Study of the Effect of the Electron Beam Parameters on a 0.4 THz Second Harmonic Gyrotron

The performance of the electromagnetic wave with power of over 100 kW at 0.4 THz is very attractive in plasma diagnostics; the 0.4 THz second harmonic gyrotron is strict with the quality of the electron beam. The quality model of the electron beam is built in practical engineering in this paper. Based on the self-consistent nonlinear beam-wave interaction theory for gyrotrons, the relationship among the quality of the electron beam, the performance of the terahertz gyrotron from the aspects of the orbital-to-axial velocity ratio, the guiding center radius, the spread of the velocity, and the thickness of the electron beam of the designed gyrotron is studied. The results show that the gyrotron is insensitive to the voltage and current of the electron beam in a wide range, and sensitive to the orbital-to-axial velocity ratio and the guiding center radius of the electron beam. The efficiency decreases when the electron beam spread is deepening, and the deepening has a little improvement when both guiding center and velocity spreads are involved in the beam-wave interaction.