Hi Adil,
Sorry for the slow reply - I had a vacation day and then a long weekend.
Here's what I think.
* I'm not sure any of the tests you ran prove that the preamp isn't
the cause of the issue. That was kind of a long shot, though, so maybe
it's not useful to worry about the preamp at this point.
* The fact that the experiment works with PLW1 and fails with PLW1.7W
is interesting to me. I wonder if there's a hard limit, or if there's some
range of powers where you can acquire a spectrum but something might be starting
to fail.
* I would still recommend opening up the amplifier and checking for loose
internal cable connections. This might not help anything, but hey, couldn't
hurt, right?
If it were my system I would probably run a popt on a simple PROTON experiment
and vary PLW1 between 8W and 12.7W in steps of, say, 0.1W. I would watch the
data as it was acquired and see if I could see something changing in the spectrum
as you got to higher powers. When the instrument started giving errors you can
use the command popthalt to stop the popt and save the acquired data.
Or, you might be able to get more information by doing the following instead:
load up a PROTON experiment and then open that amplifier webpage. Start the
experiment using the gs command instead of zg (this repeats the first scan of
the experiment and doesn't save the data) and watch the reflected power reading
in the amplifier webpage, and the FID at the same time. In the gs interface
that opens up, I believe there's a tab that will allow you to adjust the transmitter
power. You can change that in 0.1W increments and see what the reflected power
does at different power levels. And see if the FID changes more than you'd expect.
(The amplitude will change as you get further from or closer to the 90 degree pulse,
but nothing too weird should happen.) And I think the amplifier page should
auto-refresh. You might need to wait a few scans for the amplifier page
to refresh at the correct time to get a reasonable reflected power reading.
There is one other thing I would suspect might cause similar issues that is
not the amplifier. And would duplicate the fault with multiple probes. Each
preamp has a 50 Ohm reference that it uses for tuning the probe. If that goes
bad, the probe will not be tuned to the proper frequency, even though it might
look like it is. If that were bad, you would get high reflected power, and
you would see the same effect for all probes. Did you actually calibrate the
proton pulse at 8W or did you simply calculate what it should be? I would
also be interested to know if the 8W pulse is correct. If the 8W pulse is
correct, this indicates that the probe is properly tuned and the 50 ohm reference
in the preamp is probably not the problem.
Cheers,
Mike
From: main_at_ammrl.groups.io <main_at_ammrl.groups.io> On Behalf Of Muhammad Adil Raees via groups.io
Sent: Friday, July 21, 2023 1:43 AM
To: main_at_ammrl.groups.io
Subject: Re: [AMMRL] AVANCE NEO Amplifier Gives Mismatch Fault
Hi Mike,
Thank you for these suggestions. The error initially started to appear only
with 13C dept experiments and wasn't that much frequent. Then with the passage
of time, went frequent, and started with other experiments also, like 1H,
water suppression, and COSY. I have attached the screenshots of the error
that exactly appears. Closing the error dialog box and repeating "zg" on
the same file sometimes work making sure no problem is with the routing. The
13C broadband experiments with pulse program zgpg30 or zgpg works smoothly
and I never have this problem with broadband experiments.
Bruker personnel remotely checked our system for this. While he was connected,
we tried with a different RF cable first and then doubled the length by joining
two cables together with a connector but it didn't help too. The actual P1 and
PLW1 in our system are 10us and 12.7W and then when we changed P1 and PLW1 to
12.5us and 8W then the zgpr water suppression experiment worked fine on the
standard sucrose sample and if we kept the power level to 0 then the error
didn't persist. Does this test confirm that the preamp isn't a culprit? what
information can be extracted from this test?
Thank you
Adil
--
Muhammad Adil Raees, Ph.D.
Manager NMR Facility
The Central Laboratory
Syed Babar Ali School of Sciences and Engineering
Lahore University of Management Sciences
Opposite Sector-U, D.H.A. 54792, Lahore
+92-330-2866755
adil.raees_at_lums.edu.pk<mailto:adil.raees_at_lums.edu.pk>
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Received on Tue Jul 25 2023 - 08:47:21 MST