A gas-ion source with a grid-stabilized plasma cathode

A two-stage source of a broad beam of gas ions is described. The source contains a grid-stabilized plasma cathode and an anode stage with a multicusp magnetic field. The emission current of the plasma cathode (which is based on a glow discharge with a hollow cathode) is controlled between 0.1 and 1 A. The voltage that is applied to a bipolar diode between its cathode grid and anode plasma and determines the energy of fast electrons ranges from 50 to 200 V. The operating pressure of the argon in the anode stage is 4 × 10^–3–1 × 10^–1 Pa. A beam of argon ions having an energy of up to 5 keV and a current of >100 mA is formed by a two-electrode ion-optical system with a working area of 50 cm².__________Translated from Pribory i Tekhnika Eksperimenta, No. 2, 2005, pp. 107–111.Original Russian Text Copyright © 2005 by Gavrilov, Kamenetskikh.     

An Ion Source with an Open-End Small-Sized Anode

A small-sized gas-discharge ion source is described. The source contains a cylindrical hollow cathode made of a ferromagnetic material with longitudinal magnetization of up to 16 mT; a cone-shaped anode and a cathode-reflector in the form of a tube situated in axial symmetry inside the hollow cathode; and an external thermionic cathode. The overall dimensions of the ion source without the thermionic cathode are 45 × 44 mm. The source ensures an argon ion beam current of up to 80 mA at a discharge current and voltage of 1 A and 115 V, respectively, and a pressure of 1.5 × 10⁻² Pa in the chamber. The minimum operating pressure is 0.8 × 10⁻² Pa.__________Translated from Pribory i Tekhnika Eksperimenta, No. 3, 2005, pp. 147–149.Original Russian Text Copyright © 2005 by Stognij, Zavadskaya, Koryakin, Lobko, Yurchenko.     

An arc generator of a broad plasma stream

The design and basic parameters of an arc plasma generator based on a combined cathode are described. The cathode consists of a hot tungsten filament located in the hollow cathode. A plasma stream with a cross section of 150×10 cm² and a density of ∼10¹⁰ cm⁻³ at a pressure of 0.1–1 Pa is generated at a discharge current of up to 60 A without a cathode spot. The plasma generator can be utilized for final cleaning and activation of surfaces of materials and articles before depositing functional coatings on them and in plasma-assisted deposition by using either vacuum arc or magnetron discharges.     

A Wide-Aperture Source of Oxygen Ions with a Hollow Cold Cathode and Magnetic Multicast

A gas-discharge source of oxygen ions is described. The source contains an anode and a hollow cold cathode with one extracting grid (extractor) placed at the opposite end to the anode. The hollow cathode has three multicast magnetic systems of permanent polarity. The first system is placed inside the cathode near the anode, the second system is situated outside the cathode opposite to the first one, and the third system is placed below the second one near the extractor surface. Like poles of the first and second magnetic systems are directed towards each other. The second and third systems have poles of similar orientations. Using this source, a beam of oxygen ions with a current density of up to 0.5 mA/cm² and nonuniformity of <5% was obtained across a 200-mm-diameter area at a distance of 120 mm from the face of the ion source. The source offers the following optimum performance characteristics: a discharge current of 0.4–1.2 A, oxygen flow rate of 9–12 cm³/min, and extracting voltage of 400–600 V. No limitations were revealed on the service life of a source operating in optimal modes.     

Broad beam sources of fast molecules with segmented cold cathodes and emissive grids

Experimental study of fast neutral atom and molecule beam sources with rectangular and circular cross-section of the beam up to 0.8 m² is carried out and the study results are presented. The fast particles are produced as a result of charge exchange collisions between gas molecules and ions accelerated by potential drop between the plasma emitter of the beam source and the secondary plasma inside the processing vacuum chamber. As the emitter is used a glow discharge plasma, whose electrons are confined in an electrostatic trap formed by a cold hollow cathode and an emissive grid, which is negative both to the cathode and to the chamber. In order to prevent from breakdowns between the emitter and the cathode at a current in the cathode circuit up to 10 A as well as between the emitter and the grid at a voltage between them up to 10 kV the cathode and the grid are composed of isolated from each other segments, which are connected to power supplies through resistors. When resistance of the resistorR > U/I ₀, where U is the power supply voltage and I ₀ is the minimal current of stable vacuum arc for a given segment material, then transition from the glow discharge to the steady-state vacuum arc is totally excluded in spite of numerous breakdowns of microsecond duration due to contamination of the source electrodes during its operation with dielectric films and other stimulants of the arc.     

