Durations of transient glow discharge after static and overvoltage breakdowns have been investigated in helium, nitrogen and hydrogen at sub-atmospheric pressure. The result shows that the glow duration is much larger in helium than that in other used gases. The duration of transient glow after static breakdown is rather shorter than that after overvaltage breakdown. Furthermore a continuous glow discharge with a large crosssection was produced in a high frequency range of 25 kHz-100 kHz at sub-atmospheric and atmospheric pressures. The length of transient glow duration is correlative with the ease of production and stability of the continuous glow discharge.

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In the studied auto-expansion circuit-breaker, about one millisecond before current zero, the arc centers itself on the axis of the system and gets longer because of the gas flowing from the upstream to the dowstream volume. The imagined solution to determine the arc root position inside the hollow electrodes, consists in embedding small Rogowski coils within the electrode material, close to the inner surface. Experimental results showed that sometimes the arc stretches out, then gets shorter suddenly, then gets longer again. But, if the arc is centered during a minimum critical duration, it remains permanently centered until current zero.

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In this paper, a theoretical model allowing to plot the breakdown voltage VB as a function of the pressure×gap distance product (pd) is presented for a D. C. corona discharge. For a parabolic point, it is shown that Paschen-like curves are obtained, the result being dependent on the point tip radius. Finally, this model is compared to experimental results obtained in nitrogen and air.

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Deposition of carbonitride films was realised by Plasma Enhanced Chemical Vapour Deposition (PECVD) method using 13.56 MHz discharge in a CH₄-N₂- Ar mixture. Principal dissociation and recombination products were analysed by optical emission spectroscopy (OES) and mass spectrometry (MS) for different experimental conditions. Actinometric measurements were used to test the tail of the Electronic Energy Distribution Function (EEDF) and to estimate the main creation and destruction processes of some excited states. Electronic temperature variation was estimated in nitrogen plasmas by emission spectroscopy measurements and chemical titration was used to determinate atomic nitrogen rate in N₂ and N₂- Ar post-discharge regions. Most part of these diagnostics were associated with infrared spectroscopy (IRS) and chemical composition analysis of the amorphous C-H(N) films deposited on SiO₂ or Zr substrates. Emission spectroscopy and mass spectrometry analyses of an oxygen plasma created after deposition processes have permitted to estimate N, C and H evolution relative rates in the film, as a function of experimental parameters. Correlations between the plasma chemistry processes and film properties were used to suggest experimental conditions permitting to create a higher concentration of carbonitride species in the gaseous phase and to increase nitrogen rate in the film.

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The distribution of microdischarges in time and space, the influence of dielectric surface on microdischarges, and the characteristic of ozone generation were studied using electrical and optical methods. As a result, the phenomenon of a chain of microdischarges occurring in a brief period could be observed. In addition, it was found that the microdischarge characteristic, collective microdischarge phenomenon, and ozone yield varies according to the surface condition of the dielectric electrode. The ozone yield was high with a glass surface and low with a ceramic surface.

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A model is described that facilitates calculation of pressure rise due to internal fault arcing in flameproof enclosures of the type used in underground coal mines. In the model arc energy is assumed to heat the gas in the flameproof enclosure, the only energy loss from the gas being by mass loss through flamepaths around the enclosure lids. Calculations are compared with measurements made with flameproof equipment, and the effect of initial flamepath width on pressure rise is established.

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A kinetics model has been developed to study the chemical composition of a decaying SF₆ arc plasma in the presence of impurities such as copper, carbon and water, proceeding from electrode and nozzle erosion or desorption in real SF₆ circuit-breakers. The model is based on the following main assumptions: the plasma is in thermal equilibrium (only one temperature for all the species); the plasma is homogeneous; the pressure remains constant during the decay; the transient temperature evolution is previously imposed. Experimental gas analysis by chromatography, after arcing in a circuit-breaker has confirmed the main results of the calculation: proportion of SOF₂ is much more important than that of SO₂F₂ and very low formation of S₂F₁₀ molecules.

