Normal Zone Propagation in a ${\rm MgB}_{2}$ Conduction Cooled Test Magnet

In order to investigate the quench behavior of conduction cooled MgB₂ magnets, a 100 mm inner bore diameter, 0.84 T at 20 K magnet has been built and tested. The test magnet consists of 4 double pancakes wound with the MgB₂/Ni -Cu-Fe tape produced by Columbus. Each coil is cooled by means of a 2 mm thick copper disk placed during winding at the middle of the double pancake; after winding the double pancakes have been separately epoxy impregnated. Several experiments have been performed inducing a local transition in the coil by means of a controlled heater placed on the double pancake surface. The propagation of the normal zone has been monitored by means of 8 voltage probes positioned along the tape during coil manufacturing. Each voltage probe detects the voltage drop across a tape length of 30 mm. The experiments have been performed at different temperatures while keeping the magnet current constant during quench. In the paper we report an analysis of the quench propagation velocity measurements and a numerical investigation of the thermal and electrical behavior of the magnet.