A source of broad homogeneous beams of low-energy (∼0.5 keV) gas ions

A source of gas ions (argon, oxygen, nitrogen, etc.), the operating principle of which is based on the use of a glow discharge in an electrode system of a wide-aperture hollow cathode and anode in a magnetic field, is described. The exit aperture diameter of the hollow cathode, increased up to a size close to the ion beam diameter (10 cm), ensures the uniform ion emission of the plasma generated in the discharge region near the anode. A decreased angular divergence or increased ultimate ion-beam current density is achieved by a change in the potential drop in the space charge sheath between the plasma and the ion optics. The source generates broad (50 cm²) slightly diverging (ω/2∼3°–5°) ion beams with energies of 300–1000 eV at a beam current density of ∼0.5 mA/cm².     

A plasma generator based on nonself-sustained low-pressure glow discharge with a large-volume hollow cathode

The results of studying nonself-sustained glow discharges in an electrode system with a hollow cathode with a volume of 0.25 m³ are presented. A high-current (up to 35 A) nonself-sustained glow discharge at low pressures (0.3–1.0 Pa) is initiated and sustained with the help of an auxiliary cold-hollow-cathode arc discharge. When the current of a nonself-sustained glow discharge increases from 2 to 35 A, its burning voltage changes from 40 to 300 V. These values are much lower than the voltage for a self-sustained glow discharge in the same electrode system. At a discharge current of 30 A, the electron concentration at the center of the hollow cathode is n _e ∼ 10¹⁰–10¹¹ cm⁻³ and the electron temperature is T _e ≈ 2 eV. The discharge considered can be used in the system for modification of materials and products.     

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.     

A Test Bench for the Shock Loading by an Electrical Explosion of Foils

Pulsed mechanical loads on objects are produced upon an electrical explosion of metal foils with an area of <400 cm². A bank of 48 ИК 100-0.4 УХЛ4 capacitors is mounted in four metallic tanks with oil insulation and stores an energy of up to 96 kJ. Each two capacitors are switched by a thyratron and transfer a current along a cable line to a common electrical explosion unit. Twenty-four spark gaps operate with a time spread of ±3 ns relative to the trigger pulse and have an electric strength margin of ∼80%. The total inductance of the circuit is ∼70 nH. The discharge current amplitude reaches 1.68 MA, and its oscillation quarter-period lasts ∼1.8 µs. Various designs for the electrical explosion unit, based on an aluminum foil 7 µm thick, and methods for measuring the mechanical impulse values are described. The distribution of impulse over the foil area is controlled by the number of exploded foil layers. All of the test bench units can be transported and promptly put into operation at a new site.__________Translated from Pribory i Tekhnika Eksperimenta, No. 4, 2005, pp. 101–106.Original Russian Text Copyright © 2005 by Gerasimov, Zolotov, Kul’gavchuk.     

A source of broad electron beams with a self-heated hollow cathode for plasma nitriding of stainless steel

The principle of operation and characteristics of a broad electron beam source based on the discharge with a self-heated hollow cathode and widened anode part are described. The source is intended for the ion nitriding of metals in the electron beam plasma. The influence of the current density (1–7 mA/cm²) and ion energy (0.1–0.3 keV) on the nitriding rate of the 12X18H10T austenitic stainless steel is studied. It is shown that the maximal nitriding rate is reached by the combining of the minimal bias voltage across the samples (100 V) and maximal ion current density, which ensures the dynamic oxide layer sputtering on the sample surface. The electron source, in which electrons are extracted through a stabilizing grid in the direction normal to the axis of the hollow cathode, ensures the radially divergent electron beam formation with a 700-cm² initial cross section, a current of up to 30 A, and initial electron energy of 0.1–0.5 keV. The source stably operates at nitrogen-argon mixture pressures of up to 3 Pa.     

