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Electrons in vacuum vs electrons in a sphere

  1. Feb 6, 2017 #1
    I know that in a sphere or other geometric conducting objects there is no E field inside because all the charge resides on the outside of the object canceling any inside field , although if I were to focus an electron gas in a vacuum chamber in some circular shape , all the electrons would want to repel each other , I wonder what is the trick that makes those electrons hold on closely next to each other in a solid object , is it the atomic structure of metals for example where the electrons cannot escape from the material so they are held even though they would like to repel away like in the vacuum condition ?

    I wonder is there any mechanism by which one could make a “virtual” sphere or some kind of structure on which those electrons could stick to without flying away.

    I ask this because I was reading about electrostatic fusion approaches like the polywell and I thought the electron well in the middle is very hard to get and even maintain because all the electrons want to repel yet putting a conductor like a thin metal ball would destroy the ball due to heat and radiation , so I was thinking maybe there is another way of trapping those electrons and canceling the inner field as for them not to repel one another.

    Just a thought , what can you say ?
  2. jcsd
  3. Feb 6, 2017 #2


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    The positive nuclei of the atoms exerts a force that holds them onto the sphere.

    You have to create an electric or magnetic field to hold them in place, but electric fields cannot be used because, as you've seen, it gets canceled out on the inside. That leaves magnetic fields, which have cusps between the magnets that allow electrons to leak out of the center of the device. The polywell charges the electromagnets (or rather the frame holding the electromagnets) with a positive charge so that any electrons that leave the device are attracted back towards the center.

    I don't see an other way of holding electrons in place other than magnetic fields, but perhaps some creative engineering will change things in the future.
  4. Feb 6, 2017 #3

    jim hardy

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    you might read Philo Farnsworth's fusor patents. As i recall he used some clever math to describe his electric fields.
  5. Feb 7, 2017 #4


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    There are many ideas for holding charged particles -'magnetic bottles' etc.. The Toroidal arrangement of coils is the most successful and it's what is used for the tight containment of plasma for fusion. The geometry of magnetic fields yields a more suitable approach because you can get 'endless' field lines which can trap charged particles for a long time as they go round and round the loop. E fields have 'ends' on their field lines. (+ and -) . Look up Zeta Thermonuclear Reactor.
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