Alexander A. Bogdashov

The paper presents the results of the first experiments on the investigation of an inverted gyrotron or a gyrotron rectifier, a device which, unlike a conventional gyrotron, converts incident microwave power into direct current (DC) power. In the experiment, by means of cyclotron-resonance interaction with a thin solid initially rectilinear 8.4 keV/0.54 A electron beam, microwave radiation at a frequency of about 34 GHz with a power of 13 kW is converted by it into a power of 15 kW of a 70-μs pulse current that flows through a 51.4 kΩ resistor connecting the device collector to ground. The achieved efficiency of microwave-to-DC power conversion, taking into account the power to drive the electron beam, is 80%.

The effect of passive mode locking is observed experimentally in a Ka-band helical-waveguide gyro-BWO equipped with a delayed feedback loop containing a saturable cyclotron-resonance absorber. Generation of periodic trains of 1.4-ns electromagnetic pulses with a repetition of 5.3 ns is obtained. The peak power of the pulses is three times higher than the average level of the radiation power.

The design and results of the first hot-test experiment on a gyrotron backward-wave oscillator (gyro-BWO) using a newly proposed microwave circuit are presented. The gyro-BWO employs an interaction circuit based on a quasi-optical transmission line that directs a Gaussian wave beam along a zigzag path with vertical and oblique segments periodically spaced along the longitudinal axis. A resonant cyclotron beam-wave interaction occurs in the regions where the beam intersects the wave perpendicularly, resulting in low sensitivity to particle velocity spread, similar to that of a gyrotron. The device was hot-tested in a continuous wave (CW) mode, generating microwave radiation in the form of a Gaussian beam with powers of 0.2-1.2 kW and frequencies in the 90-195 GHz range. 15 bands were measured, within which the generation frequency linearly and continuously changed as the magnetic field or accelerating voltage were varied. Due to the unique dispersion properties of the zigzag gyro-BWO, these bands cover the entire operating range with a fill-factor of approximately 70%. This is significantly greater than that of any other experimentally tested gyrotron-type device.

Fokin A.P., Ananicheva S.A., Bogdashov A.A., Gitlin M.S., Gashturi A.P., Luchinin A.G., Orlovskiy A.A., Tsvetkov A.I., Glyavin M.Yu.//2023

An overview of the main principles of operation and design for major components of the gyrotron travelling-wave tube (gyro-TWT) based on a helically corrugated waveguide is presented.