An X-ray mapper for the Mu2e experiment

We report on the construction and performance of a scanner using a collimated x-ray beam to find the positions of wires, straws, slots and spheres. The technique is based on measuring the transmission rate of the beam, and their positions can be determined ~25 μm accuracy. The spheres or slots attached to the detector can also be optically surveyed externally to transfer the coordinates of wires and straws to other detector systems. The scanner was developed for the Mu2e straw tracker but may have a wide range of applications.