Modleing of drive induced oscillations: Capabilities and limitations

Drive Induced Oscillations (DIO) manifest themselves as spurious oscillations at frequencies close to the edges of pass-band of periodic structure in vacuum electronic devices operating in the large signal regime. DIO in coupled cavity TWTs (CC-TWTs) is most known effect and it has been extensively studied experimentally¹ since it is the major limiting factor of achievable power of wide band CC-TWTs. However, DIO appearance is not limited to CC-TWTs. Modeling of DIO both numerically and analytically is challenging problem due to strong non-linear electron beam bunching and severely different built-up times for processes at operating and DIO frequencies². We are presenting a new multi-frequency hybrid approach to DIO modeling implemented in 2D design code TESLA-CC³ and discussing advantages and limitations of this approach. The comparison between simulated and measured¹ onsets of DIO in CC-TWTs shows very promising agreement.