Generating particle beams of controlled dimensions and divergence: I. Theory of particle motion in aerodynamic lenses and nozzle expansions

Peng Liu, Paul J. Ziemann, David B. Kittelson, Peter H. McMurry

Research output: Contribution to journalArticlepeer-review

428 Scopus citations

Abstract

A particle beam is produced when a particle-laden gas expands through a nozzle into a vacuum. This work discusses the theoretical basis of a novel method for producing highly collimated and tightly focused particle beams. The approach is to pass the particle-laden gas through a series of axisymmetric contractions and enlargements (so-called aerodynamic lenses) before the nozzle expansion. Particles are moved closer to the axis by a lens if the particle sizes are less than a critical value and particles can be confined very closely to the axis by using multiple lenses in series. Since particles close to the axis experience small radial drag forces, they stay close to the axis during nozzle expansion and therefore form a narrow particle beam downstream. The major effects that limit the minimum beam width are Brownian motion and lift forces on particles during the nozzle expansion. Simple theoretical models are developed in this work to estimate the minimum particle beam width set by these effects. While the Brownian-motion effects occur for all types of particles, the lift-force effects only occur for nonspherical particles but are often much greater than the Brownian-motion effects.

Original languageEnglish (US)
Pages (from-to)293-313
Number of pages21
JournalAerosol Science and Technology
Volume22
Issue number3
DOIs
StatePublished - Jan 1 1995

Bibliographical note

Funding Information:
This research was supported by Contract No. SRC/MJ-225 from the Semiconductor Research Corporation. We thank the University of Minnesota Supercomputer Institute for a computing grant and Prof. Juan Fernandez de la Mora for his helpful insights and comments on our work.

Copyright:
Copyright 2016 Elsevier B.V., All rights reserved.

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