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The laser scattering techniques are very powerful for the diagnostics of impulse discharges. Characteristics of gas temperature, density of Cu atoms from electrodes and electron density in and near an impulse discharge channel at an air pressure of 66.7hPa were investigated. The gas temperature took much higher values in the constricted regions of the channel, especially in the two regions near the tips of anode and cathode along the positive column. At the transition from glow to arc, the gas temperature and the densities of Cu atoms and electrons in the discharge channel became high with a rise of discharge current, and reached maximum values of 4800K, 9×10¹⁸m^-3 and 8×10²³m^-3, respectively. Both the positions of peaks of the gas temperature and the density of Cu atoms moved quickly from the inside toward the outside of discharge channel; their moving velocities decreased from 1200m/s to 200m/s within 20μs.

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To prevent severe faults in GIS, studies on the relation between UV irradiation and degradation of insulating material are presented. By using the measurement system of discharge-light-emission, quantitative measurement of the discharge light is carried out, and the absolute emission power of the discharge is obtained. On the one hand, the degradation of insulating material is evaluated employing sample materials which are irradiated by a UV-laser. The result is obtained that the volume or the surface resistance decreases as the amount of irradiation increases.

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We report the designs and performances of He-Cd⁺, He-Kr⁺, He-Ar⁺, He-Se⁺, He-Cu⁺ (CuBr) and Ne-Cu⁺ (CuBr) lasers excited with the transverse capacitively coupled radio-frequency -discharge. At the similar laser output parameters the designs and operation of the radio-frequency excited lasers are much simpler than those of the hollow-cathode discharge lasers. Under singleline operation the radio-frequency excited He-Cd⁺ laser delivered output powers of 60mW at 441.6nm, 36mW at both 533.7nm and 537.8nm, and 14mW at both 635.5nm and 636.0nm. The output powers of the He-Kr+ laser were 22mW at 469.4nm, and 11mW at 431.8nm. Both lasers exhibited the rms noise-to-signal ratio (0.4-0.6%) much lower than that of conventional positive column He-Cd⁺ lasers. Using a He-CuBr gas mixture laser action on four infrared CuII lines (740.4nm, 766.5nm, 780.8nm and 782.0nm) was achieved and with a Ne-CuBr gas mixture laser gains on 14 UV-lines between 240.3nm and 272.2nm were observed.

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The purpose of this study is to elucidate the role of charges appearing on the opposite surface of a solid insulator in causing flashover along the insulator surface. The experimental apparatus used is consisted of two coaxial hard glass cylinders with a gas layer in between. Application of a magnetic field in the axial direction of the cylinders affects its surface flashover voltage. Appearance of an aurora-like discharge in the gas layer causes a sudden reduction of positive impulse flashover voltage. This study makes clear the relation between the aurora-like discharge and the surface flashover by obtaining the relation between the pressure of the gas layer and the magnetic flux density on the probability of the appearance of the aurora-like discharges quantitatively.

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In order to enhance the etching rate at lower pressure, an electron-beam assisted inductively coupled plasma (ICP) reactor was developed, in which the electron-beam was injected into the reactor through a thin polymer film, and a pattern of 0.2μm was etched on an Si wafer. We discussed the peculiarities of plasma produced by the above reactor in comparison with the data we got as a result of probe measurements. It was found that the electron-beam injection into the ICP decreases the floating and the plasma potentials and increases the electron temperature and the density slightly.

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Under high E/n condition, electrons gain high energy in discharge space. It is expected that many excited molecules are also generated in the space. If it is possible to utilize these molecules for surface processing, many functions may be introduced onto materials. However it is very difficult to estimate number density of neutral molecules generated in the space, because in a high E/n condition the electron energy distribution is not in equilibrium. The authors have used a Monte-Carlo method to estimate an electron energy distribution in discharge under high E/n. In this study, the number density of excited molecules and the flux onto materials were calculated under steady state condition using a Monte-Carlo method.

