K. P. Savkin

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.

Generation of multicomponent ion beams by a vacuum arc ion source with compound cathode

This paper presents the results of time-of-flight mass spectrometry studies of the elemental and mass-to-charge state compositions of metal ion beams produced by a vacuum arc ion source with compound cathode (WC-Co(0.5), Cu-Cr(0.25), Ti-Cu(0.1)). We found that the ion beam composition agrees well with the stoichiometric composition of the cathode material from which the beam is derived, and the maximum ion charge state of the different plasma components is determined by the ionization capability of electrons within the cathode spot plasma, which is common to all components. The beam mass-to-charge state spectrum from a compound cathode features a greater fraction of multiply charged ions for those materials with lower electron temperature in the vacuum arc cathode spot, and a smaller fraction for those with higher electron temperature within the spot. We propose a potential diagram method for determination of attainable ion charge states for all components of the compound cathodes.

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.

Generation of multiply charged refractory metals in an electron-cyclotron resonant discharge in a direct magnetic trap

The possibility of additional ionization of refractory metal ions in the vacuum arc plasma injected to a magnetic trap due to additional heating of electrons by microwave radiation under the conditions of electron-cyclotron resonance is demonstrated. High-power short-wave radiation of gyrotrons used in experiment makes it possible to work with a higher (on the order of 1013 cm−3) density of the plasma and to ensure the confinement parameter at a level of 3 × 108 cm−3 s at an electron temperature sufficient for multiple ionization.

Boron ion source based on planar magnetron discharge in self-sputtering mode.

An ion source based on a planar magnetron sputtering device with thermally isolated target has been designed and demonstrated. For a boron sputtering target, high target temperature is required because boron has low electrical conductivity at room temperature, increasing with temperature. The target is well-insulated thermally and can be heated by an initial low-current, high-voltage discharge mode. A discharge power of 16 W was adequate to attain the required surface temperature (400 degrees C), followed by transition of the discharge to a high-current, low-voltage mode for which the magnetron enters a self-sputtering operational mode. Beam analysis was performed with a time-of-flight system; the maximum boron ion fraction in the beam is greater than 99%, and the mean boron ion fraction, time-integrated over the whole pulse length, is about 95%. We have plans to make the ion source steady state and test with a bending magnet. This kind of boron ion source could be competitive to conventional boron ion sources that utilize compounds such as BF(3), and could be useful for semiconductor industry application.

Measurement of total ion current from vacuum arc plasma sources

The total ion current generated by a vacuum arc plasma source was measured. The discharge system investigated allowed ion collection from the arc plasma streaming through a hemispherical mesh anode with geometric transparency of 72 percent. A range of different cathode materials was investigated, and the arc current was varied over the range 50-500 A. We find that the normalized ion current (Iion/Iarc) depends on the cathode material, with values in the range from 5 percent to 19 percent and generally greater for elements of low cohesive energy. The application of a strong axial magnetic field in the cathode and arc region leads to increased normalized ion current, but only by virtue of enhanced ion charge states formed in a strong magnetic field.

Extreme-ultraviolet source based on the electron-cyclotron-resonance discharge

An extreme-ultraviolet (EUV) source based on a low-pressure discharge sustained in a magnetic trap by the high-power millimeter-wave radiation under electron-cyclotron-resonance (ECR) conditions is discussed. Multiply charged ions are efficiently generated and excited in such a discharge (tin ions injected into the trap from a vacuum-arc discharge were used) and emit line radiation in the desired wavelength range. A radiation power of 50 W in a wavelength range of 13.5 nm ± 1% and an efficiency of about 1% for the conversion of the micro-wave radiation absorbed in the plasma to the extreme ultraviolet radiation were achieved in the preliminary experiments.

High-energy metal ion implantation for reduction of surface resistivity of alumina ceramic

In this work, the possibility to increase the surface conductivity of ceramic insulators through their treatment with accelerated metal ion beams produced by a MevvaV.Ru vacuum arc source is demonstrated. The increase in surface conductivity is made possible due to experimental conditions in which an insulated collector is charged by beam ions to a potential many times lower than the accelerating voltage, and hence, than the average beam ion energy. The observed effect of charge neutralization of the accelerated ion beam is presumably associated with electrons knocked out of the electrodes of the accelerating system of the source and of the walls of the vacuum chamber by the accelerated ions.

Ion angular distribution in plasma of vacuum arc ion source with composite cathode and elevated gas pressurea)

The Metal Vapor Vacuum Arc (MEVVA) ion sources are capable of generating ion beams of almost all metals of the periodic table. For this kind of ion source, a combination of gas feeding with magnetic field allows the simultaneous generation of both metal and gaseous ions. That makes the MEVVA ion source an excellent instrument for science and application. This work presents results of investigation for ion angular distributions in vacuum arc plasma of Mevva-V.Ru ion source for composite cathodes and for elevated gas pressure. It was shown that for all the cathode materials, singly charged ions have wider angular distribution than multiply charged ions. Increasing the working gas pressure leads to a significant change in the angular distribution of gaseous ions, while with the distribution of metal ions gas remains practically unchanged. The reasons for such different influences are discussed.

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.