How does a klystron tube look?

A klystron tube is typically a cylindrical or elongated metal tube, often with a glass or ceramic envelope, showcasing distinct internal components. It contains multiple cavities or resonators that facilitate the amplification of microwave signals. The tube usually has a cathode at one end, which emits electrons, while the other end may have an output coupling structure. Overall, the design is engineered to manage high-frequency signals and is often mounted in a metal housing for shielding and support.