Experimental observation of chaotic oscillations with 1.5% bandwidth in gyrotron with high excess over starting current

The complex dynamics of the gyrotron is experimentally studied for operating current which is 1000–1500 times higher than the gyrotron starting current. Whereas in the experiment the electron beam current was only 0.2 A, a very high normalized current parameter is obtained through the operation at the lowest mode of a cylindrical waveguide. At the frequencies of about 33 GHz, the chaotic generation was observed with a spectrum bandwidth of up to 500 MHz that correspond to a relative bandwidth of 1.5%. This value is significantly higher than the bandwidths of chaotic signals obtained in previous experiments with gyrotron devices. The experimental results are in good agreement with the results of the theoretical analysis, which are based on the averaged equations taking into account the finiteness of the electron transit time through the interaction region.