Thursday, July 26, 2012

Industrial Nucleonics Revisited

Praxair: courtesy PJ Singer @ Citydata
On a drive back home from Chicago on I90/94, I will pass the Praxair facility, where they have three air separation towers. (During the holidays, they put christmas lights on top to make them look like candles, aww). The towers use a cryogenic air separation technique that goes back to Carl Von Linde's laboratory setup in 1895. With the compression, refrigeration, and liqufaction of air (originally for pure scientific purposes, and based upon refrigeration techniques developed as early as 1853 by J.P. Joule and W. Thompson) Linde quickly realized he could adapt the technique for industrial purposes to produce separate bottled gases of exceptional purity. Not surprisingly, the output is reflective of our source atmosphere, with nitrogen (78%) and oxygen (21%) the largest products, followed by carbon dioxide, argon, neon, krypton, xenon, etc.

Fast forward to 1911, Heike Kammerlingh Onnes, the brilliant Dutch physicist, has recently produced liquid helium in his veritable factory of a physics laboratory at Leiden. When he dropped mercury into the liquid helium, he noticed that the mercury lost all resistance to electricity at the frigid temperature of 4 degrees Kelvin (-452F). The mercury sample had become a superconductor. Over time, many other materials - at much higher but still very cold temperatures - were found to become superconductors.

Various explanations were proposed, but in 1957, three physicists, John Bardeen, Leon Cooper, Robert  Schrieffer, developed what is now called the BCS theory of superconductivity, in which it was explained that electrons form Cooper pairs in an interaction with the cooled media - basically, within the lattice of atoms they are paired up by vibrations called phonons. That's the standard explanation for zero electrical resistance, but what exactly are Cooper pairs and are fermions (particles subject to the exclusion principle) the only beneficiaries of this phenomenon?

The other curious beast of the supercold realm is the BEC: the Bose-Einstein Condensate. BECs are dilute collections of atoms that, when cooled down, start to behave as if they have lost their individual identities: as if the entire collection of atoms is one big atom.

The rather naive observation, that these regimes seemed to share a superficial commonality, made me wonder, if electron can form Cooper pairs in a BCS system, why not other particles? More specifically, could free neutrons form Cooper pairs in a BEC? Neutrons when confined in a nucleus are stable, but free neutrons, outside of the stabilizing field of the nucleus, for whatever reason, tend to beta decay into protons after about fifteen minutes.  Why? I don't know. Would coupling of neutrons as a Cooper pair increase their decay lifetime? I don't know, but a few nights ago, it prompted this comment some few essays back:
"It occurred to me the other night (and I wasn't even stoned) that one should be able to get neutrons to pair up like Cooper pair electrons in a superchilled environment, and get a BCS-BEC (Bardeen Cooper Schrieffer) - (Bose Einstein Condensate) crossover, kind of a paired superconducting neutrons, a lased di-neutron beam, and sure enough, you can do it. Dig that!"
Admittedly, it all now sounds rather geeky and masturbate-y. Nevertheless, it turns out I'm not the only one that has asked this question (although of course, the lased di-neutron beam portion would be politely snickered at). But it's nice top know my hunches pan out more often than not.

So, there are a number of questions I ask. What exactly is a Cooper pair?

Neutrons are electrically neutral, which a neutron beam cannot be manipulated as proton and electron beams can. But neutrons do have a magnetic moment and spin, which means they can be manipulated in extremely strong magnetic fields, in the realm of 2-3 Tesla (the Earth's magnetic field strength is 31-58 microTeslas, depending where on Earth you measure). Can a thermally cooled, Cooper paired neutron beam be more easily manipulated?

These attributes - superconductivity, superfluidity - seen at near-Absolute zero temperatures, are also seen at extremely high temperatures: namely, the quark-gluon plasmas at the beginning of the Universe, and also re-created in places like the RHIC in Brookhaven. Is there a connection? How to exploit it if  so?

One hundred years after the first successful production of liquid helium (a mere 60 cubic centimeters first produced in 1908), some 193 million cubic meters are now produced. 96 metric tons of liquid helium is used to cool the superconducting magnets in the Large Hadron Collider at CERN.

I've got to wonder, how long before Bose-Einstein Condensates are mass produced and used on a comparable industrial scale? Given current trends, my $1 bet is 2030 at the latest. And then? And then what?

Although neon is the fourth most abundant element in the universe, argon is 500 times more abundant in our atmosphere. This is so because neon is lighter than argon, and most probably escaped Earth's atmosphere a very long time ago. Argon is important in industry as a welding gas. I have a hunch though, that neon may turn out to be much more important in the long run.

And then? Then what? Well, if I knew what the industrial applications of BECs beyond current applications were, I wouldn't tell you. I'd tell a tech investor. But my guess is, the obvious applications (nano-fabrication/ultra-precise measurements/quantum information and computing) will not be the real true industrial application. My guess is it will be something that, if we now, would make us shit our pants in astonishment.

But my guess is, to borrow from the movie "The Graduate", the word of the future will be "phonons".

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