Investigation of ultrawideband pulses in wideband helix traveling wave tubes

Summary form only given, as follows. 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 results of a new model for analysis and numerical simulation of transient TWT excitation. The analysis applies a 1D linear model to examine pulse propagation in a TWT, including dispersion, space charge effects, and attenuation. Nonlinear effects are investigated using a 1D numerical particle-in-cell simulation. Fields are calculated using the pseudo-spectral time-domain (PSTD) method with a modification to incorporate helix waveguide dispersion effects into a 1D model. Progress with 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, with multiple access ports that allow diagnostic access to the wave as it propagates along the tube.