Specific features of wide-aperture hollow cathode discharge in helium

The characteristics of wide-aperture discharge with a hollow cathode in helium have been studied under the conditions of predominating electron generation via photoemission from the cold cathode. In this regime, currents exceeding by an order of magnitude those for the conventional abnormal discharge have been obtained. The current-voltage characteristics are independent of the helium pressures in a range of 5–15 Torr, which is a distinctive feature of the photoemission dominated discharge with electron beam in the system under consideration.     

Model of glow discharge between an electrolytic anode and a metal cathode

High Temperature - The results of the numerical simulation of the glow discharge between the pin cathode and the electrolytic anode are presented. The electron concentration distribution for the...     

Axial evolution of the negative glow in a hollow cathode discharge.

The purpose of these studies was to examine the axial evolution of the negative glow in a hollow cathode discharge. The time-average negative glow profiles along the central axis of a hollow cathode were recorded for 81 pulse widths over the range of 5-25 microseconds in increments of 0.25 microseconds at a constant interpulse delay of 206.4 microseconds. Subsequent numerical processing yielded the instantaneous negative glow profile. The negative glow was viewed through a mesh-covered slot along the length of the hollow cathode. The negative flow profiles were imaged using a vidicon video camera. A PC-based frame grabber digitized the video images and stored them for subsequent processing.     

Specific features of wide-aperture glow discharge in helium

The characteristics of wide-aperture discharge in helium have been studied for a cathode diameter of 19.5 cm and a cathode-grid anode distance of 3 cm. It is established that the properties of discharge in this system are substantially different from those of a usual abnormal discharge. The difference is manifested in the bending of current-voltage characteristics, their pronounced dependence on the helium pressure, a nonmonotonic dependence of the electron beam generation efficiency η on the discharge voltage U, and an anomalously high efficiency (η ≈ 100%) in the range of U ≈ 350–1000 V.     

Operating characteristics of the hollow anode glow discharge ion source

In this work, a new shape of a glow discharge ion source with axial extraction has been designed and constructed. High output ion beam current can be extracted axially in a direction normal to the discharge region without using extraction system. Optimization of the distance between the anode and the cathode has been determined using argon gas. It is found that the optimum gap distance between the anode and the cathode is equal to 3.5 mm, where stable discharge current and maximum output ion beam current can be obtained. The discharge characteristics of the ion source at different operating gas pressures have been measured at this optimum distance between the anode and the cathode. A disk of Teflon insulator has been put between the anode and the cathode. This disk was covering the cathode area and reducing the discharge area on the cathode surface for discharge confinement, therefore, a higher output ion beam current could be obtained.     

空心阴极等离子体放电结构的优化设计

 低温等离子体表面处理可以有效克服液相处理法存在的环境污染、耗能大和成本高的缺点,对材料表面进行清洗、活化和接枝处理,而设计一个合理的低温等离子体放电结构能够较好地改进表面处理的质量．通过建立CRFHCP空心阴极等离子体放电的数学模型,分析影响低温等离子体放电的关键因素,并设计了不同电极配置方式、样品位置和不同远区空心阴极结构的众多方案．通过接触角测定、表面能计算、SEM照片等方式,对不同方案下处理前后的疏水性PP薄膜形态结构进行表征分析．实验结果发现：远区径向喷嘴式空心阴极等离子体放电结构处理的薄膜表面比其他处理方式具有较小的接触角和较大的表面能．这表明采用优化设计的CRFHCP空心阴极等离子体放电结构,可以较其他结构更为有效地改善材料表面的亲水性能．     

Spectral diagnostics of plasma discharge between a metal cathode and liquid anode

The results from studies of an electric discharge between a metal cathode and liquid anode at atmospheric pressure are presented. We investigate the discharge shape, the plasma emission spectrum, the electron concentration and temperature, and the molecule temperature; we analyze the continuous emission in the plasma spectrum and perform infrared thermography.     

Ion sputtering of cathode surface in a hollow cathode discharge

In this paper, ion sputtering of cathode material in a specific type of glow discharge—hollow cathode discharge (HCD)—is analyzed. To estimate both real sputtering yield and screening effect of the buffer gas, two different methods—combination of experimental and analytical approach (applicable for Ar buffer gas only) and use of Monte Carlo simulations—are used. The latter, which is introduced for the first time here, can be used for any buffer gas. Real sputtering yield S_k is estimated by Monte Carlo simulations for several commercial HCD lamps with Ne buffer gas: Ne-Li (0.046), Ne-As (0.862), Ne-Ca (0.337) and Ne-Cd (1.069).     

Energies of particles at the cathode of a glow discharge

A Monte-Carlo calculation has been carried out to obtain the energy distribution of ions and neutrals at the cathode of a glow discharge, assuming charge exchange collisions in different fields. The comparison with the previously studied case of linear field is good. Depending on the parameter L/λ (ratio of length of cathode dark space to mean free path of atoms in the gas) the following information was obtained in addition: average number of collisions, relative contribution of number of collisions to the energy distribution, and average energy of the neutrals.     

