American Association for Aerosol Research - Abstract Submission

AAAR 39th Annual Conference
October 18 - October 22, 2021

Virtual Conference

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The Dual Polarity Spider: A Fast, Compact, Particle Mobility Spectrometer

STAVROS AMANATIDIS, Gregory Lewis, Steven Spielman, Ryan Ward, Yuanlong Huang, Benjamin Schulze, Susanne Hering, Richard Flagan, Aerosol Dynamics Inc.

     Abstract Number: 463
     Working Group: Instrumentation and Methods

Abstract
Mobility-based particle spectrometers have become the de facto reference method for measurement of submicrometer and ultrafine aerosol size distributions. Yet the conventional instruments are large and heavy, and thus not appropriate for field deployments. The “Spider DMA” is a small, radial-flow differential mobility analyzer recently developed for applications requiring high portability and fast time resolution, such as moving platform deployments. The instrument is designed to operate at 0.3 L/min aerosol flow and 0.6 – 1.2 L/min sheath flow, and provides sizing in the 10 – 500 nm range with a moderate resolution of R = 2 – 4.

Here, we present key features of the “Dual Polarity Spider DMA”, a next generation design that provides size classification of particles with either positive or negative charge. This is realized by employing a recently developed high-voltage supply that can generate accurate upscan and downscan voltage ramps of both positive and negative polarity. We discuss the key changes incorporated in the new DMA design, that enable robust and efficient classification across its operating voltage range from -5000 V to +5000 V. Transfer functions in scanning-voltage mode are evaluated through finite element modeling, and through tandem DMA experiments with both positive and negative particles. Moreover, we report a comparison of its performance in measuring ambient size distributions against a conventional mobility particle sizer, over a testing period of several days of continuous operation. The data show agreement in the shape, number concentration, and geometric mean diameter for ambient aerosols, corroborating the compact Spider DMA efficacy for fast, accurate ambient size distribution measurements.