Melting tungsten for a good cause

Over the past two years ITER physicists and engineers, along with many scientific colleagues within the fusion research community, have been working to establish the design and physics basis for a modified divertor—the component located at the bottom of the huge ITER vacuum vessel responsible for exhausting most of the heat and all of the particles which will continuously flow out of ITER’s fusion plasmas. 

Our current Baseline begins plasma operations with divertor targets armoured with carbon fibre composite (CFC) material in the regions that will be subject to the highest heat flux densities. After the initial years of ITER exploitation, in which only hydrogen or helium will be used as plasma fuel producing no nuclear activation, this divertor is to be replaced. The replacement—a variant of the first component but fully armoured with tungsten—would be the heat and particle flux exhaust workhorse once the nuclear phase, using deuterium and then deuterium/tritium fuel, begins.

In 2011 the ITER Organization proposed to eliminate the first divertor and instead go for the full-tungsten („full-W”) version right from the start. This makes more operational sense and has the potential for substantial cost savings. By June 2013, the design was at a sufficiently advanced stage and we were confident that the necessary tungsten high heat flux handling technology was mature enough to invite external experts to examine our progress during the full-W divertor Final Design Review

But making a choice to begin operations with tungsten in the most severely loaded regions of the divertor is not just a question of having a design ready to build. 

Tungsten, a refractory metal with high melting temperature (3400 Celsius), is a much more difficult material than carbon when it comes to handling very high heat loads and running the plasmas which ITER will require to reach good fusion performance. Why? For two principal reasons: as a metal, tungsten will melt if the heat flux placed on it is high enough; also, as an element with high atomic number it can only be tolerated in minute concentrations in the burning plasma core.

Carbon, on the other hand, does not melt but sublimes (passing directly from solid to vapour) and is low atomic number, so can be tolerated in much higher quantities in the core plasma. Unfortunately, carbon is a difficult option for ITER nuclear phase operations as a result of its great capacity for swallowing up precious tritium fuel and efficiently trapping it inside the vacuum vessel. Tungsten retains fusion fuel only at comparatively low levels.

Why is melting such a problem? Because a melted metal surface is no longer the flat, pristine surface which is installed when the component is new. One of the ways the ITER divertor is able to handle the enormous power flux densities which will be carried along the magnetic field lines connecting to the target surfaces is to make the target intersect the field lines at very glancing angles, so that the power is spread over a wider surface. But a small angle means that any non-flat feature on the surface will receive a higher-than-average heat flux and can be further melted, producing a cascade effect.

The ITER full-W divertor design goes to great lengths to make sure that there is no possibility—on any of the many thousands of high heat flux handling elements—of an edge sticking up (for example, as a result of mechanical misalignment) that could overheat and begin to melt under the relentless bombardment these components receive during high power operation. However ITER’s size means that it will have the capacity to reach a value of stored energy in the plasma more than a factor of 10 higher than the largest currently operating tokamak, JET (EU). When some of this energy is released in a rapid burst (for example due to very transient magnetohydrodynamic events such as ELMs), some melting is possible—even if all edges have been hidden by clever design.

We intend to stop this happening as much as possible by applying ELM control techniques, but occasional larger events cannot always be excluded. So one of the big physics questions we have tried to answer over the past two years is: what exactly happens when a burst of energy, sufficient to melt tungsten, strikes our divertor targets?

Until recently we had only rather complex computer simulations with which to establish the physics design specifications. One of the main worries was not just that energy bursts could roughen up and damage divertor component surfaces, but that the very rapid melting induced by the burst could lead to the expulsion, or spraying, of micro-droplets of tungsten back into the plasma leading to intolerable contamination and a decrease in performance.

The computer simulations say this shouldn’t happen, but the process of melt ejection is so complex that experiment is the only sure test. But how to test the behaviour under conditions which only ITER can create? Well, as far as tokamaks are concerned, the only place where this was even conceivable was at JET, in which natural ELM energy bursts can be generated at levels similar to those expected for controlled ELMs in ITER. The problem is that these comparatively benign transients will not melt a tungsten surface!

In an experiment proposed and planned jointly between JET and the ITER Organization over the past two years, a small region of one of the full-W modules in the JET divertor was carefully modified to create a situation which every divertor designer would do anything to avoid—a deliberately misaligned edge.

The JET divertor modules are made up of about 9,000 small tungsten plates („W lamellas”), bound together by a complex spring loading system. The lamellas are only 5 mm wide and about 60 mm long with 1 mm gaps between neighbouring elements. For the experiment, a few lamellas were machined to make a single element stand up out of the crowd, presenting an edge of about 1.5 mm on average to the plasma in one of the hottest zones of the divertor.
The result: reassuringly unsurprising! Although there was some evidence suggesting the occasional ejection of very small droplets from the melted area, there was very little impact on the confined plasma. As the ELM plasma bursts repetitively melted the edge of the misaligned lamella, the molten material continuously migrated away from the heat deposition zone, accumulating harmlessly into a small mass of re-solidified tungsten (see video at left, courtesy of EFDA-JET). The JET plasmas with 3 MA of plasma current were able to produce ELM plasma pulses very similar to the lowest amplitude events we need to guarantee for 15 MA operation in ITER—a fact which makes the experiments very relevant from a plasma physics point of view.

