The electron optics system and beam-wave interaction for novel W-band sheet beam klystron

The cold fluid model theory was used for studying the transport and its instability for the sheet electron beam in the uniform magnetic field. The results show that if the focusing magnetic field and the filling factor of the beam in tube are increased, the Diocotron instability will be decreased to achieve a transportation in a long distance. Based on above results, 3D simulation method was employed to design and optimize the electron optics system for the W-band sheet beam klystron. 2D macro-particle model for sheet electron beam was proposed to develop a beam-wave interaction simulation program code for SBK, named SBK2D. The beam wave interaction processes in the W-band SBK with 8 multi-gap cavities are calculated using the SBK2D. The simulation indicated that a 69 kW peak power output at high frequency with efficiency of 24%, gain of 37 dB, and 3dB bandwidth of 100 MHz at 3 dB can be derived. The W-band sheet beam tube was manufactured according to the design. The transmission rate and cross-section experiments were performed with the beam voltage in the range of 20~82 kV, beam current of 0.5~4.27A, and the length of tunnel of 100 mm. More than 98% transmission rate with the beam cross-section about 10 mm×0.5 mm were obtained.