Electromagnetic simulation of a 32-GHz, TE/sub 021/ gyrotron

A simulation study with experimental parameters of a 32-GHz gyrotron operating in the TE/sub 021/ mode is presented. Beam electrons with typical energy of 40 keV and transverse-to-axial velocity ratio ranging from /spl alpha/=0.8 to /spl alpha/=2.0 are injected into the cavity to drive electromagnetic oscillations from noise. On the basis of an electromagnetic particle-in-cell (PIC) code, a parameterization study is carried out to determine the dependence of output power upon pitch ratio and beam current. A comparison of the PIC simulation results with the predictions of the fixed-field approximation on considering Gaussian and asymmetric profiles has indicated close agreement between field parameters and conversion efficiency corresponding to both approaches.