G. Yushkov

Effect of the pulse repetition rate on the composition and ion charge-state distribution of pulsed vacuum arcs

The plasma composition and ion charge-state distributions of pulsed vacuum arcs have been investigated for carbon, aluminum, silver, platinum, and tantalum cathodes using a time-of-flight (TOF) charge-to-mass spectrometer. With the exception of carbon, it was found that all results depend on the arc pulse repetition rate, a fact which, up to now, has not been reported in the literature. It is shown that adsorption of gas on the cathode between are pulses leads to contamination of the metal plasma and to a reduction of metal ion charge states. These usually undesired effects can be avoided by operating at high arc pulse repetition rates of order 10 Hz or more. The results can be interpreted in terms of cathode spot type 1 (on contaminated cathode surfaces) and type 2 (on clean surfaces) which are well known from their different brightness and erosion behaviour. The transition between these modes was found to be gradual.

Manipulating large-area, heavy metal ion beams with a high-current electrostatic plasma lens

We describe some experimental investigations of the manipulation of high-current, large-area beams of heavy metal ions using a high-current electrostatic plasma lens. Beams of carbon, copper, zinc, and tantalum ions (separately) were formed by a repetitively pulsed vacuum arc ion source, with energy in the range about 10-140 keV, beam current up to 0.5 A, initial beam diameter 10 cm, and pulse length 250 ms. The plasma lens was of 10-cm internal diameter and 20-cm length and had nine electrostatic ring electrodes with potential applied to the central electrode of up to 7 kV, in the presence of a pulsed magnetic field of up to 800 Gauss. The current density profile of the focused beam was measured with a radially moveable, magnetically suppressed Faraday cup. The results show that the focal length of the lens and the profile of the transported beam can be controlled by variation of the lens magnetic field and electrode potential distribution. Under optimum operating conditions the ion beam current density at the focus was compressed by a factor of up to 30. We also carried out some preliminary observations of the effect of the plasma lens on the ion charge state distribution of the beam. Here we outline the principles underlying plasma lens operation and summarize the experimental observations we have made of the lens performance in this large-area. high-current regime.

Measurements of secondary electrons emitted from conductive substrates under high-current metal ion bombardment

Abstract The yield of secondary electrons induced by primary ion impact is measured for conditions relevant to metal plasma immersion ion implantation. A vacuum arc ion source provided metal ions in the energy range 5–175 keV. The target materials were placed in a Faraday cup, and the secondary electron yields were determined by measuring the current of the Faraday cup with and without electron-suppressing magnetic field. By using a time of flight method, yields for individual ion charge states could be determined. The yields found depend on the ion species, their energy, and the target material. They are in the range 1–10 electrons per ion for the conditions investigated. It was found that the yields are almost independent of the ion charge state and increase with increasing ion energy.

Generation of Multiply Charged Ions in the Plasma of a Vacuum Arc Discharge

This paper presents the results of a study on the generation of multiply charged ions in the plasma of a vacuum arc discharge. The average charge of ions in the plasma is increased by using a strong magnetic field, a current “burst,” or an accelerated electron beam. The results of measurements of the ion charge distribution for each case are reported.

Technological Ion Sources Based on a Vacuum Arc Discharge

Technological ion sources of the TITAN type have been developed at the Institute of High Current Electronics, RAS, for the last ten years. These sources generate wide-aperture high-current beams of gas or metal ions and also mixed two-component gas-metal ion beams with a controllable component ratio. This is possible due to two discharge systems combined into one discharge system of the source. Metal ions are obtained with a vacuum arc discharge and gas ions are generated with a constricted hollow-cathode low-pressure arc discharge. This paper describes the principle and peculiarities of operation of the given sources, their design, parameters, and fields of application. A modified version of the Mevva ion source is considered. The design of this version is based on the results of studies conducted using the TITAN source.