Electrostatic collimation of aerosols and the enhancement of fine particle sampling.
Published: 2006
Language: eng
Number of pages: 178
ISBN-13: 9780494217788
Description: A multitude of inertial sampling methods currently permit the selection of nearly any size of particle from the gas phase of an aerosol. Despite their success and high efficiency, these systems are challenged by intrinsic restrictions on operating pressures and flow rates, which necessitate designs that are sometimes extreme in their complexity and physical requirements. This work proposes the use of electrostatic methods as a promising alternative, and presents several novel designs for charge-based selection.A series of recommendations for future applications of electrostatic selection methods is offered in conclusion. A pilot study developed and tested a prototype electrostatic aerosol concentrator with very promising initial results, including a highly desirable inversion of the performance curve, and strongly recommends the further development of additional novel applications of electrostatic selection methods.A novel design for a corona particle charger was coupled with an electrostatic lens to produce a prototype electrostatic aerosol collimator. This charge-based sampling system was used to generate an aerosol beam from airborne particles. The beam produced was more acute (less than 350 microns in diameter) than any inertial beam reported to date. Furthermore, the performance of the ES collimator reversed the size bias of the inertial collimator, and preferentially sampled smaller particles.Using ions as an analog for ultrafine particles, a novel electrostatic lens was produced to demonstrate the advantage electrostatic methods offer over inertial sampling. The lens also provided a 100-fold improvement over existing ion sampling technology and was used to collimate ion source currents ranging from 30 pA to 7 nA, increasing the ion signal strength at the target by factors of 20 to 130 times that of the unaided signal.The inertial collimator commonly used in online aerosol sampling displays the size-dependent particle selection characteristic of all mass-based sampling methods. In this work, a custom-built inertial aerosol collimator illustrated this inherent size bias using a procedure specially developed to visualise sampling behaviour. By this means, the inert ially-generated aerosol beam was found to display a highly size-dependent radial distribution of its constituent particles. The observed tendency for particles to retain their collimation was limited to those larger than one micron in diameter.
Notes: Source: Dissertation Abstracts International, Volume: 68-01, Section: B, page: 0456.

Thesis (Ph.D.)--University of Toronto, 2006.

Electronic version licensed for access by U. of T. users.