Optimisation of the operation regimes for the water-based condensation particle counter
Keywords: detection efficiency, condensation particle counter, ultrafine particles
AbstractA water-based condensation particle counter (CPC) TSI 3785 is a new step for the ultrafine particle measurement technique. A new instrument was examined in this study. Detection efficiency was investigated experimentally using different temperatures of the saturator and of the growth tube. The experiments showed that detection efficiency can be improved by increasing the temperature of the growth tube and decreasing the saturator temperature. Fitting a two-free parameter equation to the experimental data, the cut-sizes D50% were determined. The determined cut-sizes were comparable with the other three widely used fitting equations. The cut-sizes were studied by changing the growth tube temperature from 40 to 65 °C and varying the saturator temperature from 10 to 30 °C. For the purpose of the study, the instrument operation regime (saturator and growth tube temperatures) can be optimised by selecting the needed cut-size. The cut-sizes can be changed in a wide range. The smallest detected cut-size D50% was 4.2 nm, and the largest 14.6 nm. In the default operation regime, the instrument cut-size was 5.9 nm. The detection efficiency of the studied TSI CPC 3785 was compared with the ultrafine TSI CPC 3786. The results showed that the studied CPC can be optimised to the regime having a smaller cut-size than the cut-size of the ultrafine CPC in the default regime. Thus, the tested TSI CPC 3785 had the lowest detection limit (D50%) of 4.2 nm, and the TSI CPC 3786 had 4.6 nm for the silver particles.