Dc Test Results Of The Demo Tf React&Wind Conductor Prototype No. 2

In 2013, the EUROfusion organization launched the preconceptual design studies of the fusion DEMO tokamak. Several options of superconducting magnet design are investigated within the scope of the project. The magnets based on Nb3Sn, namely the Toroidal Field (TF) and Central Solenoid (CS) coils, can be made either using the Wind&React technology, as in ITER, or React&Wind (RW) technology with potentially significant costsaving benefits. Within the R&D program of the Swiss Plasma Center, the first full-size DEMO TF RW conductor prototype, RW1, was manufactured and tested in 2015-2016. The second, improved prototype, RW2, was built and tested in 2017-2018. The experimental results collected over several test campaigns performed on four assemblies of RW2 rated for 63 kA at 12.23 T are presented. The current sharing temperature T-cs of the latest RW2 assembly in DEMO operating conditions reached 7.16 K after 1000 electromagnetic cycles and four thermal cycles. This T-cs corresponds to the effective strain epsilon(eff )= -0.27%, significantly exceeding the design requirement of T-cs >= 6.7 K. If RW2 have been used in ITER TF coils, the T-cs at 68 kA and 10.9 T would be 7.42 K, i.e., approximately 1 K higher than most of the ITER TF samples, and that with only 55% of Nb3Sn used in ITER TF conductor. The tests of RW2 proved that the cost-saving potential of the React&Wind technology is enormous.