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Of Interest

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An 8,000-piece ITER mockup that is both a technical achievement and a piece of art. (Sculpture by Sachiko Akinaga; photograph by Hironobu Maeda).
Forget about tungsten, beryllium, niobium-tin and other exotic materials—the new trend in tokamak design these days is plastic.

The learned public was introduced to this new concept in the June issue of Scientific American. The US monthly's four-page article titled "Fusion's missing pieces" was illustrated with a stunning cutaway of a partially completed ITER Tokamak made of ... Lego bricks.

All parts were in place, clearly visible and perfectly rendered in spite of the limitations of the Lego bricks' sharp edges: a D-shaped toroidal field coil suspended from a crane, the central solenoid, sections of the vacuum vessel, blanket modules, the divertor, feeders ...

This 8,000-piece ITER mockup was both a technical achievement and a piece of art. It is the work of Japanese Lego bricks artist Sachiko Akinaga, who began playing with Legos at age 5 and later developed her hobby into an artistic quest.

"As a little girl in Tokyo," she says, "I would never tire playing with Legos. It gave me a lot of confidence and joy. I could not believe I could create objects that I had first pictured in my mind ..."

A graduate of the Toyo Institute of Art and Design in Tokyo, Sachiko has come a long way from what she considers her first work of Lego art: a box of tissues decorated with Indians dancing around a signal fire, a pond, and a crocodile that she created in 2002.

Over the years her work has evolved into a more and more sophisticated form of expression, culminating with her now-famous "Let's go to the Earth Park!"—an impressive project made with about 40,000 Lego bricks.

Last year, when the The New York Times decided to illustrate its winter travel issue with a logo made of Legos, representatives at the Lego Group led the newspaper's editors to Sachiko.

Although it included only 15,000 blocks, the Lego structure was four times larger than her "Earth Park." The artist confided to The New York Times that she worked for eleven days on the logo, including "many days nonstop, in 16-hour shifts"...

The iconic "T" logo (in gothic font) appealed to Sachiko for what she calls a "secret reason": it also stands for the word tanoshi, which means "fun" in Japanese.

The New York Times cover caught the eye of several art directors and magazine editors in the US, among them those at Scientific American.

"Editors there gave me a cutaway view of the ITER Tokamak and a link to the ITER website. Needless to say, I knew absolutely nothing about fusion energy. Understanding the structure of a tokamak was very difficult. Basically, I used five images from the ITER web site."

As with every Lego creation, the hardest part in building the ITER model was to make the rounded shapes—and there are many in a tokamak. Overcoming this difficulty owes as much to Sachiko's technique as to inner workings of the viewer's brain. "Legos create what is very close to a pixelated effect that the human eye and brain smooth out," explains the artist. "When you look at an angled sphere made with bricks, your brain makes it appear round. I find this mental process very exciting ..."

Sachiko's rendition of the ITER Tokamak is both realistic and naïve, as a Lego construction should be. There are workers pushing a trolley loaded with pipes; others signalling to a crane operator with both hands as the delicate operation of installing a toroidal field coil is proceeding.

Of course, it won't happen exactly this way during the assembly of the machine. Like all artists, Lego artists are entitled to some poetic license.

High-speed video image of the MAST plasma obtained at the start of an ELM.
New images from the MAST device at Culham Centre for Fusion Energy could find a solution to one of the biggest plasma physics problems standing in the way of the development of fusion power

MAST, the Mega Amp Spherical Tokamak, is the first experiment to observe finger-like lobe structures emanating from the bottom of the hot plasma inside the tokamak's magnetic chamber. The information is being used to tackle a harmful plasma instability known as the edge localized mode, which has the potential to damage components in future fusion machines, including the key next-step ITER device.

Edge localized modes (ELMs) expel bursts of energy and particles from the plasma. Akin to solar flares on the edge of the Sun, ELMs happen during high-performance mode of operation ("H-mode"), in which energy is retained more effectively, but pressure builds up at the plasma's edge. When the pressure rises, an ELM occurs—ejecting a jet of hot material. As the energy released by these events strike material surfaces, they cause erosion which could have a serious impact on the lifetime of plasma-facing materials.

One way of tackling the problem is ELM mitigation—controlling the instabilities at a manageable level to limit the amount of harm they can do. MAST is using a mitigation technique called resonant magnetic perturbation; applying small magnetic fields around the tokamak to punch holes in the plasma edge and release the pressure in a measured way. This technique has been successful in curbing ELMs on several tokamaks.

The lobe structures that have recently been observed in MAST are caused by the resonant magnetic perturbation, which shakes the plasma and throws particles off course as they move around the magnetic field lines in the plasma, changing their route and destination. Some particles end up outside the field lines, forming finger-like offshoots near the base of the plasma. Changing the shape of a small area of the plasma in this way lowers the pressure threshold at which ELMs are triggered. This should therefore allow researchers to produce a stream of smaller, less powerful ELMs that will not damage the tokamak.

First predicted by US researcher Todd Evans in 2004, the lobes—known as homoclinic tangles—were seen for the first time during experiments at MAST in December 2011, thanks to the UK tokamak's excellent high-speed cameras. CCFE scientist Dr Andrew Kirk, who leads ELM studies on MAST, said: "This could be an important discovery for tackling the ELM problem, which is one of the biggest concerns for physicists at ITER. The aim for ITER is to remove ELMs completely, but it is useful to have back-up strategies which mitigate them instead. The lobes we have identified at MAST point towards a promising way of doing this."

