English: Magnetron section transverse to axis.

Section through a magnetron from a microwave oven. The magnetron has a diameter of about 4 centimetres.

There is a central cathode which is grey in colour. Everything else is copper and forms the anode.

Around the anode, a total of 10 'spokes' are connected to the exterior of the magnetron. There are 5 'plain' spokes that are alternated with 5 'notched' spokes (the notches can be seen near the outer ring). Each pair of adjacent spokes (i.e. a plain spoke and a notched spoke) forms a resonant cavity.

Around the cathode, two concentric rings (an inner ring and an outer ring) can be seen. The inner ring electrically connects the notched spokes; the outer ring electrically connects the plain spokes. The inner and outer rings are known as 'strapping' rings and ensures that the magnetron operates in the 'pi' mode.

For the notched spoke that is roughly at the 'ten o'clock' position, the notch has an output coupling loop that extends upwards and out of the top of the photo. The output coupling loop is used to couple microwave energy out of the magnetron so that the microwave energy can heat up food in the microwave oven.

Incidentally, note that the magnetron shown in this photo is almost exactly the same as the magnetron shown in another photo on the magnetron page: