Design of an Electron Optical System for a 220 GHz Sheet Beam Traveling Wave Tube

The design and simulation of an electron optical system (EOS) for a 220 GHz sheet beam traveling wave tube (SB-TWT) are presented in this paper, which includes a bidirectional compression electron gun (E-gun) and a periodic cusped magnet-quadrupolar magnet (PCM-QM) focusing structure. CST simulation results show that this E-gun can produce a sheet electron beam with an emitted current of 0.1 A at a beam voltage of 30 kV and its cross-section at the beam waist is 0.7 mm x 0.1 mm. Under the focusing of the PCM-QM, the sheet electron beam can be stably transported through an 80 mm-long beam tunnel with a cross-sectional size of 0.826 mm x 0.143 mm. A high transmission rate of up to 99.7% is obtained.