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Helium 4 and photon ?

  1. Feb 23, 2010 #1
    When helium 4 is a super fluid can it seep through a glass container , I know it can crawl out of the glass due to the van der walls interaction . But I’ve got mixed answers about the seeping through the glass .
    And does a photon propagate through space in a similar way an electron wave propagates through space .
     
  2. jcsd
  3. Feb 23, 2010 #2
    Helium-4 is only a superfluid when cooled to below its lambda point, 2.17 Kelvin (271 C), at which point it enters the Helium II state, yes it will crawl up walls, yes it can seep through glass. Helium is generally used to test leak rates of vacuum chambers and such because it has such a small molecular diameter and is inert, the only inert substance which will leak thrrough pores or cracks at such a small scale - take a look at healium leak detectors. As you'll know if you've ever had a helium balloon it will leak through the pores in that over time, the same happens with glass, both as a gas or as a superfluid.

    Addressing the Helium-4 part - Helium-4 is the most frequent, Helium 3 is quite "rare" and has one neutron, 4 has two neutrons, however they're both stable.
     
  4. Feb 23, 2010 #3
    thanks for the answer.
     
  5. Feb 25, 2010 #4
    Raekwon, the use of Helium as a leak detector is because it is inert and very small. However, this is much different than anything having to do with superfluid 4He. It's used to test leaks when it is in the gas phase, but the thing about superfluid, is that it has a macroscopic quantum phase, which allows it to flow without dissipation.
     
  6. Feb 25, 2010 #5
    That's what I said?

    Okay maybe I should have separated it a little, but I meant as the gas - hence just saying Helium rather than State II, that's also why I used a balloon as an example, I'm sure we all know nobody fills balloons with superfluids :P
     
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