Finite bandwidth and space charge effects in the MUSE model

Summary form only given. We have recently developed a new one-dimensional nonlinear model of a Traveling Wave Tube (TWT) being driven by an input signal with multiple frequencies. The MUltifrequency Spectral Eulerian (MUSE) model is ideally suited to predict the pre-saturation evolution of drive, harmonic, and intermodulation frequencies when there are many closely-spaced drive frequencies. The primary benefits of MUSE include reduced computation time for dense input spectra and enhanced analytic tractability over the conventional "disk" model. Since MUSE uses an Eulerian description of the electron beam it can not predict saturation accurately. However, the model is of practical use since TWTs are often driven with backed off input levels during multifrequency excitation so that they do not saturate. The first formulation of MUSE did not incorporate a frequency dependent cold circuit phase velocity, frequency dependent interaction impedance, or beam space charge. In this paper we present an enhanced MUSE model that accounts for these physical effects. Several test cases are presented and compared with a disk model. Additionally, we discuss the foundation of the MUSE model and comment on some physical insights elucidated by the model.