Turbomolecular, Oil diffusion or Getter pump

Every fusor and fusion system seems to need a vacuum. This area is for detailed discussion of vacuum systems, materials, gauging, etc. related to fusor or fusion research.
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byron addams
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Turbomolecular, Oil diffusion or Getter pump

Post by byron addams »

I am wondering witch type of pump is best suited for my tasks.
Diff pumps are messy and slow but are verry reliable and robust.
Turbo pumps are fast but delicate and easy to break.
And i dont know much about getter pumps but they sound good.
Trying to keep the magic smoke from getting out.
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Finn Hammer
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Re: Turbomolecular, Oil diffusion or Getter pump

Post by Finn Hammer »

Byron,

I am not quite sure what your task is, but if it is a fusor, and even a diversity of vacuum tasks, then you could have a look at this thread:

viewtopic.php?f=18&t=13936

Where I detail the transition from scroll pump to diaphragm pump in a turbo scenario.

Others have stated that once you have tried that combination, you will never go back, and I already tend to believe them.

Cheers, Finn Hammer
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Mark Rowley
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Re: Turbomolecular, Oil diffusion or Getter pump

Post by Mark Rowley »

Byron,
Diffusion pumps arent "messy". They're a sealed system just like the oil in a roughing pump. I couldn't imagine any diffusion pump working if there was even the slightest of leaks. I run a water cooled diff pump but many others run a "finned" air cooled pump if you don't like water. Personally it's been no issue or mess. Small pond pump and a bucket set to the side, no clutter or mess. Besides, ultimately you're going to need liquid coolant anyway for your fusor if you plan to conduct any sustained high output runs for activation work.

What's nice about diffs are their bulletproof design and their ability to pull a vacuum much deeper than what's required for a fusor. A TMP does the same but will generally pull an even deeper vacuum which is good for other projects, but certainty not needed for a fusor. And as you stated, they're fast. I'm not sure how important "fast" is on a fusor, I suppose it depends on the person. My diff pump can bottom out the vacuum gauge in a little less than 15 minutes. During those 15 minutes, I'm generally conducting other necessary prep work (that all operators have to do) before starting a neutron producing run. So the 15 minutes of warmup time is inconsequential.

If money is a concern a diff will be your best bet. TMP's are comparatively expensive unless you find a stellar deal (they do happen). And as far as TMP fragility is concerned, you don't have to look far in the archives (or the FB fusor groups) to find some costly failures.

Last thoughts.... TMP's are generally high volume pumps. If you plan on running a small chamber, throttling may be difficult or problematic. They can really eat up the deuterium fast unless you have proper valving (on the pump side). Check the archives on that issue as well.

To be fair though, when TMP's work good, they are darn nice.

Mark Rowley
John Futter
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Re: Turbomolecular, Oil diffusion or Getter pump

Post by John Futter »

getterpumps are usually used only on sealed systems ie like vacuum tubes. Some ultra high vacuum systems use them to pump pesky gasses like hydrogen that ion pumps and the like do not pump well getters are usually switched on at 10^-7 or preferably 10^-8 millibar and will help to get to ultimate vacuums of 10^-10millbar.
The ones I have used have come from
https://www.saesgetters.com
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Maciek Szymanski
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Re: Turbomolecular, Oil diffusion or Getter pump

Post by Maciek Szymanski »

The diffusion pumps are for me "the ultimate solution in high vacuum creation". The price/reliability/speed and final pressure combination are unbeatable by any other pump. I would not use any other high vacuum pump until I do not have any special requirement for which I can sacrify other diff pump advantages - like the need for very clean, oil free vacuum or no warm up time requirement. Or if the money is not an issue. A TM pump even if bought cheaply with the cable and controller still may be very expensive in case of failure (until you are not Richard Hull of course). Failure of the diff pump is rather unlikely expect the burning of the heater - not more expensive than repair of the electric oven.
“Begin at the beginning," the King said, very gravely, "and go on till you come to the end: then stop.” ― Lewis Carroll, Alice in Wonderland
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Richard Hull
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Re: Turbomolecular, Oil diffusion or Getter pump

Post by Richard Hull »

I ran a diff pump from 2004-2019 with fusor IV with out ever removing or servicing it in any manner over the entire period. When I took it apart the oil looked good and the pump was clean. I took it apart and got the xmas tree cleaned of oil and dried the pump body for storage. I installed my first turbo and it worked great! Until a series of repetitive arcs in fusor V managed to kill the controller electronics. Fortunately, I was able to repair the controller over a one month period of depressing effort. I love the Turbo, of course now that I have used one, but if this turbo goes down for good, I am back on the old forced air cooled diff pump forever. As already noted, the speed of the turbo is just not needed in a fusor situation where fusors of a maximum of 8" diameter are being pumped.

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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byron addams
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Re: Turbomolecular, Oil diffusion or Getter pump

Post by byron addams »

I think i will go with a diff pump.
i just wanted some other opinions from people to make sure that i was making the best decision.

thank you for the advice.
Trying to keep the magic smoke from getting out.
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