A compact Aerosol Mobility Imager (AMI) for instantaneous particle size distribution measurements, part II: Experimental demonstration and characterization

A compact Aerosol Mobility Imager (AMI) has been developed to provide rapid measurements of aerosol size distribution. The design and model evaluation of AMI are presented in the preceding paper. To experimentally demonstrate the feasibility of the new AMI concept, we characterized the performance of a prototype AMI, which consists of the mobility separator from an existing Fast Integrated Mobility Spectrometer (FIMS), a newly designed extraction growth cell (EGC), and an optical detector. Monodisperse aerosols with diameters ranging from 15 to 200 nm were generated using a Differential Mobility Analyzer (DMA) and measured by the prototype AMI and a condensation particle counter (CPC) in parallel. The mean diameter measured by the prototype AMI agrees well with the DMA centroid diameter, with a maximum deviation of <3%. Comparison of the particle concentrations measured by the prototype AMI and CPC indicates a detection efficiency of nearly 100% for particles with diameters of 15 nm or larger. The measured responses of the prototype AMI to DMA-classified aerosols are generally in agreement with the calculations, indicating that the AMI transfer function and mobility resolution can be well predicted based on simulated particle trajectories. The experimental results demonstrate that AMI is capable of rapid and accurate aerosol size distribution measurements while maintaining a sufficient mobility resolution for measurements of ambient aerosols.