Analysis of the limits of applicability of a photomultiplier as part of a laser Doppler anemometer

We study the possibility of application of the methods of laser Doppler anemometry for the noncontact measurement of the velocity of moving media in various phase states. We mention the specific features of the conditions of application of laser Doppler anemometers and, in particular the fact that, in numerous cases there exist restrictions on the use of photomultipliers. With an aim to find an alternative to the classical photomultiplier of a laser Doppler anemometer, we study three types of photomultipliers: classical electric vacuum photomultipliers, silicon avalanche multipixel photomultipliers, and photomultipliers with microchannel plate. We performed physical experiments aimed at measuring the velocity of aero- and hydrodynamic flows by laser Doppler anemometers with photomultipliers of the indicated three types. Actually, we measured the velocities of a rotating glass disk, of an aerodynamic flow in a channel with rectangular cross section, of an aerosol flow, and of a flooded hydrodynamic jet. The accumulated experimental data are analyzed according to the criteria of evaluation of the quality (efficiency) of operation and the ranges of applicability of the specified photomultipliers. By analyzing the physical properties of the investigated photomultipliers, we clarify their efficiency characteristics in different experiments. The ranges of efficient applications of these photomultipliers are determined for a broad class of physical experiments. The obtained results are of high importance for the researchers involved in the study of aero- and hydrodynamic flows in which it is necessary to have accurate and reliable result of measurements of the flow velocity. The optimal choice of a photomultiplier for the laser anemometers makes it possible to increase the accuracy, simplify the procedure of collecting the experimental data, and to reduce the cost of the final equipment.