Thesis-1990-Yahya.pdf (4.65 MB)
Studies of the electric discharge and its application for the excitation of high power gas lasers
thesis
posted on 2015-11-17, 09:58 authored by Ayham A. YahyaStudies of the electric discharge and its application for the excitation of high power gas lasers
The electric discharge has been studied in static and
fast flow gases at gas pressures between 50 mb and 1 b
over a range of current of between 10 mA and 1. 5 A
representative of its application to the excitation of
high power gas lasers.
The investigations have shown that the glow to arc
transition is a cathode phenomenon which may oscillate
between a glow and arc discharge at the transition current.
The oscillation appears to be inherent where neither the
glowKor the arc is stable at the transition current. The
glow to arc transition has no effect on the positive column
characteristics.
The contraction of the positive column and the decrease
in its voltage gradient as the current is increased appeared
to be related to the thermal conductivity of the gas which
indicates that the formation of streamers in the discharge
column in a fast gas flow is a local constriction due to
thermal instabilities.
The mu1tiple electric discharge has been investigated
and analysed and compared with an equivalent single
electric discharge. The investigation showed that the
coalesced part of the column has the same characteristics
of a single discharge column with the same current and
the discharge column coalesces so as to operate at the
minimum voltage which supports the Steenbeck minimum
principle. A mathematical model was established for the
coalescence of the multiple discharge based on Steenbeck' s
minimum principle which has been demonstrated
experimentally by applying an external magnetic field to
the discharge column.
The behaviour of the positive column in a fast gas
flow was investigated and mathematical models were
established for the contraction of the positive column by
the shear stress force due to the flow profile of the gas
flow in the laminar and turbulent flow regimes using gas
injection nozzles to demonstrate the effect of the flow
profile on the contraction of the discharge column and a
diffusing injection nozzle has been proposed as the optimum
design.
An injection nozzle-electrode was designed and tested
by replacing the original cylindrical injection
nozzle-electrode in a 5 kW C02 laser at a gas pressure of
50 mb. The new nozzle-electrode has resulted in a 50%
reduction in the gas mass flow rate.
History
School
- Mechanical, Electrical and Manufacturing Engineering
Publisher
© A.A. YahyaPublisher statement
This work is made available according to the conditions of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence. Full details of this licence are available at: https://creativecommons.org/licenses/by-nc-nd/4.0/Publication date
1990Notes
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.Language
- en