Particle beam focusing using radiation pressure

Abstract

Particle beam is the most widely used particle monitoring and size measurement device. The most popular method widely used to generate particle beam is the use of an aerodynamic lens, which is a single or a series of concentric orifice installed inside a circular tube. Aerodynamic lens uses the particles inertia to confine the particles in the narrow region and obtain high particle concentration. The high particle concentration is needed to improve the particle detection sensitivity. However, the width of the particle beam is limited by the given flow condition and particle size in aerodynamic lens. Therefore the particle concentration is also limited. In this study, the radiation pressure was applied to the aerodynamic lens to overcome the limits of the aerodynamic lens. The holed plano-convex lens orifice was used instead of the conventional metal plate orifice. By lens orifice, particles were formed particle beam aerodynamically and radiation pressure was introduced to particle beam simultaneously. Ar-Ion CW laser and pulsed Nd-YAG laser were used to apply the radiation pressure and He-Ne laser was used to visualize the particle beam. The light scattered images of the particle beam were captured by digital camera with expose time 3.2 seconds. After the image processing, the particle beam width was measured. In experiments, PSL particle was used and three different particle sizes of 2.5㎛, 1.0㎛ and 0.5㎛ were used for orifice Reynolds number range of between 300 and 700. The particle beam width got smaller with increased particle size and Reynolds number due to particle inertia effects without the radiation pressure. With Ar-Ion CW laser, the particle beam width was reduced. The maximum reductions of the particle beam width were 16 %, 11.4 % and 9.6 % for particle size 2.5㎛, 1.0㎛ and 0.5㎛ respectively. And small particles made narrower particle beam than one of the large particle with radiation pressure. The radiation pressure effects were increased with...