PIC-circuit hybrid model for coupled cavity traveling wave tubes

Summary form only given, as follows. A small/large signal couple-cavity traveling-wave tube (C-CTWT) PIC hybrid model is developed. The code is to determine the interaction between the electron beam and cavity both in the linear and nonlinear regime. A small signal multi-frequency TWT code can provide a description of the power spectrum produced by a low frequency modulated beam. A large signal multi-frequency TWT code is required to study the nonlinear mechanism responsible for mixing the low frequency modulation, for example, from ion noise with the high microwave frequency carrier signal. As the first step, the electron beam is modeled to be one-dimensional electrostatic with the radial behavior modeled using a space charge reduction factor. The electric field within the beam has components from both the space charge and the cavity field. The space charge field is solved by the method used in PDP1. The reduction due to the metallic boundary is also employed. The cavity field is calculated through the cavity equivalent circuit model (R, L, C mutual elements). Each cavity is modeled as a three-port equivalent Curnow circuit. Besides the input and output ports of the circuit, the circuit is coupled to the beam via a gap, the so-called beam port. The voltage across the beam port and the current through it are solved self-consistently.