Much more analysis is required to see how the results can be matched quantitatively by simulation, but the observations are clearly in qualitative agreement with theory. That’s the most reassuring part: that physics codes used to assist in component design for ITER tomorrow can be validated on experiments performed today. We will have to wait another year now for the damaged lamella to be retrieved from JET before the full picture of these important experiments can be completed, but this is already extremely valuable physics input for the important decisions coming up later this year with regard to our divertor strategy.

The dream of his life

ITER owes much to a few. At different moments in the history (and prehistory!) of the project, a handful of individuals made moves that were to prove decisive. Among this band of godfathers—whether scientists, politicians, diplomats or senior bureaucrats—Umberto Finzi stands prominently.

Finzi, who retired from the European Commission in 2004 but continued to advise the Director General of Research until the conclusion of the ITER negotiations in 2006, belongs to the generation who embraced fusion research in the early 1960s at a time when plasma physics was still in its infancy.

A physicist turned bureaucrat—he was called to Brussels to take care of setting up JET in 1978 and was appointed Head of the European Fusion Programme in 1996—Finzi played a key role in the negotiations that led to building ITER in Europe. An ITER godfather in his own right, he nevertheless insists on the „collective action” that, under four successive European presidencies, led to this decision.

Time has passed. The „paper project” whose roots go back to the late 1970s, years before the seminal 1985 Reagan-Gorbatchev summit  in Geneva, is now a reality, as tangible as it is spectacular. When he toured the ITER worksite on 30 July, Umberto Finzi took the full measure of the progress accomplished since his last visit in 2006, when all there was to see was a hilly, wooded landscape and a high pole marking the future location of the Tokamak.

„During most of my professional life,” he said, „ITER was a dream. You can imagine my emotion seeing these tons of steel and concrete. This reminds me of the famous message by Hergé¹ to Neil Armstrong: „By believing in his dreams, man turns them into reality.” 

„ITER is a difficult venture,” he added, „and difficult ventures requiretime and patience. The effort is not only scientific or technological. It lies also, and maybe essentially, in the planning and coordination.”

ITER, with 35 participating nations, could have been a Tower of Babel. „On the contrary,” says Finzi, „it is the exact opposite of a Tower of Babel, a beautiful demonstration of worldwide understanding. No project has ever associated so many different nations. To me, this is the most important aspect of ITER, a historical dimension that reaches beyond the project’s scientific and technological objectives.”

(1) Hergé (1907-1983) was a Belgian cartoonist, creator of the world-famous characters Tintin and Snowy. Between 1930 and 1986, Hergé published 23 albums of The Adventures of Tintin, selling a total of 200 million copies in 70 languages. Fifteen years before Neil Armstrong, Tintin, Snowy and other recurrent characters in the series walked on the Moon in the 1954 album "Explorers on the Moon."


An Associated Laboratory in fusion was established earlier this month between the Chinese Academy of Sciences (CAS) and the French Commission of Atomic Energy (CEA) to develop cooperation on two long-pulse tokamaks, EAST and Tore Supra, soon to be equipped with an ITER-like tungsten divertor — the project WEST.

The creation agreement was signed on 3 July by Prof Li, director of the Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP) and Gabriele Fioni, director of CEA’s Physics Science Division, CEA, at the French Embassy in Beijing. French nuclear counselor Pierre-Yves Cordier hosted the signing ceremony, with André Grosman, deputy director of the Institute of Magnetic Confinement Fusion Research (IRFM/CEA) and consular assistant Shunming Ding. 

The associated laboratory has been created to develop cooperation on CEA’s long-pulse tokamak WEST* and ASIPP’s EAST, particularly in the fields of actively cooled, metallic plasma-facing components; long-duration plasma operation in an actively cooled, metallic environment; long-pulse heating and current drive; ITER technology support; and the preparation of „Generation ITER” (see this issue’s Of Interest entry) in all of the above-mentioned areas.

Xavier Litaudon and Yuntao Song are appointed as the associated laboratory’s co-directors. They will be responsible for leading and coordinating the performance of the projects under the Associated Laboratory Agreement.

„I am enthusiastic about the CAS/ASIPP-CEA collaboration,” said Prof Li after the signature. „The cooperation between EAST and WEST will be good for all fusion communities.”

As a first step, ASIPP has already sent two young researchers to IRFM to work for one year on WEST component design and engineering.

