The Magnetic Field Stability of Double-Slit Jointless Stacked Pancake Coils After Thermal Quench

Closed coils made by second-generation high-temperature superconducting (HTS) coated conductors are promising for superconducting magnets, which operating in a persistent current mode such as MRI, NRM, and Maglev. The magnetic field stability for the HTS closed coils after local thermal quench is one of the key indicators to the design of superconducting magnet systems. It significantly affects the operational reliability of superconducting magnets. This paper presents quantitative experiments on the magnetic field stability of a jointless stacked pancake (JSP) coil after local thermal quench. The JSP coil is assembled by stacking double-slit YBCO tapes, which is a true sense of HTS closed coil without any joints. A JSP coil with inner diameter of 30 mm is impregnated by paraffin wax and its central magnetic field stability is measured after various local thermal quench energies. The relationship between quench energy and magnetic field stability time is presented. The magnetic field of the JSP coil will stay stable when quench energy is lower than a threshold value Qm. The magnetic field stability of JSP coils comes from its parallel-structure. Besides, the magnetic field stability of the JSP coil is better than the series-structure closed coil obviously under the same quench energy.