Sorry, in my earlier email, I meant to say Z6 should not be shimmed using topshim
for normal samples on cryoprobes, but instead I typed Z5. It should be Z6,
Greg
Gregory J. Heffron | Director, Biomolecular NMR Facility | Visiting Scienti=
st, Dana-Farber Cancer Institute | Department of Cancer Biology
Harvard Medical School 240 Longwood Ave. | Boston, MA 02115 | Fax :617-432-4383
________________________________
> From: main_at_ammrl.groups.io <main_at_ammrl.groups.io> on behalf of Heffron, Gregory J. <gregory_heffron_at_hms.harvard.edu>
> Sent: Tuesday, January 9, 2024 8:10 AM
> To: main_at_ammrl.groups.io <main_at_ammrl.groups.io>
< Subject: Re: [AMMRL] Shimming issues related to oscillating lock level
Hi,
One thought that occurred to me is that if you are using compressed air for
VT regulation and you use an analytical air dryer with dessicant towers, there
can definitely be cycling effects that can cause lock instability, especially
if there is a problem with the dryer. We and others have experienced this in
the past. Probably this is not it, but worth checking. The dryer switching can
cause a puff of air that leads to lock instability and associated broadening of
peaks. But this would not usually happen if your air system has a buffer tank
to prevent this issue.
Another possibility is that somehow you are shimming Z5 when doing topshim.=
This can lead to a severe temperature gradient because of high Z5 shim coil
current and the heating it causes. Normally, Z5 should not be shimmed during
topshim for cryoprobes. Again, this is not likely, but worth ruling out.
If you cannot identify a cause, you might spend the time it takes to put in
an RT probe and see if the problem happens there also. This would eliminate
the probe as the source of the problem.
Good luck,
Greg
Gregory J. Heffron | Director, Biomolecular NMR Facility | Visiting Scienti=
st, Dana-Farber Cancer Institute | Department of Cancer Biology
Harvard Medical School 240 Longwood Ave. | Boston, MA 02115 | Fax :617-432-4383
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Received on Tue Jan 09 2024 - 07:15:41 MST