials under extreme conditions, cavitation, and sonoluminescence, focusing shock waves enable myriad applications including hypervelocity launchers, synthesis of new materials, production of high-temperature and high-density plasma fields, and a variety of medical therapies. Applications in controlled thermonuclear fusion and in the study of the conditions reached in laser fusion are also of current interest. Here we report on a method for direct real-time visualization and measurement of laser-driven shock generation, propagation, and 2D focusing in a sample. The 2D focusing of the shock front is the consequence of spatial shaping of the laser shock generation pulse into a ring pattern. A substantial increase of the pressure at the convergence of the acoustic shock front is observed experimentally and simulated numerically. Single-shot acquisitions using a streak camera reveal that at the convergence of the shock wave in liquid water the supersonic speed reaches Mach 6, corresponding to the multiple gigapascal pressure range 30 GPa.