Investigation of ultrawideband pulses in wideband helix traveling wave tubes: Theory and simulation

Summary form only given. The study of pulse propagation and distortion in traveling wave tubes (TWTs) has many applications. First, it is an attractive "diagnostic method" to characterize important properties such as dispersion and nonlinear distortion over a broad frequency band.. Second, it is relevant to assessing the utility of TWTs as amplifiers for impulse radio, impulse radar, or other ultrawideband signal applications. We present initial results of new models for analysis and numerical simulation of transient TWT excitation. The analysis applies a 1D linear model to examine pulse propagation in a TWT, including beam loading, frequency-dependent gain, circuit dispersion and space charge effects. Nonlinear effects are investigated using a 1D dispersive time domain numerical particle-in-cell simulation. A novel method of incorporating the helix waveguide dispersion into a 1D telegrapher-like equation will be presented. Progress and plans for experimental investigations on the XWING tube will be discussed. The XWING (eXperimental WIsconsin Northrop Grumman) tube is a Northrop-Grumman custom modified wideband (2-6 GHz) traveling wave tube, which allows access to the wave as it propagates along the tube as well as access to the spent beam.