NIF at LLNL

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quantus
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NIF at LLNL

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NIF: National Ignition Facility
Mission: Fusion energy (among others)

Back in August (just after my last periodic check-in on their progress) they posted this: https://www.llnl.gov/news/newsreleases/ ... 08-04.html
"The yield was significantly greater than the energy deposited in the hot spot by the implosion," said Ed Moses, principle associate director for NIF and Photon Science. "This represents an important advance in establishing a self-sustaining burning target, the next critical step on the path to fusion ignition on NIF."

The experiment was designed to resist breakup of the high velocity imploding ablator (shell of the target capsule) that has degraded the performance of previous experiments by lowering compression of the target. To create this resistance, the laser power is turned up during the picket that occurs at the beginning of the laser pulse. This raises the radiation temperature in the foot or trough period of the pulse (hence the name "high-foot" pulse), increasing the stability of the ablator but reducing compression later in the implosion.

The high-foot campaign was born after systematically exploring possible causes for the shell breakup observed in a series of lower foot, more compressed experiments, and developing hypotheses for how to address the issue.

"In the spirit of what Livermore is good at, this work was born out of the fierce competition of ideas of how to fix the problem, but then coming together as a team to move the best ideas forward," said Omar Hurricane, lead scientist on the campaign. "In this particular experiment, we intentionally lowered the goal in order to gain control and learn more about what Mother Nature is doing. The results were remarkably close to simulations and have provided an important tool for understanding and improving performance."

These promising returns were the result of a laser experiment that delivered 1.7 megajoules (MJ or million joules) of ultraviolet light at 350 terawatts (TW or trillion watts) of peak power. NIF is the world's largest and most energetic laser system, which has already pushed past its design specifications of 1.8 MJ and 500 TW, leaving headroom for more exploration of this idea.
http://www.bbc.co.uk/news/science-environment-24429621
The BBC understands that during an experiment in late September, the amount of energy released through the fusion reaction exceeded the amount of energy being absorbed by the fuel - the first time this had been achieved at any fusion facility in the world.

This is a step short of the lab's stated goal of "ignition", where nuclear fusion generates as much energy as the lasers supply. This is because known "inefficiencies" in different parts of the system mean not all the energy supplied through the laser is delivered to the fuel.
It's not clear what the difference between these experiments is, but in any case, in the last month and a half, ignition became within the project's reach...
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Jason
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Re: NIF at LLNL

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quantus
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Re: NIF at LLNL

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Good explanation of what was really achieved, and clearly, "a step short" is more like a hundred steps short. Still, 99.23% loss is a lot better than 99.5% loss of energy or worse. And increases in heating efficiency are likely to have exponential benefits to energy output. Anyways, I'm hopeful this project will actually hit ignition before the other projects being run around the world. It'd be nice to get have a clean stable source of energy to run the world on before we bake it to death.
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Jonathan
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Re: NIF at LLNL

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quantus
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Re: NIF at LLNL

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https://www.llnl.gov/news/newsreleases/ ... w0IO_ldVEI
http://spie.org/x106267.xml wrote:"This latest result is very important, since it marks the first time that any approach to fusion has generated a greater amount of energy than was initially absorbed by the fuel. In fact, in the most recent experiments of the past few weeks, the fusion energy output was more than double the input," said NIF Program Director for Fusion Energy Systems Mike Dunne.
I find the last section of the article posted about ITER a bit troubling. The issues where the neutrons given off completely rearrange the atoms of the inner casing about every 2 weeks seems pretty troubling. The fact they want a billion dollars just to build a machine to launch neutrons at materials just to find materials that can absorb the radiation without destabilizing the surrounding support structures seems like a huge investment in its own right. NIF will use molten salts and other materials as the radiation shield, so much simpler materials design. Source: https://life.llnl.gov/what_is_life/lear ... fusion.php

The massive magnets at ITER also seems a bit crazy as even the engineers working on them initially exclaimed. The lasers at NIF seem much more mundane in comparison since they're not putting massive structural stress on anything. The transfer of energy is much more direct though using those magnets compared to heating water (the coolant for the molten salt shell) to drive traditional steam turbines. The turbines are a more traditional design though and better understood from a safety perspective.

NIF only requires the targets to be cryogenically frozen while the magnets need to be frozen for ITER. I'd think it's much easier to freeze tiny targets before a reaction than trying to maintain cold magnets to keep an ongoing reaction confined.

Anyways, these contrasts are why I feel a bit safer with NIF/LIFE's design and happy that ITER is halfway around the world in France.

Another reference on LIFE's design: https://str.llnl.gov/JulAug11/dunne.html
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Re: NIF at LLNL

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ITER as an org/engineering effort is completely fucked. I agree completely.

Tokamaks may or may not be the design that first achieves commercial fusion. I strongly suspect that there won't be any commercial tokamaks in one hundred years. We'll figure out simpler designs through better understanding of plasma physics.

NIF, however, does not have a commercial reactor proposal.
Success in demonstrating efficient transport of a high-energy pulse into dense plasma, development of a target design for the compression phase, and definition of a power plant concept could lead to a new energy source for the nation and the world.
It's possible that the fast ignition work NIF is pioneering will be the first commercial power plant, but they would have to prove the physics and then come up with a design before they are in the running.

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