Hollow Cathode Effect Research Articles

Simulation of N2 microhollow cathode discharge and cathode sputtering by using a PIC/MC model

The nitrogen microhollow cathode discharge and Ti cathode sputtering, bombarded by ions (N2+, N+), have been studied using a two-dimensional PIC/MCC model. The behavior of ions (N2+, N+) and sputtered atom (Ti), and the thermalization process of the sputtered atoms in a nitrogen microhollow cathode discharge are simulated. The results show that hollow cathode effect is due to electron oscillations in the overlapping negative glow under our simulation condition. The densities of ions (N2+, N+) in the microhollow cathode discharge are two orders in magnitude greater than that in the conventional hollow cathode discharge; but the distributions and sizes of the mean energy of the ions (N2+, N+) are almost the same. The density of N2+ is fivefold as much as that of N+ in the microdischarge space; however, the maximum of mean energy of the latter is twice larger than the former. For various parameters (P, T, V), the densities of ions(N2+, N+) bombarding the cathode internal surface are almost uniformly distributed, and their mean energy are almost the same. When these atoms are 0.15 mm away from the cathode. The sputtered atoms are almost thermalized completely.

Longitudinal ion source with the current self-compensation of the focused ion beam

Utilization of ballistic focusing in the longitudinal Hall-type ion source is described. It allows transformation of the ion beam shape from an “ellipsoidal” one to a linear one, as well as increasing the ion beam current density per the operating surface. Both the influence of transverse magnetic field and edge effects on the beam shape are investigated. The ion beam is charge compensated by a plasma neutralizer designed on the basis of a supplementary semi-self-maintained magnetron-type discharge and hollow cathode effect.

Plasma nitriding of AISI 304 austenitic stainless steel assisted with hollow cathode effect

The utilization of controllable hollow cathode effect for heating in plasma nitriding furnace was studied in this work. Assisted with the hollow cathode effect (HCE) arising between two coaxial cylindrical cathodes, AISI 304 austenitic stainless steel was efficiently heated and nitrided. Since the coaxial cylinders instead of treated samples were subject to high cathodic potential, the inherent shortcomings of conventional dc technique were eliminated. The nitride layers consisted of S phase when nitrided at 420°C–500°C, while precipitation of chromium nitride is present at 520°C. The higher temperature and defects caused by the cathodic ion bombardment might favor the nitriding efficiency of samples nitrided on cathodic potential.

Particle-in-cell simulations of hollow cathode enhanced capacitively coupled radio frequency discharges

A two-dimensional particle-in-cell simulation has been developed to study density enhancement of capacitively coupled rf discharges with multi-slit electrodes. The observed density increase is shown to result from a hollow cathode effect that takes place within the multi-slit electrode configuration, which forms as a result of secondary electron emission due to ion bombardment. By investigating the ionization and power deposition profiles, it is found that rf sheath heating is too weak to sustain the discharge, and that secondary electron acceleration within the sheath is the primary heating mechanism. Due to a capacitive voltage divider formed by the rf sheaths at each electrode, the area ratio of the powered and ground electrodes is observed to have a strong effect on the resulting discharge, and if the ground electrode area is too small, the voltage drop at the powered electrode is too low to sustain a hollow cathode discharge.

Uniqueness Theorem for the Non-Local Ionization Source in Glow Discharge and Hollow Cathode

The paper is devoted to the proof of the uniqueness theorem for solution of the equation for the non-local ionization source in a glow discharge and a hollow cathode in general 3D geometry. The theorem is applied to wide class of electric field configurations, and to the walls of discharge volume, which have a property of incomplete absorption of the electrons. Cathode is regarded as interior singular source, which is placed arbitrarily close to the wall. The existence of solution is considered also. During the proof of the theorem many of useful structure formulae are obtained. Elements of the proof structure, which have arisen, are found to have physical sense. It makes clear physical construction of non-local electron avalanche, which builds a source of ionization in glow discharge at low pressures. Last has decisive significance to understand the hollow cathode discharge configuration and the hollow cathode effect.

