Coincidence in time-of-flight aerosol spectrometers: phantom particle creation.
Heitbrink-WA; Baron-PA; Willeke-K
Aerosol Sci Tech 1991; 14(1):112-126
A theory that explains a mechanism for phantom particle generation by time of flight (TOF) aerosol spectrometers was presented and evaluated. The creation of open timer phantom particles by a simple TOF aerosol spectrometer was investigated by analyzing the case of an aerosol containing two monodisperse particle modes. This theoretical analysis was extended to an aerodynamic particle sizer, including a consideration of its anticoincidence detection logic. The concepts developed in the analysis were generalized to a polydisperse aerosol using a Monte Carlo simulation. The number of open timer phantom particles increased with particle size and aerosol concentration. The instrument's detection logic affected the number and size of the phantom particles as well. These were most apparent in the tails and minima of the measured distribution. It was necessary to minimize the concentration of partially detected particles in order to minimize phantom particle creation. Strategies to reduce phantom particle concentration involve reducing the concentration of small particles near the optical detection threshold of the spectrometer.
NIOSH-Author; Spectrographic-analysis; Measurement-equipment; Aerosol-particles; Analytical-methods; Airborne-particles; Particulates
Aerosol Science and Technology