E. M. Oks

Measurements of the total ion flux from vacuum arc cathode spots

The ion current from different cathode materials was measured for 50-500 A of arc current. The ion current normalized by the arc current was found to depend on the cathode material, with values in the range from 5% to 19%. The normalized ion current was generally greater for elements of low cohesive energy. The ion erosion rates were determined from values of ion current and ion charge states, which were previously measured in the same ion source. The absolute ion erosion rates ranged from 16-173 /spl mu/g/C.

The 100‐kV gas and metal ion source for high current ion implantation

The TITAN ion source is a new kind of source which can produce high current beams of both metal and gas ions simultaneously or separately. Ion beams of the elements Mg, Al, Ti, Ca, Cr, Fe, Co, Ni, Zn, Sn, Ta, Re, Y, C, He, N, Ar, and Xe have been generated. To obtain metal ions a vacuum arc is used in metal vapors created in ‘‘cathode spots.’’ To obtain gas ions a contragated arc discharge in gas current is used. The source extraction voltage is controlled within 10–100 kV. The ion current of both gas and metal was ≂1 A. The source operates in a frequency‐pulse regime at a pulse‐repetition frequency as high as 50 pps. At its normal operation the source provides a dose of 1016 ions/cm2 per minute on a 250‐cm2 area surface. The source is constructed according to the program on development of new technologies and is intended for high current surface modification and production of exotic surface alloys. At present, TITAN ion sources are utilized to modify physical‐mechanical parameters of different surfaces. ...

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. I: Basic physical processes

This paper reviews the physical phenomena that accompany the emission of electrons and ions from plasma. The development of plasma emission electronics as an independent research field is closely associated with the name of its founder, Professor Kreindel Yu. E. The well-known advantages of plasma electron emitters (plasma cathodes) are the higher emission current density, the pulsed emission capability, and the wider range of residual gas pressures. A peculiar property of the plasma cathode is the possibility of extracting practically all electrons from plasma. The parameters of an ion and electron beam extracted from plasma carry information about the physical processes occurring in the plasma. This makes it possible to invoke emission methods to study the fundamental phenomena that take place in plasma of vacuum arc and low-pressures gas discharges.

Charge-state distribution of ions in a vacuum arc discharge plasma in a high magnetic field

It is shown that the fraction of multiply charged metal ions generated in a vacuum arc discharge plasma grows substantially in a high magnetic field. This effect was observed for more than 30 different cathode materials. A relation is established between growth of the mean charge of the ions and increases in the burning voltage of the arc. It is demonstrated that the burning voltage of the vacuum arc can be ultimately increased to 160 V.

Angular distribution of plasma in the vacuum arc ion sourcea)

This paper presents measurements of the angular distribution of the plasma components and different charge states of metal ions generated by a MEVVA-type ion source and measured by a time-of-flight mass-spectrometer. The experiments were performed for different cathode materials (Al, Cu, and Ti) and for different parameters of the vacuum arc discharge. The results are compared with prior results reported by other authors. The influence of different discharge parameters on the angular distribution in a vacuum arc source is discussed.

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.

Plasma electron source for the generation of wide-aperture pulsed beam at forevacuum pressures

This article reports on design and application of wide-aperture pulsed beam source, based on hollow cathode discharge. The source is intended for electron beam generation in pressure range 2-15 Pa. Multi-aperture extraction system, used in a source, provided beam cross-section uniformity of 10% on diameter 40 mm. The limiting values of the current density, pulse duration, and accelerating voltage are 350 mA∕cm(2), 250 μs, and 10 kV, respectively. These parameters are sufficient for surface modification of various materials, including non-conducting matters.