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Fusion, adding energy while conserving the added.

  1. Nov 15, 2012 #1
    Hi an idea came in mind.Before I go further I want to say that I understand that this is just a theoretical philosophy and that in real life there are radiation losses and particle loses and all kinds of other losses.

    Ok so here's the question.Why can't fusion plasma be heated like a cup of water for example you just keep adding energy slowly until you reach the fusion or in the case of water the boiling point?
    or like lifting a huge heavy iron block by hydraulic lift adding the potential energy to the block one small step at a time.
    Ok I know that in plasma you have heat losses magnetic field fluctuations neutron escape alpha particle and all kinds of other losses and escapes that disrupt the plasma state, but if we could conserve all these particles and somehow (magically) keep them in the plasma wouldn't it be easy then to achieve fusion just by slowly heating the plasma or pressurizing it till the right conditions are achieved?
  2. jcsd
  3. Nov 15, 2012 #2


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    Of course. But we can't avoid the losses and keep the particles inside the fields. That is the substantial engineering challenge we are trying to overcome.
  4. Nov 16, 2012 #3
    Well I guess there is no way to trap a neutron without a escape and collision into the reactor wall or blanket or whatever is there first in it's way.
    Unless strong gravity could do that I guess?
    Which we don't have :D
  5. Nov 16, 2012 #4
    Isn't this what happens in stars? So all you need to do is build a star and then you're sorted. In fact, I think what you described is what actually happens in star formation.
  6. Nov 16, 2012 #5
    Yes it does happen in stars.Not only in formation but in their active life too.Gravity holds the huge mass tightly squeezed, so that the pressure /heat can build up and form a permanent plasma in the core.

    To bad we can't make artificial gravity like electromagnetic fields.Well we can in a spinning object but that's different story I guess.

    Ok two more questions.
    First.What is the more dominant plasma "keeper" in a star the huge pressure or the heat?
    Well I know pressure and heat is somehow related but as they say the sun's core has like 10 times less the heat of a typical fusion "tokamak" but many many times more the pressure that's why it achieves fusion in much lower temperature, why don't we try to get higher pressure rates here on earth in our potential fusion devices?
    As much as I have heard the Iter tokamak has like only about 10 atmospheres of pressure inside the toroid.Atleast that's what I heard in the leading Iter physicist speech.

    The second question.If we would have a huge like I don't know 40m diameter disc with magnets on the sides spinning very very fast could this achieve significant G force to do something with the gas inside of it pushing against the outer magnet wall and achieve fusion atleast some kind.?
    Because I once was playing with the artificial gravity calculator and it showed me that a 20m radius disc spinning at high speeds achieves a pretty huge g force on the side of the disc.
  7. Nov 16, 2012 #6


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    I would say neither. The layers on top of the core keep it compressed and hold everything inside. If anything I would say gravity.

    Because keeping plasma compressed and heated is VERY VERY VERY hard. It is practically impossible to compress the plasma inside a reactor anywhere close to stellar core densities with magnetic fields. Inertial confinement is much more dense however the confinement time is much much shorter than magnetic confinement, so the fusion reactions have much less time to occur. Basically you can shuffle confinement time, density, and temperature around in various ways to achieve fusion. Hold a lower temperature plasma at a high enough density for long enough and you can get the same amount of fusion as you can from a high temperature, high density, low confinement time method. Magnetic confinement has moderate confinement time, temperature, and density, while Inertial Confinement has high temperature and density, but very short confinement.

    Nope. This would be nowhere close to enough. You would tear the structure apart well before you get to the needed density.
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