Absolute Zero is 0K
March 21, 2014 9:16 AM Subscribe
James Dewar, Heike Kamerlingh Onnes, and the quest for liquified hydrogen and helium. Come for the superfluidity, stay for the Supreme Court of the Netherlands decisions and multiple lab assistants losing eyes in explosions.
Despite all the lost eyes, I don't see any safety goggles in the lab photos. It's like they hadn't just lived through the Steampunk Era!
posted by moonmilk at 10:02 AM on March 21, 2014 [5 favorites]
posted by moonmilk at 10:02 AM on March 21, 2014 [5 favorites]
For slightly more contemporary condensed matter disasters, see the 2006 post PV=nRT: It's not just a good idea....
posted by zamboni at 10:06 AM on March 21, 2014
posted by zamboni at 10:06 AM on March 21, 2014
Good to see Damn Interesting back and being, if not Damn, at least Darn Interesting.
Also interesting: PhD Comic's explanation of Cosmic Inflation that included the fact that the Universe's background radiation is about 3 degrees Kelvin, making the experiments that got lower than that even more impressive.
posted by oneswellfoop at 10:17 AM on March 21, 2014 [4 favorites]
Also interesting: PhD Comic's explanation of Cosmic Inflation that included the fact that the Universe's background radiation is about 3 degrees Kelvin, making the experiments that got lower than that even more impressive.
posted by oneswellfoop at 10:17 AM on March 21, 2014 [4 favorites]
Unmentioned in the article is that a significant portion of Kamerlingh Onnes' equipment is still on public display in Leiden, through the (excellent) Museum Boerhaave. Definitely worth a visit if you're ever in the area.
posted by fifthrider at 10:36 AM on March 21, 2014 [3 favorites]
posted by fifthrider at 10:36 AM on March 21, 2014 [3 favorites]
What fascinating piece, thank you for posting!
The individual helium atoms blur into one another and become a single "superatom", also known as a partial Bose-Einstein Condensation. This is a demonstration of Heisenberg's Uncertainty Principle, which states that the more precisely the momentum of a particle is determined, the less precisely its position can be known. Since particles below the lambda point have almost no movement, their momentums are almost entirely "known," therefore by necessity their positions become so inexact that they begin to overlap one another. In this situation atoms stop behaving like discrete things and become ambiguous smears of quantum probabilities.
For those with a physics background, how accurate is this description of Heisenberg's Uncertainty Principle? I've heard that popular science reporting often gets it wrong which has led to a lot of people misunderstanding exactly what it entails.
posted by arcolz at 10:49 AM on March 21, 2014
The individual helium atoms blur into one another and become a single "superatom", also known as a partial Bose-Einstein Condensation. This is a demonstration of Heisenberg's Uncertainty Principle, which states that the more precisely the momentum of a particle is determined, the less precisely its position can be known. Since particles below the lambda point have almost no movement, their momentums are almost entirely "known," therefore by necessity their positions become so inexact that they begin to overlap one another. In this situation atoms stop behaving like discrete things and become ambiguous smears of quantum probabilities.
For those with a physics background, how accurate is this description of Heisenberg's Uncertainty Principle? I've heard that popular science reporting often gets it wrong which has led to a lot of people misunderstanding exactly what it entails.
posted by arcolz at 10:49 AM on March 21, 2014
Someone once remarked on a thread about religion vs. science that scientists lacked wonder. This passage from the link
posted by Mental Wimp at 10:53 AM on March 21, 2014 [3 favorites]
Once this absolute zero temperature was decisively identified, prominent Victorian scientists commenced multiple independent efforts to build machines to explore this physical frontier. Their equipment was primitive, and the trappings were treacherous, but they pressed on nonetheless, dangers be damned. There was science to be done.puts the lie to that. When your curiosity is so strong that you will risk your life to satisfy it, I'd say your wonder is infinite.
posted by Mental Wimp at 10:53 AM on March 21, 2014 [3 favorites]
Interesting story, and well written.
hydrogen--an odorless, colorless gas which tends to turn into a universe if left alone for a prolonged period
Heh.
posted by ChurchHatesTucker at 10:55 AM on March 21, 2014 [9 favorites]
hydrogen--an odorless, colorless gas which tends to turn into a universe if left alone for a prolonged period
Heh.
posted by ChurchHatesTucker at 10:55 AM on March 21, 2014 [9 favorites]
Dewar's notes do not indicate whether a high-pitched apology was offered.I laughed.
