Denis K. Ulyanov

Influence of the electrons reflected from the collector on the parameters of a high-current relativistic electron beam

In plasma microwave oscillators, electrons fall onto the surface of a graphite collector, which leads to the generation of secondary electrons. The influence of the electrons reflected from the collector on the parameters of a high-current relativistic electron beam propagating in a strong longitudinal magnetic field was studied experimentally and by numerical simulations. It is shown that the penetration of the reflected electrons into the drift space can lead to a substantial increase in the depth of the potential well in the drift space, a decrease in the velocity of the beam electrons, and a broadening of the electron energy distribution function.

Visualization of the microwave beam generated by a plasma relativistic microwave amplifier

A method based on the detection of emission of a dielectric screen with metal microinclusions in open air is applied to visualize the transverse structure of a high-power microwave beam. In contrast to other visualization techniques, the results obtained in this work provide qualitative information not only on the electric field strength, but also on the structure of electric field lines in the microwave beam cross section. The interpretation of the results obtained with this method is confirmed by numerical simulations of the structure of electric field lines in the microwave beam cross section by means of the CARAT code.

A calorimetric spectrometer measuring single pulses of relativistic microwave generators

A calorimetric spectrometer measuring individual pulses radiated by wideband relativistic microwave oscillators is described. The calorimetric spectrometer comprises two calorimeters and a set of low-pass filters. In the development of such a spectrometer, the basic feature consists in the high radiation power (∼108 W) and low pulse energy (∼1 J). To prevent the microwave surface discharge, the calorimeters have a rather large area (∼0.1 m2). The calorimeters’ sensitivity is 0.05 J. Frequency responses of the filters were measured experimentally and calculated with the help of a three-dimensional version of the KARAT computer code. The experimental spectrum of a wideband relativistic microwave plasma oscillator measured in a frequency range of 5–40 GHz is presented.

Calorimetric spectrometer for measuring single microwave pulses in relativistic microwave electronics devices

Broadband plasma relativistic microwave oscillators fabricated at the General Physics Institute of the Russian Academy of Sciences have the following output parameters: microwaves are generated in a frequency band on the order of the mean frequency, the output power is -100 MW, the mean microwave frequency is 10-20 GHz, the duration of a single pulse is 20-800 ns, and the diameter of the emitting horn window is no less than 15 cm (because of the possible microwave breakdown). The spectrum of high-power broadband emission from the plasma in the course of a REB-plasma interaction was studied in experiments in a number of experiments but accuracy of measurement has been low. The authors describe a calorimetric spectrometer that has very high accuracy. The main advantage of the spectrometer is that it can measure the spectrum of the total microwave energy flux in absolute units, while the spectrometers used previously were capable of measuring only a small fraction of the total energy flux. The spectrum of the total energy flux from oscillators is the fundamental characteristic calculated theoretically and used to estimate the possible applications.

Measurement of spectrum and power of microwave radiation from relativistic plasma microwave oscillator

Experimentally studied microwave radiation from plasma waveguide when relativistic electron beam (600 keV, 2 divided by 4 kA, 100 ns) propagate axially the plasma waveguide. Spectrum of microwave radiation was measured by multi resonator spectrometer power was measured by broadband calorimeter. The calorimeter measured the total microwave energy emitted from output horn. Emitting microwave power strongly depended on plasma density, interaction length and gap between annular tube beam and annular tube plasma column. Spectrum of radiation was approximately 50%.