Investigation into phenomena observed during the interaction of a focused high-energy laser beam with high voltage electric fields
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Date
2010-04-14T07:26:55Z
Authors
West, Nicholas John
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Abstract
The work presented in this thesis extends and contributes knowledge to the field of
laser-induced breakdown of a spark gap in air. Previous work has shown that laser-
triggering of a spark gap is very effective in the case of a coaxially triggered spark
gap (where the beam is directed along the axis of the gap). Although a coaxially
triggered gap presents a very intuitive approach, it is not practical. Therefore, the
main focus of this work is to investigate how effective laser-triggering is in the case
of an orthogonally arranged gap (beam at right angles to the gap axis). The effects
of the laser beam intensity, the gap length used and the position of the plasma in the
gap were found to play important roles in the breakdown process of an orthogonally
triggered gap. It was found that directing and focusing the laser beam at right angles
to the gap axis reduces the breakdown voltage of the gap dramatically. An almost
70% reduction of the breakdown voltage of a 50 mm gap was recorded. Also, the
spatial and temporal relation between the laser-induced plasma and the resulting
arc was investigated. Although the laser-triggered arc was expected to attach to
the conductive laser-induced plasma, experiments showed that this is not the case.
Whether attachment occurs depends on the relative timing of the initiation of the
plasma and the high voltage arc and on the overall breakdown probability of the
spark gap. This represents a unique and valuable contribution to engineers working
in the field of triggered spark gaps and other high voltage triggering applications.