While we now think of a magnetron as a microwave oven component, they are important in many microwave devices including radar. They are interesting because all they can do is oscillate.

Dellavalle also notes there are several interlocks in the door of your oven, that will shut off the machine’s magnetron ...

Clearly, as your bog standard microwave oven can only handle at most one kilowatt; the ‘oven’ needed a bit of an upgrade. A 16 kW water-cooled magnetron. Why not over-drive it to 20 kW for fun?