Need for Diff Pump Baffle?

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Ed Meserve
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Need for Diff Pump Baffle?

Post by Ed Meserve »

Hello all, I am in the planning stage for my vacuum system upgrade, and I would like to know what the consensus was around the need for a cooled inlet baffle for a diff pump.

On a scale from 1 to 10, 1 being "not needed at all", and 10 being "must include", where would you place the need for a baffle?

Regards,
Ed
Ed Meserve
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Maciek Szymanski
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Re: Need for Diff Pump Baffle?

Post by Maciek Szymanski »

For a fusor I wold state 3. You will have to throttle the pump with some kind of valve to reduce the deuterium usage, so the valve will serve as the vapor trap to some extent. The main risk involved with the vapor back streaming is that after some time the insulator of the cathode stalk will be covered with the oil residues which may cause surface arcing to the shell. Generally you can expect that there will be more need for routine cleaning of the chamber and viewports.

From my experience with a water cooled baffle and not throttled pump working on silicone oil (DC704) the chamber contamination is marginal.
“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: Need for Diff Pump Baffle?

Post by Richard Hull »

Maciek is correct. 3 is about right. I never ran one over the years 2000-2019 on my diff pump, but like Maciek noted, I feel that my normal right angle 2.75 conflat chamber leak valve kept a lot of evil out of the chamber. My pump was a force air cooled type by Leybold. I was also hyper careful regarding its operation over those years. All diff pumps demand a smart and careful operator at the controls.

Believe me if I had access to even a venetian blind or chevron uncooled baffle, I would have used it. A water cooled baffle is hard to come by and a liquid nitrogen baffle is just too much trouble, but is the ideal if you pump deep. We do not need to pump deep if the fusor is the single goal for our vacuum system.

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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Ed Meserve
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Re: Need for Diff Pump Baffle?

Post by Ed Meserve »

Maciek / Richard,
Thanks for the quick response!

Regards,
Ed
Ed Meserve
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