Forgot your password?
typodupeerror
Science

Another Way the LHC Could Self-Destruct 367

Posted by kdawson
from the no-physics-whatsoever dept.
KentuckyFC writes "Just when you thought it was safe to switch on the LHC (though it won't be for a while yet), another nightmare scenario has emerged that some critics worry could cause the particle accelerator to explode. The culprit this time is not an Earth-swallowing black hole but a 'Bose supernova' in the accelerator's superfluid helium bath. Physicists have been playing with Bose Einstein Condensate (BECs) for over 10 years now. But in 2001, one group discovered that placing them in a powerful magnetic field could cause the attractive forces between atoms to become repulsive. That caused their BEC to explode in a Bose supernova — which they called a 'Bosenova,' a name that fortunately did not catch on. This was little more than a curiosity when only a microscopic blob of cold matter was involved. But superfluid liquid helium is also BEC. And physicists have suddenly remembered that the LHC is swimming in 700,000 liters of the stuff while being zapped by some of the most powerful magnetic fields on the planet. So is the LHC a Bose supernova waiting to go off? Not according to the CERN theory division, which has published its calculations that show the LHC is safe (abstract). They also point out that no other superfluid helium handling facility has mysteriously blown itself to pieces."
This discussion has been archived. No new comments can be posted.

Another Way the LHC Could Self-Destruct

Comments Filter:
  • by Goldsmith (561202) on Monday September 29, 2008 @07:18PM (#25199905)

    An expanding BEC isn't anywhere close to a supernova. This would be similar to snapping the valve off of a liquid helium tank. The guys at CERN could blow themselves up with this, but that's about it. They could blow themselves up lots of ways.

    It was called a "bosenova" because it shrinks before it expands, not because it's super destructive.

  • Worser (Score:5, Informative)

    by hcg50a (690062) on Monday September 29, 2008 @07:33PM (#25200041) Journal

    Could it be worse than melting a 40-ton magnet, which actually happened?

  • Re:First Law? (Score:5, Informative)

    by Scubaraf (1146565) on Monday September 29, 2008 @07:49PM (#25200167)
    Excellent point. Add to that the fact that superfluid helium is not a uniform Bose-Einstein Condensate and you have full debunking.
  • Re:Phase change (Score:5, Informative)

    by geckipede (1261408) on Monday September 29, 2008 @07:53PM (#25200193)
    Helium isn't explosive, it's the most inert material you can get. If you want to make it explode it's going to have to be taking in energy from the magnetic field it is in, so the LHC's helium can never explode any more powerfully than a loss of superconductivity in the magnets would do anyway. Conservation of energy.

    also, lolwtfsig
  • by Reality Master 201 (578873) on Monday September 29, 2008 @08:12PM (#25200307) Journal

    That's the point of the myth: Apollo granted her the gift of prophesy, then cursed her by making it so nobody would ever believe her predictions.

  • by Bob The Cowboy (308954) on Monday September 29, 2008 @08:22PM (#25200355)

    oh and BTW, the windshield is necessary to allow a human driver to continue breathing at today's highway speeds. it's very hard to properly exhale at 50-60 mph.

    Uh huh. And the various (admittedly foolish) motorcycle drivers I see riding on their bikes at 80mph without helmets are just holding their breath?

  • Re:First Law? (Score:5, Informative)

    by sdpuppy (898535) on Monday September 29, 2008 @08:25PM (#25200377)
    Exactly. Besides, isn't it rather difficult to make a Bose-Einstein Condensate - you need to be fractions of a degree close to absolute zero, the liquid helium used is hotter than that, like 1.9K.

    In addition, magnets have been run at that temperature before.

  • by hairykrishna (740240) on Monday September 29, 2008 @09:01PM (#25200583)
    Having run my kit car the other day without it's windscreen I can attest to this. 80mph breathing is fine; it's the gravel that makes you wish for glass.
  • by RealGrouchy (943109) on Monday September 29, 2008 @09:05PM (#25200623)

    If he's cleaning the inside of it, then he's not a janitor, he's a vacuum cleaner.

    - RG>

  • Re:Phase change (Score:4, Informative)

    by geckipede (1261408) on Monday September 29, 2008 @09:23PM (#25200753)
    Ah yes, I had forgotten that, there is a pretty hefty heat gradient allowing the helium to take heat energy from the surrounding environment. Still the point stands that there is a limited supply of energy available, it's never going to be a craterworthy explosion. I wouldn't want to be standing nearby if it did get a coolant rupture though... I have a mental image of the "I am invincible!" scene from goldeneye.
  • by steelfood (895457) on Monday September 29, 2008 @09:36PM (#25200835)

    That isn't a very good example either. Hurricanes typically gust up to 100+ MPH. Sustained winds are often less than that, 60% or so of the maximum gust speed. But more importantly, nobody really rides out a hurricane unshielded, and if anything, you can turn 180 degrees away from the winds if you need to breathe inside a storm. It's a little difficult to turn 180 degrees in a car, not to mention dangerous. I guarantee you'll have trouble breathing behind the wheel of a car without a windshield at 30MPH.

