Study of laser interaction in water flow confinement at high repetition rate

This paper presents a study on the confined interaction with water flow for two successive laser pulses. The dynamic of the renewal of water films after shock produced by the laser is observed using a high speed camera. Pressure produced by the two pulses is measured from rear free surface velocity measurements using a velocimeter interferometry system for any reflector. The results show a threshold delay between the two laser pulses for which laser/target coupling of the second pulse decreases. This depends on the spot diameter, the laser intensity, and flow rate. This threshold can be calculated from the maximum jet diameter and flow rate. At an incident power density of 3 GW/cm2, a spot diameter of 1 mm, and a flow rate of 10 m/s, the maximum repetition rate ensuring target/coupling of successive laser pulses can be 1 kHz. The results open perspective for laser shock peening at high repetition rates.