Design and operation of a pressure-controlled inlet for airborne sampling with an aerodynamic aerosol lens

Two pressure-controlled inlets (PCI) have been designed and integrated into the Aerodyne Aerosol Mass Spectrometer (AMS) inlet system containing an aerodynamic aerosol lens system for use in airborne measurements. Laboratory experiments show that size calibration and mass flow rate into the AMS are not affected by changes in upstream pressure (P-0) of the PCI as long as the pressure within the PCI chamber (P-PCI) is controlled to values lower than P-0. Numerous experiments were conducted at different P-PCI, P-0, and AMS lens pressures (P-Lens) to determine particle transmission efficiency into the AMS. Based on the results, optimum operating conditions were selected which allow for constant pressure sampling with close to 100% transmission efficiency of particles in the size range of similar to 100-700 nm vacuum aerodynamic diameter (d(va)) at altitudes up to similar to 6.5 km. Data from an airborne field study are presented for illustration.