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Question about fusion

  1. Jul 12, 2005 #1
    Question about fusion....

    What are the problems for development, continuouly power production and economical, in a nuclear fusion reactor and nuclear fusion power plant ?
  2. jcsd
  3. Jul 12, 2005 #2


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    It takes more energy to create and sustain the reaction than it produces. One of the most common approaches used magenetic fields to contain the reaction, but that takes more energy than the reaction generates, for example,
  4. Jul 13, 2005 #3


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    In a word - "breakeven".

    As of yet, we don't know how to achieve "breakeven" - that is to get as
    much energy out of the plasma as we put in to make the plasma.

    The basic approaches to fusion are "magnetic confinement" and
    "inertial confinement".

    Magnetic confinement uses machines like "tokamaks" to confine the
    plasma with magnetic fields. The problem there is that a magnetically
    confined plasma has all sorts of instabilities - and it breaks up before
    we can hold it long enough to get back as much energy as we put into it.
    Magnetic confinement is chiefly studied at the Princeton Plasma Physics


    The other approach is "inertial confinement" fusion. Here, you don't
    even attempt to try to "hold" the plasma. You create a very dense
    plasma that burns very fast, and you count on the fact that the inertia
    of the mass of the plasma will hold it together long enough to get
    useful energy. The confinement time will be very short - but if the
    fusion burn is fast enough - you could still get a useful amount of energy.
    [ After all, that's how hydrogen bombs work - they don't hold together
    very long - but they produce energy so fast that the small confinement
    time is long enough ].

    The problem with inertial confinement fusion is that we haven't been
    able to create a plasma large enough to trap the alpha particles which
    you want to do to get "ignition". That is, just as a fire uses the heat from
    combustion to keep the fire going - you want to trap the alpha particles
    to keep the fusion fire going. Previous experimental machines couldn't
    do that - but that is changing.

    The principal means of heating and compressing a plasma in inertial
    confinement fusion is with lasers - also called "laser fusion". The
    principal research centers are at Lawrence Livermore National Lab,
    and the Laboratory for Laser Energetics at the University of Rochester.

    Lawrence Livermore National Laboratory is building the NIF - the
    National Ignition Facility. This 192 beam laser should be powerful
    enough to create a plasma large enough to achieve ignition. The NIF
    building is finished, as are the first set of lasers. More lasers will be
    brought online during the next few years until the entire 192 beam
    complement of lasers is finished. See:

    National Ignition Facility at Lawrence Livermore National Laboratory:


    OMEGA laser at the Laboratory for Laser Energetics at University of Rochester:

    Another method for inertial confinement is to use large pulsed power
    sources to "magnetically implode" plasmas in what is called "Z-pinch
    inertial confinement fusion". This research is underway at the
    Sandia National Laboratory in Albuquerque, New Mexico:


    Hope that's enough to get you started.

    Dr. Gregory Greenman
    Last edited: Jul 13, 2005
  5. Jul 13, 2005 #4
    Nice post Morbius! I always enjoy reading your comments.
  6. Jul 14, 2005 #5


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    Thank You

    Dr. Gregory Greenman
  7. Jul 14, 2005 #6


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    Antiphon's question has been split into it's own thread
  8. Jul 30, 2005 #7
    What are projects about nuclear controlled fusion reactor to achieve Q > 1, or possibly obtain Q > 1.
  9. Aug 25, 2005 #8


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  10. Aug 25, 2005 #9
    Fusion is my favorite topic to discuss and read. I just found out from a friend today that undergraduates can take classes dealing with fusion, they used to only be graduate level. I looked around and found that Dr. Weston "Bill" Stacey, a former director of Argonne's fusion program, could be my professor!

    Has anyone heard of the text that is used: W. M. Stacey, Fusion Plasma Analysis, 1st Edition, Krieger, 1981?
  11. Aug 25, 2005 #10


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    Yeah, I have that book and used parts of it when I taught Fusion Engineering almost 20 years ago. I also used Dolan, but it's a set of three, which are hard to find, and I misplaced or lost Parts 2 and 3.
    Last edited: Aug 25, 2005
  12. Sep 19, 2005 #11
    Hi Morbius.

    I have a question that I think you are very capable of answering.

    Do you think that by using an array of LASERs that we could literially paint a high energy image or Photosphere shell like the sun has, but as a miniature version or virtual duplicate of a miniature star with shell and core structures?

    Do you think cloning a stars exact exterior and interior structure would be an effective means to copy the exact process within the star itself? .ie Holographic Sun created by LASER interference.

    Thanks. :smile:
  13. Sep 20, 2005 #12


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    In a word: NO.

    You aren't going to be able to "paint" or "copy" a miniature version of the Sun.

    For one thing; even if you did - it wouldn't stay the way you copied it.

    Suppose you made a ball of high temperature, high density plasma similar to what one
    finds in the interior of the Sun. It wouldn't stay that way - it would explode.

    The Sun is like a great big exploding Hydrogen Bomb. However, this Hydrogen Bomb
    is so massive that its gravity opposes the explosion and keeps the Sun stable.

    Without all that mass - and the consequent gravity - there's nothing to hold your plasma
    intact - so it would just explode.

    In a way, the fusion targets at Livermore are like these little exploding Suns.
    However, they won't have a photosphere. You get a photosphere when the distances
    that the photons of light travel are much, much less than the diameter of the object.

    Clearly, our little exploding suns are much too small to have photospheres.

    We can't just copy the ways stars do things - we have to do things that make sense on
    Earth - with the quantities of mass that we have available.

    Dr. Gregory Greenman
    Last edited: Sep 20, 2005
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