Probe Measurements in Tubular Plasma Source for Plasma Relativistic Microwave Amplifier

The results are presented from the probe measurements of plasma parameters in the tubular plasma source used in research on plasma relativistic microwave electronics. Tubular plasma is produced as a result of background gas ionization by the electron beam emitted by the annular heated tungsten cathode in the axial magnetic field. The current–voltage characteristics of the probe were obtained for three discharge currents of 5, 9, and 20 A at three plasma column lengths of 10, 20, and 30 cm. It was shown that for all discharge currents and for all plasma column lengths, the electron temperature is equal to 20 eV at the time of performing measurements. It is also shown that in this source, the plasma density does not depend on the plasma column length in the lengths range from 10 to 30 cm. It was demonstrated that the discharge current is a linear function of the probe current, which makes it possible to control the relative changes in the plasma density during the experiment. For different discharge currents, the absolute value of plasma density was estimated to be in the range of 1012–1013 cm–3.