Lengthwise Characterizations of Crystallographic Tilt in Contemporary REBCO Coated Conductors

Simulations may fail to accurately replicate the stresses experienced by no-insulation (NI) REBCO coils during operation and the resulting damage patterns observed postmortem in the coated conductor (CC). These simulations often assume that the REBCO layer's ab-planes are parallel to the CC tape plane, but in reality, the planes may deviate by several degrees. Since the nominal field angle lies close to the sharp ab-plane peak in the angular I_c of REBCO tapes, this small crystallographic tilt produces large discrepancies between expected and actual I_c, resulting in large inaccuracies for screening current stress (SCS) calculations. In this study, we use nondestructive XRD rocking curves to explore lengthwise variations in the ab-plane tilt angle in CCs from three anonymized manufacturers. We find that in two of the CCs, the tilt angles remain consistent along the length, but in the third CC, the tilt fluctuates on short length scales and wanders on long length scales. The tilt consistency loosely correlates with I_c homogeneity assessed using 77 K reel-to-reel remnant magnetization scans, though we do not find direct correlations between short-scale tilt fluctuations and I_c fluctuations. Our findings suggest that nondestructive lengthwise XRD ab-plane tilt measurements should be incorporated, when possible, into the conductor selection process when designing NI magnets.