The Magnetron is a fun and interesting device that I'm trying to wrap my head around. I have the just of it, but if anyone does not know this topic... chances are you will not be able to answer any questions.. But here is a quick 6 minute description. The video suggests at the end that this is one of the most complicated technologies of our time. So it is fun to try to comprehend it. I get the "mechanics" of the mixed fields and electrostatic nature of the ion flow, but there is limited information online. Most all magnetrons are for the purpose of microwave ovens or radar these days (maybe forever if no other purposes - if you know of any.. suggest them please). I started from the beginning looking at the Hull or single anode magnetron.. and get the just of the flow. Everything I've seen so far suggests the largest magnetrons made are in the 30cm range... and I have no idea how small they can get and still function? My question for any who may know... is how big or small can these be made? It may not be practical but can you make a magnetron as small as a thimble... or as big as a house? How do they know the best sizes? I can only see these used for radar (original purpose) and microwave ovens... the magnetrons in your home. (Warning: if anyone wishes to study magnetrons from their microwaves.. there are dangers in removing.. so read up if unaware). So my questions would be a) What determines the ideal size of a magnetron? b) What kind of waves can we produce? c) aside from radar and microwave ovens.. are they used elsewhere? Would the ion flow in interaction space still work if the magnetron was as big as a house.. or small as a thumbnail? This appears to be complicated physics... and I'm just trying to wrap my head around the science of it. Note: I have no intention of building magnetrons the size of a house or small as a thumb... but I do not yet understand why some are the size of microwaves magnetrons (10-15cm in diameter) and some are as large as 30cm in diameter. I'd also be interested in any search terms for journals, etc... or more thorough explanations than youtube. Thanks in advance... they are quite interesting devices. Certainly fun to think upon.