Particle activation and droplet growth processes in condensation nucleus counter—II. Experimental study

Abstract

An experimental study has been made of the performance of the continuous flow condensation nuclei counter with air, argon and helium serving as the carrier gas. The finite counting efficiency of the instrument has been found to be due to the non-uniform supersaturation in the condenser tube, rather than particle loss by diffusion. The final droplet size at the condenser outlet has been found to be a function of the initial size of the condensation nuclei. The final droplet size is significantly reduced when the initial nuclei size is smaller than 10 nm. For air as a carrier gas, the final droplet size ranges from approximately 10 to 13 μm. For argon, the final droplet size is about 5% smaller than that in air. In the case of helium, the final droplet size is about 15 μm and this does not depend strongly on the initial nuclei size. The activation efficiency of the condensation nucleus counter for argon is similar to that for air. However, for helium the activation efficiency is higher. The final droplet size and the activation efficiencies of the condensation nucleus counter predicted by theory are in good agreement with the experimental results in all cases.