AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
The vSANC – An Instrument for Basic Nucleation Studies and Ambient Measurements of Nanoparticles
TAMARA PINTERICH, Paul M Winkler, Paul E. Wagner, Aron Vrtala, Universitaet Wien, Vienna, Austria
Abstract Number: 160 Working Group: Aerosol Nucleation: From Clusters to Nanoparticles
Abstract Based on our experience with the Size Analysing Nuclei Counter, SANC (Wagner et al. (2003)), we developed a new versatile expansion chamber system. Well-defined uniform vapour supersaturation is obtained by adiabatic expansion. Subsequently aerosol particles, acting as condensation nuclei, cause heterogeneous nucleation and grow to visible droplets. An optical detection method, the CAMS method (Wagner (1985)), is applied utilizing multiple light scattering angles. Light fluxes at twenty different scattering directions as well as the transmitted light flux are monitored simultaneously. This enables automated determination of growth rates and absolute number concentrations ranging from ~50/cc to 10$^7/cc, independent from the aerosol flow. Growth rate measurements allow precision determination of vapour saturation ratios.
The design of the flow plan enables both active and passive operation of the vSANC. In particular the latter is of advantage when performing measurements in combination with a uDMA. The connection between inlet and expansion chamber is thermostated in order to prevent evaporation losses. Connections were built straight and as short as possible using only stainless steel tubing and pinch valves with complete and true full bore. This minimizes particle losses and enables an unobstructed aerosol flow.
The vSANC was optimised to achieve high flexibility in investigating aerosol particles from diameters of 1-2nm upwards. Depending on the pre-sampling conditions either the aerosol is already humidified and is passed directly into the expansion chamber or it first passes through a humidifier. In fact two humidifiers were implemented allowing the simultaneous use of different vapour compounds. Accordingly, information on different particle properties such as solubility or wettability can be obtained.
We present first measurement results providing precision determinations of heterogeneous nucleation probabilities and allowing evaluations of sizes of molecular clusters.
Wagner, P.E. (1985), J. Colloid Interface Sci.105, 456.
Wagner, P.E. et al. (2003), Phys. Rev. E67, 021605.