A Wideband Double-Sheet-Beam Extended Interaction Klystron With Ridge-Loaded Structure

A novel transverse-mode overlapping technology is proposed to enable significant advancement in the development of wideband extended interaction klystrons (EIKs). To obtain the individual beams with comparatively low perveance and low current density, the double sheet beams are used to drive the circuit. For the purpose of allowing the circuit to operate in the fundamental mode, two innovative extended structures, ridge-loaded barbell structure (RLBS) and ridge-loaded ladder structure (RLLS), are proposed. It is found that both the two structures are capable of transverse-mode overlapping (superposition of TM11 mode and TM21 mode) by adjusting the dimensions of the ridges. On the basis of such ideas, a wideband six-cavity circuit at 0.22 THz is designed. The input and output cavities are with the RLBS, while the idler cavities are with the RLLS. The bandwidth of the output cavity and the frequency tuning of cavities are carefully considered to preserve good gain uniformity across the continuous frequency band. The particle-in-cell (PIC) simulation results show that the maximum output power reaches 138 W with the operating voltage of 15.8 kV and each beam current of 0.3 A, and the corresponding gain is 34.3 dB. The 1-dB bandwidth is 1.95 GHz, approximately 1% of the operating frequency. The relatively small in-band ripple indicates the excellent bandwidth characteristics of the circuit.

Automated summary

This article proposes a novel transverse-mode overlapping technology for the development of wideband extended interaction klystrons. By using double sheet beams and innovative extended structures, a wideband six-cavity circuit is designed, and particle-in-cell (PIC) simulation results show excellent bandwidth characteristics.