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A component fallen from an alien star ship wouldn't look stranger than a cassette body for the °ÄÃÅÁùºÏ²Ê¸ßÊÖ divertor. Depending on the angle of view, the heavy steel structure is vaguely evocative of a sled (the alien captain's seat?) or a drakkar bow. It's got ridges, dips, protrusions, curves and angles... but nothing that allows us to give it a name from our repertory of known objects. Unless of course we know about tokamaks.   Many things about a tokamak are extreme (vacuum, heat, cold, electromagnetic loads ...). But there is a place at the bottom of the vacuum vessel where conditions are more extreme than elsewhere ─ a place where it feels like standing at the surface of the Sun.   This explains why a cassette body for the °ÄÃÅÁùºÏ²Ê¸ßÊÖ divertor does not resemble anything familiar—not only is it designed to withstand at close range the monstrous heat and radiation of a star, it must also resist the monstrous mechanical forces occasionally generated by electromagnetic loads.(1)   Arranged in a circle at the bottom of the vacuum vessel, 54 cassettes bodies—each protected by actively-cooled tungsten components—form the divertor, an essential system of the °ÄÃÅÁùºÏ²Ê¸ßÊÖ machine that will extract the heat and the helium "ash" from the burning plasma and protect the surrounding structures from thermal and neutronic loads.   Three companies, the Italian Walter Tosto, the Finn Hollming Ltd and a French-Italian consortium formed by CNIM and Simic were each awarded a contract to manufacture a divertor cassette body prototype.   In the 18 months since fabrication began, twenty-five tonnes of high-grade steel have been patiently transformed into a lean, four-tonne °ÄÃÅÁùºÏ²Ê¸ßÊÖ component. Once the prototypes are finalized, the European Domestic Agency (responsible for the procurement of the divertor cassettes) will choose the company or consortium for the fabrication of all or part of 58 cassette bodies—54 to be installed in the machine plus 4 to 6 spares.   In the Mediterranean harbour of La Seyne-sur-Mer, France, an hour and a half drive from the °ÄÃÅÁùºÏ²Ê¸ßÊÖ site, the CNIM-Simic prototype is in the last stages of completion.   The fabrication of the component was led by CNIM and shared between the two companies: the "primary segments" were machined and electron beam welded at CNIM in La Seyne, sent to Simic in Camerana, Italy, for additional tungsten inert gas welding and non-destructive controls, and eventually brought back to CNIM for final machining, verifications and functional tests.   Resting on sturdy steel supports in an enclosure inside CNIM's 3,000 m² hall, the prototype is now in the last stages of the 18-month process that progressively transformed twenty-five tonnes of high-grade steel into a lean four-tonne °ÄÃÅÁùºÏ²Ê¸ßÊÖ component.   "We are finalizing the rough machining phase," explains Eric Mercier one of CNIM's methods engineers. "Three more millimetres to remove and we're done." Tolerances are especially tight and, despite its name, the operation is so precise and delicate that it will take three weeks to remove the remaining three millimetres ...   Following finishing works, a series of operations will be performed—dimensional inspection, a hydraulic test, a hot helium leak test, and eventually functional tests that will check the mechanism for the insertion of the component into the rail running at the bottom of the vacuum vessel.   Amidst shiny metal shavings and splashes of cutting fluid the massive and elegant metal component is acquiring its final form—an alien shape to be duplicated some 60 times before being exposed to the fire and forces of the °ÄÃÅÁùºÏ²Ê¸ßÊÖ sun.   (1) The cassette bodies are designed to resist transient electromagnetic induced forces as high as 100 tonnes, which are expected to develop during a few tens of milliseconds during the most severe disruptions.