Unmentioned in the article is that a significant portion of Kamerlingh Onnes' equipment is still on public display in Leiden, through the (excellent) Museum Boerhaave.
But wait ...
Science was thenceforth in the capable hands of quantum mechanics. His helium liquefaction apparatus remains on display to this day at Leiden University.posted by Kirth Gerson at 11:06 AM on March 21, 2014 [1 favorite]
His helium liquefaction apparatus remains on display to this day at Leiden University.
Welp; missed that. That said, it's not actually on display at Leiden University; the Boerhaave is an unaffiliated national museum.
posted by fifthrider at 11:22 AM on March 21, 2014
Welp; missed that. That said, it's not actually on display at Leiden University; the Boerhaave is an unaffiliated national museum.
posted by fifthrider at 11:22 AM on March 21, 2014
That was a really well-written and interesting article, especially when dealing with a subject that can get too technical too easily for laypeople to understand. (like me.)
Also, scriptwriters need to take note:
"Researchers today are tinkering with temperatures (...) which may ultimately reveal a never-before-seen theoretical supersolid state. (...) A chunk of helium ice would behave as a single, solid, oversized, and stupefyingly slippery atom, which may be capable of passing ghost-like through certain materials. But that's another matter altogether."
Creating supersolids that can move through material objects and what if things go wrong? What if reality starts to get unbound by these huge atoms? ...could someone forward this to Valve so they can say yes, this is why there's a research base in a frozen ship, ok we'll do the 3rd one already?
posted by Zack_Replica at 11:26 AM on March 21, 2014 [2 favorites]
Also, scriptwriters need to take note:
"Researchers today are tinkering with temperatures (...) which may ultimately reveal a never-before-seen theoretical supersolid state. (...) A chunk of helium ice would behave as a single, solid, oversized, and stupefyingly slippery atom, which may be capable of passing ghost-like through certain materials. But that's another matter altogether."
Creating supersolids that can move through material objects and what if things go wrong? What if reality starts to get unbound by these huge atoms? ...could someone forward this to Valve so they can say yes, this is why there's a research base in a frozen ship, ok we'll do the 3rd one already?
posted by Zack_Replica at 11:26 AM on March 21, 2014 [2 favorites]
I would say that this was quite a cool story.
*I'll see myself out*
posted by nostrada at 11:28 AM on March 21, 2014 [1 favorite]
*I'll see myself out*
posted by nostrada at 11:28 AM on March 21, 2014 [1 favorite]
...stupefyingly slippery atom, which may be capable of passing ghost-like through certain materials. But that's another matter altogether.
I SEE WHAT YOU DID THERE
posted by slogger at 12:41 PM on March 21, 2014 [4 favorites]
I SEE WHAT YOU DID THERE
posted by slogger at 12:41 PM on March 21, 2014 [4 favorites]
Cool post.
posted by Blazecock Pileon at 12:43 PM on March 21, 2014 [1 favorite]
posted by Blazecock Pileon at 12:43 PM on March 21, 2014 [1 favorite]
Naberius, I just want to like formally recognize your comment as by far the best example of an oblique repurposing of a Rodgers & Hammerstein lyric into a multi-stage pun about crygogenics I have ever encountered.
posted by cortex at 12:49 PM on March 21, 2014 [3 favorites]
posted by cortex at 12:49 PM on March 21, 2014 [3 favorites]
Despite all the lost eyes, I don't see any safety goggles in the lab photos. It's like they hadn't just lived through the Steampunk Era!
The lack of goggles caught my eye as well (sorry). But I'm not sure that shatterproof materials like plexiglass were available at the time so I don't even want to think about what explosion + glass shards would do to one's eyes.
posted by tommasz at 1:06 PM on March 21, 2014
The lack of goggles caught my eye as well (sorry). But I'm not sure that shatterproof materials like plexiglass were available at the time so I don't even want to think about what explosion + glass shards would do to one's eyes.
posted by tommasz at 1:06 PM on March 21, 2014
Very cool writeup.
posted by So You're Saying These Are Pants? at 1:13 PM on March 21, 2014
posted by So You're Saying These Are Pants? at 1:13 PM on March 21, 2014
The story itself is littered with puns.