* WEST = W (tungsten) environment for steady state tokamak

Tiny diamond detectors for the giant ITER machine

In the world of tokamaks ITER will be a giant, weighing some 23,000 tons and measuring 30 x 30 metres. Whatever its might, however, the operation of this giant couldn’t be successful without such tiny elements as diamond detectors. These small components, only 4 x 4 x 0.5 mm, are an important part of one of ITER’s neutron diagnostics, the vertical neutron camera.

The diamond detectors, part of the Russian Domestic Agency’s procurement responsibilities for ITER diagnostics, will be manufactured at a dedicated facility at the Troitsk Institute for Innovation and Fusion Research (TRINITI) near Moscow.

Manufacturing is a sophisticated and multi-stage process, according to Nikolay Rodionov who heads the facility: „In ITER, detectors will operate under high neutron flux and high temperature, and it will be our task is to produce diamond detectors that are capable of withstanding such extreme, severe conditions.”

At the beginning of detector manufacture, the key elements—electronic-grade, single-crystal diamond plates—arrive at the material analysis laboratory where highly sensitive instruments test quality and identify defects. Next, the plates and associated metal fixings are cut to the required sizes and shapes by laser.

To correct possible defects, the single crystal diamond plates are annealed in a high-temperature vacuum oven at temperatures no less than 1500 degrees Celsius. Rid of their organic impurities by specially mixed acids, the diamond crystals are exposed to additional purification from an ion beam of oxygen or argon.

For such a sensitive component as a neutron detector, even the smallest impurities are inadmissible.

In the next stage of manufacturing a metal layer (gold, titanium, platinum or aluminum) is deposited on the diamond plate and gold or aluminum current conductors are welded on—these conductors, which at 30 micrometres thick can hardly be seen by the naked eye—collect electric charge from metal contacts. Now the detector, placed into a special mounting of thin sapphire plate and attached by two membranes of bronze or copper, is ready for installation on the vertical neutron camera.

By 2018, the specialists at TRINITI will have manufactured approximately 100 diamond detectors for ITER, including test samples, prototypes and spares. Currently, the facility has been equipped with laboratory and technical equipment for the manufacturing of dummies and test samples. For the production of prototypes and the beginning of batch manufacturing of qualified diamond detectors, additional modernization is planned to meet the requirements of the complex manufacturing operations for the diamond detector.

Click here to view a video on the manufacturing of ITER diamond detectors.

China’s HT-7 retires after 11,800 plasma shots

Next time you want to see HT-7 you will have to go see it in its new home, ASIPP’s new energy centre in Huainan (80 km west of Hefei). It will ultimately become a museum exhibit, showcasing an important period of history and bearing witness to fusion research developments in China over the past two decades.

Recently the HT-7 Tokamak was officially endorsed for retirement by the Chinese Academy of Sciences and the Ministry of Environmental Protection after a three-month review of the feasibility of retirement and the retirement plan that included an assessment of scrap equipment and environmental impact. This is the first mega-science device that has ever been taken out of service in China.

HT-7, the world’s fourth—and China’s first—superconducting tokamak entered service in 1995 and has fulfilled all of its scientific missions, running nearly 20 rounds of experiments, discharging 11,800 plasma shots, nurturing three generations of Chinese fusion scientists and achieving a 400-second record in long plasma discharges.

Its story dates back to early 1990 when Academician B. Kadomtsev, the former director of the Kurchatov Institute in Moscow, expressed his Institute’s willingness to transfer the T-7 Tokamak to ASIPP as a gift.

After discussing logistical, management and technical considerations with his colleagues, as well as the engineering and physics challenges, Academician Huo Yuping (the director of ASIPP at that time) made a quick and bold decision to accept the offer. This decision received strong support from the Chinese Academy of Sciences and other government authorities.

From 1991 to 1994 T-7, together with its subsystems, was transported to Hefei. Despite economic hardship at that time, ASIPP—with the participation and assistance of Russian scientists—pooled its human and financial resources to rebuild the T-7 Tokamak, which was renamed "HT-7" (the "H" stands for Hefei).

After commissioning in March 1995 HT-7 was put into operation the same year, a milestone marking the entry of China (after Russia, France and Japan) into the circle of nations possessing a superconducting tokamak.

In order to conduct long-pulse high-performance plasma operation and related physics research on HT-7, ASIPP developed dozens of systems and technologies such as radio frequency wall conditioning, a water-cooled graphite limiter, a1.5 MW/20-110 MHz radio frequency heating system, real-time multi-variable feedback plasma control, 2.45GHz/1.2MW lower hybrid current drive, and a 30 MW thyristor convertor in same phase anti- parallel connection with 4-quadrant circulating current operation mode.
In total, 11,8000 shots were discharged in nearly 20 HT-7 experiment campaigns, which explored graphite limiter operation mode, high parameter plasma characteristics with wave heating and drive, and long-pulse high-performance operation modes. On 21 March 2008, HT-7 achieved a 400-second plasma record with central electron temperature of twelve million degrees and central plasma density of 0.5×1019m-3.

