Braided multifilamentary Nb3Sn hollow superconductor and its magnet

Nb3Sn hollow superconductor and its magnet has been made possible by a unique fabrication process. The hollow superconductor with 250344 Nb3Sn filaments has been fabricated to have outer dimension of 5 × 6 mm and inner one of 2.4 × 3.4 mm. By "simultaneous conductor assembly and coil winding method", effective strain induced in Nb3Sn filaments can be far smaller than apparent strain. The 5 mm thick hollow conductor has been coiled into a magnet with inner diameter of 150 mm, which is equivalent to 3.3 % apparent strain, without any degradation. A test module magnet with four double pancake coils has yielded satisfactory results as expected.