The Aerodyne Aerosol Time of Flight Mass Spectrometer (TOF-AMS) is an instrument manufactured by Aerodyne Research Inc. and is used to study the chemical and physical nature of aerosol particles online. The instrument works by focusing the sampled particles into a tightly collimated beam at its inlet and skimming off the majority of the gas phase material before impacting them onto a heated tungsten surface. The non-refractory components of the particles instantly vaporise and the vapours produced are analysed using electron ionisation mass spectrometry. The particle beam can also be modulated using a chopper wheel and the particle sizes calculated by measuring their velocities. Scientifically, the instrument can deliver quantitative mass concentrations of the major non-refractory chemical species present in submicron particles (ammonium, nitrate, sulphate, organics and non-sea-salt chloride) in microgrammes per cubic metre. It is also capable of delivering these concentrations as a function of diameter as a dM/dlog(D) distribution. Further to this, information on the chemical nature of the organic fraction can be derived by inspecting the relative sizes of the peaks within the mass spectrum. In order to produce fully quality assured and meaningful results, the data must be processed offline or near-real-time. Software tools to do this have been developed by the group at Manchester with our collaborators at Aerodyne and the University of Colorado at Boulder and use Igor Pro by Wavemetrics Inc. as a platform.
ToF-AMS
Spectrometers/Radiometers