Because of HT-7 construction and operation, ASIPP has greatly enhanced its R&D capabilities and cultivated a team of engineers and scientists willing to brave hardship and challenges, a trustworthy „team of accomplishments.” In addition, ASIPP has promoted extensive international cooperation.

The valuable experience and manpower training resulting from HT-7 exploitation paved the way for the successful construction and operation of EAST and has laid a solid foundation for China’s contribution to ITER. It is also a valuable source of information for the future fusion research and projects.

To those who have worked for and on HT-7, the tokamak represents a huge part of their lives—a legend of tears and laughter. The day of 12 October 2012 will always be a day to remember for ASIPP staff: three generations of ASIPP scientists gathered in the HT-7 tokamak control room to witness the last plasma discharge of this beloved machine and to say goodbye. HT-7 did not let them down, putting a beautiful full stop to its career by giving a mighty and last shot amid thunderous cheers and applause.

At last! Time to rest, old pal.

Construction kick-off for Tokamak Complex

Early on Tuesday, 30 April the usual hustle and bustle on the fifth floor of the ITER Headquarters came to a short halt as ITER management gathered in front of a video camera to participate remotely in an event taking place at the European Domestic Agency, Fusion for Energy (F4E) in Barcelona. An event marking another milestone in the project’s history book: the kick-off meeting for Tender Batch 03, which is project code for the contract covering the construction of the Tokamak Complex plus another eight support buildings.

The Tokamak Complex will be a seven-storey reinforced concrete building with a steel-frame crane hall and a total mass of around 335,000 tons. It comprises the Tokamak Building plus the adjacent Diagnostic and Tritium buildings.  All three are connected and supported by a common basemat.

In addition to the Tokamak Complex, another eight buildings will be erected within the frame of the TB03 contract over the next 66 months, as well as 60 nuclear doors that will provide containment and radiation shielding during ITER operation and maintenance and three bridges. The scope of work comprises all civil works, heavy doors supply and implementation and finishing works.

The preparation for Tender Batch 03 began with a competitive dialogue in July 2011 and concluded with the award of the contract to the VFR consortium on 20 December 2012. The VFR consortium brings together VINCI Construction Grands Projets, Razel-Bec, Dodin Campenon Bernard, Campenon Bernard Sud-Est, GTM Sud and Chantiers Modernes Sud as well as the Spanish company Ferrovial Agroman.

„The start of this contract is one of the most important ITER milestones, as building construction is the main driving force of this project,” Director-General Osamu Motojima stated in his remarks following opening words from F4E Director Henrik Binslev. „This kick-off meeting will be recorded in the history of the project and fusion research,” Motojima went on, before he welcomed the Vinci consortium as „a new and important member” of the ITER team. „We are very much looking forward to working together closely. It will be my great pleasure to witness the daily progress from my office window.” 

Read more about the kick-off meeting on the F4E website here

How can we help?

How can we help? It was this one sentence—or rather question—addressed to ITER Director-General Osamu Motojima after his welcome address that explained why communication officers from the seven ITER Domestic Agencies, the Princeton Plasma Physics Laboratory, and from 25 European fusion associations had made their way from the different ends of the world to the ITER Headquarters last week.

The dissemination of information about the latest developments in the field of fusion research and of course the progress of the ITER project are the daily job of the communication officers working in the ITER Domestic Agencies in Oak Ridge, Hefei, Seoul, Barcelona, Moscow, Tokyo or Gandhinagar, or in one of the many fusion research facilities joined under the roof of the European Fusion Development Agreement (EFDA). For the first time since the start of the ITER Organization, the EFDA Public Information Network met on the ITER premises in southern France to exchange ideas and opinions and to discuss appropriate communication tools.

Altogether, with more than 40 people present—dedicated to spreading the word about fusion—an impressive tool in itself.

On 25th anniversary, Tore Supra enters the museum

At age 25, Tore Supra is still far from being a museum piece. It is in a museum however that the anniversary of the CEA-Euratom tokamak was celebrated last Tuesday evening in Aix-en-Provence.

Why a museum? Why not … the old priory of the Knights of Malta, now the Musée Granet, was the perfect venue for the informal commemoration, providing a large shaded courtyard for the speeches, beautiful rooms to wander through and exceptional works of art to admire…

As he briefly retraced the history of fusion research and the part played by Tore Supra, Richard Kamendje of the International Atomic Energy Agency, drew this parallel between fusion science and art:  „Every generation,” he said, „faces similar challenges. But because you are living in a certain moment in history, you answer these challenges with the tools that belong to your time.”

One of the very first fusion machines to implement superconducting coils, Tore Supra certainly rose to meet several challenges over its 25 years of operation. Originally led by the installation’s designer Robert Aymar, Tore Supra teams explored the domain of long plasma discharges, achieving a record six-and-a-half minute „shot” in 2003 that produced one Gigajoule of energy.

