A. V. Tyunkov

Generation of metal ions in the beam plasma produced by a forevacuum-pressure electron beam source

We report on the production of metal ions of magnesium and zinc in the beam plasma formed by a forevacuum-pressure electron source. Magnesium and zinc vapor were generated by electron beam evaporation from a crucible and subsequently ionized by electron impact from the e-beam itself. Both gaseous and metallic plasmas were separately produced and characterized using a modified RGA-100 quadrupole mass-spectrometer. The fractional composition of metal isotopes in the plasma corresponds to their fractional natural abundance.

Electron beam evaporation of boron at forevacuum pressures for plasma-assisted deposition of boron-containing coatings

We describe the use of a plasma-cathode electron source for electron beam evaporation of boron at forevacuum pressures (∼10 Pa) with subsequent deposition of boron-containing coatings on a titanium substrate. We analyze the process of electron beam heating and evaporation of boron, study the mass-to-charge composition of the gas and boron beam-produced plasma, apply such plasma for coating deposition, and investigate the elemental composition of the deposited film and its microhardness.

Modified quadrupole mass analyzer RGA-100 for beam plasma research in forevacuum pressure range

The industrial quadrupole RGA-100 residual gas analyzer was modified for the research of electron beam-generated plasma at forevacuum pressure range. The standard ionizer of the RGA-100 was replaced by three electrode extracting unit. We made the optimization of operation parameters in order to provide the maximum values of measured currents of any ion species. The modified analyzer was successfully tested with beam plasma of argon, nitrogen, oxygen, and hydrocarbons.

Deposition of dielectric films on silicon using a fore-vacuum plasma electron source

We describe an experiment on the use of a fore-vacuum-pressure, plasma-cathode, electron beam source with current up to 100 mA and beam energy up to 15 keV for deposition of Mg and Al oxide films on Si substrates in an oxygen atmosphere at a pressure of 10 Pa. The metals (Al and Mg) were evaporated and ionized using the electron beam with the formation of a gas-metal beam-plasma. The plasma was deposited on the surface of Si substrates. The elemental composition of the deposited films was analyzed.

Inverse time-of-flight spectrometer for beam plasma research

The paper describes the design and principle of operation of an inverse time-of-flight spectrometer for research in the plasma produced by an electron beam in the forevacuum pressure range (5-20 Pa). In the spectrometer, the deflecting plates as well as the drift tube and the primary ion beam measuring system are at high potential with respect to ground. This provides the possibility to measure the mass-charge constitution of the plasma created by a continuous electron beam with a current of up to 300 mA and electron energy of up to 20 keV at forevacuum pressures in the chamber placed at ground potential. Research results on the mass-charge state of the beam plasma are presented and analyzed.

Improved plasma uniformity in a discharge system with electron injection.

We present the results of experiments leading to improvement in bulk plasma uniformity of a constricted-arc discharge system with electron injection. The steady-state discharge was in argon, at a gas pressure of 0.5 mTorr, and operated with a main discharge voltage between 20 and 100 V and current between 3 and 15 A. The radial plasma distribution was measured with a movable Langmuir probe. We find that geometric modification of the intermediate electrode exit aperture and the main discharge cathode add little to the plasma uniformity. Improved bulk plasma uniformity is observed when a special distributing grid electrode is used and the main discharge voltage is less than 20-30 V. The application of a weakly divergent magnetic field in the region of the intermediate electrode exit aperture decreases the plasma nonuniformity from 20% to 14% over a radial distance of 30 cm. The plasma uniformity was further improved by compensating the magnetic self-field of the injected electron beam by a reverse magnetic field produced with a special electrode compensator. It is shown that an increase in discharge current causes a proportional increase in back current in the distributing electrode. The approach allows a decrease in plasma nonuniformity from 20% to 13% over a radial distance of 30 cm.

Low-energy plasma-cathode electron gun with a perforated emission electrode

We describe research of influence of the geometric parameters of perforated electrode on emission parameters of a plasma cathode electron gun generating continuous electron beams at gas pressure 5–6 Pa. It is shown, that the emission current increases with increasing the hole diameters and decreasing the thickness of the perforated emission electrode. Plasma-cathode gun with perforated electron can provide electron extraction with an efficiency of up to 72 %. It is shown, that the current–voltage characteristic of the electron gun with a perforated emission electrode differs from that of similar guns with fine mesh grid electrode. The plasma-cathode electron gun with perforated emission electrode is used for electron beam welding and sintering.

Synthesis of the boron-based coating in beam plasma using fore-vacuum electron source

Article presents the experimental results on deposition of boron-containing coating on titanium substrate by the novel method of reactive electron-beam evaporation of nonmetallic target at fore-vacuum pressures. The synthesis of the coating was made from the plasma produced by electron beam in fore-vacuum (1-10 Pa) pressure range, during evaporation of boron target followed by ionization of boron particles by the same electron beam. Analysis of the deposited coating show that the microhardness of the titanium sample increases significantly (up to 8 times) after deposition of the boron-containing coating. Results of the surface profile analysis demonstrate the decrease in surface roughness as a result of the deposition of the boron-containing film. These results, together with a high deposition rate (about 1 micron per minute), show the high efficiency of the reactive electron beam method of coating deposition during the evaporation of nonmetallic targets at the fore-vacuum pressures.

Electron beam deposition of ceramic coatings at fore-vacuum pressure

We have described a method for the deposition of ceramic coatings in which the electron beam formed by a plasma-cathode e-beam source operating at fore-vacuum pressure is used for evaporation of ceramic target material. Homogeneous nonporous alumina coatings were formed as a result of e-beam evaporation of an insulating alumina target; the coating thickness can be controlled by varying the process time and/or the beam power. Important advantages of such approach are that because of the inherent charge neutralization of the non-conducting e-beam target via low energy positive ions formed in the beam plasma, there is essentially no limit to the delivered electron beam power, and, because of the use of a plasma-cathode electron beam source, the system is compatible with quite modest vacuum such as provided by mechanical pumping only.

Sterilization of dielectric containers using a fore-vacuum pressure plasma-cathode electron source

We describe our work on sterilization of 10 ml glass and 60 ml plastic cylindrical containers using a fore-vacuum pressure, plasma-cathode, electron beam source. Beam plasma is formed inside the vessel by injection of a low-energy electron beam at 3 - 6 keV energy and current of 50 mA, at a working gas (air) pressure of 8 Pa. The gas composition was tracked by a quadrupole gas analyzer type RGA-100. As a test biological object for sterilization we used E. coli ATCC 25922 bacteria, the inner surface of each vessel was inoculated with a bacterial suspension. We find a smooth dependence of the degree of sterilization on the total energy density injected into the vessel. The efficacy of sterilization of container inner surfaces using a fore-vacuum pressure, plasma-cathode e-beam source of relatively low energy (a few keV) electrons is thus demonstrated.