A Simple Electromagnetic Analysis for Ohmic Quality Factor and RF Efficiency for 42 GHz, TE03-mode, Feebly Tapered Gyrotron Cavity

In the present paper, an electromagnetic method has been presented to calculate the ohmic quality factor of feebly tapered cavity of a 42 GHz, TE₀₃-mode gyrotron. The method has been started by dividing the input- and output-taper sections of cavity into numbers of non-tapered circular cells to present a model cavity akin to real one. Further, the ohmic quality factor of tapered cavity has been expressed as a summation of terms, each containing ohmic quality factor of a cell of model cavity. The effect of input- and output-taper angles on ohmic quality factor for a feebly tapered gyrotron cavity has been studied. Further, the values of ohmic quality factor, calculated in the present paper, have been substituted into the expression of RF efficiency, and correspondingly, the decrease of RF efficiency with increase of diffractive quality factor has been observed. It has been found that both the ohmic quality factor and RF efficiency increase with decrease of input-taper angle and with increase of output-taper angle. Out of two taper angles, the output-taper angle was found more sensitive controlling parameter for the ohmic quality factor and hence frequency selectivity as well as ohmic heating in a feebly tapered gyrotron cavity. Also, the output-taper angle has been found a more suitable parameter in tailoring the RF efficiency.