Design and construction of a hybrid-Nb/sub 3/Sn, NbTi-dipole magnet

Abstract

A two layer superconducting dipole magnet-D19H, with a Nb3Sn inner layer and a NbTi outer layer was designed, constructed and tested. The 50" bore inner layer of an exisihg NbTi dipole magnet (D19A), hia been removed and replaced with a Nb3Sn coil. The outer NbTi coil, collars, iron yoke, ring, collets and outer skin from the disassembled D19A magnet have all been reused. Employing glass insulated cable with aluminum-bronze poles and end spacers the Nb& coil was reacted at 660'C for 240 hours and fully epoxy impregnated. The design and construction uf the magnet are described and test results reported elsewhere in these pmceedingsll].

Advances in Superconducting Magnets for Particle Physics

“…A superconducting dipole, wound with Nb Sn cable, a 4-shell coil and graded conductor, was also designed and built by LBNL. The magnet recorded the maximum field of 13.5 T at 1.8 K, near to the critical current limit, in 1997 [18].…”

Superconducting magnets for accelerators and detectors

“…A natural choice would be to use NbTi in the outer shell, as it is done in solenoids. Actually the attempt to substitute the inner shell of a very good NbTi dipole, D19 at LBNL, with one Nb 3 Sn coil [9] did not reach the expected results. We think that, unlike the case of a solenoid, in dipoles the two shells are so strongly coupled mechanically, that the different mechanical and thermal properties of NbTi and Nb 3 Sn windings do not allow proper control of coil prestress and movement restraint.…”

“…In another case very thin skin collars [9], 3-5 mm thick, are used: they are intended for locking the coils in the proper position and for coil handling. In this case almost all forces are kept by the yoke-outer cylinder structure, with the advantage of a 3-5% enhancement of the field because of the closer vicinity of the yoke to the centre.…”