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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]

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]

We have theoretically investigated the transport of a sheet electron beam focused by a uniform axial magnetic field in a metamaterial-loaded waveguide. A theoretical model has been proposed to analyze the sheet electron beam transport. In this model, we have used CST simulations to obtain the mean potential on the metamaterial as the boundary condition. According to the boundary condition, the space-charge electric field and the beam curling have been theoretically analyzed. It is found that the beam curling can be greatly reduced by decreasing the spacing between the metamaterial and the sheet electron beam. This model is verified using the CST simulations. This paper can pave the way for developing brand new metamaterial-based vacuum electron devices with a sheet electron beam. [ABSTRACT FROM AUTHOR]

In this paper, a novel small tunable periodic cusped magnet (NSTPCM) system is proposed for the purpose of realizing low voltage, big current sheet electron beam propagation in a long distance in engineering, which is composed of a series of position-fixed magnet blocks in alignment and freely sliding staggered pole pieces. This kind of NSTPCM not only generates higher magnetic field in the axial direction but also realizes more convenient adjustment of magnetic field in the transverse direction. This NSTPCM system has been successfully applied in a Ka-band sheet electron beam staggered double vane traveling wave tube. The tested sheet beam transmission efficiency is $>93$ % in a 112.7-mm-length slow-wave structure under the condition of beam voltage 24.3 kV and beam current 0.8 A. Moreover, the measured output power is $>75$ W in the range from 33 to 37.5 GHz, and the maximum output power is 128 W at 34 GHz. This paper provides the foundation for the development of sheet electron beam vacuum devices. [ABSTRACT FROM PUBLISHER]