Who’s got the biggest?


At ITER, we don’t brag. But we do like to mention the exceptional dimensions of the machine we are building: the ITER Tokamak will indeed include components that, in their category, are by far the largest in the world.

In talks and presentations to the public it has become routine, for instance, to assert that the ITER cryostat will be the largest high-vacuum chamber ever built.

But recently, a young postdoc attending a presentation on ITER at the Institute of Plasma Physics in Prague took issue with this claim. It’s NASA’s Space Power Facility, the student said, that holds the blue ribbon for the largest high-vacuum chamber.

Located in Sandusky, Ohio (USA), the Space Power Facility was built in 1969 to create an environment comparable to that encountered in deep space, on the Moon or on planet Mars. It comes complete with high-vacuum, extreme cold (down to minus 195°C) and solar radiation simulation.

NASA has been using the facility for more than four decades to expose rocket components, space capsules, landing vehicles and satellite hardware to the harsh conditions of outer space. Its futuristic setting has also inspired movie makers: in 2012 the opening sequences of the blockbuster The Avengers were filmed there.

The cylindrical vacuum chamber is 30 metres in diameter and 37 metres in height—bigger, it’s true, than the 29.4 x 29 metre ITER cryostat. There is however an important difference between the two: while the aluminium Space Power Facility’s test chamber is spectacularly empty (after all, rocket stages have to fit in) the steel ITER cryostat is a very crowded place.

In ITER, because of the volume occupied by components such as magnets, support structures, the thermal shield and the vacuum vessel itself, the pump volume inside the cryostat—that is, the total volume of the chamber minus that of the components—is reduced to 8,500 cubic metres. At the NASA facility, it is almost three times larger (23,500 cubic metres).

In order to achieve high vacuum up to 10-6 Torr, one millionth time more tenuous than the Earth’s atmosphere, both installations use mechanical roughing pumps to go down to ~ 0.1 Torr, and then cryopumps to achieve the required high vacuum. While NASA’s installation can achieve high vacuum in 8 to 12 hours, the ITER cryostat will require about twice this time.

„However, the two systems are quite different," notes Matthias Dremel, an engineer in the ITER Vacuum Section. „The ITER cryostat contains thermal shields cooled to 80 K that act as pumps by condensation of the gases. What’s more, the magnets behind the thermal shield, cooled to ~4K, also act as pumps by condensation.”

Because these components are extremely cold, they significantly contribute to removing the impurities that remain in the chamber. Atoms, molecules and particles are all captured by cold surfaces: the more intense the cold … the more irresistible its holding power.

In the ITER cryostat and in NASA’s Space Power Facility we have two high vacuum chambers of approximately the same size but the latter, however spectacular, is but a big empty aluminium cylinder. The ITER cryostat, on the other hand, is a highly complex structure that must remain absolutely leak-tight despite the thousands of lines and feed-throughs that penetrate it for cryo, water, electricity, sensors, etc.

So it’s a NASA win (but not by much) when it comes to size, but when it comes to complexity—the ITER cryostat remains unchallenged by far.

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."

EAST meets WEST

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

Robert Aymar receives top superconductivity award

Robert Aymar, former director of the ITER project (1993-2003) and director-general of CERN (2004-2008), has been selected to receive the IEEE Max Swerdlow Award for Sustained Service to the Applied Superconductivity Community (2012) for his technical and managerial leadership at CERN and ITER and for the use of superconducting magnet technology in high energy physics and fusion energy projects.

The award will be presented on 15 July 2013 during the opening session of the 23rd International Conference on Magnet Technology (MT-23), which will be held this year in Boston, USA. The award consists of an engraved plaque, an honorarium of USD 5,000 and an inscribed medallion made of niobium—the metal most commonly used in superconductor applications.

The award citation recognizes Aymar for sustained service to the applied superconductivity community that has had a lasting influence on the advancement of the technology and for leadership in the development of many large-scale superconducting magnet systems such as Tore Supra, the Large Hadron Collider (LHC) and ITER. The award also recognizes his role in directing research for the next-generation devices beyond the LHC and ITER, in chairing numerous committees for the promotion of academic research, and in organizing workshops related to applied superconductivity and large-scale superconducting magnets.

Following his studies at the prestigious Ecole Polytechnique in Paris, Aymar joined the French Alternative Energies and Atomic Energy Commission CEA in 1959. Early in his career he focused on fundamental research in plasma physics and applications for controlled thermonuclear fusion.

