Development of High-Harmonic CW Gyrotron with an Operating Frequency of 1.2 THz

The report is devoted to development of a 3
^d
harmonic CW gyrotron with the record output frequency of 1.2 THz. Based on analyses of start currents we demonstrate, that improvement of mode selectivity can be achieved due to interaction with an electron beam having a specially increased (up to 30-40%) velocity spread. In such conditions the start current of a near-cutoff operating mode decreases due to influence of “slow” electron fractions in the electron beams. At the same time, the start currents of parasitic modes, which are very sensitive to the velocity spread, increases significantly. The suppression of spurious mode and selective excitation an operating TE
_15,6
mode is demonstrated in the frame of 3D particle-in-cell simulations using CST STUDIO SUITE.