Excitation of Regular and Stochastic Oscillations in a Coaxial Gyro-BWO

Theoretical studies of backward wave excitation in the coaxial tube using a resonance normal Doppler effect of an electron beam with a backward wave of waveguide (gyro-BWO) is carried out. The linear theory of excitation is built. Dependence of values of starting currents of oscillation versus length of the coaxial waveguide, energy of an electron beam, value of a constant magnetic field and ratio of initial transverse momentum of a beam to initial longitudinal momentum is found. Numerical simulation of a nonlinear regime of oscillation is carried out. Thresholds values of currents of an electron beam ensuring steady oscillation, the automodulation regime and stochastic regime are obtained. Dependences of efficiency from time at output of the generator and a spectrum of output signal power are given. For increasing of efficiency it is offered to use magnetic field profiled along an axis of a waveguide. It is shown, that the use of a magnetic field increasing by linear law allows increasing efficiency by 50 %.