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Title:Charging of Macroparticles Ejected From a Pulsed Vacuum Arc
Author(s):Rysanek, Filip
Doctoral Committee Chair(s):Rodney Burton
Department / Program:Aerospace Engineering
Discipline:Aerospace Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:Ph.D.
Genre:Dissertation
Subject(s):Physics, Fluid and Plasma
Abstract:A pulsed vacuum arc discharge emits a plasma as well as macroparticles in the form of micron-sized molten droplets of cathode material. Due to their direction of flight and submicron to 100 mum diameter, these macroparticles often pose a contamination threat for both spacecraft-based thrusters, and thin film deposition systems. The velocity, mass and charge of copper macroparticles emitted by a 100 A arc was experimentally measured, and compared to a model based on thermionic electron emission. The macroparticle velocity was determined by using a time-of-flight velocity filter. Less than 1% of collected particles are larger than 5.7 mum, but they account for 50% of the collected mass. The charge was calculated by measuring particle deflection in a transverse electric field. The model predicts, and the experimental results verify, that the charge on the macroparticles is positive, as compared to the negative charge expected for a DC vacuum arc. Experimental results show a roughly quadratic dependence of particle charge on the particle diameter (q∼D2), with a 1 mum particle having a positive charge of ∼1000 electronic charges (1.6 x 10-16 C), and a 5 mum particle having a charge of ∼25000 electronic charges. The model is particle temperature dependent, and gives q∼D2 at 1750 K and q∼D1.7 at 2200 K. Arguments are also made for limitations on particle temperature due to radiative and evaporative cooling.
Issue Date:2007
Type:Text
Language:English
Description:94 p.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007.
URI:http://hdl.handle.net/2142/85100
Other Identifier(s):(MiAaPQ)AAI3270015
Date Available in IDEALS:2015-09-25
Date Deposited:2007


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