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Electron ion seperation.

  1. Jun 11, 2013 #1
    Ok here goes one of my crazy , maybe not so questions.
    When ionization occurs , the electrons and ions form a plasma , now if that plasma would be heavily confined with a +polarity electric field , that would only confine the ions as they have the same charge and would repel from wherever the field would come but now the electrons would try to "run" to the + electric field metal plate or whatever conductor and crush into it , I hope I am getting this right so far, now if we would put some special electrodes before the plate that is charged at some + potential to confine the plasma would the electrons leave the ions and charge the electrodes , giving excess voltage on them , now if so then what would happen to the ions , can there be a ion only plasma , can the electron fully leave the atom from which it originated from and if so then I guess it must involve a certain energy level or so?

    Now I ask this partly because there was a discussion here of pF time ago about what would happen to a block of copper if it somehow lost it's electrons , and a forum member correctly said that the protons would go flying in opposite directions due to electric repulsion of the same charge and this acceleration would result in a release of energy etc.

    Now I just though , you can't take the electrons away from an atom in the typical 3 ground states of matter but what about a plasma.?
  2. jcsd
  3. Jun 11, 2013 #2

    Simon Bridge

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    Not normally, no. Plasma is a state of matter.

    If you have an ionized gas, then you can separate the charges with an electric field - OK.

    Given sufficient strength, yes.

    An ionized gas does not have to be electrically neutral, no.

    You mean the phase states - solid, liquid, and gas?
    "Ground state" usually has a different meaning.
    However, it is possible to remove all the electrons from atoms without requiring a plasma ... i.e. singly ionized hydrogen has lost all it's electrons.

    You cannot remove all the electrons from a solid of a liquid without destroying it as a solid/liquid - this is because the form relies on there being electrons there.

    Are you asking if a plasma composed entirely of bare nuclei is still a plasma?

    It would be intriguing to hear from a plasma physicist - I would say it's a yes and no -by analogy: the free-flowing electrons in a conductor can be described as an electron plasma, but it has more in common with the gas state and is referred to as a Fermi gas. The same is the case for holes - so bare nuclei in a bottle would also be a Fermi gas.

    (At the back of my mind is a little voice warning that these are classical/fundamental states and a gas of bare nuclei may be a long way from the regime where it makes much sense to talk about matter existing in one state or another.)
    Last edited: Jun 11, 2013
  4. Jun 12, 2013 #3
    No offense Simon I appreciate your help just as any other members ideas on a given subject but how does it come to be that for some specific questions I ask only Simon responds... ? :D:D
    There must be a conspiracy under all this. :D:D

    Ok jokes aside , yesterday it was kinda late and didn't get the chance to write as smooth as I wanted so now I'm about to make it more clear.

    I was thinking in terms of , okay a simple picture for ones mind.
    You have a sort of chamber with special plates of very high positive (+) electric potential to give you a strong electrical field , now you put a hydrogen gas inside that chamber under large pressure and have the gas confined by the electric field , but only the ions feel the repulsion/confinement the electrons want to run into the + charged plates , so we have some special conductors between the plates say that "suck" the electrons that are rushing to those plates and use those electrons to charge the original + plates through a capacitor or something.

    Now this is not only a picture of a weird device but also a question can anything like this that I just described can happen in real life and as you asked yes is a plasma possible were all the electrons have left and only ions remain , can such a plasma undergo the normal fusion cycle for example the deuterium +tritium = helium +alpha+neutron. Or something similar.?
    I was thinking about this because basically the protons and ions are the main fusion "players" if I understand correctly and the electron having very little mass compared to the ion is not a major player.
    Also would fusion with ions only be even harder than with the usual plasma because of the lack of electrons?
  5. Jun 12, 2013 #4

    Simon Bridge

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    The others actually have a life ... but I also have a higher tolerance for "crazy" than a lot of these folks.

    You sound like you are describing part of the operation of a Bussard Fusor.

    Go look it up.
  6. Jun 13, 2013 #5


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    You can easily separate ions from electrons and throw them into a magnetic containment device, effectively forming an ion only plasma that stays together because of the containment device. Well, maybe not easily...but it can be done.

    As for fusion...well, it depends on what type of fusion you are performing. Typical magnetic confinement requires electrons, as the combined repulsive force of half a gram of pure ions is far far too strong to keep them confined. You wouldn't be able to keep enough confined to perform any fusion.

    However, something like beam-beam fusion, beam-target fusion, or electrostatic confinement can work with just ions. They just don't work very well...
  7. Jun 13, 2013 #6
    Well yes the problem with ion electron plasma in electrostatic confinement is obviously the fact that with one type of field you can confine only one polarity of plasma particles.
    is there any approximate guess to how high a voltage (potential) would a electrostatic confinement device needed to be to hold a ion only plasma at a fusion density?
    Well I understand that it would also depend on the plasma pressure itself , the size and dimensions of the confinement structure etc.

