Experimental Study of Phase Pushing in a Fundamental-Mode Multiple-Beam Klystron

The authors present the results of experimental measurements of the radio frequency phase as a function of cathode voltage for an eight-beam four-cavity multiple-beam klystron (MBK) operated at a driven frequency of 3.25 GHz. The phase-pushing factor was measured in both the small- and large-signal regimes of amplifier operation and was found to be 0.0134deg/V and 0.0148deg/V, respectively. The experiment was also modeled with a simple analytic function and with telegraphist's equations solution for linear beam amplifiers, a multiple-beam 2.5-D nonlinear klystron code, with both methods yielding good agreement with the measured data. The low values for the phase-pushing factor are a benefit of the MBK's high-perveance operation that results in a shorter circuit length relative to single-beam devices of comparable power. These advantages contribute to the growing interest in the use of multiple-beam devices for high-power phase-sensitive applications such as advanced radar and high-data-rate digital communications