A Novel Polarized Elastic Scatter Detection Method
of Aerosol Particle Velocimetry with Reduced Errors
Due to Coincidence and Phantom Particles

Abstract

This article describes a novel polarized elastic scattering method to measure flow velocities of aerosol particles. Velocities of individual aerosol particles of mixed size, and composition have been determined from time differences between scattered light pulses as they move between two parallel laser beams separated by a fixed distance, known as a time-of-flight method. By using two orthogonally polarized laser beams, the detected light pulses can be assigned to each beam by simultaneously determining their respective depolarization ratio. This implementation of time-of-flight velocimetry provides a mechanically robust distance between the two beams, which reduces error in the measurement and improves both its precision and accuracy, but more importantly, the use of the polarization features of the scattered light reduces errors due to particle coincidence and phantom particles caused by confusion of start and stop timing pulses. This approach was developed and demonstrated in an application to provide effective timing for subsequent selective actions on individual particles downstream such as: further diagnostic measurement, electrical charging and capture. These downstream actions require accurately predicted individual particle trajectories.

Copyright 2013 American Association for Aerosol Research