Dear All
This message serves as a follow-up regarding my 800 MHz Oxford pumped magnet
issue, which has now been successfully resolved.
I would like to express my sincere appreciation to the members of this group,
particularly Corey Liu and Paulo Falco Cobra, for their valuable guidance in
adjusting the needle valve. Their detailed instructions enabled me to restore
the helium consumption to normal operating levels.
After several adjustments to the needle valve, the fridge pressure stabilized
at 14–15 mbar. The magnet temperature has remained stable over the past three months.
Cheers!
Tianzhi
-------------------------------------------------------------------
Tianzhi Wang, Ph. D.
NMR Manager
Sealy center for Structural Biology & Molecular Biophysics
University of Texas Medical Branch,
301 University Bvld, NMR dockside building, Rom 1.104
Galveston, TX 77555-1157
Email: tiawang_at_utmb.edu<mailto:tiawang_at_utmb.edu>
(409)7476821 (O)
________________________________
> From: main_at_ammrl.groups.io on behalf of Wang, Tianzhi via groups.io
> Sent: Wednesday, October 15, 2025 1:09 PM
> To: main <main_at_ammrl.groups.io>
> Subject: [AMMRL] 800 Oxford pump magnet fridge vacuum problem
Dear All
I’m having a vacuum issue with my 20-year-old Oxford 800 MHz pump magnet.
Recently, the fridge pressure suddenly increased from 15 to 21 and stayed 21
for more than 1 year, although it’s still within the specified range (9.2–25).
I also replaced the pump without any change of the pressure.
I’ve tried to locate the source of the vacuum leak but haven’t had any luck so far.
Has anyone experienced a similar issue or can offer suggestions on how to diagnose
or address this type of vacuum leak?
Alternatively, could anyone recommend a qualified engineer or service provider
familiar with Oxford pumped magnet systems who could take a look at it?
Thank you very much for your time and help.
Best,
Tianzhi
-------------------------------------------------------------------
Tianzhi Wang, Ph. D.
NMR Manager
Sealy center for Structural Biology & Molecular Biophysics
University of Texas Medical Branch,
301 University Bvld, NMR dockside building, Rom 1.104
Galveston, TX 77555-1157
Email: tiawang_at_utmb.edu
(409)7476821 (O)
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Received on Mon Feb 09 2026 - 12:05:20 MST