Imaging of a Localized Hollow Cathode Discharge

In this paper, we present the image of a localized hollow cathode discharge (HCD) in argon. There are two ways for the onset of hollow cathode effect in HCD according to the pD value (i.e., product of pressure and cathode diameter). The overlapping of opposite negative glow regions can evolve from a weak solid plasma column at a lower pD value or evolve from a ring-shaped column at a higher pD value.

Dry Sliding Wear of Active Screen Plasma Carburised Austenitic Stainless Steel

Low temperature diffusion treatments with nitrogen and carbon have been widely used to increase the tribological performance of austenitic stainless steels. These processes produce a layer of supersaturated austenite, usually called expanded austenite or S-phase, which exhibits good corrosion and wear resistance. The novel active screen technology is said to provide benefits over the conventional DC plasma technology. The improvements result from the reduction in the electric potential applied to the treated components, and the elimination of such defects and processing instabilities as edge effects, hollow cathode effects and arcing. In this study, AISI 316 coupon samples were plasma carburised in DC and active screen plasma furnaces. The respective layers of carbon expanded austenite were characterised and their tribological performance was studied and compared. Detailed post-test examinations included SEM observations of the wear tracks and of the wear debris, EDX mapping of the wear track, EBSD crystal orientation mapping of the cross sections of the wear tracks, and cross-sectional TEM. Based on the results of wear tests and post-test examinations, the wear mechanisms involved are discussed.

A Novel SPD Design for Lightning Protection of Intelligent Buildings

The surge protective device (SPD), as buildings over-voltage protective device, has been widely used in building’s power distribution system. A novel SPD based on hollow cathode effects is designed. In both air and nitrogen gas, the relationship of discharging voltage and gas pressure are measured, and the critical pressure ranges are determined in the condition of UpUp is pulse voltage protection level). The results indicate that, in the condition of the gap distance D=3 mm and the small hole diameter φ=3 mm, the operating gas pressure ranges are from 50 to 5×104 Pa. With the gap distance D increasing, the pulse voltage protection level Up is decreasing slightly. While D=3 mm, φ=3 mm, and gas pressure (nitrogen) is 600 Pa, the DC voltage protection level and pulse protection level are 784 V and 2.4 kV, respectively. In the action of 10/350 µs pulse current waveform, the quantity of transferred charge Q is 48.26 C, and the ratio energy W/R is up to 2 MJ/Ω. The results testify that the design of SPD in this paper can be used as buildings class B over-voltage protection.

Simulation of Electron Motion in a Micro-Hollow Cathode Discharge

Electron behaviors in the whole cathode space of a steady argon MHCD with a variable cathode gap have been simulated on the model of Monte Carlo collisions. As the cathode gap alters, the hollow-cathode effect in MHCDs has been studied by the variety rule of electron spacial and energy distribution. The results reveal that a too wide gap between two opposed cathodes under a settled pressure will die down the hollow-cathode effect.

Double Glow Plasma Hydrogen-Free Carburizing on the Surface of Purity Titanium

A higher hardness carburized layer was formed on the surface of purity titanium by a double glow plasma hydrogen-free carburizing technique depending on glow discharge and hollow cathode effect. High purity solid graphite was used as a source cathode and purity titanium was used as the cathode materials. Experimental results indicate that higher hardness TiC phase and dissociate state carbon antifrictionphase were formed in the carburized layer. The carbon concentration and the hardness of carburized layer distribute in the gradient along the carburized layer from the surface to the inner. The surface hardness increases more than two times. Friction coefficient of Ti materials treated by hydrogen-free carburizing reduces by about 1/2.

