Hello,
We have a similarily aged cold probe on our varian 500 (2004, and the
whole cryobay dates from then as well). Constant power and compressed air
shutdowns have plagued us recently too, as extensive renovations are going
on in our building.
I got worried about warming and cooling the probe every two weeks (which
is about the shut-down schedule at the moment), and took it out two months
ago. I haven't seen any deterioration in pulse widths or preformance over
the years, but I am pretty cautious when it comes to warming and cooling-
usually give it at least overnight under vacuum at room temperature before
initiating cooling (otherwise I get too much arcing during 13C decoupling,
no matter how much conditioning I do), and I stick with the default
cooling cycle- says 6 hours, but it is usually down to 25K after about 3
hours. Occassionally I collect data as soon as it is cold, but mostly wait
until the next day.
It's a pretty huge temperature drop that the probe goes through, so I'd be
leary of cooling it too quickly. Although on the other hand, I think the
500 cold probe is pretty robust (certainly in comparison to the 800 duds
we have had experience with), and I am just erring on the side of caution
in how I treat ours.
Good luck,
Tara
On Fri, 1 Apr 2011, Van, Que (NIH/NCI) [C] wrote:
> From: "Van, Que (NIH/NCI) [C]" <vanq_at_mail.nih.gov>
> To: "ammrl_at_ammrl.org" <ammrl_at_ammrl.org>
> Subject: AMMRL: cooling down older cryogenic probes
>
>
> Hello Everyone,
>
>
>
> We have a Varian cold-probe on our 500 NMR installed back in 2003. Our cryobay was
> retrofitted with a Leybold Coolpower 10MD a few years back. We had many power outages
> on campus in the last two years and this had resulted in many cold-probe warm-ups and
> cool-downs. My question is this, for this generation of cold-probe, how fast can one
> cool down the cold-probe? Is there any possibility of performance degradation (i.e.
> longer pulse widths even after months of usage and hard burns) with a fast cool-down,
> say within 1 to 1.5 hr? If you have a similar system, how fast do you cool down your
> probe?
>
>
>
>
>
> Sincerely,
>
> Que Van
>
>
>
>
>
> Que Van (Contractor)
>
> Sr. Scientist
>
> Laboratory of Proteomics and Analytical Technologies
>
> http://atp.ncifcrf.gov
>
> SAIC-Frederick, Inc.
>
> National Cancer Institute at Frederick
> Post Office Box B
>
> Frederick, MD 21702
> Phone: 301-846-7192
> Fax: 301-846-6037
>
> vanq_at_mail.nih.gov
>
>
>
> This e-mail and any attachments to it are intended only for the identified recipients.
> It may contain proprietary or otherwise legally protected information for
> SAIC-Frederick. Any unauthorized use or disclosure of this communication is strictly
> prohibited. If you have received this communication in error, please notify the sender
> and delete or otherwise destroy the e-mail and all attachments immediately.
>
>
>
>
>
>
>
*********************************************
Dr. Tara Sprules
Quebec/Eastern Canada High Field NMR Facility
www.nmrlab.mcgill.ca
phone: (514) 398-1721
fax: (514) 398-8254
3420 University St., Rm 023
McGill University
Montreal, QC, H3A 2A7
*********************************************
Received on Fri Apr 01 2011 - 08:12:43 MST