Study on the Supercondicting Performance of Ultra-fine Strand Nb₃Al Cables

In the straight beam lines of the SuperKEKB Tsukuba area, 16 conventional sextupole magnets have been installed at intervals of 20–35 m. To achieve high luminosity, higher precision beam tuning with sextupole magnets is required. In KEK, a study on a superconducting sextupole magnet system involving three types of corrector magnets is ongoing. Considering the operating temperature of the system, an A15 compound superconductor, Nb<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub>Al, is being studied for use as the cable material, and the development of the reaction and winding coil production with Nb<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub>Al cable has been attempted. This study developed an Nb<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub>Al ultra-fine strand superconducting cable with a strand of φ50 μm for the corrector magnets, and the critical currents of the cable were measured as functions of the bending radius and the temperature. This paper reports the temperature dependence of the critical currents of the bent Nb<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub>Al cables after heat treatment.