エアロゾル電荷中和器の試験・校正設備の構築とアメリシウム中和器への適用例 [in Japanese] Construction of a Test and Calibration Station for the Aerosol Charge Neutralizer and an Example of Evaluation of an Americium Neutralizer [in Japanese]
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The aerosol charge neutralizer is an essential device in size distribution measurement of aerosol particles by the differential mobility analyzer (DMA). It is not a common practice to calibrate neutralizers, and charged fractions of particles that passed through an aerosol charge neutralizer are assumed to follow a theoretical distribution, which is represented by the approximate equations by Wiedensohler (1988). This assumption, however, would cause significant error if the actual charged fractions deviated from theory. It is not an easy task, though, to calibrate neutralizers for many users. As part of an effort to provide calibration standards for aerosol particle measurements, we have been building an experiment station for calibration of aerosol charge neutralizers. This paper reports its construction and the method to derive particle size-dependent charged fractions. We also report measurement results of charged fractions of an Am-241 neutralizer at different flow rates, in which the location of the radiation source could be varied. We observed that, at a low flow rate, charged fractions varied when the location of the ion source was changed and deviated from theory as the radiation source was moved toward upstream while all other conditions were maintained unchanged. This indicates that the performance of neutralizers may be influenced by the exact location of the ion source in the housing, especially under low flow-rate conditions.
- Earozoru Kenkyu
Earozoru Kenkyu 22(4), 302-309, 2007-12-20
Japan Association of Aerosol Science and Technology