Magnetic Detection of Quenches in High-Field Accelerator Magnets

Development of high-field magnets for future accelerators brings new challenges and in particular the problem of reliable quench detection and localization. Traditionally, quench locations are determined by timing the propagation of the normal zone across the cable segment bounded by the neighboring voltage taps. However, applicability of this method is limited in high-field magnets due to a short time window allowed for quench propagation prior to firing the protection heaters. It becomes even more problematic for longer magnets, because a proportional increase in the number of voltage taps is required to see tap-to-tap propagation. Therefore, development of alternative quench localization techniques and improvement of the existing ones are needed. Here, we analyze three-dimensional magnetic field profiles due to a developing quench using the current redistribution model for Rutherford cable. We simulate transient field variations caused by the moving boundary of the normal zone and, as an example, attempt the model verification with the inductive quench antenna signals measured on the Nb₃Sn quadrupole magnet, HQ01. Further steps on optimizing inductive quench antenna design will be discussed.