In this study we examined performance characteristics of an ultrafine water condensation particle counter(UWCPC,TSI3786).The detection efficiency was investigated using different temperature differences between saturator and growth tube.The cut-sizes D90,D50,D10,and DO were determined by fitting a two-free-parameter equation to the experimental data.The determined cut-sizes were comparable(±8)with other two widely used fitting equations.The cut-sizes were studied changing the growth tube temperature from 65 to 78°C and varying the saturator temperature from 8 to 20°C.For silver particles the smallest detected cut-size D50 was 2.9 nm,and the largest one-4.5 nm,and in default operation conditions it was 3.9 nm.Additionally,the effect of particle chemical composition on the detection efficiency was studied.The cut-sizes D50 were 2 2.9,2.3,and 1.8 nm for silver,ammonium sulfate,and sodium chloride particles,respectively.A concentration calibration was performed with high particle number concentrations.Within ±10 accuracy the highest reliable measured number concentration was 100000 cm~(-3).The determined detection efficiency of the UWCPC was compared with other commercial CPCs(TSI3785,TSI3776,TSI3772,TSI3025,TSI3010,TSI3007)using default operation regimes of the instruments.The results show that the tested UWCPC has a larger cut-size for silver particles than do butanol-based ultrafine CPCs(TSI3776,TSI3025),but smaller cut-size than other tested TSI CPCs.In default operation regime,the tested TSI3776 had the lowest detection limit(D50=3.2 nm)of the silver particles,and the corresponding size of TSI3025 was 3.6 nm.
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