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Description
A new quench protection technique, Energy Shift with Coupling (ESC), has recently been proposed, which is very promising for the protection of high-field magnets. The ESC system includes normal-conducting coils that are highly magnetically coupled to, but galvanically insulated from, the magnet coils. When the system is activated, rapid shift of energy from the magnet to the ESC coils is achieved, which quickly results in a substantial reduction of ohmic loss in the magnet hot spot and a transition of the superconducting coils to the normal state due to transient losses. Furthermore, during the magnet current discharge part of the magnet’s stored energy is transferred to the ESC coils. ESC was successfully demonstrated at CERN on a 400 mm long flat racetrack in a structure without aperture.
In this contribution, we present the application of the ESC method to a subscale common-coil magnet named SMCC2, which was designed and manufactured by the Magnet Development (MagDev) laboratory at the Paul Scherrer Institute (PSI). The SMCC2 is a 300 mm long magnet including four stress-managed Nb3Sn common-coils and designed to reach bore and coil peak fields of about 5.3 T and 6.4 T, respectively, at a short-sample current of 9.5 kA. Protecting this magnet after a quench without using energy extraction is extremely difficult due to its very high current density, which is nearly 6 kA/mm2. The proposed ESC-based quench protection scheme relies on two ESC common-coil-type coils made of rectangular copper conductor, which are located on the outer sides of the magnet coils.
Tests were carried out at the CERN magnet test facility, successfully demonstrating ESC performance under various operating conditions. These results show that ESC is an effective and high-performance technology that can protect magnets up to very high current densities.
