M. V. Shandrikov

Gridless, very low energy, high-current, gaseous ion source

We have made and tested a very low energy gaseous ion source in which the plasma is established by a gaseous discharge with electron injection in an axially diverging magnetic field. A constricted arc with hidden cathode spot is used as the electron emitter (first stage of the discharge). The electron flux so formed is filtered by a judiciously shaped electrode to remove macroparticles (cathode debris from the cathode spot) from the cathode material as well as atoms and ions. The anode of the emitter discharge is a mesh, which also serves as cathode of the second stage of the discharge, providing a high electron current that is injected into the magnetic field region where the operating gas is efficiently ionized. In this discharge configuration, an electric field is formed in the ion generation region, accelerating gas ions to energy of several eV in a direction away from the source, without the use of a gridded acceleration system. Our measurements indicate that an argon ion beam is formed with an energy of several eV and current up to 2.5 A. The discharge voltage is kept at less than 20 V, to keep below ion sputtering threshold for cathode material, a feature which along with filtering of the injected electron flow, results in extremely low contamination of the generated ion flow.

Operating modes of a hydrogen ion source based on a hollow-cathode pulsed Penning discharge

An ion source based on a hollow-cathode Penning discharge was switched to a high-current pulsed mode (tens of amperes and tens of microseconds) to produce an intense hydrogen ion beam. With molecular hydrogen (H2), the ion beam contained three species: H(+), H2(+), and H3(+). For all experimental conditions, the fraction of H2 (+) ions in the beam was about 10 ÷ 15% of the total ion beam current and varied little with ion source parameters. At the same time, the ratio of H(+) and H3(+) depended strongly on the discharge current, particularly on its distribution in the gap between the hollow and planar cathodes. Increasing the discharge current increased the H(+) fraction in ion beam. The maximum fraction of H(+) reached 80% of the total ion beam current. Forced redistribution of the discharge current in the cathode gap for increasing the hollow cathode current could greatly increase the H3(+) fraction in the beam. At optimum parameters, the fraction of H3(+) ions reached 60% of the total ion beam current.

Low-energy dc ion source for low operating pressure

We report on an experimental study of an ion source based on a Penning discharge with a cold hollow cathode in crossed electric and magnetic fields. The minimum vacuum chamber operating pressure was 3 × 10(-5) Torr for argon and 5 × 10(-5) Torr for hydrogen. The use of a hollow cathode allowed decreasing the discharge operating voltage down to 350 V at a discharge current of ~100 mA. At a discharge current of 100 mA and beam accelerating voltage of 2 kV, the ion current was 2.5 mA for argon and 8 mA for hydrogen, and the ion beam on-axis current density 170 and 450 μA/cm(2), respectively. The current-voltage characteristics of the discharge and the radial ion beam current density distribution were measured. The influence of pressure on the discharge parameters and their time stability was investigated.

A generator of gas-metal plasma based on an electron-injection discharge

An earlier developed plasma generator based on a nonself-sustained gas discharge with electron injection was modernized and ensured production of gas-metal plasma and, correspondingly, multielement composite (including oxide) coatings with controlled compositions and fractional ratios of components. The characteristics of the discharge system are investigated, and the optimal ways to increase the coating-deposition rate are determined. The device developed stably operates in an oxygen atmosphere for a long service life and is characterized by the absence of a microparticle fraction.

Generation of space charge compensated low energy ion fluxa)

The results of an experimental study of low-energy (<200 eV) ion flux generation with space charge neutralization are presented. Argon was used as a working gas. The working gas pressure in the vacuum chamber was 2-4 x 10(-2) Pa. Ion beam was extracted from the hollow cathode of main discharge plasma by a single mesh extractor with subsequent deceleration of ions to a required energy in a layer between the mesh and the beam plasma. The ion beam current was measured on the collector located on the distance of 30-60 cm from the discharge system. The penetration of electron component from the main discharge plasma through the mesh into the region of the ion beam drift space was realized by potential barrier reduction, in conditions of the optimal extractor potential with respect to the hollow cathode. The space charge neutralization of low-energy ion beam resulted in drift space plasma potential reduction and ion beam current growth. At the main discharge current of 1 A and main discharge voltage of 300 V, the ion beam current of up to 100 mA with the ion energy of 50-150 eV was obtained.

A Bulk Plasma Generator Based on a Plasma Cathode Discharge

The design, operating features, and parameters of a bulk plasma generator based on a steady-state low-pressure discharge with the additional injection of electrons from an external emitter are described. An additional constricted-arc discharge plasma is used as an electron emitter. This type of a discharge system ensures the formation of a homogeneous and stable gas plasma with a concentration of up to 2 ×1010 cm–3 in a volume of 1 m3 at a pressure of up to 3 × 10–4 Torr in a vacuum chamber. At a discharge current of up to 10 A, its voltage is 100–150 V. The device is characterized by a high efficiency of the energy utilization and a long service life, can operate with chemically active gases, and is easy to adjust and maintain.

Decrease of ceramic surface resistance by implantation using a vacuum arc metal ion source

The results of metal ion implantation into alumina ceramic are presented. We show that the of ceramic surface resistivity depends on the metal ion spcies used for the implantation, and decreases with increasing metal ion implantation dose, decreasing by 3-4 orders of magnitude from 1012 Ohm/sq. This approach provides an effective tool for bleeding off accumulated surface charge of ceramic components that can result from interaction with charged particles flows or dielectric polarization. The method can be applied for increasing the maximum electric field hold-off of insulating surfaces in high-voltage devices.

The influence of discharge parameters on the generation of ions H 3 + in the source based on reflective discharge with hollow cathode

For hydrogen ions source based on reflective discharge with hollow cathode the investigations of the effect of discharge current and gas pressure on the component composition of the ion beam have been performed. It has been shown that the optimization of the discharge parameters makes it possible to achieve up to 70% triatomic hydrogen ions H3+ in the beam.

DC and high current pulsed magnetron discharge for generation of boron plasmas

During the last decade the high power impulse magnetron sputtering technique (HiPIMS) has been developed intensively. A self-sputtering mode can be realized using HiPIMS, for a limited number of materials used as a sputtering target, which is characterized by a fraction of target material ions in the discharge plasma at least more than a half. Pure boron is almost nonconductive and therefore conventionally requires heating of the target to operate as a magnetron discharge or vacuum arc cathode. The results of study of dc and high power pulsed magnetron discharge with pure boron target are presented. It is shown that the low-current dc discharge enables high power impulse magnetron sputtering, which, in turn, results in the self-sputtering mode of the pure boron target magnetron discharge operation, in which boron ion fraction in the discharge plasma reaches 57%. The results of such technique of boron plasma generation in comparison with vacuum arc are discussed.

Boron-rich plasma of high current pulsed vacuum arc with lanthanum hexaboride cathode

Boron plasmas are widely used in various ion beam and plasma technologies, including semiconductor ion doping. Of interest is also its use for deposition of hard coatings and surface modification to enhance the performance and lifetime of machine parts and tools. The paper reports on the generation of boron-rich plasma in a short high-current pulsed vacuum arc with a lanthanum hexaboride cathode, presents time-of-flight data on its mass-charge state, and discusses the influence of the arc parameters on the ion constitution of the boron-rich plasma.