ITER Needs To Take A Leak

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MSimon
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ITER Needs To Take A Leak

Post by MSimon »

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http://physics.about.com/b/2006/05/23/f ... -chaos.htm

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Physicists try to get around this problem by containing the plasma in a magnetic field that will keep it clear of the walls of the machine. Unfortunately, as the magnetic field squeezes the plasma tight in the center of the machine, the plasma eventually bursts through the weakest point in the field. Imagine squeezing a balloon full of water, says General Atomics physicist Todd Evans. Except the plasma is so hot and energetic that the released matter corrodes key parts of the machine.

But Evans thinks he may have a solution to the dilemma. Using a modified tokamak [Russian acronym for "toroidal (donut-shaped) magnetic chamber"] reactor to introduce chaotic static into the magnetic field, his team found that it weakens the field just enough to let some plasma leak out through the bottom, releasing the pressure on the rest of the field and preventing a more disastrous leak.

The exact nature of what happens is still unknown beyond that, but the research (published in Nature Physics) could help make the $5.5 billion (US dollars) International Thermonuclear Experimental Reactor (ITER) a success, if it can be incorporated into the design of the machine. The heat of the ITER reactor may not allow for incorporation of the conducting coils that Evans used.
A discussion of the ELM problem:

http://www.ipp.mpg.de/eng/for/veranstal ... ts/234.pdf
In ITER, these instabilities [known as edge localized modes (ELMs)] are projected (if not mitigated) to produce energy bursts every 1 s of up to 20 MJ released in 0.5 ms, resulting in impulsive energy densities on the divertor target plate approaching 400 MJmˆ{-2}sˆ{-1/2}. Such large energy densities are well above the ablative limits of divertor carbon-fiber-composite and tungsten target plate plasma facing materials planned for ITER and would hence cause premature erosion of the divertor target plates, requiring frequent replacement of divertor components. Estimates suggest that the ELM size must be reduced by a factor of 20 for adequate lifetime of these components. In recent years, a concerted worldwide effort has emerged to develop efficient and reliable ELM mitigation and suppression techniques that can be scaled to the full range of ITER regimes and more generally to burning plasmas in a generic fusion reactor design.
Aside from the impulse heat load problem there is also the problem of extracting 20 MJ/(m^2 *s) That is a 20 MW per sq m load. They are going to need a new and improved flux capacitor lined with unobtanium.

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Remember the post a way long time ago about how we should discredit ITER. And how the general consensus was that we should play nice? That was the right decision. ITER is discrediting itself.
Engineering is the art of making what you want from what you can get at a profit.

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