Low-Frequency Parasitic Space-Charge Oscillations in the Helical Electron Beam of a Gyrotron

We developed a medium-power pulsed gyrotron equipped with diagnostic systems for studying low-frequency parasitic space-charge oscillations in the helical electron beam and the energy spectrum of electrons in the collector region. Methods for suppressing parasitic oscillations are proposed and tested. An explanation of the mechanism of suppression of these oscillations is given.     

Dynamic processes in helical electron beams in gyrotrons

The results of theoretical and experimental studies of collective processes in helical electron beams in gyrotron-type devices are generalized. Main attention is paid to low-frequency oscillations associated with the development of instability in the space charge trapped between the cathode and the magnetic mirror. The mechanism of evolution of instability is substantiated and the effect of oscillations on the main parameters of the electron flow determining its quality is analyzed. Data on the suppression of low-frequency oscillations and resulting enhancement of the gyrotron efficiency are considered.     

Trajectory Analysis in a Gyrotron Electron–Optical System with Allowance for the Cathode Surface Roughness

Radiophysics and Quantum Electronics - We propose a method for considering the spread of initial electron velocities caused by the roughness of the cathode surface while performing a...     

Improvement of the helical electron beam quality and the gyrotron efficiency by controlling the electric field distribution near a magnetron injection gun

A technique for controlling the electric field distribution near the cathode of a magnetron injection gun is developed. The feasibility of improving the quality of a helical electron beam by optimizing the electric field distribution in a pulsed 4-mm-wave gyrotron is studied theoretically and experimentally. Field distributions are obtained that minimize the electron velocity spread in the beam, coefficient of electron reflection from a magnetic mirror, and intensity of parasitic low-frequency oscillations. It is demonstrated that the gyrotron efficiency can be increased through a rise in the beam quality at the optimized electric field distribution.     

Simulation of Non-Uniform Electron Beams in the Gyrotron Electron-Optical System

Technical Physics - New calculated data on the effect of emission inhomogeneities on the quality of the electron beam, which is formed in an electron-optical system of a gyrotron, have been...     

Highly Efficient Gyrotron with Multi-Stage Recuperation of Residual Electron Energy

Technical Physics - The results of complex modeling of physical processes in a gyrotron of moderate power in the 4-mm wavelength range have been presented. Methods for improving the quality of the...     

Trajectory Analysis in a Collector with Multistage Energy Recovery for a DEMO Prototype Gyrotron. Part I. Idealized Magnetic Field Distribution

Technical Physics - This paper presents the results of simulation of the collector of a prototype gyrotron designed for the DEMO project. Trajectory analysis in a collector with four-stage recovery...     

Development of the method for determining the electron velocity in a gyrotron

We have analyzed the possibility of determining the electron velocity using the data on propagation of a microwave low-power signal in a slow-wave system located in the region of electron beam formation. The diagnostic section is designed for implementing this method in an experimental gyrotron with a working frequency of 74.2 GHz and an output power of 100 kW. Numerical simulation shows that information on the longitudinal velocity of electrons can be obtained from an analysis of the frequency dependence of the amplification factor for a signal propagating in the slow-wave system at frequencies in the gigahertz range.     

Suppression of parasitic space-charge oscillations in a gyrotron

We study the influence of nonuniform electric and magnetic fields in the helical-beam compression region on the low-frequency parasitic space-charge oscillations for a moderate-power (∼ 100 kW) 4-mm gyrotron. Suppression of the oscillations is achieved by optimization of both the cathode-unit geometry in the magnetron-injector gun and the magnetic-field distribution in the region near the cavity input. The obtained data are evidence of possible effective operation of the gyrotron at elevated pitch-factor values α > 1.5 even for emitters with no highest emission uniformity (δj_e ≈ 30%). __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 49, No. 10, pp. 880–886, October 2006.