At Mitsubishi Heavy Industries' Kobe plant in western Japan, one of the world's largest milling machines is turning out sub-segments for ITER's toroidal field coil cases. These mighty steel components will constitute the main structural element of the magnet system—not only encasing 2,000 tonnes of superconducting toroidal field winding packs, but also anchoring the poloidal field coils, central solenoid and correction coils. Eighteen D-shaped toroidal field coils, spaced uniformly around the torus, will produce the magnetic field that confines the ITER plasma particles.   During ITER operation these coils—each made up of a superconducting winding pack and surrounding stainless steel coil case—will be subjected to tremendous electromagnetic loads, on the order of several hundred meganewtons (or tens of thousands of tonnes of force) per coil.   The massive case superstructure of the toroidal field winding packs is designed to resist these loads. Representing nearly one-third of the total weight of the magnet system, the encasing structures are strongly linked between themselves to support in-plane and out-of-plane forces.   On their inboard sides, closest to the central solenoid tower, the coil cases are bound together by pre-compression rings at top and bottom. On the opposite side, intercoil structures on their outboard surfaces will link them above and below mid-plane. The poloidal field coils, correction coils and the central solenoid are all attached to the toroidal field coil cases through supports that are rigid in the vertical and toroidal directions yet flexible in the radial direction.   The ITER poloidal field coils, central solenoid and correction coils will be anchored against the 3,400-tonne toroidal field coil case superstructure. In the insert, the different elements of the D-shaped toroidal field coil assembly are shown: the inner winding pack (in green), and the inner (BP, AP) and outer (BU, AU) coil case sub-assemblies. This tight integration of the different magnet systems contributes to containing and balancing the strong electromagnetic forces at play in the machine.   "The toroidal field coil structures—among the largest and heaviest components of the magnet system—support the poloidal field coils and the correction coils. Their alignment, in order to ensure the assembly of the torus and minimize magnetic field errors, calls for very tight tolerances and precise machining, both of which present significant challenges," says Arnaud Devred, deputy Magnet Division head. "The ITER Organization and the Japanese Domestic Agency have been working very closely together to optimize manufacturability; this collaboration now includes the European Domestic Agency which is the recipient of half of the toroidal field coil structures produced in Japan. The coil cases are another example where teamwork and close interaction at the working level is required to overcome both technical and schedule issues."    Japan is manufacturing 18 full case assemblies for the ITER toroidal field coils, plus a nineteenth as a spare. Each coil case is assembled from seven sub-segments that are formed into an inboard leg (seen as "AU" in the above image) and an outboard leg ("BU"). There are also inboard ("AP") and outboard ("BP") inner plates that will be installed after the insertion of the winding pack. In all, approximately 190 tonnes of high strength 316LN stainless steel is needed per coil case, bringing the weight of the coil case superstructure to 3,400 tonnes.   Following extensive manufacturing studies and full-scale trial fabrication, the manufacturing of this key structural element is underway now in Japan.   Inboard sub-segments are now manufactured in series at Mitsubishi Heavy Industries' Kobe plant; three sub-segments form the AU sub-assemblies that can be seen on the shop floor. In 2017 the first completed coil case will be shipped to Italy for the insertion of a European toroidal field winding pack. The most critical technical issue during manufacturing is the tightness of tolerances—just a few millimetres for components that, once assembled, measure 16 metres in height and 9 metres in width. Specialized welding techniques have been optimized to control distortion during the welding of steel plates that range from 6 to 40 cm in thickness.   The closure welding process—which will intervene after the winding packs have been inserted—is in the planning stages, with a mockup test and computer simulation underway to estimate and correct welding deformation. Tolerances of a few millimetres are required on the coil cases for proper assembly in the tokamak.   At Mitsubishi Heavy Industries in Kobe, coil case segments are now produced in series and the first inboard (AU) sub-assemblies have been assembled and welded.   Manufacturing is on schedule for the shipment in 2017 of the first completed case to Europe, where contractors will carry out the insertion of the first European winding pack and closure welding. Of 19 coil cases produced by Japanese contractors in the coming years, 10 will be shipped to Europe (the nine others will accommodate toroidal field winding packs produced in Japan).   The first completed toroidal field coil will reach the ITER site in 2018, shipped by the Japanese Domestic Agency. Japan is manufacturing 18 full case assemblies for the ITER toroidal field coils, plus a nineteenth case as a spare. The most critical technical issue during manufacturing is the tightness of tolerances, requiring precise machining and specialized welding techniques.

In the realm of the (plasma) ring one shouldn't be too surprised to find structures closely resembling the door to a hobbit's hole. But in this case, these large circular openings in the bioshield do not lead into the warm, comfortable dwelling of a hairy-footed creature: they are penetrations for the neutral beam injection system that will feed some 30 megawatts of heating power into the plasma.

The 2016 edition of the ITER Photobook has just been released─58 pages that cover progress in construction and manufacturing and some of the highlights in the life of the ITER Organization. Looking at the two previous editions (2014 and 2015) one can measure what has been accomplished over a period of three years ... from a mostly empty Tokamak Pit to a construction now emerging from ground level; from prototypes and mockups to actual machine components; and from the first test convoys to the regular delivery of heavy loads.   All of the ITER Photobooks can be downloaded from the Publication Centre of the ITER website ("Brochures") in pdf format.

