ab-Plane Tilt Angles in REBCO Conductors

Critical current (I-c) of REBCO tapes is strongly anisotropic with respect to the orientation of the magnetic field. Usually, I(c )is at maximum when the ab-plane of the REBCO crystal is parallel to the magnetic field. In commercial REBCO tapes, it is commonly assumed that the ab-plane is coincide with the tape plane. While in fact, the ab-plane is near but slightly tilted from the tape plane in the transverse direction. To accurately measure I(c )as a function of the field angle theta, which is defined as the angle between ab-plane and the magnetic field direction, and to design and fabricate REBCO magnet coils based on the measured I-c(theta), it is important to measure the tilt angle. In this work, we used X-ray diffraction (XRD) to measure the tilt angles at room temperature for a large number of REBCO conductors made by SuperPower Inc. Transmission electron microscopy (TEM) was also used to investigate the origin of this tilt. The measured data are presented, and the measurement uncertainty is discussed.