These are all great guess. I systematically went through
this checklist trying to determine the cause.
Receiver gain, rf power, lower magnet to floor, 50 ohm terminate the broadb
and channel at probe, turn off and isolate the lock, remove the gradient cable,
disconnect the BFB cable (Pics, VT, ect) from the iProbe, complete reboot
of NEO console. None of that had any affect. After the reboot, I
with the lock "off" I saw a crazy behavior in the lock signal...it too had a
stable oscillation riding on the level captured upon reboot.
I did leave out one piece of vital information. Thus Clemens's
answer was the closest. I had performed an LN2 fill about an hour
earlier. Out of sheer desperation, I put my finger on the LN2
boil off check valve. This is where i felt the vibration. I replace
the LN2 heat sink with a piece of tubing to remove the check valve.
and the 1H spectrum return to normal.
LN2 boil off and that valve was the cause. I have never observed
this, to this extent in the years this system has been operational.
I'll need to see of the check valve is faulty, of if the magnet needs more
time to settle before returning it to normal operation, or this is a sign
of a larger issue with the magnet. Hopefully it's just the valve.
Hope you all thought this was a fun use of the AMMRL email and something others
can learn from.
Brian
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Received on Wed Oct 01 2025 - 17:54:38 MST