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Open Doors days occur with scientific regularity at ������app (spring and autumn) and yet—due to the rapid evolution of work on site—each event offers something new. Saturday 20 May was no different: the 800 registered visitors were guided in groups of 50 across the Tokamak Building ground-level basemat—something that wouldn't have been possible just a few months ago. Under a perfectly blue Provencal sky, visitors were just a few arms' lengths from the installation arena of the world's most complex scientific instrument and the concrete wall that surrounds it.    A second stop on the tour brought participants to the European coil winding facility. A short climb, and visitors had access to the viewer gallery that runs the length of the 257-metre building, where fabrication activities have begun on one of the four poloidal field magnets that will be manufactured on site.   Specialists were on hand throughout the day at each of the tour stops as well as the Visitors Centre to guide first-time (and repeat) visitors through the complexities of fusion science and engineering, the international collaboration behind the project, and current status. ������app Open Doors days couldn't take place without their participation. In the end, ������app scientists and engineers return home as content as the day's visitors—happy to have shared their corner of the ������app story and, for many, to have experienced how their daily work translates into an awesome steel and concrete reality.

Grandfathers like to tell stories. And Robert Aymar, the "grandfather" of the French fusion community, is no exception. "Being so old," he quipped at last week's celebration of WEST's First Plasma, "I can express myself as a grandfather—not only to congratulate you, but to tell you the story of our family." Forty years ago, aged 41 and already a fusion veteran, Aymar was appointed head of the Tore Supra project, at that time one of the largest tokamaks in the world and the first to implement superconducting magnets.   One of his first decisions was to transfer all the CEA laboratories and personnel involved in fusion research to one place, Cadarache. "Everything that has happened since," he said last week, "springs from this one move."   The small audience he addressed last Thursday in Tore Supra's "home" in CEA had borne witness to much of what had "happened" over four decades—the continued exploration of plasma physics, the genesis of ������app, Tore Supra's record-breaking plasmas, the tokamak's transformation into WEST, the "vision turned  into reality" and, most important perhaps, the "building the human capital" that would one day take fusion into the industrial age.   As he led the design and construction phase of Tore Supra, Aymar recalled that his mind was equally focused on the large international collaboration that was to become ������app. "It is not by accident that ������app is being built only a few hundred metres from Tore Supra. This is what I had anticipated and planned right from the beginning."   The "family" —representatives of CEA's fundamental research department, of WEST and its governing board, and of ������app—of course knew the story. But they were delighted to hear it once again, told by an older and much-respected colleague who more than any other had contributed to writing it.

Like flashlight and smartphones, the ������app magnets—all 10,000 tonnes of them—will run on direct current (DC). And like flashlight and smartphones they will need an "adapter" to convert the alternating current (AC) coming out of the electrical distribution network. The difference, as with most things ������app, is in the size: the outlet is a combination of a four-hectare 400 kV switchyard and a set of three giant transformers; the "adapter" is a set of two 150-metre-long buildings—the twin Magnet Power Conversion Buildings—densely packed with electrical equipment.   The parallel however stops here. There is a system that neither the flashlights nor the smartphones require, yet that is essential for the safeguard of the ������app magnets—the fast discharge units.   The procurement responsibility for the electrical equipment in the buildings is shared by Korea, China and Russia. Pictured here is a converter manufactured in Korea. All and all, the twin buildings will house 32 converter units and some 2.5 kilometres of busbars. "The ������app magnet system can store up to 50 gigajoules (GJ) of energy," explains Ivone Benfatto, head of ������app's Electrical Engineering Division. "This is comparable to the kinetic energy of a superfast train, like Europe's TGVs, launched at 1,500 to 1,700 kilometres per hour ..."   In case of a "quench"—a rare but anticipated event that causes the magnet system to lose superconductivity—this huge amount of stored energy needs to be "liberated" in a matter of seconds.   The fast discharge units have a powerful switching system that opens a new path for this stored energy—a veritable "boulevard" along which this energy is transferred into a set of massive resistors located in a nearby building. There, the energy is dissipated in the form of heat.   The reliability of the fast discharge units is of utmost importance for the safeguard of the magnet system," adds Ivone. "That is why we'll have a backup system in the form of an explosive charge, that instantly 'cuts the circuit' and transfers the stored energy to the discharge resistors."   Preparing for the installation phase: specialists from the ������app, the Korean, Chinese and Russian Domestic Agencies, and the industries involved gathered for a two-day workshop at ������app Headquarters. Like all constructions on the ������app platform (with the exception of the Cryostat Workshop) the Magnet Power Conversion Buildings are part of Europe's contribution to the project.   Procurement responsibility for the equipment in the buildings is shared by Korea (18 converter units and one master control system), China (14 converter units) and Russia (fast discharge units and some 2.5 kilometres of busbars for a total weight of 350 tonnes).   At the end of the year 60 to 100 workers (technicians from the Korean and Chinese Domestic Agencies plus contractors) will begin installing the equipment.   Last week, specialists from the ������app, the procuring Domestic Agencies, and industry met at ������app Headquarters to discuss what Ivone calls "cohabitation during installation works."   "It is important at this stage to sort out respective responsibilities, and discuss installation sequences, onsite installation management, the details of finishing operations, and a host of other practical issues ..."   Just like plugging the adapter into the socket—with a bit of added ������app complexity.

