Experimental Observation of Chaotic Generation at 1.5% Spectral Width in a Gyrotron under Large Supercriticality Conditions

A complex chaotic dynamics in a gyrotron was experimentally observed under conditions of high supercriticality corresponding to 1000–1500-fold excess of the beam current parameter over the starting value. At electron beam currents typical of gyrotron test setups, this excess has been achieved by a transition to excitation of the lowest mode of a cylindrical waveguide. Chaotic generation regimes were observed in a 33 GHz frequency range with a spectral width of 500 MHz and record narrow relative width below 1.5% These results imply considerable progress in comparison to previous experiments with gyrotron type devices and are in good agreement with theoretical analysis based on a system of averaged evolution equations derived with allowance for finiteness of the transit time of electrons via the interaction space.