Design and manufacture of a Nb3Sn 16T demountable insert solenoid for a high field testing system

In the framework of the characterization and quality control of the Nb3Sn s trand for the manufacturing of the ITER (International Thermonuclear Experi mental Reactor) Model Coils, the Applied Superconductivity Laboratory at EN EA (Ente per le Nuove Tecnologie Energia Ambiente) Frascati decided to incr ease the background field of its facility for I-c measurements from 14.5 T up to 16 T, The upgrade was obtained by an insert coil designed and manufac tured by Ansaldo CRIS (Consorzio Ricerche Innovative per ii Sud), Naples, I taly. The Nb3Sn strand provided by Europa Metalli is an internal tin diffus ion high critical current density 0.90 nun wire with the following characte ristics: I-c=160 A @ 4.2 K, 16.5 T; Cu/nonCu ratio 1, The solenoid (outer d iameter 80 mm, inner bore 37 mm) was manufactured by winding the insulated Nb3Sn strand onto an AISI 316L stainless steel former and reacting it up to 650 degrees C, A self consistent unit has then been assembled, consisting of the insert module, mechanical structure and separate current leads. This allows easy installation of the insert inside the 14.5 T, 80 mm background magnet; removal is possible also in cold conditions without damage. The op erational current (113.7 A) was achieved at the first energization with a m aximum field on the windings of 16.49 T, This test has been done connecting electrically in series the background magnet and the insert, being therefo re limited by the maximum allowable current (114 A) in the background magne t. Further tests with an independent current supply to the insert will be c arried out to evaluate its performance limits.