Figure 7.

Three-dimensional rotation of a NW. The angles θ, ϕ and ψ are the angles of rotations about the x, y and z axes, respectively, and referred to as roll, pitch and yaw angles in nautical notation. The angles θ and ϕ define a random orientation of the long axis of the NW and vary in the range 3–5°, as determined from the tilt measurements. The mean value of the angle ψ defines an average orientation of the side facets with respect to the incident X-ray beam, and its variation in the range 2–4° is determined from the twist measurements.