Drive induced oscillations in coupled cavity TWTs and opportunities for their control

Results of comprehensive modeling of drive induced oscillation (DIO) excitation in CC-TWTs are presented. For modeling of DIO onset the CC-TWT design code TESLA-CC has been extended to be capable of multi-frequency simulation. The results of TESLA-CC modeling of DIO onset are in reasonable agreement with the measurements. Different techniques for DIO prevention have been studied and compared. It was found that the DIO can be suppressed efficiently by magnetic lossy elements. The results of NRL measurements of magnetic losses in Ba hexaferrites at frequencies above 30 GHz and consequent 3D EM modeling of the coupled cavity structure properties are presented.