Design, Analysis, and Simulation of a Three-Stage Stagger-Tuned, Clustered-Buncher Cavity Gyroklystron Amplifier

Abstract

A self-consistent, nonlinear analysis of the three-stage clustered-cavity gyroklystron amplifier has been developed. The investigation has been applied to the previously reported 32.3-GHz, second harmonic, three-cavity conventional gyroklystron amplifier operating at the TE02 mode for its performance enhancement in terms of bandwidth. Using the clustered-cavity analysis, a peak RF output of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim $ </tex-math></inline-formula> 310 kW, electronic efficiency <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim $ </tex-math></inline-formula> 23%, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim $ </tex-math></inline-formula> 27-dB gain have been obtained at desired 32.3-GHz frequency. The clustered-cavity device bandwidth has been obtained as <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim $ </tex-math></inline-formula> 59.5 MHz, which is significantly much higher than the conventional-cavity case, i.e., <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim $ </tex-math></inline-formula> 36 MHz. It is observed from the analytical results that the clustered-cavity approach widens the bandwidth with a slight increase in the device gain and efficiency. Furthermore, the effect of stagger-tuning in the clustered cavities on the device performance has also been explained in detail. The results confirmed that the increase in the stagger-tuning parameter to 0.5 further increases the device bandwidth to 103 MHz but with a considerable decrease in the gain parameter. Hence, there should be a tradeoff between the gain and bandwidth in terms of the stagger-tuning parameter. The analytical results obtained are verified further by carrying out the particle in cell (PIC) simulation of the designed gyroklystron amplifier using the 3-D PIC simulation tool CST Particle Studio for different values of stagger-tuning parameters. The simulated results obtained agree with the analytical results within 10%.