ESS-Bilbao Initiative Workshop. RF structure comparison for low energy acceleration.

This document compares different radio frequency (RF) structures that can be used for particle acceleration in the low energy range of 3 MeV to 200 MeV. It discusses figures of merit like shunt impedance and beam dynamics constraints for different structure types, including drift tube linacs (DTLs), coupled cavity drift tube linacs (CCDTLs), separated drift tube linacs (SDTLs), spoke cavities, and traveling wave structures. A comparison performed by the HIPPI collaboration assessed the performance of these structures based on factors like shunt impedance, beam dynamics acceptance, and mechanical complexity. Overall, no consensus structure exists for the low energy range, and the optimal design depends on project-specific parameters and future technology developments.