Studies of the electric discharge and its application for the excitation of high power gas lasers
thesisposted on 17.11.2015, 09:58 by Ayham A. Yahya
Studies 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.
- Mechanical, Electrical and Manufacturing Engineering