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by Epic (880 points)

Can someone explain the process by which a cavity magnetron produces microwaves? How do the electrons and magnetic fields interact?

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by Mythic (1.5k points)
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So you got this vacuum tube, right? Kinda looks like a little metal canister with some funky anodes and cathodes inside. Now, the key ingredient here is a strong magnetic field running along the length of the tube. We're talking a magnetic field so powerful, it would probably make your fridge magnets jealous..

Inside this magnetic field party, you got a hot little cathode just chillin' and emitting a stream of electrons. These electrons get blasted out into the vacuum and immediately feel the force of this intense magnetic field trying to make them corkscrew around the long axis of the tube.

But here's the kicker - the electrons also feel an accelerating force from the positively charged anodes in the tube. So you got this constant tug-of-war happening between the magnetic field trying to make the electrons spiral, and the electric field from the anodes trying to accelerate them towards the sides of the tube.

This sets up a really weird, corkscrew-y path for the electrons to travel along the length of the tube. And as they get nudged back and forth by the alternating magnetic and electric fields, they start to buncher up into these little rotating clouds of charge.

These rotating charge bundles are what generate the microwaves. See, as the charges spin around, they're basically acting like really tiny antennas, radiating electromagnetic waves with frequencies that correspond to the rotation speed and sizes of the charge clouds.

The cavity part of the magnetron comes into play by being carefully shaped and sized to resonate at certain microwave frequencies. It's like an air-filled waveguide that focuses and amplifies the microwaves being radiated by those spinning charge bundles.

So in a nutshell, you got powerful magnetic fields making the electrons do the corkscrew boogie, which sets up oscillating charge rotations that radiate microwaves, all focused and amplified by that precision-sized cavity resonator chamber. Wild, right?

Crank up the accelerating voltage, and you get higher rotation speeds which translate to higher microwave frequencies being generated. The bigger you make the tube and magnetic field, the more uber-powerful those microwave pulses can get.

It's basically a delicate dance between accelerating electrons, spinning magnetic fields, and carefully tuned metal cavities to extract those mighty microwaves. Not your average microwave oven, that's for sure!
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