Helium became the new last permanent gas, and consequently its liquefaction became the noblest goal.
Sir James Dewar's supply was not quite as scarce as he suggested, but he had labored alone for far too long to go Dutch on the byline.
Any others?
posted by supercres at 1:24 PM on March 21, 2014
Helium became the new last permanent gas, and consequently its liquefaction became the noblest goal.
Sir James Dewar's supply was not quite as scarce as he suggested, but he had labored alone for far too long to go Dutch on the byline.
Any others?
posted by supercres at 1:24 PM on March 21, 2014
Naberius, I just want to like formally recognize your comment as by far the best example of an oblique repurposing of a Rodgers & Hammerstein lyric into a multi-stage pun about crygogenics I have ever encountered.
Thank you. It's kind of my milieu...
posted by Naberius at 1:27 PM on March 21, 2014
Thank you. It's kind of my milieu...
posted by Naberius at 1:27 PM on March 21, 2014
I like the fact that he uses a lesser-known Douglas Adams reference without explaining it:
The modest amount of the stuff he had been able to collect behaved very curiously in general, flowing with strange characteristics and evading easy observation as if enveloped in an SEP field.posted by George_Spiggott at 1:29 PM on March 21, 2014 [3 favorites]
Any others?
I feel like it would be quicker work to go through and note the paragraphs that did not have some sort of sly groaner slipped in.
posted by cortex at 1:31 PM on March 21, 2014 [1 favorite]
I feel like it would be quicker work to go through and note the paragraphs that did not have some sort of sly groaner slipped in.
posted by cortex at 1:31 PM on March 21, 2014 [1 favorite]
arcolz: The way I was taught it is as follows: There is a minimum for the product of the uncertainties of the "two measurements"
The famous pair of measurements are momentum (often incorrectly worded as "Velocity" or, worse still, "Speed") and position. There is also another, less often mentioned in popsci, pair: energy and time. I think there are other pairs, but these are the two that are analogous in some respects and I managed to more or less get my head around them. I think they're written as:
ΔxΔp > ℏ/2
and
ΔEΔt > ℏ/2
If your browser can't render those characters then the ones on the left are "delta" characters and the ones on the right are reduced Planck constants, which is staggeringly small, so the scales where this comes into play are generally outside of anything the human mind is naturally comfortable with. The reduced Planck constant is something to do with quantums of angular momentum, to be honest I lose the threads there a little ;)
But the key thing is that these limits on measurement AREN'T about our ability to make good tools or to take good readings of our tools. They're limits in the structure of the universe. It's not just that we cannot know the exact position and the momentum simultaneously, it's that the universe can't know them either. A particle cannot both be in an exact position and have an exact momentum. And as one becomes more exact the other must become more vague.
So to get back to your point - yes, reducing the momentum down to such a low level that you're increasingly sure of it being close to 0 (which is one way of thinking about the process of approaching 0K temperature) really does cause the particles to sort of smear out in space. Because the multiple of the uncertainty in position and momentum has to be above some fixed minimum, so as one becomes smaller and smaller the other has to increase.
Equally baffling is the notion of a zero energy particle. Consider a photon, which is massless. Reduce its energy towards 0. What if it actually was 0? You could say it doesn't exist (massless, energyless - what is there?). But the entire notion of "doesn't exist" is undone by the energy/time uncertainty principle. We cannot say that something both doesn't exist (ie we know the photon's energy) as well as when it doesn't exist (ie we know its time). The result is that at really really small time-scales particles are constantly bursting into existence and then annihilating. Because at really really small time-scales the "borrowed" energy required to create them can be lost in the amount of uncertainty required to multiply up to enough to be on the plank scale.
That sounds vague and arm-wavey, but smarter minds than mine worked out that such activity could be experimentally measured via something called the Casimir Effect. Which has actually been done.
This kind of thinking is a rabbit hole. With dragons in it.
