Direct determination of 3D forces applied on a particle suspended in an electrodynamic chamber

The main motivation of the present work is to enable one to carry out a direct quantitative measurement of 3D force balance applied on a suspended particle in an electrodynamic chamber (EDC). For this, the absolute values of electric field parameters are essential. Both horizontal and vertical electric field components were analysed theoretically and experimentally. From the theoretical analysis of the motion of a charged particle in an EDC, two relationships relating motion parameters to electric field strength were found. These relationships were validated experimentally from measurements of 17 polystyrene and char particles with various densities and sizes. Consequently, the absolute 3D field parameters were determined. This method was used to determine the absolute value of the photophoretic force (PPF) and the free convection force (FCF) applied on a suspended particle. In these experiments, the particle was irradiated horizontally by a focused laser beam. Consequently, the PPF was developed horizontally whereas the FCF was developed vertically. The present measurement indicated that the PPF is much smaller than the FCF, in contrast to previous reports.

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