Design and manufacture of a Nb/sub 3/Sn 16 T demountable insert solenoid for a high field testing system

In the framework of the characterization and quality control of the Nb/sub 3/Sn strand for the manufacturing of the ITER (International Thermonuclear Experimental Reactor) Model Coils, the Applied Superconductivity Laboratory at ENEA (Ente per le Nuove Tecnologie Energia Ambiente) Frascati decided to increase the background field of its facility for I/sub C/ measurements from 14.5 T up to 16 T. The upgrade was obtained by an insert coil designed and manufactured by Ansaldo CRIS (Consorzio Ricerche Innovative per il Sud), Naples, Italy. The Nb/sub 3/Sn strand provided by Europa Metalli is an internal tin diffusion high critical current density 0.90 mm wire with the following characteristics: I/sub C/=160 A@4.2 K, 16.5 T; Cu/nonCu ratio 1. The solenoid (outer diameter 80 mm, inner bore 37 mm) was manufactured by winding the insulated Nb/sub 3/Sn strand onto an AISI 316L, stainless steel former and reacting it up to 650/spl deg/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 operational current (113.7 A) was achieved at the first energization with a maximum field on the windings of 16.49 T. This test has been done connecting electrically in series the background magnet and the insert, being therefore limited by the maximum allowable current (114 A) in the background magnet. Further tests with an independent current supply to the insert will be carried out to evaluate its performance limits.