Deflector Cavity Design for Rapid 2-D Proton Beam Scanning

We investigate the design of a 2.856 GHz deflecting cavity to provide rapid 2-D beam scanning for hadron therapy. We consider geometries for both conventional TM₁₁ modes and TE₁₁–like modes. Designs are optimized for the case of sub-relativistic protons with 150 MeV kinetic energy using simulations in HFSS to characterize the full 3-D field profile. We discuss the challenge of maximizing the transverse shunt impedance while mitigating variations in the transverse voltage as a function of distance from the nominal beam axis. These changes in the effective transverse kick can lead to significant beam profile aberrations for non-relativistic particles.