Real-Time Quartz Crystal Microbalance Detection of Aerosols Emitted from a Re-entrant Aerodynamic Focusing Inlet

CHRISTINA Y. HAMPTON (1), Raymond G. Sierra (1), Matthias Frank (2), Michael J. Bogan (1,*)

(1) SLAC National Accelerator Laboratory, Menlo Park, CA, USA (2) Lawrence Livermore National Laboratory, Livermore, CA, USA

     Abstract Number: 773
     Last modified: May 14, 2010

Abstract
One challenge in aerosol particle beam generation is the lack of tools to characterize the particle beam in situ. This is of particular concern in applications such as aerosol mass spectrometry (AMS), single particle coherent x-ray diffractive imaging (CXDI) and nanofabrication, which require highly-concentrated, narrow particle beams. Integration of real-time methods that provide feedback optimization and thus, enable improved transmission efficiency, is especially attractive when generating particle beams via an aerodynamic lens stack as the efficiency of transmitting particles generated at atmospheric pressure into a vacuum chamber is highly dependent on the relative pressures in each stage of the differentially-pumped system, on the orifice size, and on sample characteristics including concentration, solvent effects, and particle size and composition. Here, we describe the first experimental measurements of the response of a quartz crystal microbalance (QCM) to aerodynamically-focused particle beams. Aerosols generated by the nebulization of 140 nm polystyrene spheres were directed into vacuum as a particle beam via a motorized re-entrant aerodynamic lens stack equipped with a pressure flow reducer. Results of QCM response to aerosol concentration, aerodynamic focusing parameters and nebulizer flow rate demonstrate the utility of this real-time detector for aerosol particle beam characterization. This method will be used as a real-time diagnostic tool for optimizing the particle inlet transmission efficiency of aerosols generated using a variety of sources and for tuning the particle beam characteristics for a broader range of materials, including viruses, cells, soot, and other nanomaterials of interest to our CXDI experiments.