Modeling Oscillations in TWTs by Using the Tesla-Family of 2D Large-Signal Codes

As a rule, codes that operate in the time domain, such as Particle in Cell (PIC) codes, are a more natural choice as a tool to explore the stability of beam-driven devices. However, the extensive computer resources required for PIC simulation as compared with those needed for hybrid codes such as TESLA
¹
, motivate the development presented here. We report recent advances in the development of the TESLAfamily of 2D large-signal codes (such as TESLA-FW
²
or TESLA-Z
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, for example), with a focus on algorithms to model self-oscillations in TWT amplifiers. The TESLA codes operate essentially in the frequency domain, making it a challenge to find unstable modes without prior knowledge of their frequency.