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Fast Mixing Condensation Nucleus Counter: Application to Rapid Scanning Differential Mobility Analyzer Measurements

Wang, Jian and McNeill, V. Faye and Collins, Don R. and Flagan, Richard C. (2002) Fast Mixing Condensation Nucleus Counter: Application to Rapid Scanning Differential Mobility Analyzer Measurements. Aerosol Science and Technology, 36 (6). pp. 678-689. ISSN 0278-6826. doi:10.1080/02786820290038366.

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Condensation nucleus counters (CNCs) exhibit slower time response than expected due to mixing effects within the detector.This mixing produces an exponential distribution of delay times with a characteristic mixing time τ_m that ranges from 0.1 s to 0.9 s for commonly used instruments and limits their usefulness for measuring rapidly changing aerosols. Moreover, when used as detectors in the scanning electrical mobility spectrometer (SEMS; also known as scanning mobility particle sizer, SMPS), CNCs limit the speed with which size distribution measurements can be made. In order to overcome this limitation, a new, fast-response mixing CNC (MCNC) has been developed and characterized. The time response of this new detector and TSI Models 3025 and 3010 CNCs has been measured using a spark source to generate an aerosol pulse. The mixing induced response smearing of this new detector, τ_m, of this instrument is 0.058 s, which is significantly shorter than either of the other instruments tested. Its lower detection limit is about 5 nm diameter. The high aerosol flow rate of the MCNC (0.65 l min^(-1)), fast time response, and low detection limit make it an ideal detector for SEMS/SMPS measurements. Using this MCNC as a detector for the SEMS, size distribution measurements over the 5 nm to 140 nm range have been made in 3 s with minimal distortion. The size distribution of a coagulation aerosol was effectively recovered by deconvolution with scans as short as 1 s. Uncertainties in the 1 s scans result, in part, from electronics problems in the scanning DMA.

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Flagan, Richard C.0000-0001-5690-770X
Additional Information:© 2002 American Association for Aerosol Research. Received 3 December 1999; accepted 11 April 2001. This work was supported by the U.S. Office of Naval Research under grant N0014-96-1-0119. V. F. McNeill received support from the California Institute of Technology Summer Undergraduate Research Fellowship (SURF) program. The authors would like to than TSI, Inc., for providing the optical detector. The authors also gratefully acknowledge the helpful anonymous reviewer whose comments stimulated additional work in revision and significantly enhanced this paper.
Funding AgencyGrant Number
Office of Naval Research (ONR)N00014-96-1-0119
Caltech Summer Undergraduate Research Fellowship (SURF)UNSPECIFIED
Issue or Number:6
Record Number:CaltechAUTHORS:20150818-100344179
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:59679
Deposited By: Irina Meininger
Deposited On:20 Aug 2015 20:28
Last Modified:10 Nov 2021 22:23

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