In 1977, he was appointed director of the Tore Supra project in Cadarache (France) dedicated to research on the magnetic confinement of hot plasmas towards steady-state operation. He oversaw the project from conceptual design, through construction, and up to its operational kick-off in 1988 when he became head of the CEA’s Department of Fusion Research.
In 1990, he was appointed director of the Division of Fundamental Research in Natural Sciences at CEA, running a wide range of basic research programs including astrophysics, particle and nuclear physics, condensed matter and climatology, as well as thermonuclear fusion.

Aymar took charge of the international research program to prepare for ITER construction in 1994. He then spent five years as the Director-General of CERN, from 1994 on, overseeing the construction and launch of the LHC.

Since January 2009, Aymar has served as a Senior Scientific Advisor to the Chairman of the CEA.

The IEEE Max Swerdlow Award for Sustained Service to the Applied Superconductivity Community has been presented to a total of 11 individuals in the past 12 years by the IEEE (Institute of Electrical and Electronics Engineers) Council on Superconductivity. Within the applied superconductivity community worldwide, this award is considered the premier distinction for the recognition of technical service in the field.

Additional information is available at www.ieee.org

China delivers first load to ITER



It’s a long road from the Institute of Plasma Physics (ASIPP) in Hefei, China to the ITER site in southern France: 500 kilometres by route to the port of Shanghai; some 10,000 nautical miles from Shanghai to the port of Marseille-Fos; another hundred kilometres for the last leg of the journey, from Fos to the ITER site.

The distance was covered by trucks and the container ship Lyra in 38 days. Three crates that had been loaded at Hefei on 25 April were delivered to the Poloidal Field Coils Winding Building on Monday 2 June, three days ahead of schedule.

The crates contained the first batch of ITER items delivered by ITER China to the European Domestic Agency Fusion for Energy (F4E): 737 metres of dummy conductor, in three lengths, to be tested in a mockup of poloidal field coil number five (PF5). The 25-ton load was also the first ITER item to enter the large on-site winding facility.

„The conductor will be used to test the whole fabrication process,” explained Neil Mitchell, head of the ITER Magnets Division, as the crates were being unloaded and inspected. „This copper conductor will be wound, tested for tolerance, insulated, impregnated under vacuum and formed into a 'double pancake' in the same way the actual superconducting niobium-titanium conductor will be handled by F4E at a later stage. What matters here are the mechanical properties, which are similar in both the copper dummy and the actual superconductor.”

An ITER load, even when it’s only a dummy component destined for mockup testing, is not an ordinary load. The transport crates were equipped with several monitoring devices to record movement and accelerations throughout the journey; other systems monitored the pressure inside the conductors, which are filled with pressurized inert gas, to confirm that there was no contamination by damp or salt.

Verifying that the crates (and hence the conductors) had not suffered during the 38-day voyage was the first thing that Piergiorgio Aprili, from F4E, and Chen Huan and Sun Yana, representing the Chinese transporter Sinatrans, did upon the delivery of the load. The integrity of the accelerometers was verified—proof that no major shock had occurred—and the crates' „Black Box” was recovered for later analysis.

Compared with the oversized components that will soon be delivered to ITER this week’s 25-ton load appeared quite modest. However, for all those involved—ITER China, Sinatrans, F4E, the ITER Organization and the logistics service provider Daher—this was an important moment. „We have already managed several shipments of small components to and from the ITER Domestic Agencies,” explained Daher’s Laurence Prudhomme who oversaw the unloading operations, „but this is the first real heavy load we’re dealing with.”

Beginning early next year, the loads will change in scale: several hundred tons, by then, will be routine.

View an example of accelerometre data collected during the transportation of TF Coil conductor from Hefei to the Japanese port of Kobe in November 2012.

First hardware afloat from China

On Thursday 25 April, the morning silence at the Institute of Plasma Physics (ASIPP) in Hefei, China, was broken by the noise of a high powered trailer. Inside the superconductor shop of ASIPP, workers were busy preparing to load the 737 metres of dummy conductor for ITER’s Poloidal Field Coil number five (PF5)—this represents the first delivery from China to the ITER construction site in France.
 
