Cerenkov generators with overmoded one-sectional slow-wave structures

Summary form only given, as follows. Results of investigations of physical processes of interaction of a high-current electron beam and, field of overmoded one-sectional slow-wave structures (SWS) in a three-centimeter wavelength range are presented. A 3D computer code, MULTIWAVES 5.2, based on the previously developed electromagnetic linear theory of Cerenkov devices has been developed for this purpose. Dispersion diagrams of electron (including the space charge waves, cyclotron and synchronous ones) and electromagnetic waves, transmission and reflection coefficients, starting currents of symmetric and non-symmetric modes can be calculated by means of this code. Interaction of longitudinal symmetric modes with a hollow electron beam is investigated by means of a nonlinear time-domain hybrid code. The analysis of Cerenkov generators with the beam current of 10 kA formed at the diode voltage of 500 kV has been made by means of the linear code. It has been shown that depending on the beam radius, the BWO-TWT or TWT-BWO generation regimes were realized. The starting parameters for the modes TM01 and HE11 have been calculated. It has been shown that the selection of the operating mode TM01 was possible due to the beam radius variation. The influence of cyclotron absorption of the TM0m-modes (m=1-4) on the generator starting current has been studied. The generation efficiency has been calculated by means of a nonlinear code. The dependence of the generation efficiency on the SWS length has maximum. It has been shown that in the radiated power the TM01-mode was up to 90% of the total power. Numerical simulation results are compared with the experimental ones.