The R3B-GLAD Quench Protection System

The R3B-Glad superconducting Magnet provides the field required for a large acceptance spectrometer, dedicated to the analysis of Reactions with Relativistic Radioactive ions Beams. In the framework of the FAIR Project to GSI and within NUSTAR physics program, the technical study started in 2006, and the engineering fabrication is undertaken. The magnetic field and active shielding are achieved by means of 6 superconducting trapezoidal racetrack coils made of a Rutherford type NbTi superconducting cable. The coils are indirectly cooled at an operating temperature of 4.5 K by a thermo-siphon circuit, and are designed to run at a nominal current of 3.6 kA. The corresponding maximum stored magnetic energy reaches 24 MJ. The quench protection is achieved by discharging the magnet in an external resistor, with a voltage to ground of ??500 V at the beginning of the discharge. The design and the characteristics of the quench protection system are described. The computational results of the quench protection for several scenarii are presented as well as the thermal and electromagnetic behavior of the coil cases.