11 T LIQUID HELIUM-FREE SUPERCONDUCTING MAGNET

An 11 T liquid helium-free superconducting magnet designed at 6 K in v acuum using high temperature superconducting current leads was develop ed. The NbTi/Nb3Sn coil was conductively cooled down from room tempera ture to 4.1 K in 40 h by two 4 K GM-cryocoolers. In a performance test , the coil temperature rose to 6.8 K for the inner Nb3Sn coil and 5.9 K for the outer NbTi coil, while sweeping the field at 5 A min(-1). A central field of 10.7 T in a 52 mm room temperature bore was generated at an operating current of 149 A. Holding the field at 10.5 T was ach ieved continuously for 24 h at a constant coil temperature of 4.8 K. ( C) 1996 Elsevier Science Limited