Localized Measurement of a Sub-Nanosecond Shockwave Pressure Rise Time.

Jaka Petelin,Darja Horvat,Ziga Lokar,Rok Petkovsek

doi:10.1109/tuffc.2021.3115629

Abstract

In a growing number of applications, fast and localized pressure measurement in aqueous media is desired. To perform such measurements, a custom-made single-mode fiber-optic probe hydrophone (FOPH) was designed and used to measure the pressure pulse generated by laser-induced breakdown (LIB) in water. The sensor enabled sub-nanosecond pressure rise time measurement. Both the rise time and the duration of the shockwave were found to be shorter in the direction perpendicular to the breakdown generating laser beam, compared to the shockwave observed in the parallel direction. Simultaneous high-frame-rate imaging was used to qualitatively validate the novel hydrophone data and to observe the shockwave evolution. The measurements were performed also on pressure pulses emitted during the generation of miniature ( [Formula: see text] diameter) laser-induced bubbles at very small distances (down to [Formula: see text]), further demonstrating the capabilities of the small-size sensor and the ability to measure locally. The results improve understanding of LIB shockwave characteristics dependence on laser pulse energy and duration.

Highlights

VERY short and very high pressure transients in fluids, both compressive and tensile, are produced in a growing number of industrial and medical applications, for example in laser induced breakdown spectroscopy [1], shock cleaning [2], sonoporation [3], high intensity focused ultrasound removal of tumors [4], shock wave lithotripsy [5], [6] and laser vitreolysis [7]
In the case considered here, i. e. measurement of shockwave emitted during laser induced breakdown in water, the fiber optic probe hydrophone comes with a key advantage – the ability to measure and withstand very quick changes of very high positive or negative pressures that are generated during breakdown [19]
First we present single-mode fiber optic probe hydrophone measurements of shockwaves emitted by a dielectric breakdown generated in water by laser pulses having a few ns duration and a few millijoules of energy

Summary

INTRODUCTION

VERY short and very high pressure transients in fluids, both compressive and tensile, are produced in a growing number of industrial and medical applications, for example in laser induced breakdown spectroscopy [1], shock cleaning [2], sonoporation [3], high intensity focused ultrasound removal of tumors [4], shock wave lithotripsy [5], [6] and laser vitreolysis [7]. E. measurement of shockwave emitted during laser induced breakdown in water, the fiber optic probe hydrophone comes with a key advantage – the ability to measure and withstand very quick changes of very high positive or negative pressures that are generated during breakdown [19]. Single mode fibers are less sensitive than their multimode counterparts due to the lower laser light power and have stronger oscillations in frequency response, especially at lower (

PRINCIPLE OF OPERATION

EXPERIMENTAL SETUP AND RESULTS

Findings

CONCLUSION