The 2020 summer months saw some of the most massive, intense and spectacular activities in ITER Project history. July ended with heads of state and world dignitaries virtually gathered in the ITER Assembly Hall to celebrate the launch of assembly operations. August began with the arrival from Korea of the first vacuum vessel segment—an alien-looking, D-shaped chunk of steel which, once welded to 8 other similar 40-degree segments, will form the toroidal chamber where fusion reactions will occur.   By the end of the month, the time had come to move the cryostat lower cylinder out of its protective cocoon and into the Assembly Hall. The operation was spectacular: manufactured in India and assembled and welded on site, the lower cylinder is a giant steel ring, 6 centimetres thick, 10 metres high, and 30 metres in diameter—and the doors into the building offered just enough clearance for it to pass.   Once inside, and after a few days of preparation and tests, the 375-tonne component was lifted, moved along the entire length of the assembly theatre and delicately inserted into the Tokamak assembly pit. The operation on 31 August was both similar and different (and, at times, even more challenging) than the one on 26 May, when the base section of the cryostat was positioned at the bottom of the pit.   Four days into September, a fourth toroidal field coil (TF11, from Europe) arrived on the ITER site. Travelling along the ITER Itinerary now are two semi-circular magnet feeders that left Shanghai late May and arrived in France on 7 July. Next week, logistics teams are expecting vacuum vessel thermal shielding from Korea, followed shortly by the first batch of cryostat top lid segments from India.   One by one, the pieces of the giant ITER Erector set are being delivered to the construction site. Ten years to the month after the beginning of building construction and five years before the production of ITER's First Plasma, assembly has begun in earnest.

The ITER machine will require 18* toroidal field coils—the D-shaped superconducting magnets that are responsible for confining the plasma in the centre of the torus-shaped plasma chamber. Since April four of them, two from Europe and two from Japan, have been delivered to the ITER site. Although similar in shape, they differ in their packaging. Europe has opted for a tight wrap that reveals the general shape of the component and advertises the names of the institutions and companies involved; Japan has chosen a more conservative approach, with the coil encased in a rectangular frame with only its two opposite ends visible.   But whatever the packaging and whether experiencing it for the first time or the fourth, the transport of a 17-metre-long, 350-tonne component is always a spectacular event that draws small crowds on its passage.   Europe's packaging for toroidal field coils is a tight wrap that reveals the general shape of the component and advertises the names of the institutions and companies involved. Following the arrival of toroidal field coils TF9 and TF12 in April, and TF13 in July, toroidal field coil #11 (from Europe) was delivered to the ITER site in the small hours of 4 September. Its "partners" for pre-assembly, toroidal field coil #10 and vacuum vessel sector #8, are not due at ITER before 2021.   * Plus one spare  

The setting, the atmosphere, the tension, and the sequence of operations were similar, but the challenges were slightly different. The cryostat base, which was inserted into the assembly pit back in May, was an exceptionally heavy, uniform and rather rigid component. The ring-shaped lower cylinder, although much taller (12 metres vs 4), was a considerably lighter load (375 tonnes vs 1,250) and—due to its diameter, thickness and many large openings—more "flexible" and likely to deform. In addition, its mass was unevenly distributed: on one side, the neutral beam port area added significant weight, which required a specific rigging arrangement. For more than one year, since April 2019, the cryostat lower cylinder had sat in storage, solidly encased in its steel frame and carefully cocooned in airtight material. On 22 August 2020, a 192-wheel self-propelled transport trailer slowly transferred the component into the Assembly Hall, passing through the wide door with very limited clearance.   Preparing for the lifting, transfer and insertion of the cryostat lower cylinder took the better part of one week, including laser measurements, the installation of complex rigging, the connection to the overhead crane, and finally a test lift to determine the importance and range of deflections.   Some 15 hours after the beginning of operations, the cryostat lower cylinder reached its near-final position above the base section. Another week of adjustments, and the welding operations can begin. On 31 August everything was ready, and the cautious, progressive process of lifting and transferring a steel ring the diameter of the Stonehenge stone circle could begin.   By mid-day, the lower cylinder hovered just about the mouth of the Tokamak pit (see video below). An empty well at the time of cryostat base insertion, the pit has since been equipped with a number of protruding components that reduced already tight clearances to less than 10 centimetres at the narrowest points. Alignment with the cryostat base and the openings in the bioshield wall meant also that stringent rotational tolerances had to be met.   Watching the huge and almost frail component slowly slide down the pit, each opening in the steel ring aligning with the corresponding opening in the concrete bioshield, was an unforgettable experience. As the lower cylinder settled on temporary hydraulic jacks, just a few centimetres above the base, one felt a sense of awe for the precision engineering that had just been demonstrated.   Now, one week later, the lower cylinder is settled in its final position. The gap between the two cryostat sections has been reduced to just 6 millimetres or less and automatic welding operations are ready to start. Expected to last 4 to 5 months, the task will be carried out by specialists from MAN Energy Solutions—the same Indian Domestic Agency contractor that was in charge of assembling and welding the cryostat segments in the Cryostat Workshop.   Watch a video of the operation on 31 August here.  

Travelling in nondescript casing, like a mobile home designed by an uninspired architect, the first of nine sectors of the ITER vacuum vessel was delivered to ITER on 7 August. Five days later, as the housing was removed, the jewel was revealed in all its strangeness: a massive, 440-tonne, D-shaped chunk of steel, dotted with hundreds of protruding cylindrical bumps that evoked a perfectly aligned, metallic measles eruption. Once combined and welded, four sectors supplied by Korea and five supplied by Europe will form ITER's toroidal plasma chamber. As for the measles eruption, it is caused by the "flexible support housings" or "cartridges"—1,760 of them in total and approximately 200 per sector—onto which the blanket shield blocks will be attached.   Beyond its alien shape and its awesome mission, this unique industrial object carries a strong symbolic dimension. It will be the first to be "upended" to vertical and placed within the open arms of ITER's tallest assembly tool—one of the twin sector sub-assembly tools (SSATs)—to be associated with two D-shaped toroidal field coils (TF12 and TF13) and corresponding thermal shielding.   Vacuum vessel sector #6 will stand at the core of the first 1,200-tonne pre-assembly—the first to be delivered by overhead crane into the Tokamak pit. Lessons learned on this first pre-assembly operation will contribute to increased ease and faster turnaround times for all other vacuum vessel pre-assembly sequences.   For the moment, the component has been transferred to the far end of the Assembly Hall, where the ITER team has performed a helium leak test. A full report will be published in next week's Newsline.