Particle Charging and Transmission Efficiencies of Aerosol Charge Neutralizes

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Abstract
Diffusion losses and charging efficiency were measured for three types of charge neutralizers commonly used in aerosol research: two with 85Kr and one with 210Po as radiation sources. The diffusion losses were characterized at flows of 0.5 -6 1 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 1 min−1, except at concentrations ≤ 103 cm−3. The 210Po charger produced the theoretically expected fraction of singly charged particles within the uncertainty of the experiment.