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Analytical formulations for the resonant frequency of a reentrant cavity for klystron are available in the literature only for such cavities having a single beam-tunnel. An improved analytical formulation has been proposed in this paper for the calculation of cavity gap-capacitance of reentrant cavities having single and multiple beam-tunnels and its effects on the resonant frequency are studied. The results obtained through analysis have been validated against those obtained from the 3D electromagnetic field simulations and measurements. The proposed analytical formulation provides good estimation of resonant frequency of cavity with single and multiple beam-tunnels. © 2021, DESIDOC.

In an effort to enhance the bandwidth of a multiple-beam klystron having rectangular double reentrant cavity with circular cylindrical ferrule, reduction of the unloaded quality factor of the cavity was proposed by placing circular cylindrical posts extending from one of the cavity side-walls to the opposite wall in an orientation perpendicular to the electric field. A typical cavity was analyzed using 3D electromagnetic field solver CST Studio and the post-loading was found to reduce the unloaded quality factor by around 90% compared to that for no-post-loading. The proposed method was found to be the only method other than the use of passive loss to achieve this order of reduction in the quality factor with a minor increase in the cavity transverse dimensions. Post made of highly resistive material was found to have pronounced effect in reducing the quality factor. The 3D electromagnetic analysis was validated against measurements on a typical S-band cavity.

Closed-form formulation for the estimation of equivalent circuit capacitance and inductance of a rectangular double-reentrant klystron cavity with circular cylindrical ferrules was developed and us...

Equivalent circuit analysis of a rectangular double-reentrant cavity of klystron with circular cylindrical ferrule operating in the fundamental TM110 mode was developed for obtaining the lumped parameters such as capacitance and inductance by considering the cavity as a parallel resonant circuit. Resonant frequency and characteristic shunt impedance of the cavity were then obtained using these lumped parameters. Analysis was validated against 3-D electromagnetic simulations using CST Studio and measurements.

A simple method for estimation of the unloaded quality factor of single and double re-entrant cylindrical cavities was developed based on Wheeler�s incremental inductance rule. The proposed approach was benchmarked for a Ka-band re-entrant cavity against 3D electromagnetic simulation using CST Studio and also with measurements. The analysis is general and unlike the approach of Fujisawa, it could be extended to analyze the re-entrant cavity comprising dissimilar materials. The effect of surface roughness on the quality factor of the cavity also could be estimated using the present analysis. © 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group.

Broadbanding of a rectangular reentrant cavity is proposed through reducing its unloaded quality factor by loading the cavity with periodic rectangular ridges placed on cavity transverse walls and orienting them perpendicular to the electric field. The effect of ridge loading on the cavity parameters, namely, resonant frequency, unloaded quality factor, and characteristics hunt impedance was investigated through 3-D electromagnetic simulations. Ridge loading of the cavity could facilitate around 70% reduction in the quality factor without any change in resonant frequency and negligible change in characteristic shunt impedance of that of a no-ridge-loaded cavity. The simulated resonant frequency and quality factor of typical S-band rectangular reentrant cavities were validated against measurements.

Effect of surface roughness on the bandwidth of a high frequency multiple beam klystron (MBK) cavity circuit is investigated. Surface roughness reduces the surface conductivity of the base material which in turn reduces the unloaded quality factor of the cavity and increases the bandwidth of the cavity. First, effective conductivity is calculated analytically for a given surface roughness, and then it is related to the quality factor and 3dB bandwidth of the cavity. Analytical results are compared with those obtained from 3D simulations.

This paper describes the overall design of a Ku-band 19 beam klystron amplifier. The device is designed to operate near to 2.5 KV with the total beam current of 0.5A equally distributed among its various beamlets. Two new schemes of magnetic focusing arrangement have been analyzed and experimented A block window design has been incorporated for the RF input and output. First, in-house developed codes and 1D code AJ Disk is used for initial design, later commercially available 3D simulation codes like CST-studio and Ansoft HFSS have been used for final optimization of the design.

This paper describes the design and experimentation of electrostatic focusing of electron beam using a demountable vacuum measurement setup. Initially a focusing setup is designed for focusing a single on-axis low perveance beam. The design was carried out using an in house developed 2.5D finite difference electron optics code PIERCE and CST Particle Studio. This focusing scheme is being extended for multiple beams of same perveance for a compact klystron device.

This paper describes the design of an electron gun and focusing system for a multi-beam klystron amplifier. The electron gun is designed for a beam voltage of 2.5 kV and a current of 700 mA, which is equally distributed among the 19 beamlets. An electrostatic and a magnetostatic focusing system have been investigated using 2.5D and 3D simulation codes.