When a high temperature superconductor (HTS) magnet consisting of a stack of pancake coils is wound, precisely controlling both the outer diameter and number of turns in the coil is difficult, mainly due to manufacturing uncertainty of the HTS tapes. To “arbitrarily” adjust the number of turns in each pancake is often adopted to precisely control the outer diameters, which obviously jeopardizes the ideally designed field homogeneity of the magnet, an important issue particularly for nuclear magnetic resonance or magnetic resonance imaging applications. A common approach is to place intermediate metal strips in-between selected turns of the pancake coils in a way to control both the outer diameter and number of turns to the design values. Yet, if this approach is used for a no-insulation (NI) HTS pancake coil, there is concern whether or not the coil will maintain the self-protecting feature. This paper investigates this issue in experiments in a bath of liquid helium at 4.2 K. An NI pancake coil was wound with metallic cladding REBCO tapes having a 1 – 2 um stainless steel cladding layer. Multiple quench tests were performed with the coil placed in a bore of a 10 T low temperature superconductor background magnet. The post-quench behaviors of the coil were monitored in various operating currents. The tests were repeated as the coil was reconstructed with different configurations such as the number of copper strips, size of strips, and strip locations. The results are expected to provide some insight for the baseline design of our future NI-REBCO NMR or MRI magnets.
ACKNOWLEDGMENTS: This work was supported by the National High Magnetic Field Laboratory (which is supported by the National Science Foundation under NSF/DMR-1157490), the State of Florida, and the KBSI grant (D37611) to S.-G.L.