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National Ignition Facility (NIF)

  1. Sep 15, 2005 #1

    The genesis of this design as described to me is a single 980 nm Pump Diode which is fiber-optically split into 192 fiber-optical 'beam lines' using a Fiber Bragg Grating. The 'laser amplifiers' then amplifies this pulse more than 1 million times which is propagated to the target chamber.

    The design pulls power from a main grid into a 'power conditioning system', which is analogous to a giant battery which discharges this power into 10,000 'flash lamps', each around seven feet high which is opticalised into 'laser glass' which absorbs these photons and converts them into ultraviolet laser energy which is then transferred through the system to the target chamber which converts the ultraviolet photons into x-ray photons and fires onto the target, which is a tiny spherical pellet containing hydrogen isotopes, which produces a nuclear fusion reaction.

    For the nanosecond that the NIF fires, it discharges more than 1000 times the energy that the entire earth is using in that same nanosecond.

    The amount of energy required to charge this device is claimed to be only US$5.

    The reactor is scheduled to become operational in 2008.


    NIF reactor design:
    http://www.aip.org/png/images/png2.gif

    Reference:
    http://www.llnl.gov/nif/
    http://www.llnl.gov/nif/programs/dir_library.html
    http://www.llnl.gov/nif/project/lib_animations.html
    http://www.aip.org/png/html/nif.htm
    http://www.spie.org/Conferences/Calls/04/pw/lase/index.cfm?fuseaction=lasenatlab
     
    Last edited: Sep 15, 2005
  2. jcsd
  3. Sep 15, 2005 #2
    Wow, sure sounds impressive!
     
  4. Sep 16, 2005 #3

    Morbius

    User Avatar
    Science Advisor

    Candyman,

    You can see some more pictures of NIF at:

    http://www.llnl.gov/nif/project/lib_highlights.html

    For example, the 1st picture in the 3rd row shows the cables from the capacitor banks that
    Orion1 spoke of.

    The 3rd picture in the 2nd row show 2 of the 3 robots that handle / transport the laser
    amplifiers. The 3 robots are named, "Enterprise", "Defiant", and "Voyager".

    The 3rd picture in the 3rd row is of a Plasma Electrode Pockels Cell. It is a high speed
    optical switch that channel the laser pulse toward the amplifiers or out to the target.

    The 3rd picture in the 4th row shows the top of the blue target chamber.

    The 3rd picture in the 5th row shows a big crystal of KDP - Potassium DiPhosphate.
    KDP has non-linear optical properties. It can be used to double and triple the frequency
    of the laser light. The NIF neodynium-glass amplifiers actually amplify light at
    frequency in the near infrared.

    You can read more in a article from the Sept. 2003 issue of the LLNL publication
    "Science and Technology Review" written by Ed Moses:

    http://www.llnl.gov/str/September03/Moses.html

    Dr. Gregory Greenman
    Physicist
     
  5. Sep 16, 2005 #4
    Is that first picture in thr fifth row the target?

    And after thinking about this for a while, how do you get 1000 times the earth's power output in one second using only five dollars worth of energy? That seems a bit like the cold fusion claims, putting little in and getting a huge amount out.
     
  6. Sep 16, 2005 #5

    It is a 'nano'-second, which appears to approximate to 500 Terawatts.
    1 nano = 10^-9 and 1 tera = 10^12

    Basically the original photons originate from a simple 'laser diode' which can fit in the palm of your hand, however, these photons when amplified enough can catalyze a nuclear fusion reaction.

    I do not have the exact design specifications, so I cannot say how their power equation was derived. It should be listed in one of their published engineering papers.
     
  7. Sep 17, 2005 #6

    Morbius

    User Avatar
    Science Advisor

    Candyman,

    No - that's the device that holds the target in position - the target at that
    scale would be too small to really see. Here's an article from LLNL's
    Science and Technology Review that shows the target and the surrounding
    "hohlraum" in Figure 3:

    http://www.llnl.gov/str/Haan.html

    Energy IS conserved - but power - the rate at which energy flows isn't.

    You charge up the capacitors for several minutes - giving you a certain
    amount of energy - and then discharge them in a very short time - like a
    nanosecond. You don't create any energy - you just make it flow very
    fast for a very short period of time.

    The electronic flash on your camera works exactly the same way.

    Let's say we can draw 100 watts [ like a single electric light ] from the
    power grid. Let's charge a capacitor bank for 1000 seconds [ about 20 mins ].

    So we have 100,000 watt-seconds of energy or 100,000 Joules stored. Now
    let's discharge that capacitor bank in 1 nano-second or 10^(-9) seconds.

    What's the power?

    The power is energy per unit time. The energy is 100,000 watt-seconds or
    10^(5) watt-seconds. The time to discharge is 1 nanosecond = 10^(-9)
    seconds.

    The power P = 100,000 watt-seconds / (10^(-9) seconds) = 10^(14) watts
    or 100 terrawatts.

    That's twice the amount of the energy that the entire Earth uses in
    that nanosecond. We didn't create any energy - we just had to spend
    20 minutes storing energy at a rate of 100 watts [ like a lightbulb ]. We
    just discharged it fast.

    Nothing like cold fusion which claimed more energy than was put in.

    Dr. Gregory Greenman
    Physicist
     
    Last edited: Sep 17, 2005
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