NANO-PARTICLE BEAM FOCUSING IN AERODYNAMIC LENSES – AN AXISYMMETRIC MODEL

A computer code for analyzing nano- and micro-particle motions in an aerodynamic particle beam focusing system was developed. The code included an accurately model for the Brownian diffusion of nano-particles in sharply varying pressure field in the aerodynamic lens system. Assuming an axisymmetric condition, the compressible airflow and thermal field in the lens were evaluated. Lagrangian particle Trajectory analysis was performed assuming a one-way coupling model. The numerical results for particle velocity, collection efficiency and beam diameter were compared with the experimental data and good agreement was observed. The importance of the accuracy of the Brownian diffusion model for predicting of the focusing performance of the aerodynamic lenses for focusing of nano-particles was discussed. The simulation results showed that for particle diameters less than 30 nm in air, the Brownian force could significantly affect the beam focusing and particle collection efficiency.