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Nuclear Fusion Idea

  1. Oct 25, 2015 #1
    I was wondering if you could use a very strong magnetic field to produce nuclear fusion. The basic idea is a spherical cavity containing Deuterium (and possibly tritium) nuclei whose walls will be electromagnets whose fields slowly increase in strength and will repel the nuclei and thus the ball of deuterium nuclei inside becomes smaller and smaller until finally the nuclei are close enough to fuse, could this work? If not why?
     
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  3. Oct 25, 2015 #2

    Drakkith

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    Magnetic confinement fusion is currently the most popular type of fusion under investigation and a lot of literature has been written about it. How much have you read on this subject?
     
  4. Oct 25, 2015 #3
    I'm not talking about using the field to confine plasma, I was thinking of actually using the field to cause fusion by producing a more powerful electromagnetic field of repulsion from the walls of the cavity then from the protons thus forcing them to crush together and hopefully fuse
     
  5. Oct 25, 2015 #4

    Drakkith

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    Is your fuel ionized?
     
  6. Oct 25, 2015 #5
    Yes it will be ionized
     
  7. Oct 25, 2015 #6

    Drakkith

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    Then you have magnetic confinement of a plasma, which would make this magnetic confinement fusion.

    In any case, your basic idea is faulty. You can't compress the fuel until the nuclei are so close together that they fuse, as the repulsive force from the closely packed protons is much greater than the force applied by the electromagnets. Instead you would have to heat the fuel so that the kinetic energy of two colliding nuclei is great enough to overcome the repulsive force and allow them to fuse.
     
  8. Oct 25, 2015 #7
    Okay, but can I see the calculations?
     
  9. Oct 25, 2015 #8

    Drakkith

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    I haven't done any calculations.
     
  10. Oct 25, 2015 #9
    Then what do you base your claim off? Because to fuse correct me if I'm wrong but you need to give the nuclei 1MeV of force to overcome the coulomb barrier that force does not need to come from temperature, it could be done with a strong enough push, such as from an electromagnetic field
     
  11. Oct 25, 2015 #10

    mfb

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    Do you need calculations to see a human cannot throw stuff into an Earth orbit from the ground?
    In terms of missing orders of magnitude, this is much closer than the idea you suggest.

    Calculate the repulsion of two nuclei of hydrogen at a distance of 5 femtometers, and compare this to a force gradient (over 5 femtometers) from external electromagnetic fields. They are vastly different.
     
  12. Oct 25, 2015 #11

    Drakkith

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    I base it off of basic knowledge of physics. I can try to do some basic calculations later on, but I have to go apartment hunting right now. Perhaps someone else could explain things while I'm gone.
     
  13. Oct 25, 2015 #12

    berkeman

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    How much reading about nuclear fusion have you actually done? What is your background?
     
  14. Oct 25, 2015 #13
    High school student
     
  15. Oct 25, 2015 #14
    So the formula for the coulomb force is
    coulomb1.jpg
    Therefore the force between 2 Protons at 5 femtometers is 9.24N, I guess you're right it is unlikely that there could be any net energy gain of this
     
  16. Oct 25, 2015 #15

    Astronuc

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    This is a faulty understanding. Firstly, 1 MeV is a measure of energy, not force. Secondly, one can determine the energy needed by integrating force over distance applied. Thirdly, force or pressure is quite high - take the force applied between two protons, which would be the same as between two deuterons or a deuteron-triton pair at the same distance, but now multiply by 1014, and see what pressures are involved.

    Proton-proton fusion works in the sun, because the pressures are extraordinarily high, as in orders of magnitude greater than we can generate with many made systems on a large scale, the because the volume of the sun is so great.

    For terrestrial fusion systems, we generally focus on d+t, which is the easiest reaction to achieve, or d+d which is slightly more difficult to accomplish. All the while, energy is radiating out of the plasma, and neutrals tend to leak out.

    One needs to do some homework on fusion technology, magnetic confinement and inertial confinement.
     
  17. Oct 25, 2015 #16

    mfb

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    Even if we could reproduce the conditions here on Earth, it would not help. The fusion power rate in the core is about ~200 W / m3. That's a lower power density than a human has!


    Concerning the force of magnetic fields: a gradient of 100 T/m gives about 10-24 N (calculation). We need a force gradient, so let's have 100T/m per centimeter, and consider the distance of 5 femtometers as above: 7*10-37 N difference in force between the protons. The force is 37 orders of magnitude too weak.
    As comparison, the gravitational attraction between the protons is 7*10-36 N, 10 times stronger than the tiny magnetic effects. And we know gravity doesn't let hydrogen fuse.
    All those numbers might be off by an order of magnitude or two, but certainly not by 37.
     
  18. Oct 25, 2015 #17

    Astronuc

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    That is the other aspect. The power density (energy production rate) in the pp cycle is very low, besides the fact that the cross-section for the reaction is quite low.
     
    Last edited: Oct 25, 2015
  19. Oct 27, 2015 #18
    Alright my mistake about the magnetic fields the protons interaction with it will be quite small but what about if the sphere was charged instead? I did some crude calculations using coulomb's law and found that the sphere would have to be very tiny to overcome the massive forces of repulsion while my calculations say the repulsion at 5fm is 9.2N I decided to do an upper limit at 230-231N at 1fm assuming a charge of 400C so the fusion would take have to take place in a chamber with a diameter of 0.1mm which is ridiculously small and would not produce very much energy output compared to the energy going in to charge the plates but it is very tiny so a lot of these could be setup per cubic meter, so in theory could this work?
     
  20. Oct 27, 2015 #19

    Drakkith

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  21. Oct 28, 2015 #20
    Wait sorry I'm not exactly that great at physics correct me if I'm wrong but isn't that law for electrostatics? What if there is current flowing?
     
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