Building a Sun on Earth requires not only extensive heating systems but also large cooling systems for the removal of plasma heat from the tokamak. Fabrication of tokamak cooling water system piping is now underway at Schulz Xtruded Products in Robinsville and Hernando, Mississippi (US), with management oversight by the US Domestic Agency and the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Organization. The Schulz Group of Companies began manufacturing of the first supply order of nuclear grade stainless steel piping for the tokamak cooling water system in November 2016. This initial batch, which represents only a small amount of the total 36 km of piping, serves to confirm that manufacturing procedures and processes are in place for compliance with the French Orders on nuclear pressure equipment (Équipements Sous Pression Nucléaires, ESPN, and Équipements Sous Pression/European Pressure Equipment Directive, ESP/PED).   The Schulz Group of Companies, headquartered in Krefeld, Germany, has decades of experience in nuclear, oil, gas, and chemical plant industries, including providing industrial components for French nuclear facilities. Approximately 240 workers are based at the Mississippi plants, which were established in 2011.   "US °ÄÃÅÁùºÏ²Ê¸ßÊÖ has already successfully managed the design and manufacture of nuclear-class components for °ÄÃÅÁùºÏ²Ê¸ßÊÖ; we even passed a day-long assessment by representatives of the French nuclear authority for safety of pressure components," says Jan Berry, the lead for the US °ÄÃÅÁùºÏ²Ê¸ßÊÖ tokamak cooling water system team. "We are confident that we can continue to meet the rigorous French nuclear regulations."   "At the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Organization, we have established an effective division dedicated to completing the piping procurement and the final design of the tokamak cooling water system," said Moustafa Moteleb, who heads the Tokamak Cooling Water System Division at °ÄÃÅÁùºÏ²Ê¸ßÊÖ.   The tokamak cooling water system will manage the heat generated during operation of the Tokamak. The system includes 36 km of piping. Illustration: US °ÄÃÅÁùºÏ²Ê¸ßÊÖ US °ÄÃÅÁùºÏ²Ê¸ßÊÖ, managed by Oak Ridge National Laboratory, is responsible for the design and fabrication of the tokamak cooling water system, while the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Organization is under contract to US °ÄÃÅÁùºÏ²Ê¸ßÊÖ for the completion of the final system design and piping procurement.   "This approach ensures coordination during the design and delivery of components for the complex, one-of-a-kind, tokamak cooling water system, while assuring that the °ÄÃÅÁùºÏ²Ê¸ßÊÖ nuclear operator fulfils its role of surveillance as required under French law," said Moteleb.   To support construction sequencing, US °ÄÃÅÁùºÏ²Ê¸ßÊÖ delivered five nuclear-grade drain tanks for the tokamak cooling water system to the °ÄÃÅÁùºÏ²Ê¸ßÊÖ site in 2015. Fabrication of nuclear-grade piping builds on this experience.    The tokamak cooling water system is a one-of-a-kind nuclear system that is similar in complexity and scope to the cooling systems in a commercial nuclear power plant. The cooling system will have the capacity to remove up to a gigawatt of heat from °ÄÃÅÁùºÏ²Ê¸ßÊÖ systems. For perspective, a gigawatt—one billion watts—provides enough power for the needs of a small city. The cooling system also provides capabilities that are not used in power plants, such as baking and drying in-vessel components, leak detection, and tokamak maintenance. The system will interface with the secondary cooling system, provided by India, as well as with other °ÄÃÅÁùºÏ²Ê¸ßÊÖ plant systems.

For almost a week, the lobby of the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Headquarters building was occupied by two special guests. Surrounded by mountains of boxes and thousands of brightly coloured bricks, Taishi Sugiyama and Kaishi Sakane from Kyoto University had four days to build an °ÄÃÅÁùºÏ²Ê¸ßÊÖ Tokamak ... from 40,000 Lego bricks! On the fourth day, on time and on budget, the young Japanese students from Kyoto University presented their work to °ÄÃÅÁùºÏ²Ê¸ßÊÖ Director-General Bernard Bigot (right) and Director of Communication Laban Coblentz. Passionate about nuclear fusion, Taishi, 24, and Kaishi 25, are also big Lego fans. They are active members of Kyoto University's Lego club and have experience building smaller Lego models of the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Tokamak. Their previous realization, displayed at the °ÄÃÅÁùºÏ²Ê¸ßÊÖ stand at last year's Fusion Energy Conference in Kyoto, was one of the principal points of interest.   The experience gave wings to the Japanese students' ambition. Why not come to France to build a Lego model of the Tokamak,in the very place where the machine will actually be built?   In order to finance their project, they participated in the Kyoto University students challenge contest SPEC (Student Projects for Enhancing Creativity)—an event aimed at enhancing student creativity and encouraging contact between industrial companies and the university. Student teams present projects to the jury, and the winners walk away with the funds to realize them.   Taishi and Kaishi's proposal was among the 6 (out of 13) winning projects. Their travel expenses and hotel accommodation fees were funded by the University and the way was open for the two students to live a unique experience.   After four intensive days, the Japanese duo succeeded in building a 1/40th scale Tokamak mockup. "We believe in nuclear fusion," says Kaishi Sakane. "As everybody knows the creative potential of Lego bricks, we thought: why not use them in a way that promotes °ÄÃÅÁùºÏ²Ê¸ßÊÖ and nuclear fusion?"   When asked about their overall feelings after this challenging and unique week at °ÄÃÅÁùºÏ²Ê¸ßÊÖ, the students confessed that they still didn't realize it was over. "We were not certain that we could deliver on time," the students admitted. "Many staff members dropped by to say hello and take pictures. On the last day, some parts of the mockup fell down during our lunch break ... giving us some extra stress. But we succeeded and we are very proud of our achievement!"   "It is now our turn to wish good luck to the °ÄÃÅÁùºÏ²Ê¸ßÊÖ team in building the real Tokamak," smiles Taishi. "If we can do it with Lego bricks, you can do it for real!"   Taishi Sugiyama and Kaishi Sakane, from Kyoto University (Konishi Laboratory, Institute of Advanced Energy), are both studying neutronics at the Master's level.

