Components design and optimization for gyro-TWAs

Presented in this paper are the studies from a series of computer simulations, using CST (Microwave Studio), of waveguide components used in the operation of a gyro-TWA (gyrotron-travelling wave amplifier), operating in the Ka-band (26-40 GHz) frequency range. From these studies results including S-parameters, phase data and field structure have been obtained. It was found that each component had a range of operation that could be optimised through observations of the S-parameters and the phase data, while altering geometric parameters produced in the simulations. Simulations have been performed to predict the individual components of this gyro-TWA tube such as the input coupler and polariser. This would allow optimum performance for a possible future gyro-TWA, operating at the Ka-band frequency range. This investigation has been extended to take advantage of the full suite of modelling options within the Microwave Studio simulation package. Microwave Studio is a specialized tool for the fast and accurate 3D electromagnetic simulation of high frequency problems, along with a broad application range. S-parameters have been calculated for a range of circular polarisers, sever designs and helically corrugated waveguide tapers. A significant improvement in amplifier stability margin can be achieved by the inclusion of an optimised sever.