Reliable Ceramic Window Design for Electronic Devices

Abstract

The effective operations of a high voltage vacuum electronic device, such as a traveling wave tube, depends on its ability to maintain high vacuum environments. However, during temperature tests, some tubes fail because of vacuum leaks through cracks in the ceramic window. It is believed that these leaks result from RF heating at the center conductor, which caused the ceramic to crack. To obtain a general understanding of the stress field in the window structure, a closed from analytical approach is imperative. However, due to the complex nature of the problem, only the first order engineering approximation is used in this preliminary study. The theory of linear elastic fracture mechanics and the existing solutions from elastic circular plates are useful for understanding the cause of ceramic window cracks. Some simple design references have also been developed for the design of reliable ceramic windows for traveling wave tubes.