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Solid Helium Pictures

  1. Jun 14, 2014 #1
    I was not sure exactly where to put this but it involves images so I thought it was no too inappropriate here.

    I was reading the Feynman Lectures Vol.1 and he says that Helium, although not solid at absolute zero normally, can be so in high pressures. I then googled this for images but none turned up. Why is this? Can it only be done in lab conditions? Is it only done in small amounts?

    Thanks, it is just a light query but I am interested to know why.
     
  2. jcsd
  3. Jun 15, 2014 #2

    Vanadium 50

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    A few points.
    • Before asking us why something should be so, you should find out if it should be so.
    • The fact that you can't find something on Google in a few minutes does not mean it does not exist.
    • If you Google "Solid Helium" you get the image below, which is, not surprisingly, a picture of solid helium.
    • Of course it can only be produced in the lab. Where on earth would you naturally find temperatures of 2K and pressures of 25 bar? And what difference does it make? Cameras work in the lab too.

    F2.small.gif
     
  4. Jun 15, 2014 #3
    As Vanadium 50 already pointed out, even in the zero temperature limit helium requires about 25 bar pressure to solidify. At room temperature the pressure is over 100 kbar. So we cannot observe solid helium outside laboratory conditions.

    I've always liked these images of solid helium:

    http://www.lps.ens.fr/~balibar/photo.crist.jpg

    BTW photographing solid helium is not easy, since the difference in the refractive indices of solid and liquid He is quite small.

    Here are some nice videos of growing solid He etc:

    http://www.lps.ens.fr/~balibar/indexang.html#A few videos
     
  5. Jun 15, 2014 #4

    PhysicoRaj

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    In QuasiParticle's image: http://www.lps.ens.fr/~balibar/photo.crist.jpg, the Helium drop seems to solidify from 1.4K to 0.5K, but from 0.5 to 0.1k it appears to be fusing again.. not crystallising.. the one in the 0.5K picture appears to be a perfect crystal. Why this anomaly? Or am I observing it wrong?
     
  6. Jun 15, 2014 #5
    All those "drops" are solid helium, surrounded by liquid He. As the temperature is lowered, solid He goes through various transitions in the crystal shape. It forms smooth surfaces, facets, with particular surface orientations.
     
  7. Jun 15, 2014 #6

    PhysicoRaj

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    Oh I get it now. Thanks.
     
  8. Jun 15, 2014 #7
    Thanks for you response. I apologise for not being in depth in my post and for sounding naive. I will try to amend this in the future and bear your points in mind. I did find those images but I was wondering if there were any larger samples of solid helium, that sounds ridiculous sorry. In hindsight, the question was 'troubled' at best so I appreciate the tips. I was not exactly sure what I meant and I tried to explain it in the best way I could. All of your answers have clarified it though.
     
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