Development of simple nonlinear analysis code for helix traveling wave tube (SINCOHET)

Summary form only given. Formulations of nonlinear analysis in the frequency domain are basically the solutions of circuit and electronic equations in the nonlinear domain. In this study, a stationary 1D nonlinear code based on the Lagrangian disk model is developed on the basis of a simple set of analytical expressions to study nonlinear dynamics in the helix slow-wave structure used in a traveling wave tube. Analytical solutions of the electronic equation and circuit equation are developed to establish a set of simple expressions for developing a simple 1D nonlinear code, "SINCOHET", without using a numerical method at any stage. SINCOHET can handle a multi-section structure which has different dispersion, interaction impedance, loss, and pitch. The loss profiles used in the actual device are modeled as steps to consider, namely, center (Gaussian) and tip (triangular: increasing or decreasing). AC space charge effects are considered using the plasma reduction factor through the cylindrical capacitor regime. Potential depression due to the DC space charge effect is also considered. It can also consider backward waves arising due to reflections, as reflection coefficients are introduced. Results from the present simple code are compared with those from other numerical works such as LMSuite and PIC code, and found to be in good agreement.