Low-frequency parasitic oscillatons

in the 74.2 GHz moderate-power pulse gyrotron

D.V. Kas’yanenko1, O.I. Louksha1, B. Piosczyk2, G.G. Sominski1,

M. Thumm2

1 Saint-Petersburg State Polytechnical University, St.-Petersburg, Russia

2 Forschungszentrum Karlsruhe, Karlsruhe, Germany

Low-frequency (f = 10…200 MHz) parasitic oscillations remain one of the factors preventing achievement of high efficiency in gyro-devices. A 74.2 GHz, TE12,3 experimental gyrotron has been designed and manufactured in Saint-Petersburg State Polytechnical University specially to investigate influence of low-frequency oscillations on gyrotron performance and possible ways of their suppression. The gyrotron operates with a room-temperature pulse solenoid in singe-pulse 10…100 m s regime with output microwave power up to 100 kW.

In the paper, results of experiments with this tube are presented. Amplitude-frequency characteristics of the oscillations were determined in a wide range of values of magnetic field, accelerating voltage, beam current and magnetic compression ratio. The obtained experimental data are compared with results of numerical simulation of space-charge dynamics in the gyrotron trap and with results of investigations performed in gyrotron-type electron-optical systems without resonator. Possible effects of external circuit and of high-intensity microwave fields penetrating from the gyrotron resonator on spectrum of the parasitic low-frequency oscillations are discussed.

This work was supported by Forschungszentrum Karlsruhe (Germany) and Russian Foundation for Basic Research (grant N 01-02-17081).