Large Signal Field Analysis of an O-Type Travelling Wave Amplifier using a Tape-Helix Model for the Slow- Wave Circuit

To develop a large –signal field theory of a TWT amplifier using a tape-helix model for the slow- wave circuit. This theory, is expected to form the basis for an efficient TWT design code.

The large- signal field theory of an O-type travelling wave amplifier developed in for the sheath- helix model is proposed to be generalized to the present case of a tape helix.

The large signal field theory of a TWT amplifier, expounded in, is based on a coupled Eulerian-Lagrangian formulation, that is, the boundary value problem for the Maxwell’s equations is formulated in Eulerian coordinates whereas the electron ballistic equations are formulated in Lagrangian coordinates. The key step in the solution procedure was a representation of the electromagnetic field components as nonlinear functionals of the electron- arrival time through a sequence of Green’s functions for the slow- wave circuit. Substitution of this functional representation for the axial electric field component into the electron ballistic equation made it possible to recast the latter into the fixed-point format for a nonlinear operator in a suitable function space. The fixed point, and therefore the solution for the electron- arrival time, and hence the solution for the electromagnetic fields could be obtained by the method of successive substitutions. Numerical computation of the amplifier parameters could then be readily carried out once the solution for the field vector was available.