Ken,
You actually do not need that great of a vacuum for a helium transfer line
(imho) because the line will cryopump down to a much higher vacuum once it
has liquid helium flowing inside it. That is, you only need a sufficient
vacuum to not generate an ice bridge upon cooling. That is, a rough pump
is all you need.
Of course, the better the vacuum, the less helium that gets consumed freezing
out the remaining gas in the vacuum jacket of the line. In practice, however,
there is always a little helium left over when doing a fill, so the amount of
liquid helium consumed in freezing the gas in the vacuum jacket is inconsequential.
Jeff
> From: main_at_ammrl.groups.io On Behalf Of Kenneth Sharp-Knott via groups.io
> Sent: Wednesday, October 22, 2025 9:42 AM
> To: main_at_ammrl.groups.io
> Subject: Re: [AMMRL] He Transfer Line pumpdown tool - Which one does this use?!
As a follow-up, what is the recommended time to pump on the transfer line
with a turbo? What vacuum level are you shooting for?
Thanks!
Ken Sharp-Knott
Manager of Analytical Services and the NMR Facility
Department of Chemistry
Virginia Tech
(540)267-6502 (Cell)
(540)231-0885 (Office)
________________________________
> From: main_at_ammrl.groups.io on behalf of falcocobra via groups.io
> Sent: Monday, August 18, 2025 11:53 AM
> To: main_at_ammrl.groups.io
> Subject: Re: [AMMRL] He Transfer Line pumpdown tool - Which one does this use?!
Hi Ken,
This looks like a cryofab line. I can't really tell if the inside nut is
threaded, but if it matches the thread from my second picture, you can get
an adapter from cryofab.
Best,
Paulo
--
Paulo Falco Cobra | Scientist II - Facility Manager
NMRFAM <
https://nmrfam.wisc.edu/ > - University of Wisconsin Madison
E paulo_at_nmrfam.wisc.edu
P (608) 265-3303
A 433 Babcock Drive, Madison, WI. 53706
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Received on Wed Oct 22 2025 - 08:09:16 MST