Improvement in the Design of Metal-Ceramic High Voltage Feedthroughs for use in High Energy Particle Accelerators

Large high-voltage devices operate in particle accelerators to steer charged particles in the desired direction. Solid and hollow rods of sintered alumina are used as insulating supports and high-voltage feedthroughs to power the electrodes of these electrostatic systems. The performance of the systems is often limited by voltage breakdown along the surface of the ceramic insulator (so-called surface flashover) or discharge between feedthrough and vacuum tank, which can lead to significant disruptions in terms of overall machine efficiency. Available results on the influence of the mechanical preparation, thermal history and particular cleaning techniques on commercially obtainable alumina samples have been studied in order to investigate possibilities for better preparation methodology of the insulating supports. Also the influence of the relative position of the feedthrough inside the vacuum tank on the high-voltage breakdown behaviour has been studied. This paper describes the theoretical and practical background of the problem. The results and findings about the influence of insulator parameters as well as feedthrough design are presented and recommendations are made for a better ceramic insulator preparation methodology combined with a changed overall design, which could lead to improved and more reliable functioning of the equipment.