Comparison between conventional and hollow cathode magnetron sputtering systems on the growing of titanium dioxide thin films: a correlation between the gas discharge and film formation

This paper reports the deposition of titanium dioxide thin films on p -type Si(100) substrates using two techniques called conventional magnetron sputtering (CMS) and hollow cathode magnetron sputtering (HCMS). The influence of the plasma parameters on the film characteristics (topography, morphology and crystallinity) was investigated. Films were deposited at different oxygen concentrations (in the Ar + O 2 gas mixture) and axial distances for fixed values of working pressure (5.0 mTorr) and DC power (55 W). They were analyzed by profilometry, AFM and XRD. The gas discharge was diagnosed by single Langmuir probe and OES. Under experimental conditions used in this work, results show that HCMS favors the growing of rutile phase due to the increase of the energy on the film surface caused by the hollow cathode effect. On the other hand, films deposited by CMS present preferentially anatase phase due to the low energy transferred to the growing film. Further studies regarding the influence of plasma properties on the films formation were done in order to understand the plasma-surface correlation.

Numerical study on rectangular microhollow cathode discharge

Rectangular microhollow cathode discharge in argon is investigated by using two-dimensional time-dependent self-consistent fluid model. The electric potential, electric field, particle density, and mean electron energy are calculated. The results show that hollow cathode effect can be onset in the present configuration, with strong electric field and high mean electron energy in the cathode fall while high density and quasineutral plasma in the negative glow. The potential well and electric filed reversal are formed in the negative glow region. It is suggested that the presence of large electron diffusion flux necessitates the field reversal and potential well.

The Effect of a Multihollow Cathode on the Self-Bias Voltage of Methane RF Discharge Used for a-C:H Deposition

In this work we report the measurement of the self-bias voltage of radiofrequency (RF) capacitevely coupled plasma, with a multihollow cathode and methane precursor, used for amorphous hydrogenated carbon (a- C:H) thin film deposition. The plasma is produced in the incident power and pressure ranges between 20 - 300 W and 10 - 100 mTorr, respectively. It was found that the self-bias voltage Vdc is a linear function of the square root of the incident power WRF. The relationship between the self-bias voltage and gas pressure P is established; this gives an empirical relation for (p/p0)y . From this result, the pressure p0 corresponding to the transition from hollow cathode effect to hollow cathode arc effect is determined.

Observation of the hollow cathode effect from a dielectric cathode

The hollow cathode effect (HCE) is investigated in the dielectric hollow cathode structure in a Ne–Xe mixture at 4%. The influence of the dielectric is shown experimentally by the relationship between voltage and current peaks. The linearity of reduced current density confirms the existence of the HCE and shows that cathode fall has the same value at every pD condition. Varying the pD, the variation in the discharge mode can be measured with IR intensity emitted from the plasma and photographs of discharge in the visible part of the spectra. Voltages and current in the range of 3 kV at 10 µA were used. We suggest an electrode configuration reinforced in cathode sputtering for the display panel and light source using the dielectric hollow cathode discharge (DHCD), and introducing a mechanism of the DHCD mode.

Electrochemical Corrosion Behaviors Using Double Glow Forming TiN Multi-Permeation Layer

A new process technique that TiN permeation layer consisted of diffusion and deposition layer was synthesized on the surface of mild carbon steel has been firstly introduced, mainly according to plasma point discharge, hollow cathode effect and reactive vapor deposition technique. The surface appearance of this layer formed was uniform, compact and fine TiN cellular structure, a diffusion transitional region existing between the deposition layer and substrate. The surface texture was TiN deposition layer + TiN + Ti solid solution diffusion layer. From surface to inner Ti and N elements appeared graded distribution. This paper also mainly investigated the electrochemical corrosion behaviors of this multilayer. The polarization curves of specimens in 10% H2SO4 corrosive media were measured. The eroded surface morphologies were also surveyed by SEM. The results indicated that the erosion resistance of multi-permeation layer was increased many times than PVDTiN and a mild steel substrate, and almost equaled to that of compound process TiN layers.

