An innovative tuning system for superconducting accelerating cavities

Frequency tuning systems for accelerating cavities are required to compensate static and dynamic frequency perturbations during beam operation. In the case of superconducting cavities, these are commonly tuned by deformation of the cavity wall in specific places of the geometry. Nevertheless, considering the mechanical properties and the frequency versus displacement sensitivity of some accelerating structures, tuning by deformation does not allow meeting the requirements. Inspired from the “room temperature technology”, an alternative tuning technique by insertion of a helium-cooled superconducting plunger has been studied and validated for the superconducting Spiral2 accelerator.