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Old 11th December 2015, 1:11 AM   #1
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Default German "Stellarator" goes online - first plasma produced

After about nine years of construction, one year of preparatory tests, and spending 1 billion Euro, the fusion facility “Wendelstein 7-X” was officially put into operation in Germany today and produced helium plasma at 10 million degree for the first time. They will start experimenting with hydrogen in January 2016. The target is hydrogen plasma, which needs 100 million degree.

Wendelstein 7-X

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The purpose of Wendelstein 7-X is to evaluate the main components of a future fusion reactor built using stellarator technology, even if Wendelstein 7-X itself is not an economical fusion power plant.

The Wendelstein 7-X reactor is the largest fusion device created using the stellarator concept which was the brainchild of physicist Lyman Spitzer. It is planned to operate with up to 30 minutes of continuous plasma discharge, demonstrating an essential feature of a future power plant: continuous operation.

The name of the project, referring to the mountain Wendelstein in Bavaria, was decided at the end of the 1950s, referencing the preceding project from Princeton University under the name Matterhorn.[3]




Interesting competition with the much more (15 times) expensive ITER project based on the Tokamak design.

Last edited by chainbolt; 11th December 2015 at 2:46 AM.
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Old 11th December 2015, 6:22 AM   #2
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A better discourse on this stellarator here: http://news.sciencemag.org/physics/2...nuclear-fusion

The Tokomak and Stellarator are based on the same design concept. The Stellarator attempts to solve one of the challenges the Tokomak design faces but introduces much greater manufacturing and engineering challenges.

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By 2003, W7-X was in trouble. About a third of the magnets produced by industry failed in tests and had to be sent back. The forces acting on the reactor structure turned out to be greater than the team had calculated. “It would have broken apart,” Klinger says. So construction of some major components had to be halted for redesigning. One magnet supplier went bankrupt. The years 2003 to 2007 were a “crisis time,” Klinger says, and the project was “close to cancellation.”
It's still too early to be popping the champagne.

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Approval to go ahead is expected from Germany’s nuclear regulators by the end of this month. The real test will come once W7-X is full of plasma and researchers finally see how it holds on to heat. The key measure is energy confinement time, the rate at which the plasma loses energy to the environment. “The world’s waiting to see if we get the confinement time and then hold it for a long pulse,” PPPL’s Gates says.
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Old 13th December 2015, 8:04 PM   #3
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The Tokomak and Stellarator are based on the same design concept.
I think the objective is the same, but the Tokomak and Stellarator design concept are much different. And that's the reason why both designs have different names in the first place, and it also explains why the required investment is much lower for a stellarator. The basic idea of the stellarator is to use areas of differing magnetic fields to cancel out the forces on a particle as it travels around the confinement area. The tokamak provides the required twist to the magnetic field lines not by manipulating the field with external currents, but by driving a current through the plasma itself.

The design difference is very apparent if you see the inside of the devices. Because stellarator uses areas of differing magnetic fields the inside looks like a twisted tube or intertwined coils.

Here is a schematics display of the stellarator design. You can easily see the twisted tube that confines the plasma.





German 7X Wendelsetin Stellarator



Japanese Helical Stellarator



Because a Tokamak device is driving a current through the plasma itself, it looks just like a round tube. The concept does not require a "twisted" geometry.

Here is how a tokama device looks like. Example: ITER.



As you can see, the design of a stellarator and tokama device is much different, simply for the reason that they are based on different technical concepts. It seems the stellarator design is cheaper and provides for more stable results, while the more challenging tokamak design could provide for better results.

Last edited by chainbolt; 14th December 2015 at 1:44 AM.
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Old 14th December 2015, 6:36 AM   #4
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I think the objective is the same, but the Tokomak and Stellarator design concept are much different.
The objective of all fusion reactor designs is the same, produce usable energy from nuclear fusion.
Beyond that there's several different classes of approach, one will produce pulses of energy and others are continuous.

On the pulsed front there's ideas such as Dense Plasma Focus being explored. If that can be made to work and is commercially viable....Well both the Tokomak and Stellarator will be white elephants.


Both the Tokomak and Stellarator are continuous and the underlying concept is the same. Hold a plasma using magnetic confinement that's hot and dense enough to produce more energy from nuclear fusion than is used heating and confining the plasma. Both these designs are trying to avoid what Dense Plasma Focus embraces, pinching of the plasma.

Maybe the Stellarator is a better way to achieve plasma confinement than the Tokomak. Whichever one proves to be the best will be the one the next generation goes with. Regardless both still face the same issues.

Once we have a way of confining the plasma undergoing fusion a way still has to be found to get usable heat out of the plasma. A way to remove the fusion products and a way to inject fuel into the plasma has to be found. A lot of the money being spent on ITER is going into addressing these challenges. Whatever solutions to the challenges ITER finds are applicable to both the Tokomak and Stellarator designs.
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Old 14th December 2015, 7:13 AM   #5
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On the pulsed front there's ideas such as Dense Plasma Focus being explored. If that can be made to work and is commercially viable....Well both the Tokomak and Stellarator will be white elephants.
In my very inexpert opinion, that's the one that needs buckets of money thrown at it.
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Old 14th December 2015, 7:49 PM   #6
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In my very inexpert opinion, that's the one that needs buckets of money thrown at it.

