A new method to position the APS dipoles with the use of a laser tracker

The alignment requirements for the synchrotron light sources have increased to the limit of today`s alignment techniques. Some components such as dipoles can only be positioned after having obtained a three-dimensional outline of the as-built magnet. The laser tracking system provides the unique opportunity to map the dipole gap and relate the information to the outside reference marks for the placement of the magnet. In this case the Leica SMART 310 laser tracker is used as a 3D coordinate measuring system that provides the necessary information of twist, roll, sag, and gap changes over the full dipole length. On the basis of this information the best fitting plane is calculated to obtain the average roll angle for the positioning of the dipole. This paper describes the basic principal of this alignment technique and demonstrates the achieved results with examples.