Research Of RF Excited Technology For 3kW RF-excited Slab CO₂ Laser

The diffusion cooling high power Radio Frequency?RF? excited CO₂ laser has been widely used in laser cutting and welding industry because of its high efficiency and small size. In this thesis, RF power generator, RF slab discharge and voltage distribution for large slab area, impedance matching circuit and the debugging of the 3kW laser RF-excited system have been systematically studied. The main contributions are as follows:?1?The 45 kW self-resonant oscillated RF power generator was designed and tested. The Oscillator and amplifying circuit was designed based on the DB958 RF triode and the static and dynamic parameters were analyzed. The computing method of the external component parameter have been proposed. The input and output parameters of the RF power supply was tested, showing that the maximum RF frequency drift is 1.8% off-center. The causes of RF power supply frequency variations and the optimization method have been discussed.?2?The working principal of the RF-excited slab discharge was analyzed. The equivalent circuit model of RF capacitive discharge was used and the equivalent impedance of 240mm*1200mm electrodes was equal to a pair of 240mm*600mm electrodes in parallel. When three equivalent inductances were placed equidistantly by one side of the RF feed point on the 240*600mm electrode, the minimum voltage unevenness in the longitudinal direction was calculated as 5%,and when there were two increasing inductances placed equidistantly by one side of the RF feed point, the result turned to be 1.4%.?3?The impedance matching network connected RF power supply and laser head was designed. Impedance matching network consisting of four passive elements has been designed in consideration of the volatility of the RF power operating frequency, reflection coefficient was 0.098 responding to 2MHz RF frequency drift, the value was approximately equal to one half of the L-shaped matching network. Broadband matching network can be inserted between a single supply and two equivalent load was designed by adjusting the capacitor values at the end of Impedance matching network.?4?The impact of the RF frequency on the laser property was studied and the way frequency effected the discharging characteristics and the injected power was calculated. The results show that the impedance matching problem caused by frequency fluctuation is a major cause that deteriorates the RF slab laser performance. This problem can be solved by adjusting the parameters of the matching network.The optical properties of the RF-excited system we designed have been tested on the 3kW CO₂ laser, showing that the 3kW laser RF-excited system designing could meet the equipment requirements of practical application.