OP here again. That's what it is. There are some good pictures of a cutaway of a magnetron here: http://en.wikipedia.org/wiki/Cavity_magnetron http://en.wikip

OP here again. That's what it is. There are some good pictures of a cutaway of a magnetron here: http://en.wikipedia.org/wiki/Cavity_magnetron http://en.wikipedia.org/wiki/Cavity_magnetron It's kind of amazing that you can create microwaves with nothing more than a high voltage, a magnet, and a cavity with precisely the right shape.