Non-local model of hollow cathode and glow discharge

A general form of the non-local equation for an ionization source in glow discharge and hollow cathode 3D-simulation is formulated. It is a fundamental equation in hollow cathode theory, which allows formulation of a complete set of field equations for a self-consistent problem in a stationary glow discharge and hollow cathode. It enables us to describe the region of negative glow and the hollow cathode effect and compare calculation results of electrical dependencies (pressure-voltage) with experimental data, – under conditions of gradual appearance of the hollow cathode effect.

Transition of Discharge Mode of a Local Hollow Cathode Discharge

The discharge characteristics of hollow cathode discharge in argon in a cylindrical cavity are investigated experimentally. The voltage-current (V – I) characteristics and the light emission are measured. It is found that the discharge plasma is localized inside the hollow cavity, with an extensive Faraday dark space between the cathode and the anode. The discharge develops from predischarge to abnormal glow discharge, the hollow cathode effect (HCE) and a hybrid mode as the discharge current increases. The onset of the HCE is found for the first time by the transition from abnormal glow discharge together with a significant decrease in the slope of the V – I curve which shows a positive differential resistivity. The voltage increases proportionally with the current when the HCE is reached.

Plasma assisted parts' manufacturing: sintering and surface texturing - part II - influence of inter-cathode distance and gas pressure

The acquirements and potentiality universe of cleaning, heating and/or sputtering effects caused by plasma species bombardment phenomenon on the surface characteristics and finishing of manufactured parts treated in DC abnormal glow discharge opens a new research and development field, called here of Plasma Assisted Parts' Manufacturing (PAP'M). The adequate control of the sputtering mechanism allows the obtainment of different kinds of surface. Therefore, the design of rough or smooth surface, presenting a modified distribution of surface porosity and texturing could be idealized, in accordance with the desired surface characteristics, as the parts are simultaneously sintered and treated. This is the second part (out of two) of the work performed in hollow cathode discharge (HCD) and it presents the first results of the surface morphology's changes in the pressed iron samples and in the internal surface of the external cathode as a function of the inter-cathode distance and gas pressure. Potential applications include small diameters' cylindrical parts and components like axles, pins, pivots, and tubes and pipes presenting small internal diameters. Sputtering effects were quantified by means of mass loss, and Ra and Rz roughness measurements and qualified by means of SEM. Results indicate the sputtering mechanism is highly dependent of the hollow cathode effect, in HCD sintering and surface texturing treatments, comprising an important contribution to the development of green technologies for surface texturing, surface engineering, and part's manufacturing.

Hollow Cathode Effect in Cold Cathode Fluorescent Lamps: A Review

Various efforts within the cold cathode fluorescent lamp (CCFL) industry are underway to decrease costs and increase electrode performance. In order to understand the impact that the choice of gas mixtures and pressures, cathode shape and material might have on the lamp's operation requires a knowledge of the underlying principles governing the glow discharge. We present a review of the literature on the hollow cathode effect and glow discharges, which has particular relevance to the design of CCFL lamp electrodes used in liquid crystal displays. We show that industry-wide standard gas pressures and electrode designs cannot operate in the hollow cathode regime.

A detailed comparison of spectral line intensities with plane and hollow cathodes in a Grimm type glow discharge source

The hollow cathode discharge was investigated and compared with the plane cathode discharge in a Grimm-type source studying a large number of lines with iron and titanium as cathode materials in argon plasma. The high resolution Fourier Transform Spectrometer (FTS) at Imperial College (IC) was used for recording spectra. The intensity changes for atomic and ionic lines of iron, titanium and argon are discussed, whereby clear trends in intensity increase and reduction according to the excitation energies of the emission lines are identified. Differences in line profiles in spectra using the hollow and plane cathodes were detected. The comparison between the hollow (10–15 mm deep) and shallow (2 mm deep) cathodes gives additional information about the depth influence on the hollow cathode effect. The extended study presented in this paper is a further step towards a better understanding of the discharge processes in the glow discharge.