Possible excitation of radial satellites in high-power gyrotrons

Numerical simulations of the pre-prototype 170 GHz coaxial gyrotron for ITER, existing at FZK, indicate that high- power (~MW) excitation of a TE_mp mode is accompanied by parasitic low-power excitation of its radial satellites TE_m(p+1)and TE_m(p-1), despite the fact that the satellites are out of resonance with the electron beam. The parasitic excitation of the radial satellites limits the voltage range of oscillations of the dominant mode, and this results in lower output power and efficiency. With the inclusion of the radial satellites in the simulations, the numerical results come closer to the experimental results.