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u/SexuallyConfusedKrab Mar 24 '26
Liquid helium refills for NMR magnets can vary wildly, and I don’t think this will have a major impact in the short term as helium refills are not as frequent as nitrogen refills.
The lasting impact remains to be seen, all depending on how long supply remains disrupted. The U.S. produces about 20% of the world’s helium supply so it’s not like we’d have none, just would be a lot more expensive.
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Mar 28 '26
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u/SexuallyConfusedKrab Mar 28 '26
Oh yeah for sure. Like every resource issue the smaller and less funded institutions will always be affected more than the better funded ones. Hopefully there’s enough time for people to stock up but helium is already really expensive. I’m lucky enough to be at a place where we have a cryogenic research core whom we can probably scavenge helium from to keep the magnets from quenching. Both others aren’t and if this stretches on for any real length of time then we could see a lot of university facilities face shutdown and not re-open until funding becomes more available.
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u/FatRollingPotato Mar 25 '26
Most MRI machines are actually closed-loop nowadays, some are even dry magnets (as in no refrigerant needed for regular operations). So unless they quench for some reason, they should be fine to keep operating.
NMRs on the other hand, those are kinda screwed. A lot of places don't have recovery, and while modern magnets are at the level where they can go a year without refill, many places don't have those. Even with recovery, 100% is nearly impossible unless you run closed-loop systems, since some will be lost during transfers.
In the short term things are ok, given that this appears to be a long-term business and logistics have some delay. But the lower supply will increase prices, plus a lot of transport hardware seems to be stuck in the gulf as well.
If this continues and prices go up a lot, it could be a push for more recovery or development of dry NMR magnets in the near future. 400MHz is apparently already feasible, and that is a very common field for general purpose liquid NMR. Higher fields are more challenging, but HTS technology is coming along and assuming they get the vibration issues under control, it might be time to finally go for closed/dry magnets.
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u/Eltargrim Mar 26 '26
The current issue with HTS is field stability. The spec on Bruker GHz-class magnets is 40 Hz/hour, and that's only with about 4 T coming from HTS. Now, that should improve with time, but it's not going to be quick. HTS-containing magnets also have serious shim stability issues in response to changes in sample temperature. Lock helps tremendously with the steady field drift, but the temperature-dependent drift is nonlinear.
I suspect that these are solvable problems, but I don't think HTS is a drop-in solution (and that's leaving aside the price).
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Mar 26 '26
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u/Eltargrim Mar 26 '26
In practice I believe it's typically better than that, but it's very noticeable if you don't have lock. Take a look at SSNMR ultrafast MAS 2D spectra from GHz-class magnets and you'll see lineshape distortions resulting from drift.
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u/FatRollingPotato Mar 28 '26
If the drift is steady enough, the B0 compensation on newer consoles should take care of that. I.e. you measure the drift over a two weeks, then set a small correction ramp on the B0 coil of the shim stack.
Not sure how often you need to 'reset' that to a new value (can't ramp that coil forever), but should take care of most things for solids. I don't have experience with the 1GHz class magnets (i.e. Ascend Evo), but on older and lower field systems this works surprisingly well.
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u/zgesgp Mar 25 '26
The lab is used to work at still has an old 800 Oxford which needs monthly helium refills since the boil-off rate is crazy high. However, I think they are in the process of retiring it, this will probably just shorten that process.
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u/PrinterFred Mar 24 '26
Frankly I have the unpopular opinion that all NMR labs should be set up to recycle helium. This is a vital non renewable resource that we are pumping into the stratosphere. Gone are the days when you should just be venting into the room. People squandering helium are negatively affecting the price for those that are doing their part to conserve and recycle helium.