Numerical simulations of gyro-amplifiers

Summary form only given. Numerical simulations of gyroklystron amplifiers using the newly developed MAGY code are presented. MAGY is a self-consistent, time dependent code which is based on the reduced description of the electromagnetic fields and the electron beam in a cylindrically symmetric waveguide with an arbitrary wall radius (including jump discontinuities). The fields are represented by the transverse electric and transverse magnetic modes which are coupled by the variations of the wall radius, and by the electron beam. The mode coupling due to radius variation is shown to depend on the logarithmic derivative of the wall radius as a function of the axial position. For a proper simulation of the mode coupling at a jump discontinuity the coupling matrices are replaced by those which are computed on the basis of the mode matching transformation matrices. The electron dynamics is described using the guiding center formulation of the relativistic equations of motion with an arbitrary profile of the axial magnetic field. As an example, we compare the numerical simulations with the results of the 35 GHz and 94 GHz gyro-amplifier experiments at NRL.