Advantages of UV Lasers in Laser and Phase Doppler Anemometers for Submicrometer Particles

Abstract

For laser Doppler (LDA) and phase Doppler anemometry (PDA) measurements with submicrometer particles ultraviolet lasers with wavelengths between 240nm and 280nm are compared with lasers emitting visible radiation. UV lasers offer a main advantage in the higher signal-to-noise ratio (SNR) obtainable, since the scattered power is significantly increased at shorter wavelengths. Furthermore, for PDA the capability of making size class distinctions in the submicrometer size range is improved, as shorter wavelengths lead to steeper phase difference-to-diameter relationships. In particular, the use of ultraviolet (UV) laser light enables the size class distinction of 0.2µm from even smaller particles, that is not possible when using visible radiation. The feasibility of performing laser Doppler and phase Doppler anemometry measurements with ultraviolet laser light is confirmed by experiments.