Rigorous application of modal expansion method: an alternative way to more accurate gyrotron analysis

Accurate and numerically efficient computation of the excited electromagnetic field inside gyrotron cavities is a severe problem. Usually the analysis is simplified to a non-rigorous state. In particular, mode conversion is neglected. In this work, two different modal expansion methods are applied to a self-consistent analysis in frequency-domain as well as in time-domain. Accuracies and numerical efficiencies are compared. A numerical efficient implementation of a rigorous analysis is shown. Numerical results are compared to results from "classical" methods. The resulting analysis is discussed with respect to its applicability for a design procedure.