The kinds of devices I would like to be able to design are magnetrons, klystrons, gyrotrons, and maybe free electron lasers/masers. My goal is not to get a job in the field, but to just have enough knowledge to build some of these things myself. My first thought is plasma physics and EE, but I am hoping for some more specific advice. I am 42. In university I had trouble deciding on what I wanted to do. I did 2 years in English, 1 year in Electrical Engineering Technology, 2 years in Electrical Engineering, and then I was unable to continue for financial reasons (parent stopped paying, hehe). I would very much like to just go back to university as an undergrad and double major in physics and EE, but that's not really an option at the moment. Due to a rare sleep problem I have, I can't consistently be awake for morning classes. If I could somehow manage my sleep problem I would be asking about exactly what programs to take or what schools to go to. Or maybe I could find a university somewhere that has full physics and EE programs through evening classes or a good online university. But my general intent of this post is to ask about learning materials for self study in plasma physics, mathematics, and EE. Something like: Plasma Physics A-Z or Advanced Plasma Physics for Dummies: From the Ground Up would be nice. I wish more textbooks had the answers to problems available. The lack of them does make self-study even more difficult.