The lobes are significant for another reason; they are a good indicator of how well the resonant magnetic perturbation is working: "The length of the lobes is determined by the amount of magnetic perturbation the plasma is seeing," explains Dr Kirk. "So the longer the 'fingers,' the deeper the penetration. If the fingers are too long, we can see that it has gone too far in and will start to disturb the core, which is what we want to avoid."
The next phase of the research will involve developing codes to map how particles will be deposited and how the lobes will be formed around the plasma.

"We already have codes that can determine the location of the fingers but we cannot predict their length due to uncertainties in how the plasma reacts to the applied perturbations. Our measurements will allow us to validate which models correctly take this plasma response into account," said Dr Kirk. "New codes will mean we can produce accurate predictions for ITER and help them tame the ELM."

Click here for the pdf of this press release.

Under the sun of Provence, the delegation looks toward the Tokamak's anti-seismic "pillows" and listens to Tim Watson (pointing), director for Buildings & Site Infrastructure, as he relates the latest on ITER construction.
As a member of Euratom, Switzerland has been involved in the European fusion program and ITER from the start. And the country's interest in fusion is not only scientific. Last week, on Wednesday 20 June, 18 representatives from the Swiss industry came to the ITER site to see the project's physical progress, but also to get a first-hand update on upcoming procurements and tenders.

"There are not so many opportunities for Switzerland to participate in the building of ITER's largest components," said Michel Hübner, ITER Liaison Officer for Switzerland. "But Switzerland has some recognized niche competencies in the domain of complex electro-mechanical systems. We are therefore looking for matching tenders to be issued from the European Domestic Agency, other Domestic Agencies, or the ITER Organization over the next years. Some Swiss companies have already joined their forces and created consortiums in anticipation of ITER's demand."

The delegation's visit to the ITER construction site was preceded by an off-site meeting during which senior representatives from the ITER Organization reported on the design and manufacturing status of the major components. Philippe Olivier from the Industry Liaison Office within Agence ITER France and Kurt Ebbinghaus from the German ITER Industry Forum (DIIF) also participated in this event.

Saroj Das, ITER librarian; Dhiraj Bora, chairman of the Publication Board and DDG director of CODAC, Heating & Diagnostics; and Daniele Parravicini, DOC section leader, are charged with ensuring that—before publication—written material follows the proper approval channels.
Behind every large science project, there is a mountain of scientific text published in the form of abstracts, journal articles, papers and presentations.

ITER is no different: since the beginning of conceptual design work and continuing to this day, scientists involved in the project have regularly published scientific and technical updates in academic journals and presented written material at conferences.

The ITER Organization needs to ensure that this material that goes out "in ITER's name" has followed proper review channels and that it does, indeed, accurately represent the project. "Material presented for publication must follow specific ITER Organization procedures," stresses Saroj Das, ITER librarian. "These procedures are meant to verify that the publications contain no copyright or intellectual property issues, and that other legal issues like the disclaimer have been handled properly."

The Document Control Centre at ITER is in charge of publication services. All material to be published—whether authored by ITER Organization staff, or co-authored with Domestic Agency staff or collaborators of the two institutions—must be submitted to an internal review and approval process. These materials are centrally stored for archival purposes, and organized in the ITER Document Management System where authors can keep track of the status and history of each publication.

To ensure that ITER's publication procedure is followed and that publications are in line with the ITER Baseline, a Publication Board has been constituted of technical representatives from every ITER Directorate. Any written material with potential intellectual property or export control implications is forwarded by the Board to the appropriate bodies.

"Our role is an important one, since the material published on ITER in these scientific and technical works is reported to the world," says Dhiraj Bora, chairman of the Publication Board. "We also try to sort out delicate issues such as authorship." The Board Chair, who has the delegated responsibility of approving all ITER-related scientific or technical publications, signs the final Permission to Publish form when the material has completed the internal review process.

For the largest annual or biennial fusion conferences, dedicated review boards are created with representatives of the ITER Organization and the Domestic Agencies. These review boards can receive hundreds of documents. "For the 27th Symposium on Fusion Technology in September (SOFT 2012)," says Saroj, "we have already received 46 abstracts from ITER Organization staff, and 78 abstracts from the Domestic Agencies."

A new class of publication will soon be available through the ITER website. ITER Technical Reports—in-depth documents on scientific and technical activities concerning the project—are aimed toward the broader technical and scientific community. The regular publication of these reports will significantly increase the documentation on the ITER Project accessible through the web.

Friction stir welding—one of the techniques to be addressed in the study. Copyright: TWI
Testing components in a rigorous manner and identifying possible improvements before assembling them is a fundamental step in a project as technologically complex as ITER. The need for leading expertise and knowledge transfer is high on the agenda.

In line with the above considerations, a framework contract has been signed between ITER's European Domestic Agency Fusion for Energy and TWI Ltd, the World Centre for Materials Joining Technology, for a maximum value of EUR 800,000 over a period of four years. TWI will provide the European agency with know-how through engineering studies, assessments, technical audits and qualification procedures in the area of joining of components and non-destructive testing technologies.

The results will feed into the manufacturing processes of key structural components like the vacuum vessel and magnets, in-vessel components and the remote handling systems. In addition, modelling activities will be carried out in the areas of heat transfer, prediction of distortions and residual stresses. 

The European Domestic Agency has already identified that the first engineering activities will concern the vacuum vessel and the toroidal field coils. A task on friction coefficient testing is envisaged for the vacuum vessel, while the quality of the welding procedure will be assessed for the toroidal field coils.