In magnetrons, is it the accelerating electrons or alternating fields within the anode that produce the microwaves?

Question

Doing a report for a school project and want to get to the bottom of the radiation source within a microwave oven:

According to Maxwell's equations don't the accelerating electrons (accelerating because they are changing direction relatively circularly) create the magnetic field which creates an electric field which creates a magnetic field (EM Radiation).... ?

In this video (link below) he attributes the EM radiation entirely to the LC circuit's changing of fields (which is undeniably happening and surely producing radiation). My problem with this is that the electric and magnetic fields that are made by the anode should be out of phase with each other according to LC circuit concepts, which to my understanding is not true of EM radiation. Other research of mine continually seems to show that it is the first option I mentioned that generates the microwaves for heating, rather than the second. Do they generate the same frequency or is only one of these EM wave sources valid....? If both are true, which makes the proper frequency for heating food, 2.45GHz?

https://www.youtube.com/watch?app=desktop&v=5DpYlnHT-0s (location in video: 4:10)

Any help would be desired, and soon please! Thanks

Answer 1

A magnetron shoots a stream of electrons past a series of cavity resonators in a circle. A DC magnetic field bends the stream into a circle that passes by the resonator openings over and over again. Just like blowing air across the top of an empty beer bottle triggers the oscillation and produces an acoustic note, so does blowing a spray of electrons across the entrance to the cavities. Once the oscillations begin, the circulating electron stream becomes bunched at the oscillation frequency and the magnetron locks in on that frequency mode and the oscillation amplitude shoots up. The oven cavity then fills with microwave radiation bled off the magnetron and your food cooks.

The E and B fields in the cavities have to be out of phase in order for resonance to be established in them. Each cavity stores energy in an E field when the B field is a minimum and then feeds that energy back into the B field on the next half-cycle: the energy then sloshes back and forth between E and B over and over again.

The circulation of the electron beam around and around the cavity openings makes the process particularly efficient- up to 70% of the initial beam energy gets converted into microwaves in this way, which enabled very high-powered radar sets during and after WWII- and very cheap microwave ovens today.