Abstract
Abstract. Multiple-charge inversion is an essential procedure to convert the raw mobility distributions recorded by mobility particle size spectrometers, such as the DMPS or SMPS (differential or scanning mobility particle sizers), into true particle number size distributions. In this work, we present a fast and easy-to-implement multiple-charge inversion algorithm with sufficient precision for atmospheric conditions, but extended functionality. The algorithm can incorporate size distribution information from sensors that measure beyond the upper sizing limit of the mobility spectrometer, such as an aerodynamic particle sizer (APS) or an optical particle counter (OPC). This feature can considerably improve the multiple-charge inversion result in the upper size range of the mobility spectrometer, for example, when substantial numbers of coarse particles are present. The program also yields a continuous size distribution from both sensors as an output. The algorithm is able to calculate the propagation of measurement errors, such as those based on counting statistics, into on the final particle number size distribution. As an additional aspect, the algorithm can perform all inversion steps under the assumption of non-spherical particle shape, including constant or size-dependent shape factors.
Highlights
Mobility particle size spectrometers are widely used in aerosol science and have enjoyed broad application in both laboratory and field studies (Knutson and Whitby, 1975; Kousaka et al, 1985; McMurry, 2000)
The algorithm can incorporate size distribution information from sensors that measure beyond the upper sizing limit of the mobility spectrometer, such as an aerodynamic particle sizer (APS) or an optical particle counter (OPC)
We present the theoretical framework of a new inversion algorithm that inverts electrical particle mobility distribution from a mobility particle size spectrometer in conjunction with data from an aerodynamic particle sizer (APS) or an optical particle counter (OPC)
Summary
Mobility particle size spectrometers are widely used in aerosol science and have enjoyed broad application in both laboratory and field studies (Knutson and Whitby, 1975; Kousaka et al, 1985; McMurry, 2000). Knowing the bipolar charge distribution (Wiedensohler, 1988) and the instrument responses of the differential mobility analyser (DMA) and the particle counter or condensation particle counter (CPC), it is possible to convey the electrical particle mobility distribution into the true particle number size distribution. This procedure has been called multiple-charge inversion (Alofs and Balakumar, 1982; Kandlikar and Ramachandran, 1999). The deviations were attributed, among others things, to different physical constants and charging probabilities used, different solutions to the matrix inversion problem, and different approaches of how to discretize, pre-process and post-process the data Few of such inversion routines have been designed to handle size distribution information from multiple sensors. The new capabilities of the algorithm are illustrated for two example cases
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