Evaluation of homogeneous droplet formation inside UCPC (TSI model 3025)

The droplet formation characteristics inside an Ultrafine Condensation Particle Counter (UCPC, TSI model 3025) were tested changing working temperatures of the counter as well as flow rates and carrier gases. The onset of homogeneous nucleation was determined as a function of the temperature of the saturator and condenser. Preliminary tests were carried out using the UCPC for measurements of homogeneous nucleation rates of n-butanol vapour. The observed nucleation rates were compared with those predicted by classical nucleation theory and by self-consistent correction to the classical theory. Homogeneous droplet formation at nearly standard operation conditions of the UCPC were observed for carrier gases such as air and nitrogen. Moreover, in helium particle formation was observed already at standard operation conditions of the UCPC.