RF measurements and control of higher order modes in accelerating cavities

In RF cavities, built at BINP for electron-positron storage rings, special tuners are provided for higher order modes (HOMs). The HOM tuners effect on different modes in different ways. Electrical characteristics and tuning curves of cavity modes are measured. Using these experimental data, the beam-cavity interaction at higher order modes is analyzed for different HOM tuner positions. There are combinations of HOM tuner positions, at which the cavity caused beam instabilities may occur, and there are combinations, at which they may not. The last ones are recommended for routine cavity operation.