Experimental Study of a Four-Cascade Gyrotwistron Operating in Maximum Efficiency Mode

Abstract

We propose, basing on the results of earlier works, to minimize the length of the drift section between the last intermediate cavity and the output section under the simultaneous condition of the absence of coupling between them, in order to expand the gain band of a multi-stage gyrotwystron in the region of high electron beam currents, which is most important for powerful gyro-resonance devices. The predicted possibility was confirmed in the process of studying experimentally a fourstage gyrotwystron operating in the maximum efficiency regime, i.e., with the length of the third drift section significantly shorter than the lengths of the first and second drift sections. In a gyrotwystron with the operating TE₀₁ mode at a frequency of 9.25 GHz, the accelerating voltage U₀ = 16 kV, and the electron beam current I₀ = 3. A, a gain bandwidth of 1.8% at half the output radiation power level with an efficiency of 28% and a gain of 26 dB was achieved. The measured values of the bandwidth and efficiency significantly exceed the values (1% and 21%, respectively) achieved at a beam current of 3.0 A in a three-stage gyrotwystron operated in the maximum gain regime, i.e., with the length of the first drift section approximately equal to the length of the second drift section.