Soot Particle-Aerosol Mass Spectrometer SP-AMS
The second aerosol mass spectrometer used in our group is the external page Aerodyne aerosol mass spectrometer (AMS). Opposite to the ATOFMS, which gives information on the mixing state by single particle measurement, the AMS is capable of determining the particulate mass concentration of various non-refractory (NR) aerosol species. NR refers to an aerosol particle evaporation temperature of approximately 600 °C. The instrument used by our group is further equipped with a soot particle (SP) unit. This unit allows to extend the range of detectable aerosol species to refractory material by evaporating the particles at temperatures of up to 4000 °C via light absorption.
As to the standard setup of the AMS (Jayne et al., 2000; Canagaratna et al., 2007), the entire aerosol enters the instrument through a Liu-type aerodynamic lens (section particle beam generation). The cascade of narrowing apertures reduces the aerosol gas phase concentration by a factor of 107 while simultaneously focusing the aerosol particulate phase into a narrow beam. In the size range from ~60 nm to ~600 nm the lens exhibits a particle transmission of 100 %. The particle beam traverses a differentially pumped sizing chamber, which allows for the determination of the vacuum aerodynamic diameter by particle time of flight (PToF; section aerodynamic sizing). The data acquired in this mode allows for a size resolved mass analysis of the particles. At the end of this chamber, the particles hit a conical surface heated to approximately 600 °C, the so called vaporizer (section particle composition). The non-refractory parts of the particles evaporate and the resulting vapors are ionized by 70 eV electron impact (EI) and transferred into a time of flight mass spectrometer from external page TofWerk, Thun, Switzerland.
In the case of the SP‑AMS setup (Onasch et al., 2012), the AMS is extended by a SP-unit in which a diode-pumped Nd:YAG creates a continuous wave intra cavity laser beam of 1064 nm wave length. If the particles contain light absorbing refractory (LR) material, the particles will evaporate prior to hitting the vaporizer. The SP‑AMS can be run in the SP‑mode exclusively by removing the tungsten vaporizer.
So far, the instrument was deployed in several measurement campaigns investigating commercial aircraft engine exhaust. Wood combustion particles were investigated during a measurement campaign at University of Applied Sciences Northwestern Switzerland. Furthermore, the instrument was a center piece of two studies investigating different laboratory generated soot particle types. One of these studies was the SP‑AMS Inter-comparison Campaign (SIC), which is up to now the only inter-comparison campaign of the SP instruments.
References:
Canagaratna, M. R., Jayne, J. T., J.L., J., J.D., A., M.R., A., Zhang, Q., Onasch, T. B., Drewnick, F., Coe, H., Middlebrook, A., Delia, A., Williams, L. R., Trimborn, A. M., Northway, M. J., DeCarlo, P. F., Kolb, C. E., Davidovits, P., and Worsnop, D. R.: Chemical and microphysical characterization of ambient aerosols with the aerodyne aerosol mass spectrometer, Mass Spectrom. Rev., 26, 185-222, external page doi:10.1002/mas.20115, 2007.
Jayne, J. T., Leard, D. C., Zhang, X. F., Davidovits, P., Smith, K. A., Kolb, C. E., and Worsnop, D. R.: Development of an aerosol mass spectrometer for size and composition analysis of submicron particles, Aerosol Sci. Tech., 33, 49-70, external page doi:10.1080/027868200410840, 2000.
Onasch, T. B., Trimborn, A., Fortner, E. C., Jayne, J. T., Kok, G. L., Williams, L. R., Davidovits, P., and Worsnop, D. R.: Soot Particle Aerosol Mass Spectrometer: Development, Validation, and Initial Application, 46, 804-817, external page 10.1080/02786826.2012.663948, 2012.