The annual end-of-year meeting of the International Tokamak Physics Activity (ITPA) was held at ITER Headquarters from 6 to 8 December. There are dozens of tokamaks operating around the world and many regularly give direct support to ITER design activities and operational planning. The ITPA allows the global coordination of these research laboratories, helping with the exchange of people and ideas, including the clear communication of ITER priorities.   The meeting was attended by program directors, ITER staff, and the leaders of the seven ITPA "topical groups," each of which looks after a specific aspect of tokamak physics and operation. Director-General Bigot opened the meeting with a warm welcome that outlined the staged approach to assembling ITER, progress in construction, the successful completion of 2016 milestones, and general efforts to maximize the efficiency of the organization. The meeting was smooth and productive. Results from the past year were reviewed and the proposed activities for 2017 were discussed.   A highlight from a presentation on the research program in Japan reported that the poloidal field coils for JT60-SA—a Broader Approach* machine under construction that is similar to ITER but about half the size—have been built to accuracies of less than 1 mm, much lower than their design specifications of 5-10 mm ... a clear demonstration that large components can be built to very high standards.   The International Tokamak Physics Activity (ITPA) provides a framework for internationally coordinated fusion research activities. In December 2016, the group's annual end-of-year meeting was held at ITER Headquarters. There was a change of leadership at the end of the three-day session, with ITPA Chairman Abhijit Sen of the Institute for Plasma Research in India completing a successful three-year term. His responsibilities were passed to Sergey Konovalov of the Kurchatov Institute in Russia, who reaffirmed the contributions made by the ITPA and spoke positively about the high level of coordination with ITER.   The last item on the agenda was a tour of the worksite. The participants commented on the dramatic progress achieved in 2016 and the atmosphere of activity generated by the 1,600 people who were working on the platform that morning.   * In parallel to the ITER Agreement, which established the ITER Organization, an agreement for complementary research and development called the Broader Approach was reached between the European Atomic Energy Community (Euratom) and the Japanese government in 2007. More on the Broader Approach here.

Extending out from the openings in the ITER vacuum vessel (or "ports") are components called port stub extensions that will be welded to the vacuum vessel sectors before the assembly of the main vessel in the pit. The first completed port stub extension—for upper port #12—has successfully passed pressure and helium leak tightness tests. The tension was tangible as observers assembled at the test stand saw the pressure gauge reach the 3.78 MPa mark.   Would there be any trace of pressurized water escaping the system? The tolerances on the massive double-wall stainless steel structure were tight, the welding a challenge. After half an hour of mandated holding time, with all eyes on the gauge, there was a collective sigh of relief. The full pressure test of ITER's first completed upper port stub extension (#12) had been completed successfully.   The upper port stub extension is made of single and double-wall sections. Not pictured is the port extension that will be welded to the port stub in the the Tokamak Pit and that will connect to the cryostat through cryostat ducts. The ITER vacuum vessel has 44 openings, or ports, on three levels (lower, equatorial and upper) that are used for equipment installation, utility feedthrough, vacuum pumping, and access into the vessel for maintenance. The upper ports are characterized by a trapezoidal/rectangular cross-section due to a slight upward slant. This has to be taken into account in the design of their port structures, including port stub extensions and port extensions. Each port stub extension includes double-wall and single-wall parts (see diagram).   In respect of French regulations on pressure equipment (ESPN), which apply to the ITER vacuum vessel, a full pressure test followed by a helium leak test to confirm the high vacuum tightness of the component were performed in the presence of an Agreed Notified Body* (ANB) before the final machining of upper port stub extension #12.   The tests were carried out at MAN Diesel and Turbo in Deggendorf, Germany, subcontractor to the Efremov Institute in Russia. Russia is responsible for the supply of 100% of the upper ports. The tests were performed at the end of last year on the premises of the German company MAN Diesel and Turbo in Deggendorf (the main sub-supplier for the port stub extensions) as part of Russia's procurement of the upper ports. The main supplier for this procurement is the Efremov Institute in Saint Petersburg.   The test campaign will be followed by some final machining and the integration of the single wall part before the comprehensive final testing of the complete assembly. When completed, the 20-tonne stub extension will be shipped to Hyundai Heavy Industries in South Korea where it will be mounted on vacuum vessel sector 6. It is expected to arrive by June of this year.  *An Agreed Notified Body (ANB) is a private company authorized by the French Nuclear Regulator ASN to assess the conformity of components in the pressure equipment category (ESPN).

In 2012 the ITER Organization retained the European company DAHER to provide global transport, logistic and insurance services for the transport of components from supplier factories to the ITER site. Since that date, DAHER has worked with all ITER Members on their transport needs, including the transport of exceptionally sized loads. The company manages all ITER logistics operations from a control room established in Marignane, France, close to the international airport that services the Marseille region. In November 2016, the ITER Organization strengthened its ongoing relationship with DAHER with the signature of a new framework contract for the establishment and management of a central distribution centre located at the arrival port for all components shipped by sea (Fos-sur-Mer, France). A warehouse space of 12,000 m2 has been fully refitted for ITER component storage. The central distribution centre will allow DAHER to match the rhythm of component deliveries to ITER's assembly needs. Read the DAHER press release here.

Precise conditions are necessary to achieve fusion reactions inside of a high-temperature plasma. In addition to raising the temperature and the density in the core region of the plasma, which is confined by strong magnetic field, it is also necessary to control the edge region to prevent particles from moving in the direction of the vessel wall.  A precise understanding of this edge region of the plasma—and accurate predictions of its behaviour—is one of the important topics of fusion research around the world. At the National Institute of Fusion Science (NIFS) in Japan, two researchers have succeeded in running a micro-level simulation of a plasma "blob" in the edge region by using their institute's Plasma Simulator supercomputer. By marrying the supercomputer's computational capacity with a newly developed calculation program, they were able to calculate the movement of one billion particles. Their research results advance the understanding of the behaviour of the plasma edge and improve prediction accuracy. See the full article on EurekAlert!/AAAS.