Core of fusion device completed: Last steel seam on Wendelstein 7-X closed

Jun 05, 2013 by Isabella Milch
Last steel seam on Wendelstein 7-X closed
Precision work: One of over 250 ports being brazed in the plasma chamber. Credit: IPP, Anja Ullmann

The last open seam on the steel outer cover of the Wendelstein 7-X fusion device was closed last week. The core of the research device is thus ready as basic skeleton and can go into operation at the Greifswald branch institute of Max Planck Institute of Plasma Physics (IPP) in 2014.

The objective of fusion research is to derive energy from fusion of , just as happens in the sun. To ignite the fusion fire, the fuel in a future power plant has to be confined in magnetic fields and heated to temperatures exceeding 100 million degrees. Wendelstein 7-X, the world's largest fusion device of the stellarator type when completed, is intended to investigate the suitability of this configuration for a power plant. With 70 large coils in continuous operation it is then to produce a highly stable and thermally insulating magnetic cage confining the plasma.

The ring-shaped device is being installed as five almost structurally identical modules: Each of the five sections of the plasma vessel, along which 14 magnet coils are strung, is enclosed by a steel outer sheath, weighing altogether 120 tons. Assembled like slices of cake on the machine's foundation, the five modules form a steel ring from which numerous connection ports protrude. These link the apertures of the plasma chamber through the coil region with the outer vessel. Later, measuring instruments, pumps and heating facilities will be affixed here.

The 254th and last port was brazed in between the plasma vessel and outer vessel with millimetre precision on 28 May 2013. The elaborate port installation lasted a good two years. This was preceded by an equally long test phase – "a huge training session" as installation head Dr. Lutz Wegener put it – during which the methods for exact placement and connection of the variously configured ports to the bizarrely shaped plasma vessel were developed. One of the many challenges: As stainless steel inevitably shrinks at the seam when it is brazed, the components are distorted and change position. This had also to be allowed for when brazing the five modules of the device together: Calculations and tests during installation planning had predicted here up to eight millimetres shift per seam, this being intolerable since the ports and the subsequently connected measuring instruments would be looking at the wrong place in the plasma.

Last steel seam on Wendelstein 7-X closed
View of the Wendelstein 7-X fusion device from above: All of the 254 ports are installed. Credit: IPP, Anja Ullmann

The solution: The module to be brazed, exactly monitored by laser tracker measurements, was shifted on sliding bearings about eight millimetres away from its firmly attached component opposite. Then, to prevent anything shifting, several welders began together to close the two brazing gaps of both the plasma chamber and the outer sheath. For the multi-layered seams with a total length of 40 metres the specialists of the MAN Diesel Turbo company took several weeks, during which the heavy module – in keeping with the shrinkage – slowly returned to its initial position in tenths of a millimetre steps. "It is a veritable work of art to guide in the right direction such a big and heavy component during brazing", states Karsten Liesenberg, who is responsible for the vessel installation concept: "If the laser trackers showed that the module was not being shifted exactly parallel, the brazing crew had to change over to the opposite side of the seam so that the component was again put on the right track". This precision work was repeated on the other four module boundaries. The ring is meanwhile closed and all five modules are in place with the required two millimetre precision.

Till installation of Wendelstein 7-X is completed in 2014, there are still a few tasks to be done, such as linking the magnets to their power and helium supplies and doing the interior of the plasma vessel. This will be accompanied by provision of the systems for heating the plasma, the supply facilities for electric power and cooling, machine control and finally the numerous measuring instruments for diagnosing the behaviour of the plasma.

