A Three-Cell Superconducting Deflecting Cavity Design for the ALS at LBNL

Deflecting RF cavities may be used to generate subpicosecond x-rays by creating correlations between longitudinal and transverse phase space in electron bunches in radiation devices. Up to 2-MV defecting voltage at 1.5-GHz is required for 1.9-GeV electron beam at the Advanced Light Source (ALS) of Lawrence Berkeley National Laboratory (LBNL). In this paper, we present a conceptual design for a 1.5-GHz three-cell superconducting RF cavity and its couplers. The cavity geometry and its shunt impedance at the deflecting mode are optimized using MAFIA code. The cavity impedances from lower and higher order modes (LOMs and HOMs) are computed as well. Possible schemes for damping most harmful LOM and HOM modes are discussed and simulated.