Spectrum-based alignment of SIRIUS undulators

Abstract In-vacuum insertion devices have their magnets positioned just a few millimeters from the electron beam orbit. Due to this proximity, the emitted radiation spectrum is highly sensitive to misalignments of the device’s magnetic center. Such misalignments can lead to photon flux losses, spectral shifts toward lower energies, and harmonic bandwidth broadening. This work presents the application of a spectrum-based alignment method to one of the new SIRIUS insertion devices, aiming to optimize its spectral performance at the beamline.