C-ToF-AMS - Compact Time of Flight Aerosol Mass Spectrometer

• 

  The C-ToF-AMS (Drewnick et al., 2005) has been designed to provide real-time quantitative information on size-resolved mass loadings for volatile and semi-volatile molecular components present in/on ambient aerosol particles. Unlike laser-desorption/ionization instruments that provide a qualitative or semi-quantitative picture of the full chemical composition of individual particles, the AMS is designed to provide quantitative composition information on ensembles of particles, with limited single particle information.
  The AMS consists of three main parts: an aerosol inlet, a particle sizing chamber, and a particle composition detection section. The different sections are separated by small apertures and differentially pumped. The aerosol inlet contains an aerodynamic lens that focuses the particles into a narrow beam (~ 1 mm diameter). The particle size range is approximately 40 to 700 nm. Size-dependent particle velocities created by expansion into the vacuum are used to determine particle size through a particle time-of-flight measurement. The focused particle beam is modulated by a rotating wheel chopper operating at about 100 Hz with a ~2% duty cycle. Time-resolved particle detection after a known flight distance gives the particle velocity from which the vacuum-aerodynamic diameter of the particles is obtained. Detection is performed by directing the particle beam onto a resistively heated roughened surface under high vacuum (~ 10-7 Torr). Upon impaction, the volatile and semi-volatile components in/on the particles flash vaporize. The vaporization source is integrally coupled to an electron impact ionizer at the entrance of a time-of-flight mass spectrometer that is triggered with a rate of ~25 kHz. The detected mass spectra of the vapourized aerosol particles can be converted into a mass concentration by an ion-per-molecule calibration and the known inlet flow.

Name	C-ToF-AMS - Compact Time of Flight Aerosol Mass Spectrometer
Measured species	Aerosol Particles
Method	Thermal desorption, electron impact ionization and time-of-flight mass spectrometry
Quantity	Size and chemical composition of aerosol particles
Size range	40–700 nm
Location	Mounted inside the aircraft

References

Drewnick, F., S. S. Hings, P. DeCarlo, J. T. Jayne, M. Gonin, K. Fuhrer, S. Weimer, J. L. Jimenez, K. L. Demerjian, S. Borrmann, D. R. Worsnop, (2005): A new Time-of-Flight Aerosol Mass Spectrometer (TOF-AMS) : Instrument Description and First Field Deployment, Aerosol Science & Technology 39, 637-658.

http://www.mpic.de/en/research/particle-chemistry/group-schneider/research/c-tof-ams.html