According to the Procurement Arrangement signed between the Chinese Domestic Agency and the ITER Organization, China will fabricate 64 conductors for ITER’s poloidal field coils, including four dummy conductors for cabling and coil manufacturing process qualification. ASIPP is responsible for all the poloidal field conductor fabrication in China. The fabrication of the PF5 dummy was completed in by ASIPP in 2011.
 
„This is the very first batch of ITER items to be shipped from China to the ITER site in Cadarache," said Luo Delong, Deputy Director-General of ITER China. Before, conductors for the toroidal field coils had been shipped to Japan and Europe. "This milestone is a further step for the ITER project. According to our schedule, we will now start massive production of conductors this year. Our goal is that all procurement items from China be supplied consistent with the ITER schedule and with ITER quality requirements.”

According to the shipment schedule the PF5 dummy conductors, which left Shanghai on 30 April, will arrive at the ITER site on 5 June.

In dealing with the press, openness is key

On 22 and 23 April, the ITER Organization welcomed 19 science journalists from the European Union’s Science Journalist Association (EUSJA). This was the result of an initiative taken jointly by the Russian journalist Viola Egikova, vice-president of EUSJA, and ITER Communication to present ITER and the project’s underlying fusion science and technology to a group of selected science journalists.

The two-day program included a visit of the worksite and presentations by several ITER scientists and engineers on status of the project, plasma physics, the chemistry of tritium, etc. Interviews were also organized at the requests of the journalists.

As Head of Communications, I believe it is essential to work with the press and to handle their requests as swiftly as possible, as there is still a huge information gap and major communication needs relative to ITER and fusion. In my opinion, the aim is not so much the information that you deliver but the openness and the dialogue that you establish (or make visible) … and  the respect for journalistic work.

„Indeed, I was pleased to see the openness of the ITER Communication team,” said Amanda Verdonck, a free-lance Dutch journalist who participated in the EUSJA visit. „But I was really impressed by the scale of the project and the sophisticated scientific knowledge that has gone into the machine. And I will be further impressed to see all this functioning! Like your videoconference system — quite impressive to me!”

Discussing experiments and aligning priorities

The 10th Integrated Operation Scenarios (IOS) International Tokamak Physics Activity (ITPA) meeting was held in the ITER Council Chamber from 15-18 April 2013. There were 30 external participants from the ITER Members and a number of representatives from the ITER Organization. The external participants include representatives from the main magnetic fusion devices and modellers from the ITER Members.

The purpose of the meeting was to discuss the experiments and modelling being carried out around the world in support of the ITER design and plasma operation as well as to align the priorities for future R&D with the latest ITER priorities. The IOS Topical Group (TG) is one of seven topical groups in the ITPA whose main role is to integrate plasma operation scenarios for burning plasma experiments, particularly for ITER, including inductive, hybrid, and steady-state scenarios. The IOS-TG also recommends physics guidelines and methodologies for the operation and design of burning plasma experiments. The ITPA topical groups all meet every six months in one of the countries of the ITER Members. This was the first time the IOS-TG met at ITER, allowing the members and experts of the IOS-TG to see first-hand the progress in ITER construction. 

Experimental and modelling results were presented from Alcator C-Mod, ASDEX-Upgrade, DIII-D, JET, JT-60U, and KSTAR of ITER-relevant plasma operational scenarios. Experimental results concentrated on inductive and hybrid scenarios; modelling of steady-state scenarios was also presented. Modelling of burning plasma and energetic particle physics were presented as well as plasma rotation in ITER and their impact on operational scenarios. The predicted plasma rotation profiles in hybrid scenarios were strongly peaked with rotation up to nearly 200 km/s, corresponding to about 4 kHz rotation in ITER in the centre. The effects of the Edge Localized Mode (ELM) coil fields on fast ion losses comparing vacuum fields and the plasma response were also shown, indicating that when the plasma response is included, the fast ion losses are acceptable even at high performance with the maximum ELM coil current.

The IOS-TG also concentrates on plasma control including experiments and modelling of profile control as well as development of the preliminary design of the ITER plasma control system (PCS). A review of the PCS conceptual design was presented as well as an action plan for how the experimental and modelling programs within the ITER Members can contribute to developing the PCS preliminary design for First Plasma and early hydrogen and helium plasma operation. Modelling of control of the entry into a burning plasma regime was also presented. A proposal was made to integrate experiments and modelling of plasma control schemes for ITER in existing experiments so that these control schemes can be developed before ITER operation to reduce run time on ITER for control scheme development. A request was made for the ITPA to provide control priorities for the ITER actuators starting with a few phases of plasma operation. 

