Hi Jessica
I do not believe that there is a liquid helium probe - the helium cryo probes
used a closed loop refrigeration system with helium as the refrigerant - the
temperature of the coil and preamp is maintained around 14 to 17 K.
The helium used is higher purity than UHP (forgot the grade) but it is several
times more expensive than UHP grade helium.
Unless there is a leak, you use helium only when cycling the system (warmup/cooldown).
Assuming only a few cycles/year, the tank should last many years. In the 17 years
I’ve had my probe, we’ve gone through 3 tanks, and there were
periods where we had issues with the heat exchanger causing many extra cycles
and also a time when the sample changer losing samples in the probe (user error).
I keep a spare tank just in case.
Besides indirect costs (electrical, site,etc), and the initial cost, the only
real cost are the yearly PMs - which are pricey. Helium cost although high for
each tank - since it lasts long - is small. Unless you plan on swapping probes
frequently, which you don’t. Pretty much my probe stays in the magnet
(except when samples got dropped in the magnet w/o spinner due to sample changer -
hasn’t happened for a long while, cross fingers)
We never had issues with the probe with one small exception - there was minor
manufacturing defect (sensor not reading correctly, worked fine otherwise )
when new and we opted for a planned repair. Since it was planned, we had a
loaner with no trouble. It went to Switzerland and took over a month to come back.
We are in the top floor of a fairly tall building and to get rid of heat the
compressor throws of, we have a heat exchanger system using a Haskris (closed
loop water circulates between cryoprobe compressor and Haskris refrigeration
system; then the Haskris is cooled by separate water system circulated to heat
exchangers on the roof). If something goes wrong with that system, then the
cryoprobe compressor heats up and then the system shuts down gracefully.
Hope this helps - let me know any questions.
Cheers
George
On Aug 31, 2023, at 7:15 AM, Roberts, Jessica <jroberts_at_ohio.edu> wrote:
Hi everyone,
Thank you all so much for your responses. I am happy to know it is a closed
loop system; I just wanted to make sure what all the added expenses are you
have to deal with in order to benefit from the probe technology itself. A
few things I should have included in the original email:
1. I would likely keep the LHe cryoprobe installed and not do probe switches
in that instrument. Goal is to acquire a second instrument, and hopefully have
a Prodigy probe installed on one that could then be used for switching to other
probes based on user needs, and one instrument to run LHe cryoprobe exclusively.
2. I am hoping to install the LHe onto a Bruker 400 MHz Avance.
How robust are the probes themselves? In addition to the added coldhead/regular
maintenance expenses, how often have you had the probe go down/require additional
Bruker visits/had to send the probe in for repairs?
Thanks again everyone!
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>
--
-=-=-=-=-=-=-=-=-=-=-=-
Groups.io Links: You receive all messages sent to this group.
View/Reply Online (#494): https://urldefense.com/v3/__https://ammrl.groups.=
io/g/main/message/494__;!!PvDODwlR4mBZyAb0!XX6Vo6AZPzMGphF9VGexx5IObGBzb1S4=
aQyIteqUNfd4kBVNlI66D6ltEZfBduxXNciMATDzkQDBS_kUF1ELXA$
Mute This Topic: https://urldefense.com/v3/__https://groups.io/mt/101067096=
/7559972__;!!PvDODwlR4mBZyAb0!XX6Vo6AZPzMGphF9VGexx5IObGBzb1S4aQyIteqUNfd4k=
BVNlI66D6ltEZfBduxXNciMATDzkQDBS_mjY5Z1Sg$
Group Owner: main+owner_at_ammrl.groups.io
-=-=-=-=-=-=-=-=-=-=-=-
Received on Thu Aug 31 2023 - 04:45:50 MST