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That represents more than 1,600 tonnes of equipment and approximately 100 large components.

 

Some of the elements arriving in September are "captive," meaning that they need to be installed in advance of other large components in the lower region of the Tokamak machine due to their size or position. Two are so large that they will be packaged in crates measuring 20 x 10 metres¡ªnearly the size of a tennis court¡ªrequiring handling as Highly Exceptional Loads as they travel by barge and road to the °ÄÃÅÁùºÏ²Ê¸ßÊÖ site from the Mediterranean Sea.

 

°ÄÃÅÁùºÏ²Ê¸ßÊÖ's Chen-Yu Gung, who leads the Magnet Feeder Group, compares the sequencing plan to the rules that govern traffic on the roads: "If there is a violation during the assembly process, and sequencing is not followed scrupulously, this could lead to clashes and gridlocks."

 

Counted among the largest systems to be procured for the machine, °ÄÃÅÁùºÏ²Ê¸ßÊÖ's 31 magnet feeders cover distances of 30 to 50 metres to ferry cryogens, power and instrumentation from the "warm" exterior environment outside the machine and cryostat in to the "cold" superconducting magnets operating at minus 270 ¡ãC. Under the procurement responsibility of °ÄÃÅÁùºÏ²Ê¸ßÊÖ China, each feeder is manufactured in three fully instrumented segments, which are shipped to °ÄÃÅÁùºÏ²Ê¸ßÊÖ for final assembly on site.

 

 

Next is the duct-like cryostat feedthrough, which provides a conduit for the power, cryogenic and instrumentation equipment as it passes through the concrete bioshield and cryostat and into the vacuum environment. The first of these¡ªthe cryostat feedthrough for poloidal field coil #4¡ªwas installed in the Tokamak Pit last year. (As the only one with a unique elbow bend, it had to take its place in a lower gallery before the concrete foundation ring supporting the cryostat was completed.)

 

Finally, the in-cryostat feeder is the segment that actually connects to the superconducting coils. These components take on a variety of shapes as they bend and turn inside the crowded space of the cryostat to reach the magnet connections. The largest elements arriving in September¡ªtwo semi-circular-shaped in-cryostat feeders for the bottom correction coils¡ªfall into this category.

 

The work to join the feeder segments will be carried out on site by specially trained contractors. The highly complex components inside the feeders (high-current busbars, high voltage cable conduits, cryolines, etc.) must be connected before the exterior casing is sealed. The most delicate¡ªand complex¡ªpart of the job is the realization of 228 superconducting joints to connect different segments of the busbars, or to connect the busbars to the coil terminals. (More on the challenges of superconducting joints here.)

 

 

On average, it will take 8 months to assemble one feeder (from the gallery to the coil terminal) including cabling and joints. Superconducting joints will take around 1.5 months each. "It's easy to see the challenge we are facing in planning for the assembly of all 31 feeders, especially given the number of other parallel activities related to machine assembly inside of the cryostat and the tight schedule to finishing the work before cryostat closure in late 2024."

 

Patrick's team has clearly defined the construction work packages for feeder assembly and developed the logical sequencing of work within the highly integrated Tokamak assembly scenario. For the complex joint operations, the team is enhancing the operational guidelines that were developed during the qualification phase of individual processes. A space for training and certifying technicians and inspectors in advance of the first assembly activities is also foreseen.

 

"Strictly controlling operator skill as well as each assembly task is the best way to ensure the quality of these joints, which have a critical role to play in the proper functioning of the °ÄÃÅÁùºÏ²Ê¸ßÊÖ magnets," according to Patrick and Chen-Yu. "We fully understand the stakes and we are ready for the challenge."