Counting efficiency measurements for a new condensation particle counter

The counting efficiency of a new condensation particle counter (Palas UF-CPC) was tested and the lower detection limit regarding the diameter of graphite particles was determined. The influence of the supersaturation of the working fluid butanol was investigated which was varied by adjusting the condenser temperature at a fixed saturator temperature. As expected, the lower detection limit decreased strongly with decreasing saturator temperature. However, a limitation was reached at a particle size of 5 nm which can be explained by a limitation in the growth kinetics for droplets growing on small condensation kernels and an insufficient residence time in the condenser for these particles to grow beyond the detection limit of the optical counter.