Fast ferroelectric phase shifters for energy recovery linacs

Fast phase shifters are described that use a novel barium strontium titanate ceramic that can rapidly change its dielectric constant as an external bias voltage is changed. These phase shifters promise to reduce by similar to 10 times the power requirements for the rf source needed to drive an energy recovery linac (ERL). Such phase shifters will be coupled with superconducting radiofrequency cavities so as to tune them to compensate for phase instabilities, whether beam-driven or those caused by microphonics. The most promising design is presented, which was successfully cold tested and demonstrated a switching speed of similar to 30 ns for 77 deg, corresponding to <0.5 ns per deg of rf phase. Other crucial issues (losses, phase shift values, etc.) are discussed.