European contractors and invited guests celebrated an important project milestone last week at the European winding facility in La Spezia, Italy. The first 110-tonne winding pack produced in Europe for the toroidal field magnet system is ready to be transferred to contractor SIMIC for the final assembly operations, including insertion into a massive steel case. Each winding pack, or central core, is formed from seven stacked double pancakes—double layer assemblies of niobium-tin superconductor wound into a D-shape, inserted into mechanical support structures called radial plates, and insulated. The resin impregnation of the full stacked assembly was one of the final steps performed in La Spezia, carried out to electrically insulate the component and create a rigid assembly (photo).Since the beginning of qualification activities on the European winding line (semi-winding in 2012, full prototype double pancake in 2013), hundreds of people from dozens of companies have contributed: superconducting strand producers in China, Europe and Russia; the ICAS consortium (Italian firms ENEA, Tratos Cavi and Criotec) for jacketed conductor material; CNIM (France) and SIMIC (Italy) for the radial plates; the ASG consortium (ASG Superconductors, Italy; Iberdrola Ingeneria, Spain; and Elytt Energy, Spain) for winding operations; and now SIMIC (Italy) for cold testing and insertion into coil cases. It's what ������app Director-General Bernard Bigot—who was present at the ceremony on 18 May—calls a good case study of the ������app Project as a whole ... a "melting pot of knowhow and expertise." "The success of the ������app Project depends fundamentally on successful partnerships between what I would call 'global neighbours,'" said the ������app Director-General to the group that had assembled in La Spezia. "The ������app Project is built on this condition: partnership is a prerequisite, as not a single ������app Member could afford to build ������app alone in a reasonable time. If our large international partnerships perform well, each partner contributes its expertise and unique capacity. We complement each other, we all learn from each other, the interfaces are well-managed, the project succeeds, and everyone wins." The European Domestic Agency is responsible for the procurement of nine toroidal field coils plus one spare; the Japanese Domestic Agency, which is responsible for nine others, also recently produced its first winding pack. The first 17-metre tall, 310-tonne completed toroidal field coil (winding pack plus steel case) will be shipped to the ������app site in 2018. See the story on the Fusion for Energy website here.

H‐mode—or the sudden improvement of plasma confinement in the magnetic field of tokamaks by approximately a factor of two—is the high confinement regime that all modern tokamaks, including ������app, rely on. It was observed for the first time rather by accident (read more here) and to this day the physics behind H-mode remains not fully understood. Scientists at the Princeton Plasma Physics Laboratory (PPPL) in the US have made a step in the direction of elucidating the phenomenon by simulating, for the first time, the spontaneous transition of turbulence at the edge of a fusion plasma to H-mode. The research was achieved with the extreme-scale plasma turbulence code XGC developed at PPPL in collaboration with a nationwide team. This massively parallel simulation, which reveals the physics behind the transition, utilized most of a supercomputer's power—running for three days and using 90 percent of the capacity of Titan at the Oak Ridge Leadership Computing Facility (the most powerful supercomputer for open science in the US). "After 35 years, the fundamental physics of the bifurcation of turbulence into H-mode has now been simulated, thanks to the rapid development of the computational hardware and software capability," said C.S. Chang, first author of the April Physical Review Letters paper [118, 175001 (2017)] that reported the findings. Co-authors included a team from PPPL, the University of California, San Diego, and the MIT Plasma Science and Fusion Center. Seung-Hoe Ku of PPPL performed the simulation. Read the full report by John Greenwald on the PPPL website.

Sébastien König's core competence is in planning and scheduling; his passion is in understanding the workings of the Universe. In his previous life, before joining ������app in 2013, he worked for large projects all over the world—aluminium smelters, hydroelectric power dam construction, iron ore mining, and a host of other ventures that require painstaking computing and the integration of thousands of different parameters. All the while he kept observing the sky, tracking the passage of the International Space Station from his backyard, vacationing in Namibia with his wife and children to visit the HESS gamma ray observatory, or joining a group of amateur astronomers for a tour of the major US and European observatories in the Chilean Andes.   His latest family expedition, in February, took him to Iceland in search of the green plasmas of aurora borealis. The experience was a perfect demonstration of how careful planning and thorough contingency management can lead to the one of most intense of celestial experiences.   "I planned this trip like I plan for a project," says Sébastien, "first selecting the opportunity window that matched the moonless nights during the northern lights season from October to March to the kids' school vacations; then making hotel reservations that, depending on weather conditions, I could cancel at the last minute without penalty."   Most important perhaps were the two applications that Sébastien relied on—one from the Icelandic weather service that precisely maps the position and altitude of clouds, the other from the national road service that gives real-time information on the state of roadways.   And, luck (cum preparation), of course, plays its part.   Armed with his tools and information, Sébastien was able to treat his family to unforgettable visions. "It's like a stage show, almost choreography. Thin luminescent drapes seem to slowly fall from the sky, barely moving; then you see them dance with what appears to be sudden euphoria. It's something that reaches very deep inside."   In the gallery below, you will get a sense of what the green plasma experience feels like.