Unipolar charging of nanometer aerosol particles in a corona ionizer

Abstract

A corona ionizer for unipolar charging of nanometer-sized aerosol particles has been constructed and evaluated. Charging efficiency and particle deposition loss (electrostatic and diffusional) have been measured for particle mobility-equivalent diameters below $\text{10}\text{nm}$, at different aerosol flow rates, different corona polarity and voltages, and also at two different positions of the corona electrode tip. Even though electrostatic deposition of charged particles within the ionizer was relatively large at high corona voltages, charging efficiencies as high as about 30% for $\text{10}\text{nm}$ particles could be achieved for positive and negative corona. This figure is almost one order of magnitude higher than that attainable with radioactive bipolar chargers, and similar to that recently reported for other types of unipolar chargers developed by several researchers.