As part of the ITPA response to the question of starting ITER with an all-tungsten divertor, the IOS-TG discussed the effect of a tungsten divertor on operational scenarios. Reports from DIII-D, ASDEX Upgrade, and C-Mod compared operation with carbon walls and metal walls. Although there were some differences, it was generally believed that ITER would be able to learn how to operate with beryllium walls and an all tungsten divertor.

Modelling of ITER and JET current ramps were also presented indicating the differences between operation with carbon walls and with the ITER-like wall on JET. Since the peak in radiation for tungsten occurs around a temperature of 1 keV, the radiation from tungsten will be peaked near the edge in ITER. There is still a question about whether or not the tungsten transport into the core can be controlled to a sufficiently small value.
Modelling of steady-state fusion plasma scenarios was also presented to understand how the present heating and current drive systems should perform as well as what upgrades might be required to meet the long-pulse goals of the ITER program. The modelling includes simulation of sawtooth control, kinetic integrated modelling, and parameter scaling from existing experiments to ITER steady-state regimes. An update was also given on the latest proposed changes to the steering of the electron cyclotron heating and current drive system that was followed by extensive discussion.

In summary, the meeting provided valuable information on recent experiments and modelling of ITER plasma operation scenarios. Actions for the ITPA members and experts to help define the preliminary design of the ITER plasma control system were agreed upon. Continued experiments and modelling to demonstrate ITER operational scenarios for the inductive, hybrid, and steady-state scenarios were presented. A special report on the impact of an all-tungsten divertor on ITER operational scenarios was also discussed at length. 

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.

F4E appoints Henrik Bindslev as new Director

Henrik Bindslev was appointed last Friday 25 October as the new Director of the European Joint Undertaking for ITER and the Development of Fusion Energy (Fusion for Energy). He is currently the Vice Dean for Research at Aarhus University, Faculty of Science and Technology.

Stuart Ward, Chair of the Fusion for Energy Governing Board, took the opportunity to congratulate Henrik Bindslev on his new position and thanked all members of the Board for their collaboration taking together this important decision.

"I am honoured to have been appointed Director of Fusion for Energy at a time that Europe’s contribution to ITER enters a decisive stage and rapid progress will be made on all fronts. It is the moment to engage actively with Europe’s industry and fusion community to honour our commitment to this prestigious international project" said Bindslev.

Henrik Bindslev has been engaged in energy research for more than 20 years and has considerable experience in research management, both in Denmark and internationally. He is currently Vice Dean for research at Aarhus University, Faculty of Science and Technology and past Chair of the European Energy Research Alliance (EERA). He is a delegate to the European Strategy Forum on Research Infrastructures (ESFRI) and Chairman of ESFRI’s Energy Strategy Working Group.

Previously, he was the Director of Risø DTU, the Danish National Laboratory for Sustainable Energy, managing 700 members of staff.
He was educated at Denmark’s Technical University and completed a DPhil in Plasma Physics at the University of Oxford. He worked as a fusion researcher at different facilities including ten years at the Joint European Torus (JET), Europe’s biggest fusion research device, and has published more than 150 papers.

The Director is appointed by Fusion for Energy’s Governing Board for a period of five years, once renewable up to five years. The appointment is made on the basis of a list of candidates proposed by the European Commission after an open competition, following a publication in the Official Journal of the European Communities.


ASDEX Upgrade breaks record for power exhaust

A world record in heating power, in relation to the size of the device, has been achieved by the ASDEX Upgrade fusion device at Max Planck Institute of Plasma Physics (IPP) in Garching: This was made possible by a sophisticated control system.

For the first time world-wide, a fast feedback control facility ensures, on the one hand, that the millions of degrees hot high-power plasmas needed are produced and, on the other, that the wall of the plasma vessel is not overloaded, this being an important result on the way to a fusion power plant.

[…] The hitherto unattained heating power of 14 megawatts per metre with respect to the radius of the device was achieved without overloading the divertor plates.

Read more here


Pneumatic Shutter for Nuclear Fusion

From 2020 onwards, the ITER fusion reactor will demonstrate how nuclear fusion can be used as an energy source. However, inside the reactor, the plasma at a temperature of 100 million degrees presents scientists with huge challenges. Direct contact would destroy important optical instruments within a short period of time.

