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Miniature dual-corona ionizer for bipolar charging of aerosol.

Authors
Qi-C; Kulkarni-P
Source
Aerosol Sci Tech 2013 Jan; 47(1):81-92
NIOSHTIC No.
20041668
Abstract
A corona-based bipolar charger has been developed for use in compact, field-portable mobility size spectrometers. The charger employs an aerosol flow cavity exposed to two corona ionizers producing ions of opposite polarity. Each corona ionizer houses two electrodes in parallel needle-mesh configuration and is operated at the same magnitude of corona current. Experimental measurement of detailed charge distribution of near-monodisperse particles of different diameter in the submicrometer size range showed that the charger is capable of producing well-defined, consistent bipolar charge distributions for flow rates up to 1.5 L/min and aerosol concentration up to 107 per cm3. For particles with preexisting charge of+1, 0, and -1, the measured charge distributions agreed well with the theoretical distributions within the range of experimental and theoretical uncertainties. The transmission efficiency of the charger was measured to be 80% for 10 nm particles (at 0.3 L/min and 5 uA corona current) and increased with increasing diameter beyond this size. Measurement of uncharged fractions at various combinations of positive and negative corona currents showed the charger performance to be insensitive to fluctuations in corona current. Ion concentrations under positive and negative unipolar operation were estimated to be 8.2 x 107 and 3.37 x 108 cm -3 for positive and negative ions; the n-t product value under positive corona operation was independently estimated to be 8.5 x 105 s/cm3. The ion concentration estimates indicate the charger to be capable of "neutralizing" typical atmospheric and industrial aerosols in most measurement applications. The miniature size, simple and robust operation makes the charger suitable for portable mobility spectrometers.
Keywords
Ionization-chambers; Electrical-charge; Particulates; Particulate-sampling-methods; Magnetic-fields; Magnetic-properties; Measurement-equipment; Analytical-processes
Contact
Pramod Kulkarni, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, 4676 Columbia Pkwy, MS: R7, Cincinnati, OH 45226
CODEN
ASTYDQ
Publication Date
20130101
Document Type
Journal Article
Email Address
PSKulkarni@cdc.gov
Fiscal Year
2013
NTIS Accession No.
NTIS Price
Identifying No.
B20121218A
Issue of Publication
1
ISSN
0278-6826
NIOSH Division
DART
Priority Area
Manufacturing
Source Name
Aerosol Science and Technology
State
OH
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