Planar Distributed Three-Beam Electron Optics System With Narrow Beam Separation for Fundamental-Mode TWT in W-Band

A planar distributed three-beam electron optics system with narrow beam separation is investigated in this article for W-band fundamental-mode staggered double vane traveling wave tube (TWT). An integrated electron gun with control electrode for planar distributed three-beam array has been constructed based on the grid loaded method, which is a general method to obtain planar multibeam array by 1-D compression. Then, the uniform magnetic focusing system is constructed for planar distributed three-beam array, where the peak value of axial magnetic field
${B}_{z}$
can be achieved 4600 Gs. The pole piece with novel stepped hole is considered in this magnet system, which can reduce the transverse magnetic field disturbance effectively. The optimization of the magnet structure and magnetic saturation analysis of the pole piece is fully considered to ensure the transmission stability of the three-beam array and reduce the volume of the whole system. The simulation results show that the three-beam array can transmit 70 mm with the transmission rate of 100% under the uniform magnetic focusing system. The whole system stability is verified, including the assembly error, working voltage fluctuations, and variations of magnetic field. The designed electron optics system can be used for the fundamental-mode staggered double vane traveling wave tube in W-band to improve the high output power in future.