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Thread: Liquid Helium/MRI Machines

  1. #1 Liquid Helium/MRI Machines 
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    Aug 2012
    Hello everyone, I have very little chemistry education, but am trying to teach myself the basics through a combination of wikipedia, youtube, and sources like this forum. So anyway, I was researching helium and read that a large percentage of the world's supply is used to cool the magnets used in MRI machines. Sources always state that they use liquid helium for this purpose because of its low boiling point. This confuses me. Wouldn't you want to use an element with a high boiling point if you wanted it to remain cold and in the liquid state? (I read the wikipedia article "Superconducting Magnet" and its subheading "cooling", but am still in the dark). Thanks in advance for any assistance!

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  3. #2  
    Brassica oleracea Strange's Avatar
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    Oct 2011
    Interesting question. It might be more accurate to say that it is used because of its low melting (freezing) point. Most other materials would solidify at those low temperatures. So it is the only material that is a liquid at a few degrees above absolute zero.

    But I think they just mean that it needs to be cooled to a low temperature (below its boiling point) to become a liquid.

    Hydrogen might be an alternative (depending on the temperature) but it is highly explosive if it leaks (which it will). Helium is inert and so no risk.

    Without wishing to overstate my case, everything in the observable universe definitely has its origins in Northamptonshire -- Alan Moore
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  4. #3  
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    Its boiling point is -269 degrees centigrade. But if you cool things with liquid Helium, You get very strange properties, for example, some materials lose their electrical resistance. So liquid Helium is used for magnets when you need very powerful magnets,
    for example, as you mentioned earlier, they're used in magnetic resonance imaging in hospitals.
    Last edited by hishamnajam; November 2nd, 2012 at 07:56 AM.
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