If you really want to pimp your microwave you can add a couple extra strong magnets externally to one pole of your magnetron. This asymmetry will prevent multip

If you really want to pimp your microwave you can add a couple extra strong magnets externally to one pole of your magnetron. This asymmetry will prevent multiple loops by electrons around the magnetron's internal chamber and increase the spectral purity of your magnetron output. (because all electrons have the same energy the first trip, but multiple different energies the subsequent trips).