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Concave formation on the current profile on the plane electrode in negative corona was reported. The authors tried to clarify the condition of concave formation. From the results, it is assumed that N₂ (A³ ∑_u⁺) molecules act an important role. To confirm this speculation, experiments in uniform ticld at low pressure were carried out. The results show many similarities on variation of current with time and/or with NO concentration between different experimental conditions, one is corona in atmospheric pressure and the other is non-selfsustaining discharge under uniform field in low pressure. Thus, accumulation and quenching processes of N₂ (A³ ∑_u⁺) molccules is proposed to cxplain the phenomena on current profile.

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We measured hold-off voltages in typical pseudo spark discharge gaps for four different working gases: He, Ne, Ar, and N₂. The effect of the cathode hole diameter on the hold-off characteristics was also investigated. In order to understand the present observations, a simple Monte Carlo simulation of electron and ion motions in the pseudo spark gap was carried out in He.

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Characterization of surface discharge phenomena is difficult because of numerous factors which affect the phenomena. This paper reports on an investigation into the fundamental characteristics of surface discharge in air at atmospheric pressure. The developing length of the surface streamer L is determined by V_s which is the instantaneous voltage of the high voltage electrode when the streamer occurs. L changes linearly with V_s. When the surface streamer develops over 60mm in length, the relationship between L and V_s deviates from a linear one and the value of L tends to saturate with increasing V_s. It is observed that as a streamer develops a steep pulse current of greater than 10¹⁰A/s flows. The voltage drop due to the inductance of the power supply circuit is too large to be disregarded.

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We have investigated the motion of electrons in a new, high voltage segmented hollow cathode discharge, applicable as an efficient pumping source for charge transfer excited UV metal ion lasers. We have used Monte Carlo simulation of the electrons' motion to obtain the spatial distribution of ion production, electron energy distributions, and the fraction of oscillating electrons in the discharge. We present the results of an analysis of the effects of the longitudinal magnetic field, the number of electrode segments and the cathodeanode surface ratio. The results of the simulations explain the experimentally observed behaviour of the investigated discharges. Our study with a longitudinal magnetic field confirms the existence of oscillating electrons even at relatively high pressures.

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The rates for production of the compounds S₂F₁₀, S₂OF₁₀, and S₂O₂F₁₀ have been measured both in spark and continuous, constant-current negative glow corona discharges generated using point-to-plane electrode gaps in 'pure'SF₆ and SF₆/O₂ gas mixtures containing up to 10% oxygen by volume fraction. In the case of corona discharges in pure SF₆, the S₂F₁₀ concentrations were measured as a function of time during discharge operation using a gas chromatograph-mass spectrometer for gas pressures in the range of 100kPa to 500kPa and at discharge currents between 2μA and 80μA. The charge rate-of-production of S₂F₁₀ from negative corona is observed to drop with decreasing discharge current, and the yield curves exhibit nonlinearities in the early stages of the discharge associated with "conditioning" of the point electrode. The initial nonlinearities become more pronounced with increasing gas pressure. The absolute yields of S₂OF₁₀ and S₂O₂F₁₀ were measured as a function of O₂ content in SF₆ for both negative glow corona (40μA and 200kPa) and spark discharge (80J/spark and 100kPa). The gas analysis in the case of spark discharges was performed after each spark using a cryogenic enrichment chromatographic technique. When O₂ is added to the gas, there is a dramatic drop in the S₂F₁₀ yield from both types of discharges with a corresponding increase in S₂OF₁₀ yield from the spark and S₂O₂F₁₀ yield from the corona discharge. The results can be explained within the framework of a plasma-chemical model from considerations of the competition among the reactions of SF₅ radicals produced by dissociation of SF₆ in the discharge with SF₅ itself as well as with O₂ and O, and the relative degree of O₂ dissociation in the two types of discharges.

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