Applications of advanced materials technologies to vacuum electronic devices

The applications of advanced engineering materials in modern vacuum electronic devices are reviewed. Unique materials with desirable thermal, mechanical, electrical, and magnetic properties are playing a crucial role in raising the average power capability, bandwidth, and efficiency of microwave and millimeter wave amplifiers and oscillators. Five major materials-related topics and technologies are covered in this article: diamond electromagnetic windows and electrode supports; electromagnetically lossy composite ceramics for control of instabilities; methods of cooling metal structures; pyrolytic graphite beam collectors and electron-gun modulation grids; and rare-earth permanent magnets for confining electron beams. For each topic, this article reviews the background physics. describes the importance of the technology to vacuum electronics, presents illustrative examples of how such technologies perform, and reviews current results from the literature.