Transport of Charged Particles in Gas Streams

Abstract

This paper presents a brief description of electrodynamic screens and their applications for: (1) minimizing deposition of charged particles inside sampling tubes and (2) transporting charged particles away from nonconducting substrates for shielding and removal of contaminants. Ring electrodes attached to the inner wall of a sampling tube were used to produce a radial confinement force on the charged particles when an ac field was applied. Effects of varying the applied voltage and the frequency of the ac field are discussed. The higher the voltage, the stronger the confinement force on the charged particles, but the upper limit of the voltage is set by the breakdown of the dielectric medium between the rings. The distribution of the electrical field was calculated using a single-phase electrodynamic field, and the motion of particles inside the tube was computed using a theoretical model. Experiments were performed to design an optimal configuration of the electrodynamic screen. A computer model of the electrodynamic sampling tube for several ring-type electrodes with different wire and ring diameters, and for different spacings between rings, has been developed. Experimental data are compared with the values predicted from the model. Applications of the electrodynamic screen for sampling and measuring charge-to-mass ratio distributions of particles are discussed.