Forevacuum Pressure Research Articles

Effect of collector potential on the beam-plasma formed by a forevacuum-pressure plasma-cathode electron beam source

We consider the beam-plasma formed by an energetic electron beam at fore-vacuum pressure, when the beam is terminated by an electron collector plate. We show that in the pressure range of 1–10 Pa, the dependence of beam-plasma density n on the electron beam collector potential φ has a maximum. The maximum plasma density nm at the optimum collector potential can be much greater than the plasma density when the collector is at ground or at floating potential. The nonmonotonic dependence n(φ) is found to be caused by the contribution of secondary electrons from the collector to plasma generation.

High-Efficiency Electron Source with a Hollow Cathode in Technologies of Thin Film Deposition and Surface Treatment under Forevacuum Pressures

It is shown that low-energy beams with a high efficiency in a wide range of beam currents can be obtained in electron sources with a hollow cathode in the forevacuum pressure range. By varying the geometrical parameters of the electrode system and electromagnetic optics of the electron source, we succeeded in reaching the efficiency at a level of 0.9 for an accelerating potential of 1 kV and beam currents from 100 to 300 mA. The parameters affecting most strongly the efficiency and stability of operation of the electron source with a hollow cathode have been determined.

Narrow-aperture electron beam in the forevacuum pressure range as a tool for dimensional processing of silica glass

The paper gives overview of the results of using narrow-aperture electron beam generated by a forevacuum plasma electron source as a tool for treatment of electrically non-conductive materials, such as technical glass. Effectiveness of electron beam treatment of non-conductive materials is caused by almost complete neutralization of target charge on the treated surface. Charge neutralization occurs due to ion flow from beam plasma generated while transporting the beam through forevacuum pressure area. The study demonstrates the possibility to control depth and form of milling by changing modes of electron beam treatment. Combined use of electron beam and automated system for beam deflection and sweep makes possible to perform dimensional processing, particularly cutting and milling with complex trajectory. Milling rates were experimentally found depending on treatment time and mode. The suggested method of silica glass treatment represents an alternative for traditional treatment methods.

Generation of Ribbon Electron Beams by Fore-Vacuum Plasma Sources Based on the Discharge with an Extended Hollow Cathode

The paper presents results of investigation into the special features of physics of fore-vacuum plasma sources of ribbon electron beams. The main difficulties encountered in the development of sources of this type are demonstrated. Conditions that allow one to increase the emission current density with simultaneous preservation of high degree of beam current homogeneity are determined. On the basis of the described physical features in the fore-vacuum plasma sources operation, the main directions in the development of the electron sources generating beams in the fore-vacuum pressure range are proposed.

Narrow-aperture electron beam in the forevacuum pressure range as a tool for dimensional processing of silica glass

Narrow-aperture electron beam in the forevacuum pressure range as a tool for dimensional processing of silica glass

The possibilities of dimensional electron-beam processing as applied to selective sintering of oxide ceramics in the forevacuum pressure range

The paper presents the results of studies devoted to an effect of deviation and scanning parameters on the value of power density of a focused electron beam generated by a plasma electron source in the forevacuum pressure range. It is shown that the change in the beam power density does not exceed 20% with an angle of beam deviation within 20 degrees in the investigated pressure range of 6-8 pascals in air. The results of selective sintering of powder system of zirconia-alumina by an electron beam generated by a forevacuum plasma electron source are demonstrated.

Surface treatment by the ion flow from electron beam generated plasma in the forevacuum pressure range

The paper presents research results of peculiarities of gas ion flows usage and their generation from large plasma formation (>50 sq.cm) obtained by electron beam ionization of gas in the forevacuum pressure range. An upgraded source was used for electron beam generation, which allowed obtaining ribbon electron beam with no transmitting magnetic field. Absence of magnetic field in the area of ion flow formation enables to obtain directed ion flows without distorting their trajectories. In this case, independent control of current and ion energy is possible. The influence of electron beam parameters on the parameters of beam plasma and ion flow – current energy and density – was determined. The results of alumina ceramics treatment with a beam plasma ions flow are given.

Surface treatment by the ion flow from electron beam generated plasma in the forevacuum pressure range

The paper presents research results of peculiarities of gas ion flows usage and their generation from large plasma formation (>50 sq.cm) obtained by electron beam ionization of gas in the forevacuum pressure range. An upgraded source was used for electron beam generation, which allowed obtaining ribbon electron beam with no transmitting magnetic field. Absence of magnetic field in the area of ion flow formation enables to obtain directed ion flows without distorting their trajectories. In this case, independent control of current and ion energy is possible. The influence of electron beam parameters on the parameters of beam plasma and ion flow – current energy and density – was determined. The results of alumina ceramics treatment with a beam plasma ions flow are given.

