The Wendelstein 7-X (W7-X) Stellarator

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Dennis P Brown
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The Wendelstein 7-X (W7-X) Stellarator

Post by Dennis P Brown » Thu Oct 22, 2015 10:28 pm

Interesting article on the Stellarator machine. Looks to be Nov time frame when a real plasma will be ignited ... so to speak ... to test its ability to create a stable magnetic field. Discuses the advantages vs. Tokamaks (and the real issues with any Tokamak.)

http://news.sciencemag.org/physics/2015 ... ear-fusion

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Re: The Wendelstein 7-X (W7-X) Stellarator

Post by Paul_Schatzkin » Sat Oct 24, 2015 4:28 pm

Goodness.

I read that article. Admittedly, I don't fully understand the process involved (who can?), but it doesn't sound to me like it's any less complicated than a tokamak. A "fusion reactor designed in Hell" – indeed.
Stellarators face the same challenge as all fusion devices: They must heat and hold on to a gas at more than 100 million degrees Celsius—seven times the temperature of the sun’s core. Such heat strips electrons from atoms, leaving a plasma of electrons and ions, and it makes the ions travel fast enough to overcome their mutual repulsion and fuse. But it also makes the gas impossible to contain in a normal vessel.

Instead, it is held in a magnetic cage.
And it's still "magnetic" confinement, which strikes my (admittedly ill-informed) sensibilities as trying to wrestle delicate forces with brute force. It took more than a MILLION MAN HOURS to build this thing? It might "work," but it'll never be economically cost-effective.

It just seems to me that fusion should not be so complicated.

Even Robert Hirsch has thrown in the towel on tokamaks (see post elsewhere). How much longer before this "twisted tokamak" follows suit?

Millions and billions for magnets, and what's it gotten us besides a big hole in the ground in France?

I'll grant you this much.... it's an "artful" looking contrivance. I look forward to seeing it some day in a museum.

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Re: The Wendelstein 7-X (W7-X) Stellarator

Post by Dennis P Brown » Sat Oct 24, 2015 4:57 pm

The stellarator is, of course, a magnetically confinement fusion system - except for direct drive systems (or atomic bombs, too) magnetic containment is pretty much all we have. Electric field confinement has, to date, not been shown to be viable. That said, the magnetic field of a stellarator is significantly simpler than a Tokamack's nor does it have a number of other issues specific to that design - and these issues, frankly, can't be overcome - like when the field fails in a Tokamak for any reason, the energy in the plasma can cut right through the containment vessel and destroy anything else in its path (like the extremely expensive magnet, for instance.) Further, Stellarators offer far more stable field and can readily be designed so that sections can be easily removable for service and replacement units installed - not something a Tokamak can really be designed to do. Whether the Stellarator creates a better plasma than a similar sized Tokamak will soon be determined and depending on that result, the direction of magnetic fusion will very likely be determined. My bet is on the Stellarator.

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Re: The Wendelstein 7-X (W7-X) Stellarator

Post by Rich Feldman » Fri Dec 11, 2015 6:39 pm

Just heard that they fired up the 7-X machine yesterday.
http://news.sciencemag.org/physics/2015 ... ear-fusion
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Re: The Wendelstein 7-X (W7-X) Stellarator

Post by Steven Sesselmann » Fri Dec 11, 2015 11:56 pm

We have had a stellarator at the Australian National University (ANU) for a long time, it is a large complicated machine which costs a fortune to maintain and run. It is used to teach plasma physics, but my understanding is it has never produced a single neutron from fusion, apparently it can't reach fusion temperatures so no one has ever bothered running it with deuterium.

In fact the ANU have a reasonable size fusion research team and they don't even have a fusor or an accelerator capable of doing fusion. When I asked the head of department why, he said they want to provide a safe environment for students. (unless things have changed in the last two years).

I think this is a disgrace considering it is the place where Sir Mark Oliphant did his pioneering work on fusion. https://en.wikipedia.org/wiki/Mark_Oliphant
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Re: The Wendelstein 7-X (W7-X) Stellarator

Post by Richard Hull » Sat Dec 12, 2015 5:09 am

So many here do not know that the discoverer of fusion was Oliphant. Likewise, many do not know that fusion was discovered 4 years before fission even though its application to produce usable energy still languishes as a mere pipe dream nearly 60 years after fission energy was used to produce electricity. Many key players names are shoved into the background in physics simply because they were not meteoric like Rutherford, , Curie, Einstien, Oppenheimer and others. You would need to read rather deeply to know of Ida Noddack, Otto Frisch and many others.

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Re: The Wendelstein 7-X (W7-X) Stellarator

Post by Dan Knapp » Sat Dec 12, 2015 12:36 pm

Oliphant did his pioneering fusion work at the Cavendish Laboratory in Cambridge. He went to the ANU after the war and established the physics lab there. It can be argued that Cockcroft and Walton actually did the first fusion when they bombarded lithium with protons.

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