Now that I've typed all that someone will probably come along and correct it all. My excuse is that I have far for excitement for this subject than I have knowledge in it, and I spend too long on wikipedia for my mental well being.
posted by samworm at 1:34 PM on March 21, 2014 [9 favorites]
The famous pair of measurements are momentum (often incorrectly worded as "Velocity" or, worse still, "Speed") and position. There is also another, less often mentioned in popsci, pair: energy and time. I think there are other pairs, but these are the two that are analogous in some respects and I managed to more or less get my head around them. I think they're written as:
ΔxΔp > ℏ/2
and
ΔEΔt > ℏ/2
If your browser can't render those characters then the ones on the left are "delta" characters and the ones on the right are reduced Planck constants, which is staggeringly small, so the scales where this comes into play are generally outside of anything the human mind is naturally comfortable with. The reduced Planck constant is something to do with quantums of angular momentum, to be honest I lose the threads there a little ;)
But the key thing is that these limits on measurement AREN'T about our ability to make good tools or to take good readings of our tools. They're limits in the structure of the universe. It's not just that we cannot know the exact position and the momentum simultaneously, it's that the universe can't know them either. A particle cannot both be in an exact position and have an exact momentum. And as one becomes more exact the other must become more vague.
So to get back to your point - yes, reducing the momentum down to such a low level that you're increasingly sure of it being close to 0 (which is one way of thinking about the process of approaching 0K temperature) really does cause the particles to sort of smear out in space. Because the multiple of the uncertainty in position and momentum has to be above some fixed minimum, so as one becomes smaller and smaller the other has to increase.
Equally baffling is the notion of a zero energy particle. Consider a photon, which is massless. Reduce its energy towards 0. What if it actually was 0? You could say it doesn't exist (massless, energyless - what is there?). But the entire notion of "doesn't exist" is undone by the energy/time uncertainty principle. We cannot say that something both doesn't exist (ie we know the photon's energy) as well as when it doesn't exist (ie we know its time). The result is that at really really small time-scales particles are constantly bursting into existence and then annihilating. Because at really really small time-scales the "borrowed" energy required to create them can be lost in the amount of uncertainty required to multiply up to enough to be on the plank scale.
That sounds vague and arm-wavey, but smarter minds than mine worked out that such activity could be experimentally measured via something called the Casimir Effect. Which has actually been done.
This kind of thinking is a rabbit hole. With dragons in it.
Now that I've typed all that someone will probably come along and correct it all. My excuse is that I have far for excitement for this subject than I have knowledge in it, and I spend too long on wikipedia for my mental well being.
posted by samworm at 1:34 PM on March 21, 2014 [9 favorites]
I'm just impressed no one made the obligatory Simpsons goggles reference.
Ah, shoot, no one else....
posted by Chrysostom at 1:38 PM on March 21, 2014 [1 favorite]
Ah, shoot, no one else....
posted by Chrysostom at 1:38 PM on March 21, 2014 [1 favorite]
For those with a physics background, how accurate is this description of Heisenberg's Uncertainty Principle?It's pretty good. Samworm has a good explanation.
If you like an alternative, you can also think about it in terms of de Broglie wavelengths. Everything that has some momentum, p, has an associated wavelength, λ = h/p. The wavelength is the smallest "size" you can assign to your object: if your object is much bigger than its wavelength, you can safely treat it classically, but if your object is roughly the same size as its wavelength, you'd better think about quantum mechanics.
Atoms and molecules in a solid or a liquid tend to be separated by a few tenths of a nanometer (the size of the electron cloud). For most materials at room temperature the atom wavelengths are a few hundredths of a nanometer, and so you're allowed to talk about a solid as a bunch of atoms wiggling around their rest positions on the grid. For helium at 2K, the average de Broglie wavelength is more than a nanometer, and so each helium atom is overlapping with many dozens of its neighbors. Liquid helium is a quantum fluid because the atoms' wavefunctions overlap.
This handwavy explanation doesn't explain why there's a sharp phase transition from fluid to superfluid at 2K, but it gets you part of the way there.
posted by fantabulous timewaster at 2:50 PM on March 21, 2014 [1 favorite]
As the author of this article and a long-time Metafilter reader, it makes me happy to see this link, and (most of) the attendant comments. Thanks!
