Hi everyone. I'm new here. This is probably not at all helpful, but in my
experience the Varian heat transfer through a metal coil immersed in liquid
nitrogen was much simpler, as it only required one heater instead of trying
to balance a boil-off heater against the warm-up heater. Neither JEOL or
Bruker do it that way; both go the boil-off route. Which also requires stopping
the VT to refill the dewar, at least with the dewars I've used. If anyone
knows what the advantage of the boil-off approach is, I would like to know.
Thanks!
Dr. Charles Garner
Associate Professor and NMR Supervisor
University of Memphis
> From: main_at_ammrl.groups.io On Behalf Of Roberts, Jessica via groups.io
> Sent: Thursday, July 11, 2024 2:48 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 Fri Jul 12 2024 - 13:07:18 MST