Exploiting 2-1/2 D TWT simulations to maximize the efficiency of the Hughes 8815HR TWT

Summary form only given, as follows. Beam efficiency, the RF output power divided by the electron beam power, is a critical parameter for the commercial success of a traveling-wave tube (TWT). Over the past thirty years, TWT designs have consistently established higher efficiency levels by developing advanced design techniques for analyzing parametric changes to the electron gun, helix geometry, and especially, the electron-beam collector. Advanced TWT simulation codes have emerged in recent years that offer the capability to simulate the electron-RF interactions with enhanced dimensionality on desktop computers. The Naval Research Laboratory has developed one such code, known as GATOR and another was developed by the NASA Lewis Research Center. These codes track the electron beam in two spatial and three momenta coordinates, and provide the TWT designer with more information on the electron beam dynamics than has traditionally been available. In this paper, we present the results of our effort to design a collector for the Hughes 8815HR TWT based on the results of the 2-1/2 D simulations performed by GATOR and the NASA Lewis code. The simulation results will be compared to experimental measurements of the RF performance and the spent beam distribution. We also present experimental results of the performance comparisons between the old collector design and the new design based on the 2-1/2 D simulations.