X-Ray CCD setup for large-area wire chamber calibration

A X-ray setup has been developed to measure wire positions of straw tube drift detectors for the COMPASS experiment. In an automatic scanning procedure wire positions can be determined with an accuracy better than 30 μm inside an area of 3.6 × 3.6 m². This accuracy is achieved by an independent two step movement of CCD and X-ray source, combined with a large-distance calibration with the help of external reference wires. Within smaller distances of several centimeters the achieved accuracy is much higher, in the order of a few microns.