A group of 18 superconducting correction coils will be distributed around the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Tokamak at three levels. Much thinner and lighter than °ÄÃÅÁùºÏ²Ê¸ßÊÖ's massive toroidal field and poloidal field magnets, their role is to reduce magnetic error fields caused by imperfections in the position and geometry of the main coils. Series production started last year at an ASIPP laboratory in Hefei, China, where a multiyear qualification program has been carried out to ensure that the correction coils can be produced to specification despite unusual shapes and very demanding precision requirements. Compared to °ÄÃÅÁùºÏ²Ê¸ßÊÖ's huge toroidal field and poloidal field magnet systems, the correction coils appear nearly pencil-thin in the machine schematics. Weighing a maximum of 4.5 tonnes and measuring up to 8.3 metres, the correction coils are the very smallest of the superconducting magnets.   However the irregular shapes of the coils, as well as limited space for installation, creates a number of manufacturing challenges. A lengthy qualification process has been carried out by Institute of Plasma Physics of the Chinese Academy of Sciences (ASIPP), the Chinese Domestic Agency contractor responsible for the fabrication of all 18 correction coil assemblies.   Correction coils will be inserted between the toroidal field and poloidal field magnet systems in three locations around the machine: six at the top, six at the bottom, and six at mid-plane (side). The identical top and bottom coils (TCC and BCC) are rectangles that bend inward to espouse the torus shape of the vacuum vessel; the six side coils (SCC) are non-planar squares. Similar to the toroidal and poloidal magnet coils, the correction coils will be formed from lengths of superconductor wound into layers called "pancakes," insulated, vacuum pressure impregnated, and inserted inside a stainless steel case.   Work on the qualification of the coil case--the stainless steel outer shell—is progressing well. The raw material for the coil cases has been hot-rolled and extruded in prototype trials and a full-size U-shape section has been assembled, representing the bottom correction coil casing (photo). To prepare for series production, the winding line and tooling at ASIPP was first qualified according to °ÄÃÅÁùºÏ²Ê¸ßÊÖ Organization procedures in 2013. ASIPP technicians then began winding a full-size mockup of the bottom correction coil and completed its impregnation in 2014; since that date they have completed the first production bottom correction coil winding pack (eight layers of niobium-titanium superconductor) and are nearly through the impregnation stage. The seven helium inlets of the winding pack have also passed inspections successfully.   In addition, qualification of the coil case—the stainless steel outer shell that provides the structural element to the assembly—is underway. The raw material for the coil cases has been hot-rolled and extruded in prototype trials and a full-size U-shape section has been assembled, representing the bottom correction coil casing. Last but not least, the qualification of the laser closure welding for the coil case will be the final challenge to complete, ending the component qualification phase at ASIPP. To overcome this final hurdle, ASIPP has been developing a high-power laser welding machine to achieve the rigorous quality specifications in the welding of the correction coil.   The qualification activities that are progressing for the bottom correction coils will also serve to qualify the manufacturing procedures for the top coils, which are identical. For the side correction coils, similar prototyping activities are underway, including the realization and impregnation of a half-winding and the start of work on a full-scale winding. Work has also begun to qualify the side correction coil casing.   The correction coils will be arranged in groups of six around the toroidal circumference above, at and below the mid-plane of the vacuum vessel. "ASIPP has achieved remarkable progress in manufacturing and examination for the most of critical components of the correction coils in just three years," says Fabrice Simon, of °ÄÃÅÁùºÏ²Ê¸ßÊÖ's Magnet Division. "This includes the development of the helium inlet welding process and 100 percent volumetric examination, as well as the development of extruded parts of high quality stainless steel for the coil casing. The successful achievement of the qualification phases has provided a solid base for the kickoff of series production. Now, the second bottom correction coil winding is underway without any sign of schedule delay."    Throughout the lengthy qualification activities, regular reviews have permitted all actors—manufacturer ASIPP as well as magnet specialists from the Chinese Domestic Agency and the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Organization—to validate quality and manufacturability. After two manufacturing readiness reviews held in 2013 and 2016 related to the coil winding, a third review planned in March 2017 will trigger the industrial production of the coil cases. A fourth and final review is planned at the end of 2017 for the very last stages of manufacturing, from the closure weld of the casing to the terminal service box.   The two last reviews will open the way for the full speed production of all 18 correction coils.

