Broadening Bandwidth of Extended Interaction Klystron Through Nonperiodic Perturbations

Nonperiodic perturbations are incorporated into extended interaction klystron (EIK) to broaden the bandwidth, overcoming the dilemma of effective interaction between the beam and three or more axial resonances. The theoretical exploration delves into the impact of gap position perturbations on the periodic extended interaction cavity. Furthermore, application examples demonstrating multimode operation in nonperiodic cavities are presented and validated through comprehensive full-wave simulations. Subsequently, a seven-cavity interaction circuit of a G-band wideband EIK amplifier operating in 220 GHz is designed to further validate the nonperiodic design approach. The 3-D particle-in-cell (PIC) simulation predicts a constant 35-mW-drive bandwidth of 6.76 GHz and the corresponding maximum output power of 74 W for the designed power amplifier driven by a 20.6-kV, 0.25-A electron beam.