Measurement of the shunt impedance of overcoupled klystron cavities

The paper describes a measurement method for the determination of the shunt impedance Zsh = (R0/Q0)QL for over-coupled klystron cavities by field measurements in the cavity gap and a slotted line connected to the output waveguide. Losses and possible field distortions introduced by the coupling network are taken into account. An experimental check was performed on a cavity for which the characteristic impedance R0/Q0 was computed exactly. Under carefully controlled conditions a measurement accuracy of 5% can be achieved. The application of the method to the measurement of the shunt impedance of a multiple-beam ring circuit that is heavily over-coupled to a concentric line is described.