Screening currents (SC) induced by varying magnetic fields may not only affect the field quality but also cause overstressing of REBCO coated conductor coils, making it a critical issue for NMR and other high-field magnets. We present in this paper results of an experimental and analytical study, performed with small REBCO pancake coils, on SC-overstressing of REBCO coil. Because SC is presumed to increase with REBCO tape width, we have studied test coils of two widths. The terminals of each coil, φ240 mm, were joined with a resistance sufficiently low to maintain the induced current constant enough during data taking. We use a 5-T/300-mm room-temperature bore magnet to not only supply an external field, but also induce up to 1000-A current to each coil at 4.2 K. Our experiment and analysis have demonstrated, and quantified, that the greater the REBCO tape width, the severer the SC-overstressing in REBCO coil will be.
Acknowledgement: Research reported in this publication was supported by the National Institute of General Medical Sciences of the National Institutes of Health under award number 5R01GM114834-13