  Critical current (Ic) of REBCO tapes is strongly aniso-tropic with respect to
the orientation of the magnetic field. Usually, Ic 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 Ic 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 mag-net coils
based on the measured Ic(angle), 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 mi-croscopy (TEM) was also used to investigate the origin
of this tilt. The measured data are presented, and the measurement uncer-tainty
is discussed.
