Microwave production and beam transport in a multi-MW large-orbit, axis encircling, coaxial gyrotron oscillator

Abstract

Summary form only given, as follows. Large orbit, coaxial gyrotrons are currently under investigation with microwave power up to 40 MW. The electron beam is produced by MELBA (Michigan Electron Beam Accelerator) with the following parameters: 0.75-1.0 MV, 1-10 kA diode current, 0.2-1.5 kA tube current, 0.5-1.0 microsecond pulselength. The axis encircling electron beam is generated by a cusp magnetic field. Electron beam current transport through the magnetic cusp and through the microwave cavity are measured. The frequency of the fundamental coaxial mode, TE/sub 111/, is observed to be 2.34 GHz. A novel method of time-frequency analysis (TF) using reduced interference distributions is used to analyze heterodyne mixer data, TF analysis shows microwave frequency modulation with e-beam voltage modulation. Mode competition and mode hopping between TE/sub 111/ and TE/sub 112/ modes are also observed by TF analysis. Microwave cold test data are compared to operating modes of the gyrotron.