Development and fabrication of 12 tesla Nb3Sn superconductors

The fabrication techniques for large pool boiling conductors for the High Field Test Facility (HFTF) , the General Dynamics-Airco 12 T model coil, or a Fusion Engineering Device (FED) are presented. These conductors are manufactured as follows: fabrication of long continuous lengths of a high-current core are fabricated by campacting a cable of small strands in a continuously seam welded copper tube. The operating current of the HFTF conductor is at 5000 A at 12 T¹. To provide additional wetted surface areas for cooling, the reacted compacted monolith is continuously soldered to embossed copper strips Bond quality is continuously monitored with ultrasonic testing techniques. The operating current of the General Dynamics-Airco 12 Tesla model coils 12.5 kA at 12 T²and the compacted monolithic core is joined to a large aspect ratio copper stabilizer by brazing or diffusion bonding. Preliminary properties of brazed joints are reported.