Tore Supra pioneered the technology of actively-cooled plasma-facing components, real-time diagnostics, in-vacuum robotics… A quarter century after First Plasma was achieved on 1 April 1988, this accumulated expertise forms one of ITER’s major assets.

An anniversary is an occasion to reflect on the past, often with emotion, and to welcome the future, often with enthusiasm. Both Alain Bécoulet, the present Head of CEA’s Research Institute on Magnetic Fusion ( IRFM, the laboratory that operates Tore Supra), and his predecessor Michel Chatelier (2004-2008) expressed their conviction that the machine’s future will be no less brilliant and exciting than was its past.

For Tore Supra and the IRFM team, this future has a name: WEST (W Environment in Steady-state Tokamak, where "W" is the chemical symbol of tungsten). The project, which consists in installing an ITER-like full tungsten divertor, „will bring Tore Supra into the group of fusion devices that are actually preparing for ITER,” said Bécoulet. The formal decision to „go WEST” was taken by CEA on 7 March 2013; the first experiments will begin in 2015.

The „family reunion,” which was attended by ITER Director-General Osamu Motojima, several senior ITER staff and some STAC members present in Saint-Paul-lez-Durance for their biannual meeting, ended with a private tour of the Musée Granet, guided by curator Bruno Ely.

Conversations on tungsten, plasma confinement, magnetic geometry and actively-cooled components gave way to considerations, no less passionate, about art: Cézanne’s early works (eight of which are on loan to the museum), 15th century French painting exemplified by a wonderful Virgin in Glory by the Master of Flémalle, and what Ely considers to be the jewel of his museum—a small, dark Rembrandt: Self-Portrait with Béret.

In Korea, a week of meetings for key ITER components

An important week of meetings took place recently in Korea for the ITER vacuum vessel and thermal shield—for both of these key components industrial suppliers have been selected and manufacturing, pre-manufacturing or kick-off works have begun.

The 52nd ITER Vacuum Vessel Integrated Product Team (IPT) meeting and Domestic Agency collaboration meeting held on 8-10 April brought together over 30 experts from the ITER Organization, the European, Indian, Korean and Russian Domestic Agencies, and Korean industry (Hyundai Heavy Industry & AMW). During meetings hosted at the National Fusion Research Institute (NFRI) and at Hyundai Heavy Industry, participants shared the technology and experience of fabrication of the ITER vacuum vessel, ports and in-wall shielding, and discussed the development pathway for fabrication issues. A visit was organized to the KSTAR Tokamak at NFRI.

During a bilateral collaboration meeting held on 11 April, participants from the Korean and European Domestic Agencies—plus industrial suppliers Hyundai Heavy Industry and AMW—focused more particularly on the new technologies for fabrication of ITER vacuum vessel sectors, especially welding, nondestructive examination (NDE) and optical dimensional measurement. All parties agreed that such valuable collaboration would be continued in the future.

On Friday 12 April, the kick-off meeting for the ITER thermal shield was held—this key component will be installed between the magnets and the vacuum vessel/cryostat in order to shield the magnets from radiation. The contract for the design and fabrication of the thermal shield was awarded by the Korean Domestic Agency in February to SFA Engineering Corp, which is also the supplier selected by Korea for ITER’s assembly tooling. SFA presented the implementation plan for the procurement of the thermal shield during the meeting.

More than 20 responsible persons from the Korean Domestic Agency, SFA and the ITER Organization were present including Domestic Agency head Kijung Jung, SFA Chief Operating Officer Myung Jae Lee, and head of the ITER Vacuum Vessel Division Carlo Sborchia. Prior to the kick-off meeting, representatives from ITER and the Korean Domestic Agency agreed to collaborate closely to solve urgent design change requests related to assembly and interface issues.

„The thermal shield is one of the most critical procurement items in the ITER project. We will do our best in collaboration with the ITER Organization for its successful procurement,” stressed Kijung Jung.

Royalties for intellectual property: a big first for ITER!

The technological demonstration of nuclear fusion as a power source may be a couple of decades away but we don’t have to wait till then to start reaping the benefits of research at ITER. Like all journeys of discovery we will meet unexpected obstacles and discover wondrous new sights, but sometimes it is the obstacles that provide the greatest reward when, by overcoming them, new techniques are born and intellectual property is generated.

For the first time, the ITER Organization has licensed intellectual property to a third party against royalties, in compliance with the ITER Agreement and its Annex on Information and Intellectual Property. ITER’s Legal Affairs contributed to the drafting of the agreement.

With support from AMEC, a UK-based company, the ITER Organization has developed software that allows a web-based program to display data on radiation calculations throughout the ITER facilities. Due to the potential applications of this software for technological areas outside of ITER and/or fusion research and development, a private company from one of the ITER Members has requested a license in order to commercially exploit this software.

