Award Date

8-1-2012

Degree Type

Thesis

Degree Name

Master of Science in Electrical Engineering (MSEE)

Department

Electrical and Computer Engineering

First Committee Member

Robert A. Schill

Second Committee Member

Yahia Baghzouz

Third Committee Member

Rama Venkat

Fourth Committee Member

William Culbreth

Number of Pages

160

Abstract

In certain plasma discharge experiments, it has been observed that under specific conditions a plasma glow discharge column tends to seek the central location of the discharge electrodes away from the electrode edges and chamber walls. Further, the column appears to have the properties of a stabilized equilibrium plasma pinch in a glow (non-arc-like) state. This is unusual since, normally field enhancements occur on edges resulting in arc-like discharge breakdown. Also, the column of plasma that protrudes from the anode emits highly intense, non-uniform light that is uncharacteristically bright for a glow discharge.

The main purpose of this thesis is to explore the likely experimental cause and basic physics of this phenomenon. In particular, the glow discharge's secondary electron beam is explored and the consequences of this moderately energetic beam are examined. It appears that under certain conditions and assumptions, this secondary electron beam will initiate and sustain electron channeling and subsequent pinch forces due to charge repulsion, charge neutralization, and self-magnetic forces. This theory can be expanded beyond a glow discharge and be applied to any moderately energetic beam that passes through plasma, as long as the assumptions and conditions are not violated.

An experimental apparatus was also constructed to investigate this phenomenon. It delivers controlled pulses that generate stable and repetitive pinched discharges. It allows the user to change the parameters and the conditions of the discharge and to study the conditions that bring about plasma constriction. Measurement tools were integrated into the system including current and voltage probes and image analysis tools.

Finally, the conditions and assumptions built into the theory are revisited and compared to experiments and simulation, in order to discuss the applicability of the theory to a constricted glow discharge. Based on the models developed and on experimental implications, a parameter space based on the properties of the discharge has been identified that leads to the pinch of the discharge. Further, from transient discharge measurements, various properties of the pinch have been identified.

Keywords

Electron beams; Pinch effect (Physics); Plasma; (Ionized gases)

Disciplines

Electrical and Computer Engineering | Plasma and Beam Physics

Language

English


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