TY - JOUR
T1 - Aerosol charge fractions downstream of six bipolar chargers
T2 - Effects of ion source, source activity, and flowrate
AU - Jiang, Jingkun
AU - Kim, Chungman
AU - Wang, Xiaoliang
AU - Stolzenburg, Mark R.
AU - Kaufman, Stanley L.
AU - Qi, Chaolong
AU - Sem, Gilmore J.
AU - Sakurai, Hiromu
AU - Hama, Naoya
AU - Mcmurry, Peter H.
N1 - Publisher Copyright:
© 2014 American Association for Aerosol Research.
PY - 2014/12/2
Y1 - 2014/12/2
N2 - Bipolar diffusion charging is used routinely in aerosol electrical mobility size distribution measurements. In this study, aerosol charge fractions produced by six bipolar chargers (neutralizers) were measured using a tandem differential mobility analyzer system. Factors that were studied include the type of ion source (210Po, 85Kr, 241Am, and soft X-ray), source activity, charger design, and aerosol flowrate. It was found that all six types of neutralizers achieve stationary state charge distributions when the source activity is sufficiently high. For 210Po neutralizers with an initial radioactivity of 18.5 MBq (0.5 mCi), stationary state charge distributions are achieved when the source is less than 3.25 years old (residual activity no less than 0.0527 MBq). Stationary state was achieved for 85Kr neutralizers having residual radioactivity greater than 70 MBq. Source activities of 241Am and soft X-ray neutralizers are discussed. Aerosol charge fractions for six neutralizers remain reasonably invariant over a wide range of flowrates. The positive charge fractions achieved by the soft X-ray neutralizer are higher than those by the other five neutralizers using radioactive sources while negative charge fractions for all neutralizers studied are all in a similar range. This study also raises questions about bipolar charging fractions used for data inversion in some scanning mobility particle spectrometer (SMPS) systems, and underscores the need to better understand bipolar charging to achieve more accurate measurements of particle size distributions.
AB - Bipolar diffusion charging is used routinely in aerosol electrical mobility size distribution measurements. In this study, aerosol charge fractions produced by six bipolar chargers (neutralizers) were measured using a tandem differential mobility analyzer system. Factors that were studied include the type of ion source (210Po, 85Kr, 241Am, and soft X-ray), source activity, charger design, and aerosol flowrate. It was found that all six types of neutralizers achieve stationary state charge distributions when the source activity is sufficiently high. For 210Po neutralizers with an initial radioactivity of 18.5 MBq (0.5 mCi), stationary state charge distributions are achieved when the source is less than 3.25 years old (residual activity no less than 0.0527 MBq). Stationary state was achieved for 85Kr neutralizers having residual radioactivity greater than 70 MBq. Source activities of 241Am and soft X-ray neutralizers are discussed. Aerosol charge fractions for six neutralizers remain reasonably invariant over a wide range of flowrates. The positive charge fractions achieved by the soft X-ray neutralizer are higher than those by the other five neutralizers using radioactive sources while negative charge fractions for all neutralizers studied are all in a similar range. This study also raises questions about bipolar charging fractions used for data inversion in some scanning mobility particle spectrometer (SMPS) systems, and underscores the need to better understand bipolar charging to achieve more accurate measurements of particle size distributions.
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U2 - 10.1080/02786826.2014.976333
DO - 10.1080/02786826.2014.976333
M3 - Article
AN - SCOPUS:84918575012
SN - 0278-6826
VL - 48
SP - 1207
EP - 1216
JO - Aerosol Science and Technology
JF - Aerosol Science and Technology
IS - 12
ER -