Jessica,
Check to make sure that the big o-ring that seals the dewar at the top where
the clamp goes on is not cracked. If it leaks you will not get as much cold
gas delivered to the probe.
Jeff
> From: main_at_ammrl.groups.io On Behalf Of Roberts, Jessica
> Sent: Thursday, July 11, 2024 3:48 PM
> To: main_at_ammrl.groups.io
> Subject: [AMMRL] LN2 evaporator assisted VT NMR
Hi everyone,
I hope this email finds you all happy and healthy! I have been troubleshooting
cold VT NMR on my 500 MHz (Ascend 500 with Avance III HD console) instrument
and was hoping to find some insight here. I have attempted to run cold VT
NMR with two different LN2 evaporators and have had similar circumstances
occur; I am wondering if there is a configuration/firmware based issue here.
Essentially, I am trying to cool down to at least -50 C, though cooler would
be better. I have appropriately set up the instrumentation, connected the LN2
evaporator, etc, but can only cool down to 235.7 K. I have been cautious about
the condensation formation and have been keeping the probe-facing portion of
the setup dry throughout this whole process to avoid any ice-related issues.
After receiving the insufficient chilling status on the temperature control
suite, I navigated to the LN2 evaporator and dewar. After disconnecting from
the probe, there is still cold N2 gas being pushed through the line. I can
also confirm I had sufficient LN2 in the dewar at the time of the error. I
had an issue with insufficient chilling in the past, though I cannot currently
recall what temperature I was able to get down to previously. I am wondering
if there is anything software or configuration side that might be the cause?
I would suspect if the LN2 evaporator electronics were the issue, I would not
be able to cool down that far - but perhaps I am missing something!
If anyone has any insight or suggestions, I would be grateful!
Thanks all and happy resonating!
Jessica
Dr. Jessica M. Roberts, Ph.D.
Assistant Professor of Instruction
NMR Facility Manager
Department of Chemistry and Biochemistry
Ohio University
245 Chemistry
Athens, OH 45701
740.593.0038
jroberts_at_ohio.edu<mailto:jroberts_at_ohio.edu>
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Received on Thu Jul 11 2024 - 18:25:32 MST