Read the full story on the European Domestic Agency website. The European Domestic Agency is working with industry to develop the final design of the European gyrotron—an energy-generating device that will contribute to heating the °ÄÃÅÁùºÏ²Ê¸ßÊÖ plasma. Two industrial prototypes are in the works: a short-pulse gyrotron, capable of producing radio frequency of 1 MW for a few milliseconds; and a longer-pulse continuous-wave prototype, capable of producing a radiofrequency wave for several minutes.   Excellent results have been obtained for the high-power 1 MW gyrotron prototype manufactured by the French company Thales Electron Devices (TED). During testing, the gyrotron repeatedly produced up to 0.8 MW of output power during periods of 180 seconds—the maximum time possible at the test facility at Karlsruhe Institute of Technology (KIT). Assessed by an independent expert panel, the prototype's performance was compared to °ÄÃÅÁùºÏ²Ê¸ßÊÖ technical requirements in terms of power and the quality and stability of the electromagnetic waves.  In addition to the gyrotron, testing was carried out on the superconducting magnet necessary for the gyrotron to work. The next steps will now involve joining the gyrotron and magnet together and carrying out testing at the Swiss Plasma Center. Each test session will last for one hour and thus simulate the time needed for these components to work in °ÄÃÅÁùºÏ²Ê¸ßÊÖ.   In gyrotron development work, the European Domestic Agency is collaborating with the European Gyrotron Consortium—made up of the European fusion laboratories KIT (Germany), CRPP (Switzerland), HELLAS (Greece), and CNR (Italy), as well as the German USTUTT and Latvian ISSP as third parties—and Thales Electron Devices (France).  

Late January, six large steel elements of the °ÄÃÅÁùºÏ²Ê¸ßÊÖ cryostat left the port of Hazira, India for their voyage to °ÄÃÅÁùºÏ²Ê¸ßÊÖ. They represent the first tier of the cryostat lower cylinder.   The first segment was delivered on 28 February to the °ÄÃÅÁùºÏ²Ê¸ßÊÖ site;  the remaining five will follow the same route in the days and weeks to come.   Once inspected, they will be installed on the lower cylinder fabrication frame, assembled, and welded.

The Chinese Domestic Agency reports the successful arrival in France of two batches of components for the pulsed power electrical network (PPEN). In addition to the steady state electrical network (SSEN) that will supply the electricity needed to operate the plant and office buildings, °ÄÃÅÁùºÏ²Ê¸ßÊÖ will operate a pulsed power system (PPEN) to provide large amounts of power to the superconducting magnet coils and the heating and current drive systems during plasma pulses. China is supplying 100 percent of the pulsed power electrical network.    The Chinese contractor Baoding Tianwei Baobian Electric Co Ltd has manufactured three massive transformers (15 metres tall, 460 tonnes when completely fitted out). The first arrived at °ÄÃÅÁùºÏ²Ê¸ßÊÖ in June 2016 and was transferred to its permanent location on the construction platform; two others were shipped in January.   The transformers travelled with two E-houses (manufactured by CSG Smart Science & Technology Co Ltd) and 106 packages containing accessories.   The components were discharged in the French port of Fos-sur-Mer on 18 January. The E-houses have been safely delivered to °ÄÃÅÁùºÏ²Ê¸ßÊÖ; as for the large transformers, they are scheduled to arrive along the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Itinerary in March.