A study of the droplet nucleation in dependence on the gas mixture origin

This paper presents the development and validation of the Fine Aerosol Generation Unit (FAGU), a novel instrument designed to support experimental research on nucleation phenomena, particularly at the interface between heterogeneous and homogeneous nucleation. The FAGU system enables precise and independent control of key aerosol parameters, including particle number concentration, relative humidity, and temperature. A core requirement in its design was the ability to generate aerosols composed of nanometer-sized particles of a single substance, with tunable particle density—an essential capability for reproducible and systematic nucleation studies. The aerosols produced by FAGU are intended for use in controlled experiments investigating unary, binary, and heterogeneous nucleation processes, such as those conducted in expansion chambers. To verify the unit’s performance, a series of experiments were conducted using different aerosol and humidity sources, including a single-phase nozzle, a nebulizer, and surface evaporation techniques. These tests demonstrated the unit’s ability to decouple and regulate aerosol concentration and humidity independently, offering a high degree of flexibility for tailoring initial conditions in nucleation experiments. The results confirm that FAGU provides a robust and versatile platform for generating well-defined aerosol environments, making it a valuable tool for advancing the understanding of particle formation mechanisms in both atmospheric and laboratory settings.