Mode competition in a gyrotron with tapered external magnetic field

A general method is developed for the analysis of mode competition in a gyrotron with tapered external magnetic field. Exploratory calculations show strong dependence of the operating regime of a gyrotron on tapering of the magnetic held. Detailed results are presented for the gyrotron operating at the Kernforschungs-zentrum Karlsruhe with frequency 150 GHz in the TE03 mode