Undulator for the LCLS Project - Changes in the Magnet Structure Design

The design modifications of a new hybrid-type undulator with a fixed gap of 6.8 mm, a period of 30 mm and a length of 3.4 m are presented. The prior pole design included side “wings, s” which were used for precise positioning, and clamps to fasten the poles to the magnet base. This design has been replaced by a more straightforward assembly, where the pole is attached to the magnet structure base using only two screws. Tests were performed on the vanadium permendur pole material to prove that the threaded holes are easy to fabricate and are able to successfully withstand the torque required to hold the pole in place. A fixture was also developed to ensure the precise location of the poles on the base during assembly. In addition to the pole modifications, the magnet-structure base is now manufactured as one piece as opposed to three, which greatly eases assembly. Finally, a small section of the original prototype had these changes successfully implemented, and the test results are presented.