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 Kr-85 and one with Po-210 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 how in general agreement with diffusion loss theory. Charging efficiency was measured for a singly charged, monodisperse aerosol at the same hows and at concentrations of 10(3)-10(4) particles cm(-3). Neither of the Kr-85 chargers brought the charge distribution close to equilibrium at 2 l min(-1), except at concentrations less than or equal to 10(3) cm(-3). The Po-210 charger produced the theoretically expected fraction of singly charged particles within the uncertainty of the experiment. (C) 1997 American Association for Aerosol Research.