Hi everyone,
About two months ago, I asked the question: How often do you think we can switch cold probes?
After two months of renovations at work and at home, I can finally send the replies I got. Sorry for the delay.
Many thanks to all the people who gave their input. I got lots of great inputs.
Here are the replies:
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Never. Only cycles are due to power loss or chilled water interruptions.
Ryan
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We switch our cold probe out all the time (at least once/month) on our 700 MHz DD2 spectrometer. The trick, tho', is that we do this while maintaining the probe at 20K. So far we haven't run into any significant performance issues associated with these drops, and we manage to avoid all of the problems related to warm-up and cool-down cycling. By avoiding the warm-ups, I imagine that the lifetime of our probe is not as limited.
Note: we have an Agilent system, but I do recall the folks at Bruker giving us a Skype tutorial on dropping the cryoprobe and maintaining it at 20K during the drop. (We got the tutorial back when we were selecting a vendor for our new instruments). Perhaps you could drop the probe cold as well, without it being a huge risk / liability? In any case, it might be worth asking the folks at Bruker.
Darcy
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My advice is to switch cold probes as little as possible.
Jeff
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If you have a Bruker system, this becomes a real issue. We have one here with both ID and direct-observe cold probes. In practice, we just don't switch them for all the reasons you're worried about.
Agilent cold probes were designed to be pulled while cold. If you have one of them you can drop the cold probe, slide in an RT probe, and make specs in less than 20 minutes. The reverse switch is also a 20 minute affair. How I wish we had one of those, instead.
In other words, "it depends."
-DJR
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Bruker or Varian? Bruker cryoprobes are easier to deal with, though heavier. Bruker Apps lab cycles constantly between a solids and cryoprobe to do demos with no problems. Like you, I would prefer to keep my cryoprobe working constantly. Before I moved to Nebraska, I had a Varian cryoprobe (2005), which I guarded with my life, including worrying about cryocycles.
Best Regards,
Martha
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For the last few years, I have been switching our Bruker 600MHz cryoprobes every 1-3 months with no major issues. Down time is about a day, half a day if I can coordinate cool down or warm up just right. There are indeed risks in changing the cryoprobes but the chemists love that we have 1H and 13C/31P sensitivity in a cryoprobe, if only for part of the year for each. We plan cooling water infrastructure maintenance (including a Haskris water chiller) while changing the cryoprobe. And we have been able to run the non-cold, broad band probe at elevated temperatures between cryoprobe runs. Our probes also have issues with crud building up in the vacuum and swapping probes forces us to pump and flush the probes on a somewhat regular basis.
Marc
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I've been working with Varian Cold Probes since the beginning, and we still use our Mark-I/II hybrid from 2004 on a 600, as well as two later models with CS-7700 cryogenics on the 800 & 900. In all cases, I would say that we worry that they won't come back up with every thermo-cycle. Our experience is dwindling support from Agilent, which we all know will dwindle to zero eventually. It is well known that problems (such as damage to internal tuning components like chip-capacitors and soldered leads) do occur with temperature cycling, and in fact most (not all by any means, but most) problems requiring a probe-return for repair have historically been associated with a warm-up/cool-down cycle.
You are very fortunate if you are normally back up and running in 2 days because the added step of cryo-burning the 13C channel can take days after that before decoupling noise from 13C decoupling doesn't swamp out our 1H signal.
I don't have a firm answer for you, other than to say that if the ColdProbe system is working, use it for all you're worth because when it goes down there's not telling when (or if) it will come back online. At some point, I'm afraid that our Varian/Agilent ColdProbes will be a decoration on a shelf and we will long for that sensitivity of days past (I definitely won't be longing for the 11 years of headaches though).
Best wishes,
Rich
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Since I have only one cryo probe, I can only provide my feeling about this.
Not sure how it translates to the cold probe.
Every few weeks or more often I would not -
* The work involved
* The downtime
* The time required for resetting parameters
* The chance of something breaking or getting contaminated
* Wasting the extremely high purity helium required for purging with a warmup/cool down cycle
* Breaking of vacuum - means turbo pumps need to be shut down. Not good for them if done frequently and hopefully you have the yearly maintenance done on the system. If you do not have maintenance done at manufacturer intervals, then this is really increasing chances of something going out. Lifetime of the probe? I think you can close a valve to keep the probe vacuum components under vacuum? I'm not sure what will decrease the lifespan of the probe any significant amount unless the probe is dropped :-)
If you have a mass spectrometry facility, ask them how they would feel about breaking vacuum often on their system and the effect on their turbo pumps.
The pulse widths shouldn't change much so you can look at the 360 degree and tweak from there.
If you have gradient shims then re-shimming should not take too long, maybe a half hour; for manual shims you've got anywhere form a half hours to a couple of hours though.
Optimist: Every couple of months is not too bad - the good of it is that you want to have a few helium flushes a year to help minimize dirt buildup, so that aspect is actually good. But all the negatives remain, although breaking vacuum infrequently shouldn't hurt the turbo pumps, especially if (if) they changed yearly.
So I would say that if I had to change the probe every month or so, it wouldn't be too bad; but every few weeks or more frequent I'd worry a bit.
Again, my feelings, not from experience.
