Particle Charging in DC Corona Fields

After a brief review of the currently accepted theory of particle charging in corona fields in air by both ionic bombardment and diffusion in the dark space surrounding the dc corona glow, the paper presents some of the recently published findings on particle charging within the corona glow. The study was made possible by the discovery that additions of CO2 to air in a 5 to 20% range will increase a cylindrical positive corona glow to a size which is sufficiently large to allow particles to be dropped on to various trajectories parallel to the corona wire and their charge to be measured. The influence of the shape of the particles when exposed to corona charging is also discussed.