Th. Kauffeldt

Differential electrical mobility analysis : A theoretical study

ABSTRACT The subject of this work is the theoretical investigation of slowly scanning differential mobility analyzers (DMAs) which are, e.g., utilized to determine DMA transfer functions and to measure particle mobility distributions. A model to describe such systems is introduced and applied to investigate three different regimes of input mobility distributions: 1) a mobility distribution much narrower than the DMA transfer function, 2) a mobility distribution of about the same width as the DMA transfer function, and 3) a mobility distribution much wider than the DMA transfer function. Cases 1) and 2) are relevant for DMA transfer function measurements utilizing tandem differential mobility analyzer (TDMA) systems. For either regime, it is not possible to determine DMA transfer functions directly from the concentration distributions measured at the outlet of a DMA. For these cases, a deconvolution procedure is needed. Therefore, an iterative deconvolution procedure was developed. Determining DMA transfer...

ABSOLUTE ON-LINE MEASUREMENT OF THE MAGNETIC MOMENT OF AEROSOL PARTICLES

We developed a method of on-line measurement of the magnetic moment of aerosol particles. For this purpose we determine the deposition of the particles in a filter consisting of magnetic nickel screens. Deposition is governed by the dipole force magnetic particles experience near the magnetized wires of the screens. The number concentration at the in-and outlet of the filter is measured by optical particle counters. The so called single fiber efficiency is derived directly from the measured data as a function of particle size, particle magnetic moment and fiber magnetization. The relationship between this dimensionless value and the magnelic moment is obtained by a computer simulation using trajectory analysis. The method is tested with equally sized iron/iron oxide particles in the size range from 40 to 170nm.

On-line measurement of the magnetic moment of aerosol particles

Abstract At the first time an on-line measurement of the magnetic properties of aerosol particles is presented. It is based on determination of the penetration of a magnetic filter. For testing the method iron oxide particles have been used.