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The Spectrum for a pure electron plasma

  1. Nov 10, 2014 #1
    Hello All,

    In this recent Navy publication, a team of researchers said they have discovered cusp confinement. This could be a major step towards fusion power. I am working on a write up of this publication. I am trying to understand their inferometry data. As far as I can tell, the plasma was made of (in order by strength):

    1. Electrons (likely the greatest component)
    2. Hydrogen ions/neutrals
    3. Carbon
    4. A noble gas of some kind
    5. Air/junk (negligible amount)

    These things were probably (+), (-) and neutrals.

    Does anyone have the spectrum for a pure electron plasma?
  2. jcsd
  3. Nov 10, 2014 #2


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    Plasmas usally are macroscopically electrically neutral, consisting of electrons and ions from the original atoms.
  4. Nov 10, 2014 #3
    This experiment specifically went for (-) plasma; AKA the "quasineutral" assumption does not apply. The Navy/LANL team injected 3 amps of electrons for 150 microseconds at 7,200 volts. This is what the device looked like compared to earlier (2005) experiments:


    This was inside a cube vacuum chamber, 45 cm a side. The electron guns were the blue objects. The plasma guns are in red. For a shot, the Navy had control of three variables: (1) plasma gun (2) electron gun and (3) the containing magnetic field. Here is a timeline of one shot:


    This experiment had five stages to it:

    1. Control - The chamber is under vacuum (no pressure is given) and magnetic fields are on.

    2. Injection - This is when the electron and plasma guns are switched on.

    3. Formation

    4. High Beta Mode - This is the fabled "cusped plasma confinement"; long predicted, never observed.

    5. Dissipation

    The navy is proving all of this by interpreting the radiation off of the cloud. For example their hard X-ray data shows high plasma confinement.


    Much of their data comes from shielded detectors, reading a light signal. In visible, X-ray, ect.. I need a better understanding of expected output from a plasma cloud like this. For example, if the cloud was just deuterium the light coming off of it would look like this:


    In this case, the navy blocked all but the H-Alpha line. That is the spike at 656 nanometers.

    Unfortunately, I can only guess at what the plasma was made of (see my list above). The odd component was carbon. Normally, the system would be deuterium, deuterium+, electrons and a trace of junk. They injected carbon. Finally, I know there are formulas to predict these spectra and that maybe a good place to start.
  5. Nov 11, 2014 #4


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    I won't try to answer your question, since it is not an area of expertise for me. However my guess is that how the plasma is generated would be a major determining factor.
  6. Nov 11, 2014 #5
    A pure electron plasma doesn't have a spectrum. You need some other ion species in there. There are two major types of light emission from a plasma: line emission and bremsstrahlung. Line emission comes from electrons bound to nuclei, so there is none from free electrons. Bremsstrahlung comes from the interaction between two different species in a plasma, such as electrons and hydrogen ions. You don't get bremsstrahlung from a pure electron plasma.
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