Analysis of a low magnetic field TEm11gyroklystron amplifier†

Large- and small-signal numerical calculations are presented for a two-cavity, low magnetic field gyroklystron amplifier operating in the TE m11 whispering-gallery mode. The gyroklystron system modelled consists of a bunching cavity and an output cavity separated by a drift tube. For operation of both cavities at TE511, gain and emission efficiency are studied for a high energy (γ = 1·6), low axial velocity (βVerbar; = 0·1) electron beam. Prebunching prior to the output cavity in the gyroklystron leads to an increase of the maximum efficiency by more than a factor of two over that obtained from operating the output cavity as an oscillator. Model calculations are presented which show that magnetic field tapering greatly reduces the effects of any initial axial velocity spread in the electron beam, allowing high gain (≳40 dB) and high efficiency (25-30%) to be achieved.