    Regardless, the car analogy is inappropriate. The physical effects of high levels of stress on the human body have been well studied for many centuries now. It hasn't necessarily been well understood, and there haven't been latin-based names for every little phenomena, but the effects have been known.

    With the LHC, we're entering uncharted territory, and not in the sense of parting the next clump of bushes to see what's behind. It is uncharted territory in the sense that we're charging through the next clump of bushes to see what's on the other side when we're legally blind and have left our glasses at home. It's probably more trees on the other side, but there's always a chance of a cliff. And while it's not that easy to fall even if there was a cliff, it's possible to slip on some wet foilage or trip on a low branch or root.

  • by ultracool (883965) on Monday September 29, 2008 @10:42PM (#25201173)
    Maybe I can explain it, since I work with BECs. Whether atoms repel or are attracted to one another depends on the magnetic field they are in. A Feshbach resonance is a kind of magnetic field resonance at which the strength of attraction or repulsion is enhanced. If you set the magnetic field to a value where the attraction is strong, you can get a Bosenova (and yes, the name DID stick). You can have resonances at many magnetic field values, not just high ones. Most alkali atoms have a dozen or more resonances in the range of hundreds of gauss, so a really high magnetic field isn't anything special. The way Feshbach resonances work is by tuning hyperfine splitting. Helium-4 has no hyperfine structure and the atoms repel one another, therefore you can't force them to be attractive by tuning the magnetic field.

    I don't know how this FUD even came up. It's such a ridiculous idea to begin with.

  • by Anonymous Coward on Tuesday September 30, 2008 @12:57AM (#25201859)

    Magnetic fields of precisely tuned strengths (not particularly strong fields) can make certain atoms in an ultra-cold, ultra-low-pressure gas attract each other. It is only at much lower temperatures than that of liquid helium, in the more-than-icy stillness of nanokelvin gases, that the gentle collapse and rebound caused by sudden atomic attraction could ever be considered an explosion. 'Bosenova' was an apt name, but only by remote analogy.

    The attraction effect does not work on helium, because there are no He-2 molecular states to provide a Feshbach resonance. And it does not work on liquids, because in a liquid the ordinary interactions between atoms are so much stronger anyway than anything this Feshbach effect would induce. It has nothing to do with superfluidity per se; it's a phenomenon of cold, dilute gases, which happen also to become superfluid in some cases. So no LHC liquid helium is going to go Bosenova.

    Superconducting magnets themselves are quite dangerous if not handled properly. They can indeed explode: look up 'superconducting magnet quench'. The risk scale here is that of wrecking LHC equipment, however, not of turning the big ring into a crater. And it has nothing to do with Bosenovas.

  • Bull (Score:3, Informative)

    by Liquid Len (739188) on Tuesday September 30, 2008 @01:37AM (#25201995)
    FWIW, where I work, we operate a superconducting tokamak (Tore Supra) with Niobium-Titanium alloy coils, supercritical helium for cryogeny and pretty nasty magnetic fields everywhere. A quench occured when the machine was switched on the first time (in 1988), because of an identified defect in the superconducting wire. But since then, the magnet has been working flawlessly and the coolant, monitored in real time, never exhibited any kind of unexpected phenomenon.
    Also, people have been constantly working on this stuff since then, with even larger currents (hence larger magnetic fields) and I think it's pretty safe to assume that the LHC is gonna be fine (at least this part of the machine).
  • by sanosuke001 (640243) on Tuesday September 30, 2008 @07:33AM (#25203277)
    http://en.wikipedia.org/wiki/Bosenova [wikipedia.org]

    A bosenova or bose supernova is a very small, supernova-like explosion, which can be induced in a Boseâ"Einstein condensate (BEC) by changing the magnetic field in which the BEC is located, so that the BEC quantum wavefunction's self-interaction becomes attractive.

    In the particular experiment when a bosenova was first detected, this procedure caused the BEC to implode and shrink beyond detection, and then suddenly explode. In this explosion, about half of the atoms in the condensate seem to have disappeared from the experiment altogether, remaining undetected either in the cold particle remnants or in the expanding gas cloud produced.

    That's actually pretty interesting. So, it won't happen unless the magnetic field is changed in such a way that the quantum wavefunction becomes self-attractive (whatever that means.) So, don't do that and we're all set? Though, the part about it making atoms disappear is pretty cool. I wonder what actually happens to them...

  • Re:Phase change (Score:2, Informative)

    by geckipede (1261408) on Tuesday September 30, 2008 @07:44AM (#25203373)
    A BEC happens when spin 0.5 fermions combine in pairs to form something vaguely like integer spin bosons. The number of effective particles halves, the mass doesn't.
  • by mikej (84735) on Tuesday September 30, 2008 @08:15AM (#25203625) Homepage

    It's impopssible for superfluid helium to 'go nova'. This impossibility is well understood by theory - It's not that there's a miniscule-but-nonzero chance, as there is that the LHC could spontaneously produce tiny dragons - In this case it's *impossible*.

    Here's the explanation:
    http://anticrackpot.blogspot.com/2008/09/there-will-be-no-bose-novae-at-lhc.html

    And a personal request: Take a second to look some of this stuff up before you post an article like this that fuels unfounded (indeed, indefensible) fears.

Your own mileage may vary.

Working...