As to generating gradient echo profile as a diagnostic tool for dirt in
probe, I don't have much experience with that. But I want to add that if
there is an insert glass breakage, it shows up noticeably in the profile,
more so with 1H profile that can be generated as a 3D image.
Topshim can be run with the option "topshim 3d map" and it will retain the
datasets from which we can examine the before and after field maps (it
usually deletes the datasets after shimming is done).
Rajan
On Thu, Jan 4, 2024 at 11:03 AM DrSpin <rajanp_at_uw.edu> wrote:
> 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 on behalf of Kenneth Sharp-Knott via 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 Washington Seattle, WA 98195 phone : 206
> 685 2581 fax: 206 685 8665 email: rajanp_at_uw.edu
> ____________________________________________________________________
>
>
>
>
--
____________________________________
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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Received on Thu Jan 04 2024 - 11:11:04 MST