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22 September 2011 Velocity and size estimation of nanoparticles down to 75nm with nano LDA
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Laser Doppler anemometry offers a non-intrusive in-situ flow measurement method both for scientific and industrial environments, especially in extreme conditions. Compared to the commercial LDA systems Nano-LDA device was developed for simultaneous flow measurement, particle counting and sizing down to the nanometer size range. High detection sensitivity was reached by applying single photon avalanche diodes with photon correlation technique and special techniques for particle counting (burst selecting) and individual burst signal processing. In this paper verifying measurements are performed with Palas 2.0 iP aerosol generator and differential mobility analyzer down to 75nm paraffin particles, which is in accord with the lower size limit of the generator. In case of individual particle velocity estimations the low SNR signal requires special prepare of the autocorrelation function such as unfolding, zero padding and windowing. A detailed discussion is shown for the role of the different techniques in velocity estimation. The amplitude technique in the particle sizing requires a calibration process to determine the intensity loss of the system. The model-based algorithm supports the calibration by the complete simulation of the measurement process and light scattering. By this way a single calibration measurement for one kind of monodisperse particles can be enough. The model-based algorithm is tested by measurements with monodisperse particles of different sizes set by the DMA.
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Lenard Vamos and Peter Jani "Velocity and size estimation of nanoparticles down to 75nm with nano LDA", Proc. SPIE 8167, Optical Design and Engineering IV, 816727 (22 September 2011);

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