I don't think the Focus Fusion people need much more funding at this stage. Their current issue seems to be corrosion of the tungsten electrodes caused by the presence of oxygen in the chamber.
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Old 15th December 2015, 2:41 AM   #7
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The objective of all fusion reactor designs is the same, produce usable energy from nuclear fusion.
LOL

The OBJECTIVE of fusion reactors is the same. The DESIGN is different. Stellarator and Tokomak follow different designs, that's the reason why they have different names in the first place.

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Maybe the Stellarator is a better way to achieve plasma confinement than the Tokomak. Whichever one proves to be the best will be the one the next generation goes with. Regardless both still face the same issues.
Right, therefor it's seems to be meaningful to try both concepts.

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Old 15th December 2015, 9:07 AM   #8
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LOL

The OBJECTIVE of fusion reactors is the same. The DESIGN is different. Stellarator and Tokomak follow different designs, that's the reason why they have different names in the first place.
Noooo

Both the Tokomak and the Stellarator are intended to produce self sustaining fusion from a (very) high temperature low density plasma using magnetic confinement. Magnetic confinement has issues and the Tokomak and Stellarator take different approaches to solving that specific issue within the one class of fusion reactors.

Efforts such as the one being run at the National Ignition Facility are in a different class. It uses a high density plasma contained by inertia.

The name "Stellarator" is a bit misleading as it implies some similarity to stellar objects. Stellar objects such as our sun have high density low temperature plasma that enables sustained fusion. Confinement happens thanks to gravity. The NIF facility produces conditions much closer to that in the Sun then either the Tokomak or Stellarator.


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Right, therefor it's seems to be meaningful to try both concepts.
It goes beyond that really. The ITER people are as confident as can be that their machine will produce self sustained fusion for long enough for materials to be tested and diagnostics run. Many Tokomaks have been built over the past 50 years, there's even ones other than the one at ITER under construction. Tokomaks are well understood entity. The Stellarator is only now a feasible solution to the magnetic confinement problem.

When / if ITER does achieve sustained fusion for a reasonable period of time (minutes) it will then spend years running diagnostics and investigating the materials science problems. That means robotic devices have to able to get inside the machine to change out components. It'll be too radioactive inside the containment vessel for humans to enter for a period of time. The regular shape of the Tokomak makes this much easier. A robotic arm that could reach every point in the Stellarator would require many degrees of freedom. There's a much higher risk of something going wrong requiring testing to stop until it was safe for a human to enter.

Here's a pretty easy read of the whole Tokomak - Stellarator competition: https://en.wikipedia.org/wiki/Stella...on_to_tokamaks

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It is generally argued that the development of stellarators is less advanced than tokamaks, although the intrinsic stability they provide has been sufficient for active development of this concept.

The three-dimensional nature of the field, the plasma, and the vessel make it much more difficult to do either theoretical or experimental diagnostics with stellarators. It is much harder to design a divertor (the section of the wall that receives the exhaust power from the plasma) in a stellarator, the out-of-plane magnetic coils (common in many modern stellarators and possibly all future ones) are much harder to manufacture than the simple, planar coils which suffice for a tokamak, and the utilization of the magnetic field volume and strength is generally poorer than in tokamaks.
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Old 15th December 2015, 10:23 AM   #9
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Is that duct tape?

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Old 15th December 2015, 12:05 PM   #10
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Is that duct tape?

image
Maybe to prevent leakage? The plasma seems to be quite "fluid".
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Old 15th December 2015, 12:41 PM   #11
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H R Geiger should sue.
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Old 17th December 2015, 8:21 AM   #12
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Of some actual relevance to this discussion:

https://www.ipp.mpg.de/16931/einfuehrung

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Achieving these objectives does not require producing an energy-yielding fusion plasma. This is because the properties of an ignited plasma can largely be transferred by the ITER tokamak to stellarators. Wendelstein 7-X can therefore dispense with the use of the radioactive fusion fuel, tritium, thereby greatly reducing costs.
The Stellarator we're discussing will not even attempt to produce energy yielding fusion.
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Old 4th February 2016, 11:03 AM   #13
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Default German science nerds turn on new fusion reactor

The global nerd community is getting excited about the new German experimental fusion reactor, which is a departure from the usual Tokamak design.

So far, Germany has wasted more than a billion dollars on this giant test tube - money which would have been better spent on stimulating Germany's pathetically flat property market.

The German president hopes that fusion energy may provide the nation's formidable industrial sector with a source of cheap yet clean energy. Germany's president earned a Doctorate in Physics and worked as a professional scientist.
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Old 4th February 2016, 11:07 AM   #14
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Insightful post, I enjoyed it while lamenting the country I live in at the same time...
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Old 4th February 2016, 11:10 AM   #15
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Real achievement is worth more then BS money ever will be. So no they havnt wasted any money at all.

Good on them for not letting big banks run the country i suppose, this is as big as the moon landing for who ever gets it going and could be the fix for climate change.

also its only half a billion, if it works its worth trillions.
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