Influence of gas pressure on electron beam emission current of pulsed cathodic-arc-based forevacuum plasma electron source

We describe our experimental investigation of the effect of background gas pressure on the emission parameters of a pulsed cathodic-arc-based forevacuum-pressure plasma-cathode electron source. We find that increased gas pressure over the range 4–16 Pa significantly reduces the beam current rise-time and significantly increases the emission current amplitude. For example, at a discharge current of 20 A, increasing the working gas pressure from 4 Pa to 16 Pa increases the emission current from 8 A to 18 A and shortens the beam rise-time from 50 μs to 20 μs. This influence of gas pressure on the electron beam parameters can be explained by the effect of arc discharge current switching from the anode to emission. In our case, the current switching effect is caused by increased working gas pressure. In the forevacuum pressure range, the increase of the electron emission current with the growth of gas pressure is due to a rise in the emission plasma potential which is caused by ion back-streaming from the plasma formed in the electron beam transport region. A model describing the influence of gas pressure on the electron emission from the plasma is presented.

Millisecond Pulsed Arc Discharge in a Forevacuum-Pressure Plasma-Cathode Electron Source

We have explored the parametric behavior of a quasi-continuous (1.8 ms) vacuum arc discharge operating as plasma source of a forevacuum-pressure plasma-cathode electron beam source. The current-voltage characteristic of the arc is presented and we show that the discharge becomes unstable at a current below 5–6 A (for our copper cathode). The operating discharge voltage increases weakly with increasing arc current over the pressure range 3–15 Pa. At a pressure greater than 15 Pa the arc shows two possible modes, differing in discharge voltage, as observed earlier for submillisecond arcs. The ratio between the currents to the hollow and plane anode sections are measured to study the arc modes. It is shown that discharge current and pressure affect that ratio. The influence of the arc modes on the electron emission in the forevacuum pressure range is discussed.

Особенности генерации пучковой плазмы в изолированной металлической полости в форвакуумной области давлений

Особенности генерации пучковой плазмы в изолированной металлической полости в форвакуумной области давлений

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.

Electron beam focusing features in a plasma electron source under forevacuum pressures

Features of focusing electron beams generated by a forevacuum plasma source under pressures of 10–30 Pa are investigated and the principle possibility of obtaining submillimeter beams is demonstrated. A beam power density of 105 W/cm2 is reached at an electron beam diameter of 0.6 mm. The obtained beam parameters offer opportunities for precision electron beam processing of dielectric materials, including hightemperature alumina ceramics.

Focus on materials, semiconductors, vacuum, and cryogenics

Focus on materials, semiconductors, vacuum, and cryogenics

Sintering of oxide and carbide ceramics by electron beam at forevacuum pressure

Novel approaches for electron beam sintering of zirconia and silicon carbide ceramics have been investigated: application of forevacuum pressure plasma-cathode to compensate the charge induced by the electron beam on the green compact surface, and previous dry powder compaction under powerful ultrasound assistance. Dense YSZ ceramics with submicron and micron grains have been consolidated by electron beam sintering after powder compaction using ultrasound.

Diagnostics of beam plasma produced in dielectric cavity at fore-vacuum pressures

The results of the probe and optical measurements of plasma parameters produced during the injection of the electron beam with the energy of 3-8 keV and current of 30-60 mA into a dielectric cavity at the argon pressure of 2-12 Pa are presented. The possibility of continuous injection of the electron beam into the cavity without current-collecting electrodes inside is demonstrated. The axial distribution of the values of the plasma parameters (density, electron temperature and floating potential) in the cavity is discussed. The plasma concentration in the cavity is shown to be approximately 20% higher, and the electron temperature 1.5-2 times higher, than in the case of generating the plasma in the free space of the vacuum chamber.

Газо-металлическая электронно-пучковая плазма для осаждения оксидных покрытий в форвакуумной области давлений

Газо-металлическая электронно-пучковая плазма для осаждения оксидных покрытий в форвакуумной области давлений

Исследование оптического излучения пробоя ускоряющего промежутка форвакуумного широкоапертурного импульсного плазменного источника электронов

Исследование оптического излучения пробоя ускоряющего промежутка форвакуумного широкоапертурного импульсного плазменного источника электронов

Особенности электронно-лучевого испарения керамики на основе оксида алюминия в форвакуумной области давлений

Особенности электронно-лучевого испарения керамики на основе оксида алюминия в форвакуумной области давлений

Состав газовой атмосферы при взаимодействии электронного пучка с порошком оксида алюминия в форвакуумной области давлений

Состав газовой атмосферы при взаимодействии электронного пучка с порошком оксида алюминия в форвакуумной области давлений