Nonstationary oscillations of gyrotron backward wave oscillators

Summary form only given. The nonstationary oscillation of the gyrotron backward wave oscillator (gyro-BWO) was studied by the steady-state analysis and the time-dependent simulation. The steady-state analysis gives the equilibrium states of the gyro-BWO, which stabilities can be examined by the time-dependent simulation. Comparisons of the numerical results show that the gyro-BWO becomes nonstationary while the trailing field structure completely forms due to the dephasing energetic electrons. The radiated wave in the trailing field structure is backward propagating to interfere with the main internal feedback loop of the gyro-BWO. Therefore, the frequency discrepancy between the radiated wave from the trailing field structure and the oscillation in the contracted field structure causes the alternative appearance of the field contraction and expansion, which forms the nonstationary oscillation of the gyro-BWO. The frequency separation from the central resonant frequency of the gyro-BWO and sidebands is scaled with the field amplitude of the contracted field structure, which shows that the nonstationary oscillation of the gyro-BWO is essentially different from the self-modulation of the gyromonotron.