Construction and Test of a 7 T Metal-as-Insulation HTS Insert Under a 20 T High Background Magnetic Field at 4.2 K

This paper presents the construction and the test results of a metal-as-insulation (MI) HTS mock-up insert for a 10 T HTS insert. Two MI double pancake (DP) coils were fabricated using 6 mm wide GdBaCuO commercial coated conductor tapes. Each of them has an inner joint between the top and bottom pancakes. They were made using nearly the same parameters as the DP coils designed for the 10 T HTS insert. Each DP coil was tested in LN2 bath at 77 K to measure its inner joint resistance and critical current (Ic) values. After the assembling process of the DP coils, charging tests of the MI mock-up magnet were performed to evaluate current carrying capacity, stability, and mechanical strain issues of the HTS insert under various background magnetic fields in a LHe bath at 4.2 K. These results show that the MI mock-up magnet was stably charged nearly up to its calculated Ic under background fields in the range of 0-20 T without any thermal and mechanical damage even though it experienced a quench due to unstable cryogenic conditions. In addition, the HTS insert generated a field of 7 T at 417 A (engineering current density of 660 A/mm
²
) in a background magnetic field of 20 T, which yields a combined field of 27 T.