Electron motion analysis of a radial-radiated electron beam in a radial-line drift tube with finite magnetic field conducted

Radial-radiated electron beam is widely employed in radial-line structure microwave devices. The quality of the electron beam has a crucial effect on the operating performance of these devices. This paper analyzes theoretically this electron motion in a radial-line drift tube with finite magnetic field conducted. The beam width, spatial period, and fluctuation amplitude are quantitatively analyzed with different beam current parameters. By the particle-in-cell simulation, we examine the theoretical analysis under the condition of a designed realistic coil configuration. It indicates that the derived beam envelope function is capable of predicting the radial-radiated beam trajectory approximately. Meanwhile, it is found that the off-axial z-direction magnetic field, in spite of its greatly slight amplitude, is also one necessary consideration for the propagation characteristic of the radial-radiated electron beam. Furthermore, the presented electron motion analysis may be instructive for the design of the ...