Burst laser ablation in distilled and heavy water

Abstract

The laser water ablation initiates several physical effects: ionization of atoms and optical breakdown of the liquid, phase explosion and cavitation, shockwave propagation, and even the potential to yield neutrons. The goal of this paper is to compare ablation plasma glow and thermal changes in distilled and heavy water under single pulses and bursts of ultrashort laser pulses. The laser ablation was performed beneath the water surface in a circular laser scanned trajectory. There were two regimes of water ablation: burst regime and single pulses ablation. The absorption processes and ablation plasma glow were evaluated with visible and infrared cameras, fast silicon detector and thermocouple. The study revealed that the heavy water ablation process is 3.5 times more intense in the burst regime with the same laser power. Unexpectedly, the plasma glow with a lower power density of laser 2.6ꞏ1013 W/cm2 was four times higher than with higher power density of 8ꞏ1013 W/cm2. In burst mode and at a higher power density, heavy water produced nearly two times higher plasma glow.