Investigations on the Effect of the Electron Beam Misalignments on a Continuously Frequency-Tunable Gyrotron

The effect of the electron beam misalignments, including the parallel shifted electron beam and the tilted electron beam on the operating frequency, the beam-wave interaction efficiency, and the frequency-tunable range for a continuously frequency-tunable gyrotron has been studied based on a self-consistent nonlinear beam-wave interaction theory. And the effect of the parallel shifted electron beam on the starting current has also been investigated based on linear theory. It is found that the misaligned electron beam has a little effect on the operating frequency and the frequency-tunable range but a significant effect on the beam-wave interaction efficiency. The misaligned electron beam has a different effect on different axial modes, the influences on the operating frequency, the frequency-tunable range, and the beam-wave interaction efficiency of a higher order axial mode are more obvious. Meanwhile, the influence of the parallel shifted electron beam on the starting current is significant; not only the order of magnitude of starting current increases, but the operating magnetic field is also changed. These results present that the effect of the misaligned electron beam is significant; the electron beam misalignments should be taken into account and avoided in the design and fabrication of a continuously frequency-tunable gyrotron.