Proposal for the Alignment of the “Loose End”*

The “loose end ” of the girder presents an alignment problem because there is no beam based alignment procedure available to position it. The positioning always depends on the fiducialization of the undulator. A direct way to position the “loose end ” to the next quadrupole is to measure their fiducials in relation to each other. By spanning a wire over a distance of several girders, each undulator and quadrupole can be measured by reading its distance to the wire with a portable wire sensor. The pitch of a girder can be determined by measuring height differences at different points on the girder. To measure the height differences a portable HLS is used. During the measurements of the portable system the permanent Wire Position Monitor and the permanent HLS are used to monitor the interim movements of the girder. After the initial alignment the position of the “loose end ” can be monitored with the permanent systems in relation to the quadrupoles. Portable wire measurements A wire is spanned over 6 girders using the space at the long breaks to setup stands for the wire. To measure the position of the wire, capacitive wire sensors (Fogale WPS-2D) ar