Focusing of Aerosols into a Particle Beam at Pressures from 10 to 150 Torr

Abstract

The study of aerosols including chemical an alysis h as been substantially advanced after the development of aerodynamic focusing lenses. Test results of 2 such lenses are presented; 1 operating at pressures between 15 and 80 Torr an d the other at higher pressures between 30 and 175 Torr. The lenses consist of 7 single ori® ces separated by spacers and contained in a tube of abou t 10 cm in () length. Ori® ce diameters ran ge from 1.40 to .25 mm, while the exit holes nozzles are smaller. Lamin ar gas¯ow within a lens produces a n arrow particle beam wh ich is directed into a vacuum chamber for an alysis of beam width an d position, aerosol transport ef® ciency, linearity, and other parameters. The lenses were tested () both with spherical monodisperse oil particles .34± 4 m m diameter as well as () nonspherical solid NaCl particles .19± .85 m m simulating larger particles with lower density. Both lenses produce narrow aerosol beams with diameters smaller than 4 mm abou t 90 mm downstream of the nozzle. Although nonspherical particles broaden the aerosol beam by a factor of 2± 4, this fact allows a distinction between liquid and solid nonspherical aerosols. Beam ch aracteristics are well reproduced wh en lenses are dis-an d reassembled. The transmission of aerosols through each of the 2 lenses is a nearly linear function of the pressure. Transmission ef® ciencies have been measured to be above 90%.

Formation of solid particles in synoptic-scale Arctic PSCs in early winter 2002/2003

“…Two identical independent gondolas were equipped with the following instrumentation. An aerosol composition mass spectrometer (ACMS) measured the chemical composition of individual PSC particles (Schreiner et al, 1998;Schreiner et al, 1999b). A condensation nuclei (CN) counter and three optical particle counters (OPCs) measured particle size distributions .…”

Transmission Efficiency of an Aerodynamic Focusing Lens System: Comparison of Model Calculations and Laboratory Measurements for the Aerodyne Aerosol Mass Spectrometer

“…Understanding the transmission efficiency of these systems is important with respect to quantifying the overall performance of an aerosol mass spectrometer. Lens systems have been investigated via numerical calculations (Liu et al 1995a;Wang et al 2005a;2005b;Zhang et al 2002;, but few studies have focused on comparing the models to actual performance (Jayne et al 2000;Liu et al 1995b;Schreiner et al 1999;Tobias et al 2000). The work presented here compares model and measurement results and is motivated by the need to understand the efficiency of the lens system used on the Aerodyne Aerosol Mass Spectrometer (AMS) for quantifying aerosol particle measurements.…”

“…They have the capability of efficiently separating particles from the gas phase and delivering the particles in a narrow beam into high vacuum. Thus, it is natural to link these lenses to particle mass spectrometers, and a number of aerosol mass spectrometers have been developed which use aerodynamic lens systems (Gard et al 1997;Jayne et al 2000;McMurry 2000;Murphy and Thomson 1997;Schreiner et al 1999;Su et al 2004;Zelenyuk and Imre 2005;Ziemann et al 1995). Understanding the transmission efficiency of these systems is important with respect to quantifying the overall performance of an aerosol mass spectrometer.…”

Atmospheric Measurements of Sub-20 nm Diameter Particle Chemical Composition by Thermal Desorption Chemical Ionization Mass Spectrometry

“…This has been accomplished primarily by the use of aerodynamic focusing lens systems (Liu et al 1995a, b;Mallina et al 2000;Schreiner et al 1999;Zhang et al 2002), whose transmission efficiency degrades significantly for particle diameters smaller than 20 nm. Recently, new instruments have been introduced that have been designed specifically for the characterization of ultrafine aerosol.…”