Based on the principles of the ITER Agreement and its Annex on Information and Intellectual Property, the company was granted a non-exclusive, non-transferable, worldwide license to access, use and sub-license the software, software package and source code or any substantial part of it. For their part, the Domestic Agencies will be entitled to a licence by the ITER Organization, as is foreseen in the Annex on Information and Intellectual Property of the ITER Agreement.

Nuclear fusion produces radiation in the form of neutrons and gamma rays. The fusion machine is therefore designed to withstand this radiation and the buildings to shield the workers and the public. For the engineers designing the disparate components that make up the ITER machine, it is necessary to know the radiation levels that their particular system is likely to encounter.

This calculation is done by running massive computer simulations of how radiation travels through the complex geometry of pipes, walls, floors, doors and staircases of the ITER complex. Radiation maps result—something like electronic atlases showing what the radiation levels will be in every room for different operating states of ITER and during cask transfer.

How do you create an atlas accessible to anyone who needs it, easy enough to interpret, and containing all the information they need?

For this, you need a database capable of holding millions of 3D maps, a way to display them, and access through the intranet. This might sound easy enough but this was one of those occasions where unforeseen problems were encountered. The ITER Organization successfully developed a specially designed computer application to link the various tools and provide a communication protocol between them.

Korea awards contract for ITER thermal shields

The Korean Domestic Agency signed a contract with SFA Engineering Corp. for ITER thermal shields on 28 February. The contract covers the detailed design of manifolds/instrumentation, the manufacturing design and the fabrication of the thermal shield system. „For us, this is a big step forward for the Korean contribution to ITER,” said Myeun Kwon, president of the National Fusion Research Institute, after the signing.

SFA is a leading company in industrial automation with much experience in the procurement of advanced equipment related to fusion, accelerator, and space technology. SFA was deeply involved in the manufacturing and assembly of the Korean tokamak KSTAR.

The ITER thermal shield will be installed between the magnets and the vacuum vessel/cryostat in order to shield the magnets from radiation. The thermal shield consists of stainless steel panels with a low emissivity surface (<0.05) that are actively cooled by helium gas, which flows inside the cooling tube welded on the panel surface. The temperature of helium gas is between 80 K and 100 K during plasma operation. The total surface area of the thermal shield is approximately 4000 m2 and its assembled body (25 m tall) weighs about 900 tons.

The key challenges for thermal shield manufacturing are tight tolerances, precision welding, and the silver coating of the large structure. The thermal shield also has many interfaces with other tokamak components. „The Korean Domestic Agency is satisfied with this contract because the thermal shield is one of the most critical procurement items in the ITER project. We will do our best in collaboration with the ITER Organization to successfully procure the ITER thermal shield,” said Hyeon Gon Lee, DDG of the Korean Domestic Agency, on the occasion of the contract signature.

Fusion, with a touch of science fiction

An imposing object stands at the heart of the Tom Hunt Energy Hall in the recently opened Perot Museum of Nature and Science in Dallas, Texas.

The four-metre-high structure is a mock-up of the ITER Tokamak—or, rather, a designer’s „interpretation” of the science of fusion and of the flagship device of fusion research.

Those familiar with the arrangement of components that make up an actual tokamak—central solenoid, vacuum vessel, toroidal and poloidal field coils, divertor, piping and feeders—will be a bit lost when gazing upon the towering mockup.

This is intentional. „Our goal was to create a sense of wonder in our visitors that might inspire them to learn more about the subject,” explains Paul Bernhard, whose team designed and installed the 700-square-metre Tom Hunt Energy Hall. „We see our tokamak as based in science, but coloured by a future vision influenced by science fiction—a somewhat cinematic element that you might imagine seeing in a new Star Trek film…”

The result is indeed spectacular. Although Bernhard’s tokamak looks a bit like a thermonuclear mushroom cloud—a „purely coincidental” similarity due to the geometry of the large rounded shape containing the brightly glowing "plasma" suspended over the narrower central core—it is a truly astonishing work of science art.

The moment of awe passed, visitors can experiment with a neon/argon plasma, manipulating it with a magnet; have a hands-on experience with actual toroidal field coil and central solenoid conductor sections provided by the US Domestic Agency; or watch video clips.

Impressed by the „amazing potential of fusion energy,” Bernhard and his team sought to „pass along [their] sense of inspiration.” In stimulating curiosity and enthusiasm for the sciences, a bit of artistic license can’t do any harm.

Looking for "a model of engagement"

Fusion research is deeply indebted to Australia: it was the Australian Mark Oliphant who, under the guidance of Ernest Rutherford, realized the first fusion reaction at Cambridge’s Clarendon Laboratory in 1933, and it was in Australia where the only tokamaks outside the Soviet Union operated between 1964 and 1969.

Over the past half-century, the country’s small but active fusion community has developed a strong reputation, carrying out seminal theoretical work in plasma physics, developing significant plasma diagnostic innovations and making important contributions to fusion materials research.

