Re: Cold pumping magnets
mayne@chemistry.utah.edu
Mon, 13 Dec 93 12:35:24 MST
>Charlie-
> I was pleasantly surprised to hear that you routinely cold pump your
>Varian and Oxford magnets. I had Varian pump one XL-200 magnet and it
>seemed to be a rather delicate operation, and I was told at the time that
>one could not pump the Oxford magnets! At this point, I guess my question
>has to do with the equipment you use for this pumping. Did you buy an
>official, authorized Varian kit, put your own together, or what? I
>suspect that a description of this would be of interest to the entire
>mailing list, especially if it is especially inexpensive or cost effective.
>Perhaps you could forward this to Dennis Edwards if he was the one that
>was responsible for obtaining the necessary hardware. Hints and advice
>are always appreciated as well!
>
>Thanks,
>Steve Silber SILBER@TAMCHEM BitNet
>Texas A&M University SILBER@CHEMVX.TAMU.EDU InterNet
>Department of Chemistry (409)-845-1745 (voice)
>College Station, TX 77843-3255 (409)-845-4719 (fax)
I will reply to this for the benefit of the whole group. We just use a
helium leak detector system. It was not cheap; I don't remember how much,
maybe ten to twenty thousand dollars. We have enough magnets that we could
justify it. If it really costs $10K to have Varian do it, that wouldn't
take much justification. I guess the $10K includes doing the seals and
recryoshimming, but we find we can put off doing that more or less
indefinitely. Obviously, if you accidentally break vacuum, you have a
nearly certain quench on your hands, and a badly moisture contaminated
dewar, but due care makes this a fairly remote possibility. We even let the
students continue to use an instrument for routine things while it is being
pumped.
Dennis is not in today, but I'm sure he can respond with more details when
he returns.
Charlie
Charles L. Mayne
University of Utah
Dept. of Chemistry
Voice: (801)581-7413
FAX: (801)581-8433
E-mail: mayne@chemistry.utah.edu