Aerosol Charge Neutralization by a Radioactive Alpha Source

Liu, Benjamin Y. H.; Pui, David Y.H.; Lin, Bangjiang

doi:10.1002/ppsc.19860030304

Cited by 45 publications

(10 citation statements)

References 8 publications

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“…Aerosol neutralization using a Po-210 and Kr-85 radioactive source has been shown to be effective in imparting a Boltzmann charge equilibrium distribution to a low or modcrately charged aerosols, corroborating the findings of Liu et al (1985Liu et al ( , 1986. Charge neutralization is very important to reduce the magnitude of unwanted electrostatic ef- …”

Section: Discussionsupporting

confidence: 79%

Particle Charge Distribution Measurement for Commonly Generated Laboratory Aerosols

Forsyth

Liu

Romay

1998

Aerosol Science and Technology

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103

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ABSTRACT. An improved particle charge analyzer system has been developed to measure the absolute charge distribution of common generated laboratory aerosols. The charge analyzer system consists of an integral cylindrical mobility analyzer used in conjunction with an optical aerosol spectrometer, with computer assisted operation and data reduction. The charge analyzer collects aerosol particles over an absolute electrical mobility range from 4.2:1:10-~ to 400 cm2/(stat -Volt second) and flow rates that can vary from 0.3 to 30 liters per minute. The charge analyzer has been used to investigate the nature of spray and contact electrification during aerosol generation by measuring the residual charge distribution on the liquid and solid generated particles. In addition, the neutralization of charged particles by bipolar ions also was studied using conventional neutralizers that use ionizing radiation from alpha and beta sources. Charge distribution measurements were performed on alumina dust (Al), Arizona road dust (ARD), potassium chloride (KCI), sodium chloride (NaCl) and di-octyl sebacate (DOS) liquid particles. Aerosol generation devices include a Collison atomizer, a condensation aerosol generator and a fluidized bed dust generator. Our work provides experimental charge distribution data for comparison with simple models of electrification theory. Experimental results showed that charge levels of atomized KC1 and NaCl particles were high and decreased as the dissolved ion concentration increased. DOS particles generated by evaporation-condensation were both neutral and moderately charged. These conclusions support the existence of a dipole layer at the liquid-gas interface that interacts with dissolved particles and changes their charge state. Alumina and ARD generated by the fluidized bed disperser are highly charged due to strong contact electrification during dispersion. In most cases, the charge on generated aerosols could be reduced to Boltzmann charge equilibrium conditions by commonly used radioactive neutralizers.

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Section: Discussionsupporting

confidence: 79%

Particle Charge Distribution Measurement for Commonly Generated Laboratory Aerosols

Forsyth

Liu

Romay

1998

Aerosol Science and Technology

Self Cite

103

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“…This is slightly larger than the n•t value of 8.2 × 10 5 s/cm 3 estimated above based on the fitting of Fuchs numerical modeling to measured charging efficiency (in unipolar operation). Both of these estimated n•t values are much larger than the n•t value of 2.5 × 10 5 s/cm 3 , which Liu et al (1986) noted to be a lower limit for obtaining equilibrium distribution (for particles with 0 or 1 preexisting charge) in a bipolar atmosphere in a Po 210 charger.…”

Section: Discussionmentioning

confidence: 71%

Miniature Dual-Corona Ionizer for Bipolar Charging of Aerosol

Kulkarni

2013

Aerosol Science and Technology

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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 10 per cm. 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 A 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 × 10 and 3.37 × 10 cm for positive and negative ions; the · product value under positive corona operation was independently estimated to be 8.5 × 10 s/cm. 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.

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“…The structure of the 210 Po aerosol charge neutralizer is similar to that of the 85 Kr aerosol charge neutralizer; its half-life is about 138 days. The 0.5-mCi 210 Po source gives nearly eight times the saturation current compared to the 2.0-mCi 85 Kr source (Liu, Pui, & Lin, 1986). The tested neutralizers were 2 years-old and 4 months-old, respectively, for 85 Kr and 210 Po, after their manufacturing.…”

Section: Methodsmentioning

confidence: 99%