Regardless, thanks all for the kind words.
posted by Hot Pastrami! at 3:05 PM on March 21, 2014 [13 favorites]
Good to see Damn Interesting back and being, if not Damn, at least Darn Interesting.I find this curious, as most of my recent writings are subjects I've wanted to cover for years, yet had lacked the time to properly research. So in my mind the recent stuff is more interesting than the older stuff. But my opinion is not without bias. Could it be the fact that recent articles are of a greater average length than those of the past? Or perhaps the ravages of age are affecting both my writing and my ability to assess it.
Regardless, thanks all for the kind words.
posted by Hot Pastrami! at 3:05 PM on March 21, 2014 [13 favorites]
The famous pair of measurements are momentum […] and position. [….] I think there are other pairsThese are called conjugate variables; that wikipedia page has a list of a few more. People familiar with mathematics, acoustics, or signal processing will notice the Fourier transform connection: a short-duration signal necessarily has a wide spread of frequencies; a narrowband signal necessarily lasts for a long time; the momentum of a particle is the Fourier transform of its wave equation (which corresponds to its probability density as a function of position).
These pairs of variables are also the symmetries and conservation laws that are related to each other by Noether's Theorem (one of those astonishing mathematical insights into physical phenomena).
posted by hattifattener at 7:12 PM on March 21, 2014 [2 favorites]
Just want to pay my compliments to the author. Fantastic article (and also, to borrow a phrase from a comment in another thread, a ripping good yarn)!
posted by saulgoodman at 8:29 PM on March 21, 2014 [1 favorite]
posted by saulgoodman at 8:29 PM on March 21, 2014 [1 favorite]
That's a marvelous article, Hot Pastrami; I had no idea Onnes was the discoverer of superconductivity, and I thought it was particularly interesting the way you showed that Onnes' very openness, in contrast to Dewar's jealous secretiveness, could deserve part of the credit for his priority in the liquefaction of helium since it took a "professor" touring the lab on the day of the experiment to point out that the helium might already have been liquefied as Onnes and his group were fretting about what had gone wrong to keep the temperature from continuing to fall.
I also thought it was a wonderful irony that Dewar was concerned that his catastrophic accidents would cost him his chance to be first to liquefy hydrogen:
I tried to Google up who that perceptive professor was because I seem to remember from another account that he's much more of a science household name than Onnes is, but I couldn't find it-- and I did wish you had emphasized a bit more that the reason the temperature was not falling the way Onnes thought it should was not merely that the thermometer was immersed in a liquid, but that it was immersed in a liquid at one of its critical points, namely its boiling point.
posted by jamjam at 9:10 PM on March 21, 2014 [2 favorites]
I also thought it was a wonderful irony that Dewar was concerned that his catastrophic accidents would cost him his chance to be first to liquefy hydrogen:
In March 1896, just when these laboratory calamities seemed certain to steal Dewar's scientific prize, he received a letter from Kamerlingh Onnes, wherein the Dutchman confided:when it actually seems entirely possible from Onnes' letter that Dewar's very (and very careless) accidents were the reason the city objected to Onnes' experiments in the first place!I have not been able to repeat your splendid experiments for since your last letter it was impossible for me to work at low temperatures and that for a reason you will be astonished to hear. The municipality of Leiden has made objections as to my working with condensed gases and has not been content with asking that additional means of precaution are taken, but is gone so far to claim in August last that my cryogenic laboratory be removed from the city! Not withstanding that never any notable accident happened in all the years I have been working there...
I tried to Google up who that perceptive professor was because I seem to remember from another account that he's much more of a science household name than Onnes is, but I couldn't find it-- and I did wish you had emphasized a bit more that the reason the temperature was not falling the way Onnes thought it should was not merely that the thermometer was immersed in a liquid, but that it was immersed in a liquid at one of its critical points, namely its boiling point.
posted by jamjam at 9:10 PM on March 21, 2014 [2 favorites]
Paying my compliments to the author as well. Really enjoyed the article and reminded me of how badass and awesome those "classical physicists" really were. Much like ye olde mathematicians except you know with more exploding lab equipment and lost eyes, though less duels I think.