    Also I was thinking to myself is it possible to use the electrons that are stripped of when ionizing the gas to feed them into some electrodes that would result in excess voltage that could partly used to get the high voltage needed for the confinement of ions?
    Atleast theoretically I think this could be done.
  8. Jun 13, 2013 #7


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    About 30kv I believe. I think it depends on the exact setup of your fusion device. The Fusor that amateurs build at home uses about 30kv-50kv if I remember correctly. The higher the voltage the more fusion events you have.

    Honestly, I don't know.
  9. Jun 14, 2013 #8
    No Drakkith I wasn't thinking of a fusor in a typical way they are built with those inner outer grids charged at opposite potentials to accelerate and confine the ions to the center.
    I was thinking more in terms of a physical sphere or something like that which has charged metal plates around it in such a fashion that the electric field points inward rather than outward as it would in a closed round sphere made from metal.
    And then with no inner grid or structure to degrade over time from the ion collisions just a empty middle and plates around the confinement structure at high potentials to have strong electric fields to confine and put (exert) pressure on the ion plasma.
    I know it would be extremely hard without electrons as the ions would tend to fly apart due to repulsion now how high of a voltage one would need on the plates at such a theoretical setup.
    An approximate.

    I honestly don't know , hope you have a clue. :D
  10. Jun 14, 2013 #9


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    I don't think your setup would do anything. Putting a bunch of charged plates in such a configuration is almost exactly like a charged sphere. The potential inside the containment sphere would be practically the same everywhere and you wouldn't be able to confine the ions. I think so at least.
  11. Jun 15, 2013 #10

    Simon Bridge

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    @Crazymechanic: I could, of course, go through the process of exploring the ideas you have and refining them into the kind of thing that would actually do something ... however, from your earlier description, it looks like you'd end up with a Bussard fusor.

    It would be very difficult to get a static electric field to confine a plasma ... but, even if you did, the more charged the plasma the harder it will be to get it to fuse.

    You have been attempting to explore ideas qualitatively, in "plain language", which are best handled mathematically. If you are serious about these sorts of things then you will learn the real EM models and the math that go with them. You honestly will not get anywhere until you do.
  12. Jun 17, 2013 #11
    Well no Simon I am not trying to produce or describe a fusor , not even a Bussard fusor.
    The idea of the central electrode to which the ions accelerate to due to electric field and then collide to fuse .
    The fusor has the drawback of that the central electrode is in the middle of he "action" so it wears out pretty fast.

    By the way I am doing this because I study this kind of material and these concepts that I ask here are a model which helps me better understand the way plasmas behave etc.
  13. Jun 17, 2013 #12

    Simon Bridge

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    And this is not a fusor because...

    A central electrode is pretty much, by definition, in the middle of the action isn't it?

    In that case you definately need to learn the math.

    By the time I'm done working through the misconceptions here, you will end up with something very like one of these fusors you don't like. Plasma physics is hard - there are no qualitative shortcuts. Learn the math.

    Good luck :)
  14. Jun 19, 2013 #13
    The thing here is that I have the lack of being good at numbers but I love physics and enjoy thinking and also doing some.
    I'm learning this as a hobby because my academic interest is more electronics than plasma physics etc.Even though they just as many other physics areas have something in common.

    Speaking about the fusor and what I tried to describe I could post a drawing later to show more clearly what I wanted.
    The thought is to accelerate ions only with an electric field then confine them with a positive electric field and then in a tube kind of structure put some pressure on them in the way of their acceleration so that they would run into the field with high energies , but that alone wouldn't be enough , we wold need something that keeps them in that high pressure electric field are so that they would like to "stay around" and "have fun" or in other words fuse.
    And for that I have a question is there any such possibility to put a negative electrode with an corresponding negative field after the positive one that would confine them in a manner that they (the ions) feel the negative electrode but cannot get to it being pushed back by the positive field.

    Even though this is just a theoretical though , like a small hole for a tiger through which he feels the meat but cannot get it and has to stay hungry. :D

    As the biggest drawback of a fusor is the fact that the ions accelerate to high velocities and fuse in the area of the central electrode but they also destroy the electrode as they physically impact it and also loose their energy.
    But is there any known way to make those ions "stay hungry" for the negative field and never really get to the origin of it , thus fusing in the way of trying to do so.

    I will attach a small fast drawing on the thought in mind.It doesn't have all the details i inteded but the main though like a ion repelling confining field at the end of the tube which is positive but then a little or many little holes or slits through which the negative field would be felt and the ions could concentrate there at those regions , if it can happen at all.

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