Many Australian fusion physicists are closely associated to the ITER project. While Australia is not an official Member, these physicists are eager to see their country engage with it. As yet, no formal institutional collaboration has been established.

On his visit to ITER, last September, Australian National University physicist Matthew Hole, who chairs the Australian ITER Forum, shared his hopes for Australia to become more involved.  "ITER," he said, "will define the fusion research program for at least the next generation. We’re keen to be part of that enterprise …"

How could Australia be more closely associated to ITER? The question was at the centre of the „very useful conversations” that Adi Paterson, the Chief Executive Officer of the Australian Nuclear Science and Technology Organisation (ANSTO), had with the ITER management when he visited here on 20 February.

„A project the size and scope of ITER cannot be limited to only seven Members,” explains Paterson. „ITER has to think of countries like Australia that can connect to the project in a very effective manner outside of a full membership arrangement and potentially form a new model of engagement.”

In this context, ANSTO has an important role to play. „My job is to help define and implement a coherent strategy and assist in strengthening the fusion community at home” adds Paterson. „We need to initiate exchanges, develop knowledge on the real questions of diagnostics, 3D fields, energetic particles, collision cross-sections, materials, neutronics…”

The „model of engagement” doesn’t exist yet, but both sides are eager to create one. Seeing the reality of the project’s progress comforted Paterson in his determination. Along with the obvious progress of construction and of components manufacturing, what makes ITER real in the eye of ANSTO’s CEO is „the milestone that was accomplished last November. When the nuclear safety regulator says 'you can carry on’, this is a huge accolade, and one that brought confidence to the whole fusion community worldwide.”

Fields Medal Villani sees where equations lead

There’s poetry in mathematics and this may be the reason why Cedric Villani, one of the most brilliant mathematicians of his generation, dresses as a 19th century romantic poet—long, dark riding coat; large, loose cravat that the French call a lavallière and, of course, shoulder-length hair. (Oftentimes, a large brooch in the form of a spider is also pinned to his lapel.)

A professor at the École normale supérieure and the director of the Institut Henri Poincaré, Villani, 39, was awarded the Fields Medal two years ago. The Fields—equivalent in prestige to a Nobel Prize (not awarded for mathematics)—is the highest prize a mathematician can receive.

Although not directly connected to fusion research, Villani’s work stands „at the extreme theoretical end of ITER,” exploring the properties of some of the equations that describe the behaviour of particles in a plasma, or the movement of stars in a galaxy.

In the summer of 2010, he taught a course at Marseille’s international centre for mathematics meetings (Centre International de Rencontres Mathématiques) as part of a program on mathematical plasma physics related to ITER. Last Thursday 20 December, before giving a seminar on non-linear Landau damping at the CEA Cadarache-based Institute for Magnetic Fusion Research (IRFM), he paid a visit to the ITER site with a party of IRFM physicists.

In a previous Newsline interview the Fields Medal laureate had stressed the importance, when one deals with abstractions, of remaining solidly „anchored in reality.” The mathematical equations he explores, after all, are the true foundations of the ITER project.

"Low-voltage" review opens way to contracts

Coil instrumentation in ITER consists of some 3,000 sensors whose function is to monitor the essential parameters of magnets during ITER operation.

A EUR 25 million package, coil instrumentation forms one the few direct purchases of the ITER Organization and the only fund procurement of the Magnet Division. The components will be delivered by the ITER Organization to the Domestic Agencies involved in coil procurement.

Cryogenic and mechanical instrumentation components („low-voltage” components) account for about one-third of the package’s value. Measuring temperature, displacement, strain, and deformation, the low-voltage sensors are critical. The Head of the Magnet Division, Neil Mitchell, explains: „These components cannot be maintained once they are installed. If one fails, it is lost. Of course there are redundancies, but we have to do our best to guarantee they will operate for 30 years in the harsh cryostat environment.”

On 13-14 December, all of the low-voltage components were reviewed by a panel that included members of the different ITER departments and directorates, specialists from the Domestic Agencies, and also internationally reputed external experts.

This was the third Manufacturing Readiness Review organized by the ITER Magnets Division over the last two months. The first one was conducted on the safety class quench detection system on 23 October; the second on 29-30 November for investment protection quench detection and related high voltage components.

Last week’s low-voltage review panel was chaired by Michel Huguet, a major figure in the history of the ITER project who joined fusion research in 1969 at CEA, spent 19 years at JET, and eventually headed the ITER Joint Work Site at Naka (Japan).

„The panel members were quite satisfied—I could even say impressed—by the quality of the work accomplished. Processes and strategies appear to be heading in the right direction.”

Now that the results of the qualification tests have been reviewed (ITER uses laboratories located at CERN) the next step is to release the contracts for low-voltage components, which should be accomplished in the first half of 2013.

The expo that makes fusion accessible

After Bratislava, Vienna and Liège, the Fusion Expo has moved into the centre of Aix-en-Provence, France, receiving hundreds of curious visitors during its first week.