I also happen to love the sly groaners/puns etc. That's just me though.
posted by lizarrd at 9:14 PM on March 21, 2014 [1 favorite]
I also happen to love the sly groaners/puns etc. That's just me though.
posted by lizarrd at 9:14 PM on March 21, 2014 [1 favorite]
This was a fantastic article—most definitely "Damn Interesting"! I loved the writing style. Extremely engaging and understandable. Thanks to Hot Pastrami for writing it and the OP for sharing it.
Also, I was actually a bit surprised that the limelight-hogging Dewar actually wrote a letter to the Leiden council on Onnes' behalf. I am so curious about details like this. He surely wrote it in English, so what did the council do with that letter? Did the politicians know enough English to understand what Dewar had written? How did they react? Did it help Onnes' case (doesn't seem likely, as he had to fight a court battle), or did they perceive Dewar as some kind of meddling foreigner? We may never know the answers to questions like these, but they intrigue the hell out of me.
posted by Conrad Cornelius o'Donald o'Dell at 12:16 AM on March 22, 2014 [1 favorite]
Also, I was actually a bit surprised that the limelight-hogging Dewar actually wrote a letter to the Leiden council on Onnes' behalf. I am so curious about details like this. He surely wrote it in English, so what did the council do with that letter? Did the politicians know enough English to understand what Dewar had written? How did they react? Did it help Onnes' case (doesn't seem likely, as he had to fight a court battle), or did they perceive Dewar as some kind of meddling foreigner? We may never know the answers to questions like these, but they intrigue the hell out of me.
posted by Conrad Cornelius o'Donald o'Dell at 12:16 AM on March 22, 2014 [1 favorite]
Cold ass fuck
posted by Sprocket at 12:25 AM on March 22, 2014 [1 favorite]
posted by Sprocket at 12:25 AM on March 22, 2014 [1 favorite]
I tried to Google up who that perceptive professor was because I seem to remember from another account that he's much more of a science household name than Onnes is, but I couldn't find it.Professor Franciscus Schreinmakers was his name.
I did wish you had emphasized a bit more that the reason the temperature was not falling the way Onnes thought it should was not merely that the thermometer was immersed in a liquid, but that it was immersed in a liquid at one of its critical points, namely its boiling point.I often struggle with how much detail to include...a lot of things fascinate me, and I tend to be very verbose in my writing, so much ends up on the editing room floor before I publish. I've considered the notion of offering abridged and unabridged versions of these articles, but I remain unconvinced that it's a good idea.
posted by Hot Pastrami! at 8:48 AM on March 22, 2014 [1 favorite]
It's fine.
Here are my cryostories (they are long):
In the mid-1990s, I worked at a cryocooler-manufacturing company. Their refrigerators were to be used in MRI machines, to recondense the liquid Helium that cools the MRI magnet. In those days, MRIs depended on periodic refills of liquid He, as the coolant gradually boiled off, and this was expensive. The refrigerator was based on a new technology, and not quite reliable. It ran on Helium gas, which it compressed and decompresseded in stages to get down to about 20K. The final cooling was controlled by a little electromagnetic plate valve at the coldest stage. We were doing OK on the development of the thing, but the founder of the company was telling his investors that we were in production, and they wanted to see sales. When we sold units to the big MRI manufacturers, the unreliability of the refrigerator blew up our credibility.
Another one of our customers bought the company, and a weird thing began to happen. This customer had been having problems with our machines, where they would get down to about 10k, then start warming up until they got to around 20K, then start cooling again. This went on and on, and they never got down to the target 4.2K. Machines we shipped back to our place and ran worked fine. After that company bought us, the same thing started happening to all our machines. Now, the He that they ran on was sold as 99.999% pure Helium. The new owners had insisted that we switch suppliers of the gas, because they used a different vendor and wanted to just pay one. We eventually proved to them that their vendor's "5-nines" Helium was contaminated with Hydrogen. When the cold stage of our machine reached 12K, Hydrogen ice would start to form on the little plate valve. When enough ice formed, the valve would no longer seal, and cooling would stop. When the gas got up above 14.5K, the Hydrogen ice would melt and the valve would work again, until the H2 freezing-point was reached again. They let us go back to our original vendor, but the damage was done, and we were out of work.
