Space-charge effects in nanoparticle processing using the differential mobility analyzer

We report the observation of mobility classification breakdown due to strong space-charge effects during nanoparticle processing in a radial differential mobility analyzer (DMA). A simple dimensionless group, the space-charge number, is introduced to help identify the conditions for which this phenomenon becomes important. Our analysis suggests a few DMA design features and operation conditions that should enable the accurate classification of ultrafine aerosols with high concentrations of charged particles. (C) 2001 Elsevier Science Ltd. All rights reserved.