Off-axis parameters of PAL-XFEL planar undulator

The electron beam path in a planar undulator is usually chosen at the undulator magnetic center in both the vertical and horizontal directions. In the case of the vertical-gap undulators of x-ray free-electron lasers, best efforts are paid to align the vertical magnetic center to the reference electron beam path. The twenty undulator segments are aligned vertically within 50 mu m to obtain the target K-values of the undulator segments in the PAL-XFEL hard X-ray beamline. Besides K-value, undulator phase error and beam trajectory deflection are also concerned when the undulator is misaligned to the beam path. In some cases, an off-set in the vertical direction is applied intentionally when a transverse field gradient is required. In this report, we present the systematic measurements of the phase error and trajectory deflection at vertical off-axes of a PAL-XFEL hard X-ray undulator.

Automated summary

This report presents the systematic measurements of phase error and trajectory deflection at vertical off-axes of a PAL-XFEL hard X-ray undulator, highlighting the importance of aligning the vertical magnetic center to the reference electron beam path during the alignment process.