Simulation of TWTs and twystrodes

Summary form only given, as follows. Results from simulations of the FEA twystrode using both 2-D PIC and 1-D mode-analysis methods will be presented. Efficiency, bandwidth, and gain performance are charted for varying helix pitch taper, helix length, beam current and beam voltage. FEA twystrode performance, especially harmonic content, is also charted for variations of input modulation amplitude. Efficiency enhancement for various collector configurations is also investigated. The simulations are based upon state-of-the-art FEA parameters, and realistic PPM magnetic fields. Several advances in the simulation state-of-the-art are also reported. A successful approach to the treatment of vanes in helix TWTs has been developed. Precise modeling of attenuators is now commonplace. A new "splitter" diagnostic for the 2-D PIC code MAGIC has been developed, which can separate the Poynting power flow into forward and backward directional flow, and also into the various frequency components. The latter capability has been demonstrated as a powerful tool for the investigation of intermodulation in multi-tone helix TWT amplifiers.