A Prototype Conductor by React&WIND Method for the EUROfusion DEMO TF Coils

The React&Wind (RW) method for the large Nb
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Sn magnets of the EUROfusion DEMO device was proposed in 2013 by the Swiss Plasma Center. A first short-length prototype conductor for the toroidal field (TF) coils, named RW1, was tested in the EDIPO test facility during 2015-2016 up to 82 kA at 13 T, with an effective strain matching the expected thermal strain of ≈-0.30%. After the baseline of the DEMO device was updated in 2015, the new requirements led to an updated conductor design, for 63 kA at 12.2 T. The manufacturing experience of the first prototype, named RW1, is exploited in a second short-length prototype conductor, named RW2, assembled and tested in 2017: The conductor aspect ratio is reduced, and the segregated copper wires are replaced by a solid block of mixed matrix stabilizer. Although designed for the TF coils, with dc operation, the moderate ac loss of the flat cable makes the RW2 a good candidate also for the central solenoid conductor. The Nb
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Sn strand for RW2 is supplied by WST (PRC), and the flat cable is made at TRATOS (Italy). The rationale of the design, the conductor manufacture, the sample assembly, and the test results in SULTAN are reported.