Effect of Negative Ions on Electrical Breakdown in a Nonuniform Air Gap Between a Wire and a Plane

Electrical breakdown of an axisymmetric, atmospheric pressure air gap between a wire and a plane has been investigated for a gap length of 0.5 mm. 0and 02have been identified as the negative ions affecting the discharge development in air, besides electrons and positive ions, and have been included in the electrical breakdown model. Five coupled two-dimensional transient partial differential equations describing the discharge evolution in the air gap have been solved using a finite difference algorithm developed earlier. Temporal development of the charged particle number densities, electrostatic potential, electric field, and current at both the electrodes is presented when the wire is negatively biased at 2500 V. The impact of negative ions on gap breakdown has been assessed by comparing the results of analyses with and without negative ions. It is concluded that the negative ions have negligible effect during the early stages of the discharge development. However, as the discharge evolves, the negative ions cause a net loss of electrons from the discharge. The effect is most pronounced away from the discharge axis, where peaks in the electron density occur as breakdown proceeds. Radial spread of discharge and current growth rate are relatively unaffected by the presence of negative ions, but the magnitude of total current at the electrodes has been found to decrease by a decade when the negative ions are present. Disciplines Engineering | Mechanical Engineering Comments Suggested Citation: Ramakrishna, K., Ira M. Cohen and Portonovo S. Ayyaswamy. (1994). Effect of negative ions on electrical breakdown in a nonuniform air gap between a wire and a plane. Physics of Plasmas. Vol. 1(5). Copyright (1994) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Physics of Plasmas and may be found at http://link.aip.org/link/PHPAEN/ v1/i5/p1349/s1 This journal article is available at ScholarlyCommons: http://repository.upenn.edu/meam_papers/178 Effect of negative ions on electrical breakdown in a nonuniform air gap between a wire and a plane K. Ramakrishna Materials Science. Endicott Electronic Packaging. Microelectronics Division. IBM Corporation. Endicott. New York 13760-8000 I. M. Cohen and P. S. Ayyaswamy Department of Mechanical Engineering and Applied Mechanics. University of Pennsylvania. Philadelphia. Pennsylvania 19104-6315 (Received 20 October 1993; accepted 25 January 1994) Electrical breakdown of an axisymmetric, atmospheric pressure air gap between a wire and a plane has been investigated for a gap length of 0.5 mm. 0and 02" have been identified as the negative ions affecting the discharge development in air, besides electrons and positive ions, and have been included in the electrical breakdown model. Five coupled two-dimensional transient partial differential equations describing the discharge evolution in the air gap have been solved using a finite difference algorithm developed earlier. Temporal development of the charged particle number densities, electrostatic potential, electric field, and current at both the electrodes is presented when the wire is negatively biased at 2500 V. The impact of negative ions on gap breakdown has been assessed by comparing the results of analyses with and without negative ions. It is concluded that the negative ions have negligible effect during the early stages of the discharge development. However, as the discharge evolves, the negative ions cause a net loss of electrons from the discharge. The effect is most pronounced away from the discharge axis, where peaks in the electron density occur as breakdown proceeds. Radial spread of discharge and current growth rate are relatively unaffected by the presence of negative ions, but the magnitUde of total current at the electrodes has been found to decrease by a decade when the negative ions are present.