Wendy,
More data helps. Other possibilities suggest themselves. One possibility
is your shim power supply being unstable. Stable last night but back to
fluctuating this morning. Intermitant contacts to RT shims are another
possibility. Large metal objects are not being moved within 10-20 ft of
the magnet (including floor above or below)? Shim stack is loose and
moving a bit ? Etc.
Quenches are one way events. Once they happen a power supply has to be
attached to reenergize the main coil or cryoshims coil. There is usually
a period before the quench when increased drift is observed.
Charlie
On Aug 15, 2024, at 4:54 PM, Spin-Doc <bert.heise_at_spin-doc.net> wrote:
Hi,
Could you possibly specify “lineshape deterioration” a bit
more precisely? I mean, are we talking about a change from 1 Hz linewidth at
half-height to something like 5-10 Hz (not great, but can easily be induced
by e.g. changes in the sample like bubble formation, product fallout or
solvent evaporation) or 200-2000 Hz (making up numbers, but that’s
what a failing cryoshim can easily lead to)?
A failing cryoshim is also one-way only, so lineshape is and stays bad
afterwards and an only rarely be compensated by RT shimming. Your case doesn’t
sound like a cryoshim effect to me…
Best regards
Bert
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Spin-Doc
Magnetic resonance equipment, service, training & more
Dr. rer. nat. Bert Heise
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Mail: bert.heise_at_spin-doc.net
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Representing MestreLab, Stelar & Barthel HF
Am 15.08.2024 um 22:24 schrieb Wendy Breyer <web216_at_lehigh.edu>:
Hi,
Is it possible to have a cryoshim fail intermittently? I made a full drift
measurement over 13 hours last night as outlined by Charlie Fry and saw very
little drift AND very little change in peak shape... but, on the same sample
on other days, I've seen peak shape degrade over a few hours ("lock" was on
though so I don't know if center position drift happened during those data
collections). In fact, a student used the spectrometer this morning after
me and saw large degradation in peak shape over the course of his 1.5 hour
experiment.
Thanks for all your help!
Wendy
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