V. A. Burdovitsin

On the possibility of electron-beam processing of dielectrics using a forevacuum plasma electron source

An insulated target was irradiated by an electron beam generated by a forevacuum plasma electron source operating in the pressure range of 5–15 Pa. Measurements of the target potential showed that plasma formed in the region of electron beam transport ensured the almost complete neutralization of charge accumulated on the target. This effect results in the possibility of direct electron-beam processing of nonconducting materials, including the melting and welding of ceramics.

Current status of plasma emission electronics: II. Hardware

This paper is devoted to the engineering embodiment of the modern methods for producing charged ion and electron beams by extracting them from the plasma of a discharge. Electron beams use to execute electron-beam welding, annealing, and surface heating of materials and to realize plasmochemical reactions stimulated by fast electrons. Ion beams allow realization of technologies of ion implantation or ion-assisted deposition of coatings thereby opening new prospects for the creation of compounds and alloys by the method that makes it possible to obtain desired parameters and functional properties of the surface. A detailed description is given to the performance and design of devices producing beams of this type: the ion and electron sources being developed at the laboratory of plasma sources of the Institute of High-Current Electronics of the Russian Academy of Sciences and the laboratory of plasma electronics of Tomsk State University of Control Systems and Radioelectronics.

Electron beam treatment of non-conducting materials by a fore-pump-pressure plasma-cathode electron beam source

In the irradiation of an insulated target by an electron beam produced by a plasma-cathode electron beam source operating in the fore-vacuum pressure range (5‐15 Pa), the target potential is much lower than the electron beam energy, offering the possibility of direct electron treatment of insulating materials. It is found that in the electron beam irradiation of a non-conducting target in a moderately high pressure range, the electron charge on the target surface is neutralized mainly by ions from a volume discharge established between the negatively charged target surface and the grounded walls of the vacuum chamber. This allows the possibility of direct electron beam treatment (heating, melting, welding) of ceramics and other non-conducting and semiconductor materials.

A forevacuum pulse arc-discharge-based plasma electron source

An arc-discharge-based electron source is described, which is designed for forming a pulsed wideaperture electron beam in the forevacuum pressure range (4–15 Pa). At an accelerating voltage of 12 kV, a current of 80 A was extracted from the emitting surface with an area of 80 cm2 in the submillisecond range of pulse durations. The current density distribution over the beam cross section is close to a Gaussian function, and the surface-averaged beam energy density in a pulse reached 10 J/cm2.

Surface structure of alumina ceramics during irradiation by a pulsed electron beam

The structural transformations that occur in the near-surface layer in alumina ceramics during irradiation by a pulsed electron beam generated by a forevacuum plasma electron source are studied. The modification of the surface properties of the ceramics is shown to be caused by the formation of regions consisting of close-packed and identically oriented crystallites within every grain. The crystallites are elongated: their length and width are 0.5–1.5 μm and the transverse size is 0.1–0.2 μm.

Formation of narrow-focused electron beams generated by a source with a plasma cathode in the forevacuum pressure range

Results are presented from experimental studies of the formation of focused electron beams produced by extracting electrons from the plasma of a steady-state discharge with a hollow cathode in the forevacuum pressure range. Based on the measurements of the energy spectrum and diameter of the electron beam, as well as of the emission parameters of the plasma produced in the course of beam-gas interaction, a conclusion is drawn about the excitation of a beam-plasma discharge that deteriorates the beam focusing conditions. The threshold beam current density for the excitation of a beam-plasma discharge is found to increase with accelerating voltage and gas pressure.

Behavior of an arc discharge in a forevacuum plasma source of electrons

The parameters and characteristics of a pulsed arc discharge with a cathode spot used in a forevacuum plasma source of electrons are investigated. It is shown that the accelerating voltage influences arc initiation to a lesser extent compared with an electron source based on a hollow-cathode glow discharge. At forevacuum pressures, two stages of the arc discharge may arise within the current pulse. At the beginning of the pulse (first stage), the arcing voltage is high and the fraction of residual gas ions in the plasma is significant. At the second stage, the arcing voltage drops and ions of the cathode material dominate in the plasma. The duration of the first stage grows with rising gas pressure and decreasing arc current.

Generating stationary electron beams by a forevacuum plasma source at pressures up to 100 Pa

It is shown that, as the gas pressure in a forevacuum plasma electron source increases, electric breakdown in the accelerating gap is caused by the reverse flow of ions from plasma that is generated by both the electron beam and high-voltage glow discharge (HGD). By modifying the electrode system geometry in the accelerating gap of the electron source, it is possible to provide for a two-to threefold decrease in the HGD current. This allows the upper pressure in the electron source to be increased up to about 100 Pa when air is used as the working gas and up to 160 Pa in the source filled with helium.

Charge compensation in an insulated target bombarded by a pulsed electron beam in the forevacuum pressure range

We report on the results of computation of the time dependence of the ion flux and the dielectric target potential at the initial stage of bombardment by an electron beam in forevacuum. It is shown that a satisfactory agreement with experimental data is attained with allowance for the possibility of the discharge between the target and the earthed walls of the vacuum chamber.

Potential of a dielectric target during its irradiation by a pulsed electron beam in the forevacuum pressure range

The potential induced on the surface of a nonconducting ceramic during irradiation by an electron beam in the forevacuum pressure range (5–15 Pa) remains negative, but its absolute value is much smaller than the energy of accelerated electrons. The factors affecting the negative potential of a nonconducting ceramic target are determined. The evolution of the charge injected in the ceramic is analyzed by a numerical simulation.