A Rapid Analyzer of Hydrogen Content in Solids

A prototype of a rapid analyzer of hydrogen content in materials has been developed and manufactured on the basis of a semiconductor gas sensor and a laser-assisted sampling method. The minimum hydrogen concentration measured in solids is ∼10⁻⁵ mass %, the error of measuring the hydrogen concentration is ∼7%, and the duration of the analysis is <3 min. The rapid analyzer allows measurements of the local hydrogen concentration at various points on the specimen’s surface and the hydrogen concentrations in the specimen’s layers at depths ranging from ∼1 µm to several millimeters. The analyzer was used to study the spatial distribution of the hydrogen content in steel specimens. It was shown that an increased content of hydrogen in a thin (<4 µm for a 100-µm-thick specimen) near-surface layer of maraging steel specimens leads to a substantial degradation of their strength characteristics.__________Translated from Pribory i Tekhnika Eksperimenta, No. 4, 2005, pp. 144–150.Original Russian Text Copyright © 2005 by Arnol’d, Varfolomeev, Lazarev, Polikarpov, Filippov, Yakimov, Glukhov.     

A Plasma-Cathode Electron Source for Ribbon-Beam Generation at Forevacuum Pressures

A plasma electron source producing a ribbon beam at pressures of up to 60 mTorr is described. The discharge with an extended rectangular-section hollow cathode is used as a plasma generator. Electrons are extracted through the emission slit in the anode covered by a metal mesh. The maximum electron-beam current is 1 A, and the energy is 2–6 keV. The beam characteristics are presented, and the conditions for attaining the maximum operating pressure are analyzed.     

Low-energy, high-current, ion source with cold electron emitter

An ion source based on a two-stage discharge with electron injection from a cold emitter is presented. The first stage is the emitter itself, and the second stage provides acceleration of injected electrons for gas ionization and formation of ion flow (<20 eV, 5 A dc). The ion accelerating system is gridless; acceleration is accomplished by an electric field in the discharge plasma within an axially symmetric, diverging, magnetic field. The hollow cathode electron emitter utilizes an arc discharge with cathode spots hidden inside the cathode cavity. Selection of the appropriate emitter material provides a very low erosion rate and long lifetime.     

Modernization of the Element 2 mass spectrometer

To perform direct elemental analysis of solids, it is proposed to complement an Element 2 ICP mass spectrometer commercially produced by Thermo Electron Corp. with a glow-discharge ion source based on a hollow cathode. The analyzed sample, in the form of a rod 1.0–2.5 mm in diameter and 15–20 mm in length, is set along the axis of the cathode cavity with an inner diameter of 15–16 mm and a depth of 15 mm. The cathode is placed in a discharge chamber, which, using a viton seal, is substituted for the ICP-source sampler. The use of a plasma mirror and getter evacuation of the source chamber allows a decrease in the source’s hydrocarbon background by a factor of 10³–10⁴. The ion source is evacuated by a mechanical pump of the mass spectrometer and an additional turbomolecular pump. Ion sources in a mass spectrometer are replaced (a change from one analytical method to another) within 5 min. The ion current extracted from the IS allows analysis of conducting solids with a sensitivity at a level of several ppb (10⁻⁷%) at a resolution of the mass spectrometer of 4000. Combining two easily replaceable ICP and GD ion sources in a single high-resolution analyzer significantly extends the analytical capabilities of the Element 2 mass spectrometer. Original Russian Text ? G.G. Sikharulidze, 2009, published in Pribory i Tekhnika Eksperimenta, 2009, No. 2, pp. 98–100.     

A Gas-Discharge Plasma Source for the Modification of the Potential on the Surface of an Insulator

A gas-discharge source of low-temperature plasma with the charged particle concentration of 10¹¹–10¹³ m^–3 is described. The operating characteristics of the source are considered. Experiments showed that the developed plasma source can be effectively used for the soft (without breakdowns) neutralization of both surface and bulk excess charge accumulated by insulating materials.     

