Here's a traveling wave tube amp that does 5 kilowatts: https://www.arworld.us/post/5700TP12G18.pdf?44385.7040046296
https://www.amazon.com/Tube-Guys-Norman-H-Pond/dp/0981692303
It's for an airborne ADS (i.e. pain ray). Good book if you want the detailed history of microwave tubes.