Hi,
I don't want to sound alarmist, but as it wasn't quite clear from your email or
picture: could you please URGENTLY check whether:
- the helium boiloff meter does show any boiloff
- the original check valve is still connected (facing down? not clear in the picture)
on the exit of the helium manifol - what is the pressure inside the magnet now
(hook up a good manometer to the "top" exhaust of the magnet)? Originally this was
about 0.15 psi = 10 mbar and you don't want this to be too much higher.
You want too avoid any overpressure to the magnet which may cause a quench
of a cryoshim or, of the magnet itself…
It might be possible that during the installation of the helium recovery the magnet
got subjected to some overpressure which may have lead to drifting shims.
You may be able to simply overcome this by running a 3D gradient shim (Tools -
Standard Calib - Setup 3D gradshim, you may need to activate it under Edit - Applications -
Enable 3D gradshim).
Otherwise I concur with the colleagues below - you *really* want to add a (1 m at least)
flexible tubing to prevent massive vibrations from getting directly transmitted into the magnet.
Best regards
Bert
> On Tuesday, April 1, 2025 at 11:03:18 AM MDT, Emily Crull via groups.io wrote:
>
>
> Hi everyone,
>
> I'm still working on familiarizing myself with VNMRJ 4, and our Agilent has
> recently encountered what is presenting as a shim based issue.
>
> Over our spring break (Mar 16th-22nd), we had the hook up for our incoming He
> collection system installed (featured in the picture). Since that occurred, we
> have been having noticeably broader peaks in the 1H NMR spectra and simply running
> Z-gradient shims isn't fixing the issue. This is appearing even in the Ethylbenzene
> standard we have. We're just seeing humps with no resolved coupling at all.
>
>
> Here's what I can say about the magnet itself:
> Based on the coin level I put on top of the bore, it is level, so the legs
> appear to be keeping up with the added weight from the install.
> The magnet is from 2012.
> We haven't seen a change in our Helium consumption. Our Nitrogen meter only
> registers in 5% increments and it's drop rate didn't change at all either.
> I believe I have updated the shim map using a house made D2O standard, but the
> issue still persists. The last shim map was from 2020.
> The default "Gradient shim" button in VNMRJ that appears next to the AutoLock and
> AutoTune is not improving the peak shape.
> Using the Autoshim drop down menu and selecting "Z-gradient and 4 non-spin shims"
> was sometimes resolving the issue.
> The issue is not limited to one account and is being observed on the admin account as well.
>
> Any feedback on other ways to troubleshoot the issue and/or resolve it would
> be greatly appreciated. If any other information would be useful in diagnosing
> the problem, let me know what it is and I'll try and find it.
>
> Many thanks,
> Emily Crull
> Director of Chemistry Shared Instrumentation
> emily.crull_at_mail.wvu.edu
> West Virginia University
>
> <Agilent-He-Hookup.jpeg>
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Received on Wed Apr 02 2025 - 04:22:12 MST