Glow Discharge


Also found in: Dictionary, Wikipedia.
Related to Glow Discharge: sputtering, Arc discharge

glow discharge

[¦glō ¦dis‚chärj]
(electronics)
A discharge of electricity through gas at relatively low pressure in an electron tube, characterized by several regions of diffuse, luminous glow and a voltage drop in the vicinity of the cathode that is much higher than the ionization voltage of the gas. Also known as cold-cathode discharge.

Glow Discharge

 

a type of stable, self-maintained electrical discharge in a gas. A glow discharge occurs at a low cathode temperature and is characterized by a comparatively low current density at the cathode and a high cathode drop U, which may be of the order of a few hundred volts. Although such discharges may occur at gas pressures p as high as atmospheric pressure, most investigations of the glow discharge have been carried out at pressures ranging from a few hundredths of a millimeter to several millimeters of mercury.

In a glow discharge electrons are emitted by the cathode primarily as a result of bombardment by positive ions and fast electrons; the photoelectric effect and the energy of metastable atoms, however, also play a certain role in electron emission. At

Figure 1. Appearance and parameter distribution of a normal glow discharge at a relatively low pressure: (1) cathode, (2) Aston dark space, (3) cathode glow, (4) cathode dark space, (5) negative glow, (6) Faraday dark space, (7) positive column, (8) anode region, (9) anode

pressures of the order of tenths of a millimeter of mercury or higher, a glow discharge in a long cylindrical tube is typically divided into a number of regions that differ markedly in appearance (Figure 1). The formation of these regions can be explained by reference to the characteristics of the elementary processes of ionization and excitation of atoms and molecules. The most important region, which determines the very existence of the glow discharge under the given conditions, is the cathode dark space. In this region collision ionization by electrons results in the formation of positive ions, which cause the emission of electrons by the cathode.

The voltage between the electrodes depends primarily on two parameters: the current density j at the cathode and the product pi of the pressure and the distance l between the electrodes. A general classification of the various forms of glow discharge was established in the investigations of the Soviet scientist B. N. Kliarfel’d and his students. The classification extends to the case of very small values of pl and j, where no space charge is present between the electrodes and the field is practically uniform. In Kliarfel’d’s terminology this case is called the simplest (prosteishii) glow discharge. Here, the separate regions mentioned above are absent, and the gas is ionized by electrons throughout the space between the electrodes. If pl and j are increased, two forms of glow discharge can be obtained: the normal glow discharge and the abnormal glow discharge. In the case of the normal glow discharge, electrons are emitted from only a part of the cathode surface, and j and U remain constant. An increase in current causes emission to occur from a larger part of the cathode. The abnormal glow discharge is observed at high values of j. It is characterized by a rapid increase in the voltage between the electrodes as the current is increased.

A special type of glow discharge can be obtained with a hollow cathode (a cathode consisting of a hollow cylinder or two parallel plates). In such a discharge the electrons undergo multiple oscillations between the walls of the cathode and intensely ionize the gas. Hollow-cathode glow discharges exhibit much higher current densities and much brighter glow regions than do ordinary glow discharges.

The properties and characteristics of glow discharges are made use of in technology in, for example, voltage regulator tubes.

REFERENCES

Kaptsov, N. A. Elektricheskie iavlenüa v gazakh i vakuume, 2nd ed. Moscow-Leningrad, 1950.
Granovskii, V. L. Elektricheskii tok v gaze: Ustanovivshiisia tok. Moscow, 1971.
Genis, A. A., I. L. Gornshtein, and A. B. Pugach. Pribory tleiushchego razriada. Kiev, 1963.
Acton, J., and J. Swift. Gasorazriadnye pribory s kholodnym katodom. Moscow-Leningrad, 1965. (Translated from English.)

L. A. SENA

glow discharge

An electric discharge in a gas at low pressure which produces a diffuse glow; characterized by a low cathode temperature, a low current density, and a high voltage drop.
References in periodicals archive ?
The effects of Cu and PE doping, glow discharge treatment on the morphological feature, molecular structure and tribological properties of composite coatings have been investigated.
2016) have demonstrated the use of x-ray radiography to obtain temporally and spatially-resolved 2D maps of the gas displacement inside the gap of a conventional spark plug, mainly during the glow discharge phase [20].
Provision of an optical emission spectrometer with a glow discharge source.
KEYWORDS: DC discharge, Glow discharge regions, Optical emission spectroscopy, Image
The preforms in green were sintered by plasma generated by the abnormal glow discharge of direct current, Figure 1, at an atmosphere of [H.
A Uniform Glow Discharge Plasma Source at Atmospheric Pressure.
Abbreviations DBD Dielectric barrier discharge APGD Atmospheric pressure glow discharge RF Radio frequency THPFDA Tetrahydroperfluorodecyl acrylate and tetrahydroperfluorododecyl acrylate APPR Atmospheric pressure plasma reactor FTIR Fourier transform infrared spectrometer XPS X-ray photoelectron spectroscope TOF-SIMS Time-of-flight secondary ion mass spectrometry SEM Scanning electron microscope AATCC American Association of Textile Chemists and Colorists SAO Solid add-on
In sputtering process, argon ions are produced in a glow discharge bombardment of the coating material, which leads to dislodging atoms, entry into vapour phase, followed by deposition on the substrate.
In addition to SEMs, researchers used selected area X-ray photoelectron spectroscopy energy-dispersive spectroscopy, secondary ion mass spectrometry, and glow discharge optical emission spectrometry.
In addition to classic wet chemistry, it employs advanced inductively coupled plasma, atomic absorption and glow discharge spectroscopy to ensure the optimum method for a particular application.
When dealing with solid pieces of metal down to 15mm in diameter, the glow discharge spectrometer is often the instrument of choice, a typical application being the analysis of foundry discs.
He covers elements of the theory of numerical modeling of gas-discharge phenomena, numerical simulation models of glow discharge, and ambipolar models of direct current discharges.