A 3 T 100 mm all-REBCO multi-width (MW) no-insulation (NI) magnet was designed constructed, and currently being tested at the Korea Basic Science Institute. Key features of the magnet include use of “metallic cladding (MC)” REBCO tapes, i.e., a 1-um thick stainless steel cladding layer hermetically surrounds the tape in order to increase the turn-to-turn contact resistanc of the NI coils. The magnet successfully reached its full field of 3 T at a designated operating current of 200 A that corresponds to an engineering current density of 353 A/mm2 for double pancake coils wound with the narrowest width tape of 4 mm. Recently, the magnet experienced unexpected power supply trips twice during its long-term field mapping experiment at the full field, after which the magnet was fully discharged in 5 seconds. This paper reports the transient behaviors of the magnet in details during the sudden discharge events. Key parameters to have been measured include: (1) terminal voltages of individual 32 double pancake coils; (2) temperatures at the magnet top, middle, and bottom; (3) power supply currents; and (4) center magnetic field. A lumped parameter circuit model was used to analyze the electromagnetic responses during the sudden discharge. The magnet survived without any damage after each trip of the power supply and is currently being operated normally without any performance degradation. The results imply the self-protecting feature of the MC REBCO magnet, which has been experimentally demonstrated in a magnet level for the first time.
|Submitters Country||South Korea|