Continuum-regime field charging in an electron swarm

Free electron field charging of aerosols in electrostatic precipitators was studied by using very large particles (1500-9000 μm radius) so that electron diffusion charging can be neglected. A microcomputer-automated particle charging and measurement system has been designed and constructed to facilitate this study. Free electron field charging of particles in nonelectronegative gases has been measured as a function of the applied electric field strength (from 0.25 to 4.82 kV/cm), the particle radius (from 0.22 to 0.91 cm), the charging current (from 1.5 to 8.0 μA) and the exposure time (from 1.0 to 4.0 ms, and also 5 s). The measured free electron saturation charge values strongly support the hypothesis that electron field charging has the same saturation charge limit as ionic field charging. The free electron particle charging results strongly suggest that ionic field charging theory adequately describes the field charging of particles by free electrons if the high mobility of the electrons is taken into account