Happy new year, all !
Ken, prior to the days of Topshim and gradient probes, it used to be my
practice to run a monthly round robin of all existing instruments that
included the touch up of shims and saving them in a standard file called
'stdbbo', for instance. If you do not have a particularly bad i.e.
drifting magnet, then the higher order shims used to stay pretty well in
the global minimum. So, I used to do hand shimming with the method nicely
summarized by Woody Conover (RIP, Woody !) upto the XZ2 and YZ2
combination for transverse and upto Z4 for axial (Z5 should be pretty small
if there are no serious edge effects) and then let the system run a Simplex
optimization for the entire shim set before I head home. Outermost, it
used to take about 8 hours for 20+ shims. Both for hand shimming and
overnight simplex, I use Lineshape standard 1% CHCl3 in Acetone-d6.
With the advent of Topshim, I simply run a 1H 3D Topshim on either
Sucrose standard in 90:10 H2O:D2O or an in-house decoy sample that we have
made in bulk which is Aspirin dissolved in H2O:D2O. This is the sample we
keep in all magnets when no user sample is in the magnet. So, that's my
droplet of wisdom added to your Cornucopia of tricks.
Best Regards
Rajan
On Thu, Jan 4, 2024 at 10:45 AM Sham, Shing <ssham_at_luc.edu> wrote:
> Ken,
> There is a parameter set called topshim1d2h, or something like that. That
> should help you to see the z-axis shim profile immediately.
> Also, a small shoulder peak should attach to the main peak at the
> baseline that you could not shim off with z4 if the probe is dirty or
> something stuck there.
>
> Hope this helps and good luck.
>
> Simon
>
> ------------------------------
> *From:* main_at_ammrl.groups.io <main_at_ammrl.groups.io> on behalf of Kenneth
> Sharp-Knott via groups.io <kknott=vt.edu_at_groups.io>
> *Sent:* Thursday, January 4, 2024 12:09 PM
> *To:* ammrl_at_groups.io <ammrl_at_groups.io>
> *Subject:* [AMMRL] Shimming issues
>
> I seem to waste a lot of time getting my shims in order when they suddenly
> go out of order.... Curious if anyone has a more procedural method
> correcting their system shims. I am primarily talking about Bruker
> instruments of which I have older ones which are persnickety...
>
> I am also interested in a good way to evaluate if the probe is dirty. I'm
> dealing with Prodigy probes so I can't drop them easily. I have seen
> engineers determine this by looking at the gradient profile I believe? How
> is this done?
>
> Best
>
> --
> Ken Sharp-Knott
> Manager of Analytical Services and the NMR Facility
> Department of Chemistry
> Virginia Tech
>
> (540)267-6502 (Cell)
> (540)231-0885 (Office)
>
>
>
--
____________________________________
Rajan K Paranji, Ph.D.NMR Services Manager
*Department of Chemistry**Room 65, Bagley Hall*
University of WashingtonSeattle, WA 98195
phone : 206 685 2581 fax: 206 685 8665email: rajanp_at_uw.edu
____________________________________________________________________
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