Atom-bombardment-induced electron emission from a cathode in a glow discharge: Example of an open discharge

An analysis of the glow discharge conditions shows that processes involved in this phenomenon should be described in terms of the electron emission coefficients γ determined in a technical (γ_t) rather than in an ultrahigh vacuum. The results of calculations of the electron beam formation efficiency η in a glow discharge, performed using the γ_t values, agree well with the experimentally measured efficiencies. Further refinement of these calculations is inexpedient because of unavoidable uncertainty of the γ values under real discharge conditions.     

Controlled orientation of fibers in a glow discharge plasma

We have experimentally studied the behavior of nylon fibers in a low-pressure glow discharge. The orientation of fibers deposited onto a substrate can be controlled by changing the direction of the transverse plasma density gradient. These experimental results can serve as a basis for the development of novel commercial technologies.     

Atomic oxygen in remote plasma of radio-frequency hollow cathode discharge source: Characterization and efficiency

Low-pressure, low-temperature remote oxygen plasma ignited by a radio-frequency (RF) hollow cathode discharge (HCD-L300) system is shown to be a powerful and effective source of neutral atomic oxygen (AO), useful in processing of polymeric materials. The density of AO was determined by a catalytic nickel probe as a function of pressure, RF power, oxygen flow rate and axial distance in the processing chamber. It was found to vary between ∼1×10¹⁹ to ∼1×10²⁰ atom m⁻³. The AO rich remote plasma-induced modification of wetting properties of polyimide (PI) and fluorinated ethylene propylene (FEP) surfaces has also been investigated. The wetting properties of the PI and FEP surfaces before and after exposure to the plasma were characterized by contact angle measurements and analysis. It was found that the influence of plasma surface treatment on wetting properties of FEP has an opposite effect to that of PI. On increasing the time of treatment, the surface of PI becomes more hydrophilic, whereas the hydrophobicity of FEP surface enhances. Moreover, a superhydrophobic FEP surface is produced at prolonged time of treatment. Changes in the surface morphology due to the plasma treatment were viewed under a scanning electron microscope (SEM).     

Periodic plasma structures in nanosecond discharge with a slit cathode

The spatial structure of optical emission from a transverse nanosecond pulsed electric discharge with a hollow (slit) cathode has been experimentally studied. A regular periodic plasma structure has been observed during nanosecond pulsed discharge in helium at medium pressures. Conditions of the plasma structure formation with respect to the discharge voltage and current are determined. It is shown that the observed plasma structure differs from the known types of striations.     

Surface wettability of silicon rubber after irradiation with a glow discharge plasma

Silicon rubber, PDMS, was irradiated by Ar, Ar/H₂ and Ar/O₂ plasmas to increase the surface wettability to water which was found to increase with the irradiation time for every application of plasma irradiation. The use of Ar/O₂ plasma was found to be particularly effective in enhancing the surface wettability. The aging behavior due to exposure to air, ethanol or water was also measured. In the case of continuous exposure to water after plasma treatment, the wettability could be maintained for more than several months with the water immersion.     

Stable homogeneous microdischarge at atmospheric pressure between a flat cathode and point anode

Conditions of stable operation of a homogeneous glow microdischarge in air at atmospheric pressure between a flat cathode and point anode are established and realized at interelectrode gap widths within ～1–30 μm and discharge currents within from ～10^?4 to 1 A.     

Peculiarities of electric discharge between jet anode and metal cathode

We present the results of a DC electric discharge experimental study between a jet anode and copper cathode at atmospheric pressure. We found the essential influence of the jet anode flow nonuniform character on the discharge development for different power supply regimes. Discharge burning peculiarities are revealed in the jet regime at different power supply voltages with small fluctuation in the milli-, micro-, and nanosecond ranges of the time sweep. We also determined temperatures at the copper cathode surface and its atomization. By means of the Fourier transformation, we reveal the frequency spectrum of the discharge current oscillations.     

Numerical simulation of rarefied dusty plasma in a normal glow discharge

A self-consistent model of a glow discharge, burning in a normal current density mode, with dust particles placed in it is presented. The model of a normal glow discharge is based on a diffusion-drift approximation. Within the framework of this model, the regions of a spatial charge are taken into account. The motion of dust particles in the glow discharge region is calculated using the method of molecular dynamics. The particle charge is estimated based on qualitative conceptions on the process of charging of solid particles. The proposed model is studied numerically, and the corresponding results are presented.     

Multichannel discharge between jet electrolyte cathode and jet electrolyte anode

We present the results of an experimental study of multichannel discharge between a jet electrolyte cathode and jet electrolyte anode within a wide range of parameters. We pioneer the reveal of the burning particularities and characteristics of multichannel discharge with jet electrolyte and droplet electrodes. The deviations are determined by the voltage and current probability distributions for a multichannel discharge from the normal distribution. We show the dependence of two electrolyte jets merging at the electrical parameters and the character of the jet flow.