The Tube Guys cover
The Tube Guys
by Norman H. Pond
ISBN: 0981692303
Buy on Amazon
Found in 1 comment on Hacker News
madengr · 2021-07-08 · Original thread
The tube on the cover of this book is 1 MW at 90 GHz.

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.