Design and Testing of Conduction-Cooled Splitable Superconducting Magnet for Linear Accelerators

The Dalian Advanced Light Source Beam Testing Platform requires a superconducting quadrupole magnet (with X/Y correction coils) to be installed at the end of the cryomodule to focus the beam. This quadrupole magnet has an aperture of 81 mm, a field gradient of 8 T/m, an integrated X/Y correction field of 67 Gs-m, and a magnetic length of 0.23 m. The nonuniformity of the quadrupole field within ±15 mm of the center is controlled to 0.1%, with a leakage field below 5 mGs at 10 cm from the cavity end. Considering magnetic field performance, cost-efficiency, and reliability, a conduction-cooled racetrack coil with an iron core structure was chosen, enabling the quadrupole and X/Y correction coils to share a common pole structure. Furthermore, since the SCRF cavities must be installed in a clean environment, the magnet is designed with a vertically split structure, allowing for assembly in the cryomodule after the SCRF cavity string has been installed in the clean room. This article presents the magnetic field design, mechanical structure, thermal analysis, quench protection, and manufacturing of the superconducting quadrupole magnet. Finally, the magnet was tested in a cryogenic liquid helium bath, with detailed measurements of the magnetic field distribution.