Particle Charging and Transmission Efficiencies of Aerosol Charge Neutralizers

Diffusion losses and charging efficiency were measured for three types of charge neutralizers commonly used in aerosol research: two with 85Kr and one with 21OpO as radiation sources. The diffusion losses were characterized at flows of 0.5 -{i I min - 1 typically used in atmospheric aerosol physics measurements. All of the neutralizers tested exhibited high transmission efficiencies, with losses up to 25% at the smallest tested size of 3 nm, varying with size and flow in general agreement with diffusion loss theory. Charging efficiency was measured for a singly charged, monodisperse aerosol at the same flows and at concentrations of 103-104 particles cm - 3. Neither of the 85Kr chargers brought the charge distribution close to equilibrium at 2 I min -I, except at concentrations ~ 103 cm - 3. The 210pO charger produced the theoretically expected fraction of singly charged particles within the uncertainty of the experiment.