Study of a Current-Based Quench Detection Method for CCT Magnets via a Co-Wound Superconducting Sensing Wire

To respond to the needs of the future accelerators and the upgrade of existing machines, superconducting magnet technology is continuously evolving in the direction of high fields and high current densities. As a result, a fast and efficient quench detection becomes an essential part of the magnet design in order to safely release the stored magnetic energy during a quench. A current-based detection method was initially introduced (Dudarev et al. 2014), is presented in this paper for Nb-3 Sn Canted-Cosine-Theta (CCT) type accelerator magnets, in conjunction with the current derivative sensor that is inspired by (De Matteis et al. 2018). The principle relies on a co-wound superconducting wire, placed beneath a superconducting cable. In case of a quench in the main cable, a transverse heat propagation will quench the sensing wire after a certain delay in the millisecond range. When the sensing wire is powered by a constant voltage source, the rise of quench resistance of the sensing wire leads to a drop in current, which can be detected by a current derivative sensor. In this paper, we describe this detection system and the test results in a subscale experiment where a quench is triggered by firing an adjacent heater strip. The advantages and limitations of this method, as well as the applicability to other magnets are also discussed.