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The Chinese institute ASIPP has been on the front line of research and development on the magnet feeder joints for ������app.  Teams there produced a joint qualification sample to optimize and validate key manufacturing procedures and to verify constructability within the known constraints of assembly in the Tokamak Pit.

 

This main busbar* (MB) joint sample—the type that will connect busbars to the toroidal field, poloidal field and central solenoid magnets—was recently subjected to electrical resistance tests in the ASIPP laboratory, with successful results.  A stable outcome of ~0.2 nΩ at 70 kA was achieved and preserved after thermal cycles and 30,000 mechanical fatigue cycles. These results meet the technical specifications of the Magnet Feeder Procurement Arrangement, signed in 2011 between the ������app and the Chinese Domestic Agency.

 

 

Within the framework of the MIFI collaboration (for Magnet Infrastructure Facilities for ������app) between the ������app and the French Alternative Energies and Atomic Energy Commission (CEA), the joint sample has been reproduced only a stone's throw from the ������app site. The sample was then transported to the SULTAN test facility in Switzerland—the only facility in the world capable of reproducing the magnetic fields, current intensity and temperature conditions of the ������app operational environment. This was the first opportunity to verify the performance of the joint sample in various magnetic fields and to investigate stability and current distribution characteristics—important steps to ensuring that the joints perform as expected once reproduced at ������app.

 

At SULTAN, the resistance of the joint sample was successfully tested as ~ 0.85 nΩ at 3.8 T and 68 kA (performance maintained under several thermal cycles and 1,000 electromagnetic cycles).

 

The criticality of the superconducting feeder joints stems from the fact that they can only be truly tested once the machine is up and running. "Because they are among the most risk-prone elements of Tokamak assembly, it is very important to fully qualify all processes and fully train the staff that will be carrying out the work in the Tokamak Pit," explains Arnaud Devred, who leads the Superconductor Systems & Auxiliaries Section. "The lessons learned through the manufacture and testing of the main busbar joint sample is an important step in this direction, reflecting several years of hard work at MIFI by the feeder team."

 

The details of the test results are scheduled to be presented at the 25th Magnet Technology Conference in August.