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User comments : 9

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5 / 5 (1) Jun 08, 2013
I think the article is inaccurate in that the workman shown is welding and the author incorrectly describes it as brazing. These are two entirely different processes. Accuracy in a scientific article is paramount to credibility. It would be impossible to Braze this device. Welding fuses,(melts) the two materials to join them, while brazing uses a much lower temperature allow to join the metals. Brazing is more like using the Braze alloy as a glue, the alloy being,more often than not, a less strong material.
1.4 / 5 (9) Jun 08, 2013
It is interesting to watch, how the physicists are able to build the billion dollars tokamak-like devices again and again - whereas they're not willing to replicate few dollars nickel wire experiments of Piantelli and Focardi during last twenty years. IMO it says about contemporary science a lot.
5 / 5 (5) Jun 08, 2013
It is interesting to watch, how the physicists are able to build the billion dollars tokamak-like devices again and again - whereas they're not willing to replicate few dollars nickel wire during last twenty years. IMO it says about contemporary science a lot.

What a load of BS. I know for a fact that my college physics advisor/professor worked in a team that attempted to replicate cold fusion results. As have many others over the years. Nobody's ever gotten any useful results, and predictably the field at this point is populated solely by conmen and well-meaning but incompetent amateurs.

Besides which, if you feel so strongly about it you ought to just get to work on it, rather than wasting everybody else's time with your whining. Things happen because people DO things. Obviously.
5 / 5 (4) Jun 08, 2013
Actually my advisor told me that the whole cold fusion thing was started by a chemist who was detecting neutrons coming from his experiment. He couldn't explain where they were coming from, and people started screaming about "cold fusion". It turned out that he didn't understand how to set up the neutron detector correctly, and all the data was garbage.

You can't blame him for that - it was an honest mistake that anyone can make. But everything that has happened since has just been a giant pile of unethical conduct, to the extent that anyone in cold fusion research are basically assumed to be pulling a fast one.

But of course we never hear about that stuff, now do we...
5 / 5 (4) Jun 10, 2013
Fleischman and Pons thought they detected heat, not neutrons, coming from their experiment. But many flaws in the experiment were found by independent researchers.

Georgia Institute of Technology reported detecting neutron emissions from an independently-replicated Fleischman-Pons setup. But they later retracted the announcement. They had gotten false positives out of their equipment by failing to consider the effects of temperature on the performance of the detector.

Since then the trail of cold fusion has been twisting and frustrating, both to mainstream scientists and to 'true believers.' Millions have been spent in Japan, the United States, India, Italy, and elsewhere. No consistent, replicable results have been obtained. Claims for success have emerged in several quarters, but there is no consistency in the phenomena reported, no replicability, and no plausible theory as to how or why cold fusion should work.
5 / 5 (4) Jun 10, 2013
Today, cold fusion is kept alive mainly by private individuals claiming that they have succeeded in producing devices which generate more energy than the devices require as input. The details of how these devices supposedly work are never released. There is no peer review. There is no possibility of replication. Devices never quite make it to market. Demonstrations never meet the standards of independent replicability or peer review.

Cold fusion has, in other words, become the province of clever scam artists preying on gullible 'true believers.'
1 / 5 (1) Jul 04, 2013
We need to ask the question. Is this technology really the right one ?

After 40 years, hundreds of billions of dollars, over 150 different designs, hundreds of
phd physicist, over 50 countries and what has not been accomplished ?

To date, not even 1 second of fusion reactor operation.

Any other company would be dust.

Some would say this is scientific racism at its best, others no doubt will defend
their poor speculative failings with assault of this opinion to justify their continued
failed research.

How much money is justified and for how long ?

Many small start ups looking for capital would be better served.

1 / 5 (2) Jul 04, 2013
Cold fusion has, in other words, become the province of clever scam artists preying on gullible 'true believers
You're apparently living on another planet. Why not to check the facts, available in peer-reviewed press first? The first successful cold fusion experiments were reported in 1926 already, and from this time every troll repeats the same lie again and again.
1 / 5 (2) Jul 04, 2013
Today, cold fusion is kept alive mainly by private individuals
This is another lie. The private subject don't publish anything about cold fusion and all these thousands of articles above linked are produced with researchers, who organize regular conferences across the world each year.