Source. Video sponsored by General Electric. A cool insight of this video is that a hot cathode is a more reliable electron source. Previous systems, and presumably including the discovery of X-rays, leftover gas in the tube was used. But this makes things more difficult to control, as we also want to remove as much gas as possible from the vacuum, otherwise electrons collide with the gas and lose energy before hitting the anode.
. Source. Describes in particular the rotating cathode method. Interesting observation that this is especially important since the cathode cannot cool quickly due to the vacuum.
