Experiments of unipolar diffusion charging of ultrafine aerosol particles (10–50 nm) at low pressure (0.2–0.5 atm) were performed. Aerosol charging was achieved using a novel unipolar charger which made use of a low-intensity α-ray radioactive source. The results of the experiments were compared with numerical solutions to the fundamental equations of charging. The Fuchs’ limiting-sphere charging theory in the transition regime was used for the calculation of the combination coefficients between ions and particles. Good agreement was found between experimental results and numerical predictions of the charged fraction as a function of particle diameter.
Bibliographical noteFunding Information:
This research is supported under a grant by the Particulate Contamination Control Research Consortium at the University of Minnesota. Memebers of the Research Consor- tium include: Air Products and Chemicals, Inc., AircoIThe BOC Group, Applied Materials, Donaldson Co., Inc., FSI International, GM/Delco Electronics, IBM Corporation, Millipore Corporation, Nupro Co., and TSI, Inc. The support of the Consortium is gratefully acknowledged.