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Can Plasma Be Solid

  1. Feb 12, 2012 #1
    Plasma, the fourth state of matter, is a gas that consists of ions and free electrons. If you cooled plasma would it become a liquid? A solid? What would be the properties of this plasma? would you be able to magnetically separate it?
     
  2. jcsd
  3. Feb 12, 2012 #2

    mathman

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    If you cooled a plasma, the positive ions and electrons would combine to form atoms, so you (at first) would have an ordinary gas.
     
  4. Feb 12, 2012 #3
    Ah I see says the blind man. That was probably the most likely one in my mind.
     
  5. Feb 12, 2012 #4

    Dotini

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    I'm certainly no plasma physicist, but I found the following on page 62 of the Naval Research Laboratory Plasma Formulary NRL/PU/6790--11-551, Revised 2011:

    "Complex (dusty) plasmas (CDPs) may be regarded as a new and unusual state of matter. CDPs contain charged microparticles (dust grains) in addition to electrons, ions, and neutral gas. Electrostatic coupling between the grains can vary over a wide range, so that the states of CDPs can range from weakly coupled (gaseous) to crystalline. CDPs can be investigated at the kinetic level (individual particles are easily visualized and relevant time scales are accessible). CDPs are of interest as a non-Hamiltonian system of interacting particles as a means to study generic fundamental physics of self-organization, pattern formation, phase transitions, and scaling. Their discovery has therefore opened new ways of precision investigation in many-particle physics."

    Crystallinity normally refers to the degree of structural order in a solid.

    Typical CDP experimental dust temperatures appear to be ~3 x 10^-2 - 10^2 eV.

    I hope this helps.

    Respectfully submitted,
    Steve

    Edit: I googled "coulomb yukawa crystal discharge chamber", and found a large group of papers. This one was fun to look at: http://physik.uni-graz.at/~dk-user/talks/Thoma20080213.pdf
     
    Last edited: Feb 12, 2012
  6. Mar 24, 2012 #5
    wow great questions. The obvious answser is no! you can not have solid plasmas. Plasmas are hot and when you cool them they will lose their charge.

    But plasma physics is never obvious. And would you believe it there are plasma crystals which behave like solids. They are very interesting because the scale lengths in such crystals are often quick large - millimeters even.
    nvlpubs.nist.gov/nistpubs/jres/100/4/j14and.pdf

    So how do we get a solid plasma. By putting tiny dust particles into a gas plasma. Electrons collect on the dust particles and the dust particles then repel each other creating a crystal like structure. Unlike a normal crystal which has positive ions repelling each other is a sea of electrons, in the plasma crystal we have negatively charged dust repeled in a sea of positive ions and electrons.
     
  7. Mar 24, 2012 #6
    Plasma Crystal experiment http://www.mpe.mpg.de/pke/index_e.html [Broken]
     
    Last edited by a moderator: May 5, 2017
  8. Mar 25, 2012 #7

    Dotini

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    Here is an article about electric ice, or ionized ice, or "ice XI". (Elderly readers may recall Kurt Vonnegut's "Ice 9". :biggrin:)

    http://www.newscientist.com/article/mg21128274.400-electric-ice-a-shock-to-the-solar-system.html
    Cool ice to about 60 kelvin (-213.15 °C), though, and the hydrogens rearrange themselves so they are aligned. In the resulting, perfectly regular crystal, called ice XI, there are distinct regions of positive and negative charge.

    Can it it be explained how this fails to be an example of a plasma in solid form, please?

    Respectfully submitted,
    Steve
     
  9. Mar 26, 2012 #8
    It comes down to the definition of a plasma.

    Plasma behave in a collective way. Some people define a plasma as positive and negative particles but this is not enough. The collection of charged particles must react to shield a potential so that no electric field can be sustained in the plasma - it is almost neutral though out the bulk. There must be enough charged particles of both species and they need to be close enough together that each particle influences many nearby charged particles, rather than just interacting with the closest particle. There is also a need for the response time of the plasma to be faster than the collsion time with neutrals so that the collective behaviour is not distroyed by the charged particles bumping into neutral molecules or dust particles.

    In a normal crystal like the ice example there are ions and electrons but the ions are not free to move so I would not consider this a plasma, it breaks the collision rule.Generally it is often said that plasmas are hot - the forth state of matter. This is true if we consider everything to be in equilibrium. I would say it is only true for thermal plasma and they have to be hot to survive. But nearly all plasma used in industry are not in thermal equilibrium. The are often called cold plasma. For example in the dust crystal the electrons are heated by a Radio Frequency, RF Field. The RF heats the electrons to 10,000K but the dust is cold as are the ions. The electrons lose energy in collisions with ions and dust but because the mass is so different the collision do not transfer a lot energy and any energy lost is regained from the RF field. So the electrons stay hot but everything else can be cold.

    But because the ions and electrons are still free to move and there is not too much dust then a plasma still exists and can be sustained indefinitely. The dust forms a crystall lattice inside the plasma so it is like a solid, but it shows that the solid state and plasma state can exist together. - thats why I think it is so intersting.
     
  10. Mar 28, 2012 #9
    The Sun is a plasma. Pressure increases towards the center of the star. As the plasma grows denser it becomes thicker, first like a liquid then an amorphous solid.
     
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