At the 27th Symposium on Fusion Technology (SOFT), from 24 to 28 September 2012 in Liège (Belgium), Jülich researchers are showing how the delicate instruments can be protected by means of new shutter and cooling systems. Among other options, they will present a patented shutter controlled by a pneumatic cylinder which was developed specifically for ultra-high vacuum.

For the first time, ITER will generate excess energy of 500 million watts for a duration of about ten minutes in order to provide us with experience for the construction of subsequent fusion power plants. Not only the burn chamber but the entire measuring technology has to be developed from scratch for this fusion experiment, which is being monitored by scientists all over the world.

Optical monitoring methods are indispensable for assessing the plasma properties and composition. However, optical elements in the vicinity of the plasma are exposed to extremely high loads. The plasma, largely composed of hydrogen and helium nuclei, erodes part of the surface material but also deposits contaminants. Thermal energy must be continuously removed in order to keep the temperature constant.

„The greatest technological challenge is to find suitable materials and designs to protect and cool the optical elements that can also be cleaned when they are installed in the machine” explains Dr. Olaf Neubauer from the Jülich Institute of Energy and Climate Research, Plasma Physics (IEK-4). Together with colleagues from Forschungszentrum Jülich and partner institutions, Neubauer organized the SOFT conference with more than 800 participants this year.

All the components in ITER’s burn chamber can essentially only be serviced by remote-controlled tools or robots. At the conference, Jülich plasma researchers are presenting a new fast shutter for a spectrometer that protects the optical instruments when they are not in use for measurements, in particular during ignition when most of the contaminating particles are mobile.

„In designing the structure, the main problem was that the shutter is exposed to even higher loads than the optical instruments themselves. Furthermore, a movement mechanism had to be invented that could cope with the extreme plasma conditions and the ultra-high vacuum," says David Castaño Bardawil. Conventional bearings cannot be used because of their abrasion and the Jülich solution therefore makes use of flexible arms. They are operated by an actuator that was specially developed and patented, into which helium is fed under pressure.

Electric drives cannot be used in the burn chamber due to the strong disturbing magnetic fields.  „The shutter is additionally protected by a molybdenum screen, which reflects the thermal radiation. Together with a sophisticated combination of thermally conducting and insulating materials this maintains an acceptable temperature,” says Castaño Bardawil, an engineer in Neubauer’s working group.

At SOFT 2012, other Jülich scientists are presenting new concepts for uniformly cooling the instrument mirrors under extreme conditions. „Large temperature differences arise on the mirror surface close to the cooling channels. With the aid of simulations, we optimized the cooling channels in order to minimize divergences,” explains Andreas Krimmer, who also works in the field of fusion technology. The temperature-related high pressure of the coolant causes other deformations. At the moment, researchers are testing various elastic materials in order to even out the deformations thus ensuring that in 2020 the fusion plasma can be ignited in Cadarache.
Source: Forschungszentrum Jülich

Click here to read the Press Release.




V-Day "kissing" on the winding line at ASIPP

The winding line for ITER’s correction coils  located at the Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP) in Hefei, China has been busy these days with commissioning tests. Commissioning for this 44-metre-long, 15-metre-wide, 4-metre-high winding line began in July 2012.

Part of the commissioning process includes the winding of two 2×2 turn coils, one bottom-type correction coil and one side-type correction coil. On 23 August, the winding of the 2×2 turn bottom correction coil was completed and the coil was moved to the table for temporary storage.

The winding mould for ITER correction coils, assembled in three parts, was designed by ASIPP supplier JUNENG. The mould is aligned with structural adjustments built into the winding table that were made by ASIPP supplier KEYE Company.  The two side winding mould extensions are not needed to create the BCC coils.

In preparation for the next stage of commissioning—winding the larger side-type correction coil, the winding mould extensions were "kissed" together on 24 August, which is only one day later than the Chinese Valentine’s Day (7 July on the lunar calendar). Over the next few days the mould will be measured and any necessary adjustments made; it will then be ready for the  winding of a 2×2 turn side correction coil.

Both suppliers have been able to successfully coordinate with ASIPP and with one another, delivering quality work as well as expertise  to the winding line.

With the winding of the 2×2 turn bottom correction coil complete, ASIPP has achieved an important commissioning milestone. It hopes to complete the 2×2 turn side correction coil commissioning test in September, thereby laying a solid foundation for the winding qualification.



Plasma fingers point to the taming of the 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."

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