Tapered Cavity Measurement for 42-GHz, 200-kW Gyrotron

The 42-GHz gyrotron cavity had three sections in its final design: down-taper section, up-taper section, and uniform middle section. The design of the cavity depends on the RF mode and desired power growth. The finalized design parameters of down-taper and up-taper angles are 2° and 3°, respectively, with respect to the middle section of gyrotron cavity. This cavity consists of these poorly tapered sections at both the ends of midsection. The combination of all three sections results into a complex cavity structure which is complicated and challenging to fabricate. An additional challenge in fabrication is to achieve desired designed parameters. Therefore, design realization through fabrication clearly needs dimensional measurement. The dimensional parameters of cavities such as down-and up-taper angles, uniform section diameter, taper lengths, and surface roughness measurement have their own significance and importance. This paper presents the destructive and the nondestructive methods to measure the dimensional parameters of a complex cavity structure. Further, a computational analysis is also done to represent the comparisons between the design and measured values in terms of ohmic quality factor and efficiency and reported the effects of geometrical changes.