Analysis of the Experimental Quench Propagation on a 2-km MgB 2 Coil Up to 4 T

CEA Saclay, in collaboration with the French SMI Sigmaphi, has fabricated a 50-kg solenoid with a 2-km Columbus MgB 2 rectangular wire (3 × 0.7 mm²). The magnet was powered with 100 A at about 10 K and reached 4.2 T on the wire, with an external magnetic field of 3 T. A comparison between the protection and stability theoretical study and experimental results is presented. The quench propagation measurements have been performed at various temperatures, coil currents, and external fields. More than 20 quenches have been triggered using quench heaters mainly around the nominal design condition (10 K, 4 T, and 50 A/mm² of overall conductor current). These measurements values are compared to the results of the design calculations. The differences with the numerical model are analyzed, and a possible explanation of these differences is given by not taking into account real ground insulation thickness. The validation of the experimental parameters is necessary for designing the protection of high-field MgB 2 magnets in the frame of our development program. The performances of recent MgB 2 wires allow us to reach magnetic fields over 5 T.