DIY ion pump from a microwave oven cavity magnetron tube?

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George Albercook
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DIY ion pump from a microwave oven cavity magnetron tube?

Post by George Albercook »

There are several DIY diffusion pumps out there but I hate oil in my vacuum. A very clean ultra-high vacuum can be achieved with an oil-free roughing pump (sorption for example) and a combination of ion and titanium sublimation pumps. Titanium sublimation is pretty easy (maybe current control etc.) Ion pumps are a bit more complicated but actually only a bit.

They require magnetic fields in the range of 1500 gauss and voltages in the range of 4-7k What about cutting open a cavity magnetron tube, removing the copper, and replacing it with Titanium plates and tubes. The magnetic field is about right. The same with the voltage. I have not calculated the electric field strength but they are nominally the same length and we have control of the spacing. High vacuum electrical feedthroughs are already part of the magnetron tube. We may need some additional ceramic standoffs. (Don't modify the pink ceramic it is made of beryllium.) It would not be serviceable but you could vacuum silver solder it all back together without any flux and it could work for 5-10 years without service!

Any thoughts?
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Richard Hull
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Re: DIY ion pump from a microwave oven cavity magnetron tube?

Post by Richard Hull »

Yes. My thoughts are that all of this effort is rather useless and ridiculous. If you are looking for a matchlessly clean system to go very deep, which is of no value to the fusioneer, spend the big bucks and either by a true oil free roughing pump. $$$$.... Then get a turbo pump $$$$.... Then get an ion pump $$$$. A sorption pump is a great pump provided you go through three pumped and valved stages and don't mind having to going out to get several liters of LN2 every single time you pump down. Then bake out the garbage from each stage before reuse.

In short, all of the reworking of a microwave magnetron is a bit of a pipe dream. That not one living being here would attempt. Used ion pumps can be had if you really need an ion pump. No fusion person would even need one or a Ti-sub pump.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Mark Rowley
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Re: DIY ion pump from a microwave oven cavity magnetron tube?

Post by Mark Rowley »

Heck, if one has a good roughing pump a secondary vacuum pump isn't necessary to make a small chambered fusor generate neutrons.

Mark Rowley
John Futter
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Re: DIY ion pump from a microwave oven cavity magnetron tube?

Post by John Futter »

George
you have missed the rules of this site
you have provided your real name but your first post should have been in the "Please introduce yourself area"
And this post "new User Chat Area":
An ion pump is about as useful as a bicycle to a fish for fusor building
I suggest you do alot more reading of all the sub forums an especially thew FAQ's before more posts
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Dennis P Brown
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Re: DIY ion pump from a microwave oven cavity magnetron tube?

Post by Dennis P Brown »

If your interest is clean high vac and not fusor's, certainly Richard's suggestion is spot on. As for oil diffusion pumps (DP) not being clean, with a proper cold trap they can be rather clean. As for a fusor, a DP (w/o a cold trap) is an excellent high vacuum pump. Any oil based two stage pump will then work well with a DP for a fusor. Sorption pumps for removing a vessel at atmospheric pressure require liquid nitrogen. Then one can use an ultra cold/active absorption surface pump for maintaining that high vacuum; and yes, they are ultra clean; used them before for semiconductor projects. That said, they are useless with a fusor since that requires continued gas flow that would quickly overwhelm the pump.
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