A Sheet Beam Electron Gun With High Compression Ratio and Long Transmission Distance Performance for W-Band TWT Applications

Abstract

A sheet beam electron gun with high compression ratio and long transmission distance performance for $W$ -band traveling-wave tube (TWT) is presented. A beam focusing electrode (BFE) with two pairs of unequal length outstretched structures is designed to provide equal positions of beam waist in both horizontal and vertical planes, which is beneficial to obtain large compression ratio and keep the beam cross section shape over a long distance. The operational voltage is set as 30 kV. The beam current is 0.505 A, and the corresponding cathode current density is about 5.59 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The simulation results show that the electron gun can provide a stable sheet beam under a 0.85-T magnet field. The compression ratio of the obtained sheet beam can be over 35, and the sheet beam can be transported through a 126-mm beam tunnel without interception with a 0.6 fill factor. The parameter sensitivities of the gun are analyzed and discussed as well.