PARTICLE TRAJECTORY EFFECTS IN-PHASE DOPPLER SYSTEMS - COMPUTATIONS AND EXPERIMENTS

The effects of the particle trajectories on phase Doppler measurements were explored numerically using generalized Lorenz-Mie theory. Comput ations were performed for a commercial phase Doppler system and variou s schemes for elimination of the trajectory effects were examined. It is shown that these effects cannot be completely suppressed if the rat io of the two measured phase shifts from a single receiving unit is us ed to validate the measurements. On the other hand, the errors due to particle trajectories can be eliminated satisfactorily by employing an additional receiving unit, which allows one to detect the asymmetry o f the scattered light pattern due to displacement of the particle traj ectory from the centre of the measuring volume. A preliminary experime ntal evaluation of this method is presented and discussed.