Design and development of a sheet-beam electron gun with large current for a THz traveling-wave tube

In this paper, the design, development and experimental investigation on a sheet-beam electron gun with large current for a THz traveling-wave tube (TWT), which can operate typically at 0.22 THz frequency, is reported.The cylindrical cathode is made of scandate, and the pencil electron beam is compressed into a sheet beam by an elliptical focusing electrode.The maximum beam current of 123.4 mA was predicted with the emission current density of 24.56 A/cm 2 in simulation with 22 kV beam voltage.In the sheet-beam electron gun, the distance between the emission surface of the cathode and the beam-waist was found as 11 mm, and the wide edge and narrow edge of the beam waist crosssection are 0.38 mm and 0.1 mm, respectively.The components of the sheet-beam electron gun were fabricated and subsequently assembled.Its assembly errors were detected.The simulation predicts that the beam transportation in the sheet-beam electron gun under the condition of assembly errors exceeds 96%.The study also includes the experimental characterization of the cathode emission of the gun.The preliminary experimental results of the sheet-beam electron gun indicate that the beam current of 80 mA with the beam voltage of 22 kV was obtained from the proposed design.The experiment remained useful towards development of a 0.22 THz futuristic TWT.