Detection of Fine Particles in Liquids by Laser Breakdown Method

Basic characteristics of a particle detection method using laser breakdown were studied for a system of polystyrene standard particles dispersed in ultrapure water. The method was able to detect 0.02 µm particles. The detection sensitivity decreased with the particle size due to size dependence of the laser breakdown threshold. The plasma emission delay time from the laser pulse decreased with particle size (9.8±0.8 ns for 0.04 µm, 5.7±0.8 ns for 3.0 µm). The above results suggested the possibility of concentration and size measurement of fine particles in liquids by the proposed method.