Quadrupole magnetic center definition using the Hall probe measurement technique

Abstract

The linac coherent light source [LCLS] project requires 5 {micro}m straightness of the particle beam trajectory to achieve the desired goal of x-ray multiplication. The main source of beam trajectory distortion is misalignment of quadrupoles. The LCLS project will use a beam-based alignment technique to align the quadrupoles to the needed accuracy. An initial accuracy of the quadrupole alignment not worse than 50 {micro}m is required. A different technique could be used for this purpose. It would be quite desirable to avoid using an additional magnetic measurement technique and to use the same sensors that will be used for undulator magnetic fields measurements, i.e., Hall probes. At the APS magnetic measurement facility, an APS FEL quadrupole was used to test this possibility. The results obtained from this test show that an accuracy of {+-} 50 {micro}m centerline definition is achievable and allow them to limit the necessary technique to the Hall probe only.