AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
A Water-based Fast Integrated Mobility Spectrometer with Enhanced Dynamic Size Range
MICHAEL PIKRIDAS, Steven Spielman, Chongai Kuang, Thomas Tsang, Scott Smith, Andrew McMahon, Susanne Hering, Jian Wang, Brookhaven National Laboratory
Abstract Number: 448 Working Group: Instrumentation and Methods
Abstract The laminar flow water condensation technology (Hering and Stolzenburg, 2005) and the Fast Integrated Mobility Spectrometer (FIMS, Kulkarni and Wang 2006) have been combined to capture aerosol size distributions with 1-second time resolution. Using a parallel plate geometry, the FIMS separates particles based on their electrical mobility, and then grows them in a supersaturated environment to form supermicron droplets. The droplets are subsequently laser-illuminated and detected by a high speed CCD camera. The images captured by the camera provide not only the particle concentration, but also the particle position, which is used to derive particle electrical mobility. With the water-FIMS, a multistage condensational growth is used that introduces water vapor downstream of the separation zone, so that the mobility separation can be achieved for a variety of sheath relative humidity values. The multistage growth also limits the exiting water vapor concentration to below saturation levels at ambient temperature, thereby preventing condensation on the optics.
By measuring all spanned particles sizes simultaneously, the FIMS significantly increases measurement speed and counting statistics. With the adaptation to water condensation method it is an ideal instrument for measurements of aerosols with rapid population dynamics or onboard fast-moving platforms. By employing a non-uniform electric field as described by Wang (2009), we anticipate that particles of a wide range of electrical mobilities can be simultaneously classified. A water-FIMS employing the non-uniform electric field is being developed. The performance of this improved FIMS, including its dynamic measurement size range, size resolution, and counting statistics, will be presented.
References:
Hering, S.V. and M. R. Stolzenburg (2005), Aerosol Science and Technology 39:428-236.
Kulkarni, P., and J. Wang (2006), J. Aerosol Sci., 37(10), 1303-1325.
Wang, J. (2009), J. Aerosol Sci., 40(10), 890-906.