Characterization of a new fast mixing type CPC and its application for atmospheric particle measurements

Abstract

Abstract. A new fast mixing-type CPC (FCPC) has been built based on the setup described by Wang et al. (2002). The functionality and stable operation of the FCPC was demonstrated in the laboratory as well as under atmospheric conditions. The counting efficiency was measured while the temperature difference between FCPC saturator and condenser has been set to 25, 27, and 29 K subsequently resulting in a lower detection limit between 6.5 and 8.7 nm. Above 25 nm the FCPC reached 96–97% counting efficiency compared to an electrometer used as reference instrument. The FCPC demonstrated its ability to perform continuous measurements over a few hours in the laboratory considering the total particle counting. The instrument will be implemented into the airborne measurement platform ACTOS to perform measurements in the atmospheric boundary layer. Thus, stable operation over 2 h is required and has been demonstrated in the laboratory. The response time of the new FCPC has been estimated in two ways using a time series with highly fluctuating particle number concentrations. The analysis of a sharp ramp due a concentration change results in a response time of 16 ms while a spectral analysis of this time series demonstrates that for frequencies up to 20 Hz coherent structures can be resolved.