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Angle log-periodic meander line microstrip radial sheet beam traveling-wave tube is one kind of novel minimized vacuum device with low beam voltage. To generate and focus the radial sheet electron beam, a novel radial divergent sheet beam electron optical system, including the tractable radial sheet electron beam gun and miniaturized and feasible radial small tunable periodic cusped magnetic focusing system, is proposed in this paper. The fan-shaped radial sheet beam is emitted from the cylindrical surface cathode, compressed in axial direction, and confined in azimuthal direction by the focusing electrode. Simulation results show that the total emission of the angular radial sheet beam gun is 51.2 mA with the dimensions of 0.26~\text mm \times 8 ° under the voltage of 1.7 kV, and the fan-shaped radial sheet beam can totally pass through the fan-shaped drift tunnel under the magnetic field. The experimental results are good in agreement with the simulation results. The tested angular radial sheet beam transmission efficiency is >90% in an 18.8-mm-length beam tunnel with the fill factor of 50%. [ABSTRACT FROM PUBLISHER]

A novel electron-optical system (EOS) for ${G}$ -band traveling-wave tubes (TWT) is investigated by simulation and verified by experiment. The EOS includes a sheet beam electron gun, a tunable periodic cusped magnetic focusing (TPCMF), and a collector. An elliptical focus electrode (FE) featuring a simple geometry and easy fabrication is utilized to compress the pencil beam into the sheet beam with a cross section of 0.4 mm $\times0.1$ mm. The electron gun with a cylindrical cathode of 0.8 mm diameter generates the sheet beam with voltage of 22 kV and current of 115 mA. Based on the sheet beam electron gun, the TPCMF with easy assembly and compact size is then proposed. The experimental results show that the beam transmission is 92.1% within a beam tunnel (its length 21.2 mm and cross section 0.8 mm $\times0.15$ mm). The EOS is suitable for ${G}$ -band TWT. [ABSTRACT FROM AUTHOR]

In this article, we propose a simulation method to investigate the noise mechanism of traveling-wave tube (TWT). Based on the nonlinear theory of Lagrangian description, 1-D noise model is established to analyze the shot noise and the velocity noise of the electron beam in the drift space, which clearly shows that the beam noise propagates along the electron beam with standing wave shape. The shot noise and the velocity noise can be periodically converted into each other along electron beam transmission, which is consistent with the prediction of the classical noise theory developed by Pierce and Danielson (1954). Using the nonlinear beam–wave interaction theory, the evolution process of the shot noise and the velocity noise of the electron beam transforming to the electromagnetic wave in TWT is illustrated. The calculated results show that the input position of the slow wave circuit may affect the noise power spectral density (NPSD) of the device. The proposed method can provide more intuitive and simple images to explain the noise mechanism of TWT. [ABSTRACT FROM AUTHOR]