Aerodynamic lenses

Figure 11.74 shows a similar approach to the measurement of a continuous beam of volatile and semivolatile particles with diameters as small as 0.02 /im (Tobias et al., 1999). Upon exiting the aerodynamic lensing system, the particles enter a small ( 0.1 cm3) cell whose temperature can be regulated and is typi-... 

I. Theory of Particle Motion in Aerodynamic Lenses and Nozzle Expansions, Aerosol Sci. Technol., 22, 293-313 (1995a). 

Wang, X., McMurry, P.H., An experimental study of nanoparticle focusing with aerodynamic lenses. Int. J. Mass Spectrom. 2006, 258, 30. 

FIGURE 3.5 Gas streamlines (top) and trajectories (bottom) simulations of 20-nm-diameter particles in a gas expansion from left to right in aerodynamic lenses. Reprinted with permission from Ref. [91]. American Institute of Physics. 

Schreiner, J., C. Voigt, K. Mauersberger, P. McMurry, and P. Zie-mann, Aerodynamic Lens System for Producing Particle Beams at Stratospheric Pressures, Aerosol Sci. Technol., 29, 50-56 (1998). 

A particle-sampling mass spectrometer could provide a useful approach to measuring inhalation exposure to pollutants in a wide variety of environments. One example17 employs an aerodynamic lens that samples very fine particles and creates a beam that can be modulated to give a crude time-of-flight mass distribution. The particles impinge on a hot surface, causing vaporization of constituents that can be ionized (by electron impact or photoionization) and subjected to mass analysis by any of several kinds of mass analyzers. 

Figure 3, Particle transmission efficiency through the aerodynamic lens inlet and differentail pumping system.

Zelenyuk, A., Cai, Y., and Imre D. From a lomerates of spheres Zelenyuk, A., Imre, D., and Cuadra-Rodriguez, A. L. Evaporation to irregularly shaped particles determination of dynamic shape of water from particles in the aerodynamic lens inlet an experifactors from measurements of mobihty and vacuum aerodynamic mental study. Anal. Chem., 78, 6942-6947, 2006b. diameter. Aerosol Sci. Technol., 40, 190—217, 2006a. 

Figure 4.7 Schematic of the time-of-flight aerosol mass spectrometer (TOF-AMS). Aerosol is introduced into the instrument through an aerodynamic lens focusing the particles through a skimmer and an orifice onto the vaporizer. Particle vapor is ionized and the ions are guided into the TOF-MS, which generates mass spectra at 83.3 kHz repetition rate. For particle size measurement the particle beam is chopped with a mechanical chopper and the detection is synchronized with the chopper opening time [178], Aerosol Science Technology A New Time-of-Flight Aerosol Mass Spectrometer (TOF-AMS) - Instrument Description and First Field Deployment. 39 637-658. Copyright 2005. Reston, VA. Reprinted with permission...

The setup at the Universitat Rostock utilizes an ACIS to produce a continuous cluster beam (see Fig. 3.9). The metal vapor plasma is created in the cylindrical cathode of target material. The fabricated clusters, neutral and charged are expanded through an exit nozzle and collimated by an aerodynamic lens attached to the source. The clusters then flow through a secondary pumping stage bracketed by two skimmers and are size selected by an electrostatic quadrupole deflector for deposition. 

Schreiner, J. Voigt, C. Maubrsberger, K. McMurry, P. ZiEMANN, P. Aerodynamic lens system for producing particle beams at stratospheric pressures. Aerosol Sci. 

A number of laboratories have developed TOF mass spectrometers for the analysis of aerosol particles and aerosolized bacterial spores. In these instruments, aerosol particles are brought from the atmosphere directly into the vacuum region by means of an aerodynamic lens, skimmers, and differentially pumped regions. They are then ionized directly in flight by a pulsed laser beam. While most of these studies have involved laser desorption, the addition of matrix coatings to aerosol particles in flight has been reported in a MALDI bioaerosol mass spectrometer. 

Plastic headlamp lenses have only recently become legal in Europe, and their use is now incorporated in ECE R20. However, plastic headlamp lenses have been legal in Japan for many years, and in the USA since 1979. The appropriate standard there is FMVSS 108, whose heat distortion and scratch requirements are met only by polycarbonate, with a silicone hard coating. A plastic lens only weighs half as much as glass the main incentives however are the lower assembly costs represented by plastics and the much greater design freedom, especially for flat low aspect ratio lenses, suitable for low-front aerodynamic bodies. 

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