TWT simulation, GATOR and collector optimization for the Hughes 8815HR TWT

Summary form only given. In this paper, we present the results of our effort to validate GATOR as a reliable code for predicting TWT behavior; in particular, we present the results of our GATOR model for the Hughes 8815KR TWT and compare those results to experimental measurement and to simulations performed using Qhelix, Hughes´ proprietary TWT code. The predictions from the 8815HR Gator model agree well with measured values. RF output power and phase shift agree to within 0.5 dB and 2 degrees, respectively, over a range of RF input powers from saturation-20 dB to saturation. This agreement is maintained over a 10% frequency bandwidth and at three distinct cathode voltage-current operating points that cover a 2 dB range in saturated RF output power. We also present GATOR´s predictions for the spent-beam energy and momentum distribution, compare those to measured data, discuss how parametric variations affect those distributions, and how those distributions affect collector design.