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Plasma conductance?

  1. Sep 24, 2008 #1
    hey, I have a question, it might be really stupid, but I'm probably not as smart as any of you here. Anyway:

    if you had a sustained plasma field held in place, maybe spinning in a toroidal motion, is it possible to "harvest" free electrons from the field by an anode, and feed it back into the field by a cathode? Kind of like how a fuel cell creates an H+ ion, runs the electron that was stripped through a circuit by the anode, then gives it back later through the cathode to be rejoined with oxygen. Again it may be a stupid question, and there may be no net gains from it, but I was really curious. Thanks!
  2. jcsd
  3. Sep 24, 2008 #2


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    Assuming that one is referring to a magnetically confined plasma, that approach would be problematic since it would lead to local instabilities in the plasma because of the local charge concentration and distortion of the magnetic field. There are already proven approaches such as ohmic heating in which currents are induced in the plasma. In this case, the plasma is like a single conduction coil surrounding the one leg of a transformer. Other approaches include microwave heating, neutral beam injection, and magnetic compression.
  4. Sep 24, 2008 #3
    I guess what I meant was can you at all extract electrical power from a plasma field to power a circuit? after all plasma is electrically conductive and consists of free electrons in the field.
  5. Sep 25, 2008 #4


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    Ideally one can extract excess energy (that is energy in excess of maintaining the fusion energy generated beyond what is input to acheive plasma condions and make up for losses) from the plasma. Three possibilities would be: 1) induction, i.e. using the time varying change in current in a transformer configuration to drive electrical current (AC), 2) direct conversion, in which the products of the fusion reaction are removed in such a way that the nuclei (+ ions) are separated from the electrons, which provides an electrical potential (DC), or 3) the thermal energy is passed to a mechanical system which drives a turbine-generator set, which is how most electricity is generated.
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