Nobuhiko Fukushima

Mass Range and Optimized Operation of the Aerosol Particle Mass Analyzer

We investigated, theoretically, the mass range in which an aerosol particle mass analyzer (APM) can be used for classification, and how the APM classification performance can be optimized. We listed factors that set limits to the APM, which were constraints of the rotation speed and the voltage, as well as requirements on the APM classification performance parameter, λ, that guarantee at least minimal performance in both resolution and penetration. We introduced the APM operation diagram, which is a tool to visualize the limits and mass range. We proposed to operate the APM that was considered in this study with the λ value set within the range from 0.25 to 0.5 for optimum classification performance by balancing both resolution and penetration. The mass range for the APM, with the λ value maintained between 0.25 and 0.5, was calculated to be from 0.003 to 2000 fg, which corresponds to the diameter range from 20 to 1600 nm for the density of 1 g/cm3. To verify the validity of the mass range and the idea of the optimized operation, we carried out experiments on an APM with polystyrene and sodium-chloride particles that were classified by electrical mobility. We found that the APM was able to provide bell-shaped spectra down to 12 nm, and was able to perform mass classification with an accuracy better than 5% down to 50 nm. Underestimation of mass and reduction of resolution and penetration were observed at sizes smaller than about 30 nm.

Design Considerations and Performance Evaluation of a Compact Aerosol Particle Mass Analyzer

A compact aerosol particle mass analyzer (APM) of which the size of the classifier was significantly reduced than that of the first commercial model (Kanomax Model 3600) was developed. Firstly, requirements for desired performance in classifying particle mass were set forth. Secondly, a theoretical framework for the design parameters of an APM that satisfies the requirements was formulated. Thirdly, the design parameters were determined that satisfies the requirements while reducing the instrument size. The requirements include the condition that the classification range covers from 0.001 to 1000 fg (approximately 12 to 1200 nm in size for spherical particles having the density of 1 g/cm3), and the condition that both the classification resolution and particle penetration in this mass range are higher than certain specified values. A prototype having the design parameters determined according to this theoretical framework was constructed, and its performance was evaluated experimentally. The external dimensions of the electrodes of the compact APM are approximately 140 mm in length and 60 mm in diameter. It was confirmed that the performance of the compact APM operated at the aerosol flow rate of 0.3 L/min was comparable to that of the Model 3600 APM operated at 1 L/min. Because of the reduced size and of the resultant improved portability, it is expected that the compact APM is readily applicable to field measurements. Copyright 2013 American Association for Aerosol Research

Performance of a Scanning Differential Mobility Analyzer

ABSTRACT The performance of a scanning differential mobility analyzer (DMA) combined with a condensation nucleus counter (CNC) having high detection sensitivity has been evaluated using monodisperse latex particles of 100 nm in diameter and polydisperse sodium chloride particles between 10–120 nm: 1) A method is proposed to accurately measure the delay time between the DMA outlet and the particle detector of the CNC, which is necessary to measure the particle size distribution by the scanning DMA. 2) The effect of some operating factors, such as CNC counting time and time constant of the exponentially increasing voltage on minimum achievable scanning time is examined by the experiment, and theoretical discussion is made on the basis of the mobility transfer function of particles classified by the DMA, which is related to the mobility shift during the CNC counting time. As a result, accurate measurement of monodisperse particles is completed in about 10 sec. For polydisperse particles, it takes only about ...

Development of portable aerosol mobility spectrometer for personal and mobile aerosol measurement

ABSTRACT We describe development of a portable aerosol mobility spectrometer (PAMS) for size distribution measurement of submicrometer aerosol. The spectrometer is designed for use in personal or mobile aerosol characterization studies and measures approximately 22.5×22.5×15 cm and weighs about 4.5 kg including the battery. PAMS uses electrical mobility technique to measure number-weighted particle size distribution of aerosol in the 10–855 nm range. Aerosol particles are electrically charged using a dual-corona bipolar corona charger, followed by classification in a cylindrical miniature differential mobility analyzer. A condensation particle counter is used to detect and count particles. The mobility classifier was operated at an aerosol flow rate of 0.05 L/min, and at two different user-selectable sheath flows of 0.2 L/min (for wider size range 15–855 nm) and 0.4 L/min (for higher size resolution over the size range of 10.6–436 nm). The instrument was operated in voltage stepping mode to retrieve the size distribution in approximately 1–2 min. Sizing accuracy and resolution were probed and found to be within the 25% limit of NIOSH criterion for direct-reading instruments. Comparison of size distribution measurements from PAMS and other commercial mobility spectrometers showed good agreement. The instrument offers unique measurement capability for on-person or mobile size distribution measurement of ultrafine and nanoparticle aerosol.