Nonlinear characterization and comparison with simulation of a high gain, broad band helix traveling wave tube

Summary form only given. Non-linear characterization of a 6-18 GHz, 50 dB TWT has begun. Experiment will be compared to simulation in an attempt to find and understand gain, saturation level and spectral content as characterized by input power, beam current, and input spectrum. To accomplish the experimental characterization of the tube, both total power and spectral output will be measured for various input powers, beam currents and input spectra. Heterodyning and random digital sampling methods will be used to measure the high frequency components. Gain and saturation levels can be determined from the power and spectral output data. Two models are used for the simulation, MAFIA and CHRISTINE. The eigenmode solver of the 3-D electrodynamic code MAFIA (solution of Maxwell´s equations by the Finite-Integration-Algorithm) was used to calculate the electromagnetic fields, interaction impedance, and phase velocity, over a representative section of the helix using quasi periodic boundaries. CHRISTINE is a 2-D TWT model, which simulates a helix TWT in the frequency domain.