Quench Protection of a DCT Superconducting Quadrupole Magnet Employing the Adjustable Quench-Back

This study focuses on the quench protection of a superconducting quadrupole magnet based on the discrete cosine theta (DCT) configuration. The magnet is protected utilizing a previously developed scheme that employs an adjustable quench-back, induced by a central copper strand acting as a secondary coil. For the prototype L1200, quench transients were investigated through both simulation and experimental methods. During the excitation test, the quadrupole coil reached its nominal current of 466 A after 15 quenches, successfully validating the proposed protection scheme. A comparison of the simulated and measured current and voltage evolutions was used to analyze the quench-back characteristics during the discharge process. Furthermore, to facilitate the application of this adjustable quench-back protection scheme in accelerator facilities, a cold resistor wound by constantan wire was designed, fabricated, and installed on the outside surface of magnet. This resistor serves as an adjustable element to control the transient current induced in the copper coil. The temperature evolution of the hot-spot in the superconducting coil and the cold resistor was also estimated, confirming that all temperatures remained within the safe operating range to ensure magnet integrity.