10 years later, I worked at a manufacturer of small MRI machines. (By this time, all MRIs had recondensers attached, and were seldom recharged with LHe.) I was writing manuals for the machines, and went to a local hospital to watch a field tech perform a procedure so I could write about it. I had a small camera, to capture illustrations. The MRI was in a small room about 8 feet square. The first event was when I got careless and walked too close to the machine with the camera. It got yanked out of my hand and plastered to the inside wall of the MRI. It didn't work after that. I had it repaired, but it was never quite right...
The procedure involved swapping the recondenser out. The technician was confident he could do it without "quenching the magnet," which is when the Helium all boils away in a rush. If he could get done quickly enough, the Helium would stay liquid. He took too long, and suddenly the relief valve opened, and there was a roaring geyser of really cold gas rushing up to the ceiling. The lower part of the room was thickly shrouded in fog, as all the moisture in the air condensed. The cloud was climbing rapidly upward as we evacuated ourselves from the room (because breathing pure Helium is not recommended). It took him a day to get the MRI back up and running.
posted by Kirth Gerson at 10:41 AM on March 22, 2014 [10 favorites]
Here are my cryostories (they are long):
In the mid-1990s, I worked at a cryocooler-manufacturing company. Their refrigerators were to be used in MRI machines, to recondense the liquid Helium that cools the MRI magnet. In those days, MRIs depended on periodic refills of liquid He, as the coolant gradually boiled off, and this was expensive. The refrigerator was based on a new technology, and not quite reliable. It ran on Helium gas, which it compressed and decompresseded in stages to get down to about 20K. The final cooling was controlled by a little electromagnetic plate valve at the coldest stage. We were doing OK on the development of the thing, but the founder of the company was telling his investors that we were in production, and they wanted to see sales. When we sold units to the big MRI manufacturers, the unreliability of the refrigerator blew up our credibility.
Another one of our customers bought the company, and a weird thing began to happen. This customer had been having problems with our machines, where they would get down to about 10k, then start warming up until they got to around 20K, then start cooling again. This went on and on, and they never got down to the target 4.2K. Machines we shipped back to our place and ran worked fine. After that company bought us, the same thing started happening to all our machines. Now, the He that they ran on was sold as 99.999% pure Helium. The new owners had insisted that we switch suppliers of the gas, because they used a different vendor and wanted to just pay one. We eventually proved to them that their vendor's "5-nines" Helium was contaminated with Hydrogen. When the cold stage of our machine reached 12K, Hydrogen ice would start to form on the little plate valve. When enough ice formed, the valve would no longer seal, and cooling would stop. When the gas got up above 14.5K, the Hydrogen ice would melt and the valve would work again, until the H2 freezing-point was reached again. They let us go back to our original vendor, but the damage was done, and we were out of work.
10 years later, I worked at a manufacturer of small MRI machines. (By this time, all MRIs had recondensers attached, and were seldom recharged with LHe.) I was writing manuals for the machines, and went to a local hospital to watch a field tech perform a procedure so I could write about it. I had a small camera, to capture illustrations. The MRI was in a small room about 8 feet square. The first event was when I got careless and walked too close to the machine with the camera. It got yanked out of my hand and plastered to the inside wall of the MRI. It didn't work after that. I had it repaired, but it was never quite right...
The procedure involved swapping the recondenser out. The technician was confident he could do it without "quenching the magnet," which is when the Helium all boils away in a rush. If he could get done quickly enough, the Helium would stay liquid. He took too long, and suddenly the relief valve opened, and there was a roaring geyser of really cold gas rushing up to the ceiling. The lower part of the room was thickly shrouded in fog, as all the moisture in the air condensed. The cloud was climbing rapidly upward as we evacuated ourselves from the room (because breathing pure Helium is not recommended). It took him a day to get the MRI back up and running.
posted by Kirth Gerson at 10:41 AM on March 22, 2014 [10 favorites]
Thank you, Hot Pastrami-- the great Franciscus Schreinmakers, of course! How could I have forgotten that?
posted by jamjam at 11:14 AM on March 22, 2014
posted by jamjam at 11:14 AM on March 22, 2014
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ABSOLUTE ZERO... 0K!
posted by Naberius at 9:25 AM on March 21, 2014 [2 favorites]