Cheers,
George
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We have 11 spectrometers here at the University of Illinois, and not one has a cryoprobe. Though I have only been here 4 years, there has been an overall hesitation to get a cryoprobe because they are not considered very versatile. In other words, changing the probe is quite time-consuming and risky, but this is only what I have heard. But the faculty has heard it, too. My overall opinion is that you should not change your cryoprobe unless you have to. Too risky for a long period of down time.
All that said, we are just about to buy a Bruker cryoprobe. But, at 500 MHz, Bruker now makes 10 different versions of cryoprobes. We are buying the broadband version so it has built-in versatility. We are buying a back-up ordinary probe, but we hope to never use it. The broadband probe has somewhat lesser H and C sensitivity, but still better than what we have at 500 MHz. Since we have lots of users, this choice makes sense for us.
You've asked a great question, and you'll get lots of responses.
All the best,
Dean
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I would never remove a cold probe unless there was a problem, but as you say with only one magnet you may not have a choice.
I would keep the number of changes to a minimum, and I would keep the cryoplatform running even while the probe is out. That will minimize vacuum problems later.
Pulses shouldn't change unless there has been a console repair, so a quick check should suffice.
Regards,
Phil.
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NMRFAM does quite a bit of cold probe switching, but they manage to keep the probe cold if the time out is relatively short. Bruker can do that for some magnets; you'd have to ask them. If you have a Varian/Agilent system, I don't know.
You could get more info about the probe switching from Mark Anderson at NMRFAM: wombats_at_nmrfam.wisc.edu
Charlie
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We have a Bruker Avance III 600 MHz with the Bruker DCH Cryoprobe. Back then, formerly Varian claimed that they have a cold probe that is cold swappable. At first Bruker said no but eventually they sold us a cold swappable Cryoprobe. It came with a Cryoprobe handling assist making it relatively easy and safe to take the probe in and out of the magnet without warming the system up.
We had in the past swap out the Cryoprobe for the CPMAS solids probe about once a month. I like to go slow so that I do not accidently forget or bump something. The actual swap can be accomplished in less than ½ an hour. So far I haven't notice any difference in the heater currents for the preamps or NMR coil. Although I it does not appear that swapping the Cryoprobe leads to shorter time between maintenance. I have seen at some point the helium gas consumption in the Cryoplatform went up but I could not associate it with the Cryoprobe swap. After warming up the Cryoprobe system thoroughly and replacing the o-rings between the Cryoprobe and Cryoplatform, everythings seems to be back to normal.
Still, the overhead for swaping the Cryoprobe out then back in is significant, so it is best to leave the Cryoprobe in the magnet whenever possible.
Kim
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Varian engineers told me that every cycle from cold to warm or warm to cold risks damaging the electronic components of the probe. Huge temperature changes mean thermal expansion or contraction and that's not good for circuit boards or electronics (the 1H preamp lives inside the probe at 25K). So I save warmups for the unavoidable cold head rebuild, power failures, etc.
Neil
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I have a probe that has undergone over 50 cycles, no problem. I'm in a demo lab.
Downtime is as follows.
Insertion of probe = 15 - 30 minutes
Cooldown = 3 - 4 hours
Re calibration and shimming = 30 minutes.
Warmup = 3 hours, can be set on timer. I.e. experiment runs until 5 am. Warmup starts at 6 and when you come in at 9 you can swap the probe = 15 - 30 min
Frequent changes actually increase the proficiency of the operator and less happens.
I hope this helps
Clemens
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I have two cold probes. One is on 800, another is on 750. I don't switch them all time, only if the cold probes were out of work.
Rui
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I have this situation on one of our high field systems. We have solids, RT liquids, diffusion, u-MRI and cold probe. The only way to handle this is with block reservations. We typically install the cold probe for 3 months at a time once or twice a year. We have the "remove cold" accessory from Agilent. But our Pumped 800 does not play well with it. I've seen this work on the other magnets quite well. Even if it did work well on my system, I'd only consider using it if I had to switch away from the Cold probe for less than a week.
I really don't know if there is any data that can point to the answer to (a). I've not seen and adverse affects thus far with our cold/cryo probes with more thermal cycles than the ideal. (only at service time) I spot at length with the Bruker service engineer when he was out to replace our cold head. There is no risk to the cold head/compressor system from the thermal cycle. And in affect you're prolonging it's lifetime due to less use.
I have gotten to the point that the down time is not a full two days. Active warm up the night before the switch, and then generally have the system running not too shortly the next morning. typically before lunch. the reverse situation I like to have the probe be cold over night before letting users at it so that it has a chance to really equilibrate and stabilize.
Is this ideal? No. But if its' the only system you have, then it's what you do.
Brian
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Just to let you know, we have a BSNL (N2 liquefier) for our 600MHz so warm-up and cooldown times are double (6h). However would I give up my BSNL? absolutely not.
Again, thanks to everyone and to the AMMRL committee!
Cheers,
Genevieve
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Genevieve Seabrook PhD.
Scientific Associate
NMR Research & Facility Manager
UHN, Princess Margaret Cancer Centre
Division of Signaling Biology (OCI)
MaRS, Toronto Medical Discovery Tower
4th floor, Room 4-902
101 College Street
Toronto, ONT, M5G 1L7
Mobile: 416-629-7391
gseabroo_at_uhnresearch.ca<mailto:gseabroo_at_uhnresearch.ca>
http://nmr.uhnres.utoronto.ca/ikura/nmrsuite/nmrsuite.html
Received on Mon May 04 2015 - 07:34:32 MST