A long pulse width and high extraction rate arc plasma electron beam source

Based on the principle of vacuum arc discharge under magnetic field, a novel plasma cathode electron- beam source was designed. This device can be used to regulate electron-beam current so as to improve the extrication efficiency of electron beam through regulating the exciting current and thus controlling the density of the plasma electron beam source. Experiment results showed that the arc current change with the magnetic field, to be specific, the stronger the magnetic field was, the smaller the arc current will be, then the density of plasma that penetrated the anode hole to serve as electron beam will be higher. From this experiment, it can be seen that under the condition of 10^?3 Pa air pressure, 100 V arc voltage, 30 A exciting current, we can obtain the electron beam of 40 ms pulse width, and 828 mA current in the extraction rate of 6.1%.     

A low-pressure gas-discharge ion source with a hollow cathode and an output-aperture diameter of 420 mm

A gas-discharge ion source with a hollow cathode 700 mm in diameter and 500 mm in length is described. Two small-area anodes are positioned at the ends of the hollow cathode opposite to each other. A 420-mm-diameter extracting electrode is placed along the lateral wall of the hollow cathode at a distance of 250 mm from its center symmetrically relative to the anodes. A hot cathode is placed opposite to the extracting electrode. A beam of oxygen ions with a current density of up to 0.2 mA/cm² and a nonuniformity <12% over a 420-mm-diameter area at a distance of 200 mm from the extracting electrode was obtained. The optimal operating parameters of the ion source working with oxygen are as follows: a discharge current of 0.8–1.2 A, an operating pressure of (0.6–0.8) × 10^?4 Torr, and an extracting voltage of up to 400 V.     

A Chemiluminescent Balloon-Type Nitrogen Dioxide Meter for Tropospheric and Stratospheric Investigations (NaDA)

We have developed and produced a small and inexpensive balloon-type instrument for tropospheric and stratospheric measurements of the content of nitrogen dioxide in the atmosphere, the NaDA. The instrument utilizes the reaction of liquid luminol with NO₂, which results in the emission of light in the visible spectral region, and can operate under both tropospheric and stratospheric conditions. The range of measured concentrations is ∼ 0.1–50 ppbv; the instrument’s sensitivity is ∼26000 pulses/s per 1 ppbv of NO₂ at atmospheric pressure and its mass is ∼1 kg. Field tests of the instrument have been performed. A height profile of the NO₂ distribution in the atmosphere was obtained.__________Translated from Pribory i Tekhnika Eksperimenta, No. 3, 2005, pp. 136–141.Original Russian Text Copyright © 2005 by Sitnikov, Sokolov, Ravegnani, Yushkov, Ulanovskiy.     

A Universal Ion Source with a Cold Cathode

A plasmotron source of positive low-charge ions of metals and gases with a two-stage discharge is described. The emittances of the ion beams of various elements normalized by the longitudinal velocity and extracted from the source are within 0.1 cm mrad, and the equivalent proton currents of ions accelerated by a voltage of 50 kV are 120–380 mA. A cold cathode is used in the source. Metal ions are produced in the regime of the vacuum arc discharge in cathode material vapors.     

Tribological behaviour of duplex treated Ti–6Al–4V: combining nitrogen PSII with a DLC coating

The chemical structure and tribological behaviour of Ti–6Al–4V plasma source ion implanted with nitrogen then DLC-coated in an acetylene plus hydrogen-glow discharge (bias voltage −10 to −30 kV) were investigated. The as-modified samples have a TiN/H:DLC multilayer architecture (coating resistivity 1.6×10⁹ to 2.4×10¹¹ Ω/cm) and exhibit higher hardness, especially at low loads or plastic penetrations in the order of deposition bias voltage −10, −20 and −30 kV. At a lower contact load (1 N) and higher sliding speed (0.05 m/s), frictional properties in most cases improved, as did wear properties. At a higher contact load (5 N) and lower sliding speed (0.04 m/s), friction showed almost no improvement, and wear properties deteriorated. When the material of the counterbody was then changed from AISI 52100 to Ti–6Al–4V modified as the disc (contact load 5 N unchanged, sliding speed decreased), the friction coefficient decreased (but showed no improvement compared with the unmodified sample), while wear properties deteriorated further, and wear was changed from just the disc to both disc and ball, abrasive and adhesive dominated. Transfer films, mainly made up of wear debris transferred from the disc wear surfaces, were formed on the wear scars of the counterbodies. The deterioration of wear properties of the modified samples at the higher contact load is considered to be caused by the “thin ice” effect.