RF-excited-CO2-laser with improved electrode geometry

A new laser gas flow design for transversely rf-excited CO2-lasers has been presented. Due to the imperfect electrode shape the electrical input power was limited by the occurrence of filaments in the discharge. This paper deals with improvements of the rf-electrodes. Metals with high electrical conductivity and low permeability, i.e. diamagnetic materials as copper, aluminum, and brass are proper electrode materials. Furthermore, the shape of the electrodes has main influence on the distribution of the current of the glow discharge. The use of small contoured electrodes enhances ignition of the discharge, however, the maximum input power for arc free operation is low. Electrodes with a larger outer diameter enable a streamer free discharge at higher input powers. Consequently, the electrodes were optimized concerning length, diameter, and alignment to ensure the use of the maximum electrical power available from the generator. The electrode temperature is determined by heat conduction from the discharge tube. Electrodes which are separated from the tube need no cooling. Air cooling with a blower improves the performance of the system