Quench Protection of Nb₃Sn High Field Magnets Using Heaters, a Strategy Applied to the Graded Racetrack Dipole R2D2

Abstract

The quench protection for the Future Circular Collider (FCC) 16 T Nb3Sn dipoles was based either on the CLIQ (Coupling Loss Induced Quench) system, or on resistive quench protection heaters. Several heater designs were sketched during the iterative magnet design processes. This led to identifying some rules about an effective heater design in the full-scale 14-m-long magnets. Following the FCC study, short dipole magnet models are being built to test the novel features that were envisioned for the FCC magnets. In this work, we review the principles of effective heater design, and then apply this methodology to the graded block dipole short model R2D2, which is being designed at CEA Saclay. This magnet has high current density in copper after quench, which makes the protection challenging and requires pushing the heater technology to its limits.

A Numerical Simulation of Quench Propagation in Nb3Sn Cables Covered With Protection Heaters

“…The influence of the heating station length on the heater delay (time to reach Tcs in the cable) was analyzed and compared with the literature reference [12]. The heater delay and the time to MT28-3PoA04-05 quench the entire cable is shown in Fig.…”

“…The shorter period in our case is assumed to have led to a shorter delay for the shortest heating station lengths (10-20 mm). and cable resistivity (right) for the HF cable [12].…”

“…The basic principle behind the model for heater delay simulation is based on [10], and it is complemented here with associated NZPV simulation. The simulated heater delay and NZPV are validated with literature references [11], [12]. The model allows studying heaters with arbitrary lengths of heating stations.…”

“…The model allows studying heaters with arbitrary lengths of heating stations. In future heater design it might be beneficial to use short heating stations which are optimal for high current operation and include only a few longer heater stations that are needed to protect the magnet at low current [12]. Fig.…”

CLIQ Protection Design for the Graded Nb$_{3}$Sn Research Racetrack Dipole Demonstrator (R2D2)

“…For longer magnets, in addition to energy extraction, the protection is usually designed with quench heaters alone or combination of quench heaters and CLIQ [7], [8], [9]. We studied the protection methods to see if the R2D2 could be protected with only quench heaters [10]. This paper only presents the CLIQ protection research work.…”