With accessible explanations on fusion science, ITER, and the next category of fusion device—the fusion power plant—the Fusion Expo is designed for the general public. The Expo is staffed by members of the ITER Organization, the Cadarache-based Institute for Magnetic Fusion Research (IRFM), and Agence Iter France.

„With the ITER project under construction only 40 kilometres away, there has been great interest in the Fusion Expo,” observed Michel Claessens, head of ITER Communication. „It has been a terrific opportunity to reach out to the local public and to communicate the importance of the world-scale energy project that is happening in their backyard.”

Four roundtable discussions have been programmed to address specific aspects of the project. At last Saturday’s session on „The Energy Challenge and Fusion,” Michel Chatelier, former head of fusion research at CEA; Jean-Marc Ané, a CEA physicist at Tore Supra; and Richard Pitts, senior scientific officer in the ITER Plasma Wall Interactions Section, spoke to a full house, presenting their vision of the future and how they saw fusion fitting into it.

Combined with the exhibition, such roundtables provide the public with an opportunity to voice their questions and concerns directly to the actors involved. In this respect, Saturday’s discussion was a great success.

The Fusion Expo is a travelling European exhibition funded by EFDA and the European Commission that has been operating since 2008 under the responsibility of the Slovenian Fusion Association.

You can visit the Fusion Expo through 28 November at the Office de Tourisme in Aix-en-Provence. Roundtable discussions (in French) are programmed on Tuesday 21 November, 4:00 p.m. („Provence, A Magnet for Scientific Excellence”) and Saturday 24 November, 4:00 p.m. („Fusion and ITER: Scientific and Technological Stakes”).

See also "The power of the Director-General" on the EFDA website.

Team-building initiative between Japan and Korea

A workshop on fusion technology beyond ITER was successfully held between the Japanese and the Korean Domestic Agencies on 8-9 November at the National Fusion Research Institute in Daejeon, Korea. A first event of this kind, the workshop aimed at sharing the technology and experience of ITER procurement and also at discussing the development pathway for fusion engineering and technology beyond ITER in Japan and Korea.

More than 40 experts in fusion attended from both countries, including the head of the Korean Domestic Agency, Dr. Kijung Jung, and the head of the Japanese Domestic Agency, Dr. Eisuke Tada.

As both Domestic Agencies have entered into the full-fledged process of procurement for ITER, it was beneficial to share technical know-how, and to exchange ideas in regards to meeting the procurement schedule as well as securing core technology without any loss of productivity.

In addition, the workshop contributed to building close collaboration between the Japanese and the Korean Domestic Agencies, precisely in the spirit of the Unique ITER team for the successful implementation of all commitments for the ITER project.

DEMO: time for real proposals

ITER represents a huge step towards the realization of fusion energy.  But even once ITER has achieved the expected plasma performance, a lot remains to be done before we have electricity on our grid generated by fusion.

Fusion researchers around the world are starting to seriously consider the next major step after ITER, known as DEMO, which should be a DEMOnstration power plant, producing electrical power and paving the way for the commercially viable fusion power stations that will follow.

Many conceptual ideas for DEMO designs have been produced over the years, but now that ITER construction is well under way, real proposals for DEMO are being planned.

Unlike ITER, most work on DEMO has been done without much international collaboration although Europe and Japan are cooperating on DEMO design work as part of the „Broader Approach”.  But to promote more international sharing of work on the path towards DEMO, the International Atomic Energy Agency (IAEA) arranged a DEMO Programme Workshop that was held at the University of California, Los Angeles, on 15 — 19 October. Over 60 attendees came from fusion research institutes worldwide, including all the countries that are members of ITER.

The workshop was organized around technical topics which are seen as major issues that must be addressed before DEMO can be realized:  power extraction, tritium breeding, plasma exhaust, and magnetic configurations.  There were also general talks presenting the status of programmes towards DEMO in some of the countries represented.

There are striking differences between the ideas for the plant in the views from different countries.  Concepts include tokamaks of various sizes and with varying degrees of advancement from the technology and physics of ITER.

But DEMO could also be a stellarator, or even a „hybrid” that combines fusion and fission in a single device. Some believe that an intermediate step, sometimes called a "Fusion Nuclear Science Facility" or "Component Test Facility", is needed between ITER and DEMO. Such installations would be used to develop and test systems such as breeding blankets, to supplement the work to be done using Test Blanket Systems in ITER.  Others prefer to aim for a „near-term” DEMO that would begin by testing its own components.

In all cases, significant materials development is needed, as DEMO will certainly need more advanced structural materials than those being used in ITER. According to some opinions, the planned IFMIF facility will only partly provided the materials tests needed.

With so many diverse ideas, it is not surprising that international collaboration has been scarce.  However the workshop did show that there are plenty of common areas in the R&D that needs to be performed, and IAEA will encourage collaboration over these.