Design of a Quasi-waveguide Multicell Deflecting Cavity for the Advanced Photon Source

This paper reports the design of a 2815 MHz Quasi-waveguide Multicell Resonator (called QMiR) being considered as a transverse RF deflecting cavity for the Advanced Photon Source's (APS) Short Pulse X-ray project. QMiR forms a trapped dipole mode inside a beam vacuum chamber, while High Order Modes (HOM) are heavily loaded. This results in a sparse HOM spectrum, makes HOM couplers unnecessary and allows simplifying the cavity mechanical design. The form of electrodes is optimized for producing 2 MV of deflecting voltage and keeping low peak surface electric and magnetic fields of 54 MV/m and 75 mT respectively. Results of detailed EM analysis, including HOM damping, thermal and mechanical calculations for proposed QMiR cavity are presented.