Showing papers on "Electric discharge published in 2001"

Electric discharge in water as a source of UV radiation, ozone and hydrogen peroxide

Abstract: Results are presented from investigations of multispark electric discharge in water excited along multielectrode metal-dielectric systems with gas supply into the interelectrode gaps. The intensity distribution of discharge radiation in the region covering the biologically active soft UV (190≤λ≤430 nm) has been determined and the absolute number of quanta in this wavelength interval has been measured. The potentiality of the slipping surface discharge in water for its disinfection is analysed. The energy expenditure for water cleansing is estimated to be as low as ~10-4 kWh l-1.

Triboluminescence with and without Air

Abstract: Twenty-three triboluminescent organic and inorganic materials were examined for crystal symmetry, differences between photoluminescence and triboluminescence emission spectra, spectroscopic evidence of an electrical discharge, and persistence of activity under liquids; some were also tested under other atmospheres. These experiments indicate that 18 materials were excited by a discharge, by either electron bombardment of the material or secondary excitation by the UV emissions of the surrounding gas. Five are apparently excited without a discharge, probably by the defect recombination characteristic of deformation luminescence.

Femtosecond laser-guided electric discharge in air.

Abstract: The filament due to the self-guided propagation of an infrared femtosecond laser pulse in atmospheric-pressure air is used to trigger and guide an electric discharge. The long low density plasma channel due to the filament is first heated by the Joule effect during an initial transient plasma stage. The heated channel of recombined gas then hydrodynamically expands radially. The onset of a discharge starts when the density depression on axis reaches the threshold discharge value. This model is supported by detailed experimental and numerical analysis.

Effect of electrical discharge machining on the characteristics of carbon fiber reinforced carbon composites

Abstract: This work investigated electrical discharge machining (EDM) of carbon fiber reinforced carbon composite material. The characteristics of composites machined by EDM were studied in terms of machining parameters. An empirical model of the composites was also proposed based on the experimental data. The composite material was produced by an electrical discharge sinker using a graphite electrode. The workpiece surface and resolidified layers were examined by scanning electron microscopy (SEM). Moreover, surface roughness was determined with a surface profilometer. Experimental results indicate that the extent of delamination, thickness of the recast layer, and surface roughness are proportional to the power input. The EDM process effectively produces excellent surface characteristics and high quality holes in composites under low discharge energy conditions.

Plasma focus light source with active and buffer gas control

Abstract: A high energy photon source. A pair of plasma pinch electrodes are located in a vacuum chamber (10). The chamber (10) contains a working gas which includes a noble buffer gas and an active gas chosen to provide a desired spectral line. A pulse power source provides electrical pulses at repetition rates of 1000 Hz or greater and at voltages high enough to create electrical discharge between the electrodes to produce very high temperature, high density plasma pinches in the working gas providing radiation at the spectral line of the source or active gas. A fourth generation unit is described which produces 20 mJ, 13.5 nm pulses into 2 pi steradians at repetition rates of 2000 Hz with xenon as the active gas. This unit includes a pulse power system having a resonant charger charging a charging capacitor bank, and a magnetic compression circuit comprising a pulse transformer for generating the high voltage electrical pulses at 2000 Hz or greater. Gas flows in the vacuum chamber are controlled to assure desired concentration of active gas in the discharge region and to minimize active gas concentration in the beam path downstream of the pinch region. In a preferred embodiment, active gas is injected downstream of the pinch region through a nozzle (2) and exhausted axially through an exhaust port (3) in the center of the anode. In another preferred embodiment a laserbeam generates metal vapor at a location close to but downstream of the pinch region and the vapor is exhausted axially through the anode.

Electrodeless discharge lamp lighting device

Abstract: PROBLEM TO BE SOLVED: To provide an electrodeless discharge lamp lighting device reducing the noise leaked to the outside. SOLUTION: A DC power circuit 2 converts the AC voltage of a commercial power supply 1 into the desired DC voltage. An AC power circuit 3 converts the output of the DC power circuit 2 into a high-frequency current to apply it to an induction coil 4, and the induction coil 4 generates a high-frequency electromagnetic field to light an electrodeless discharge lamp 5. A matching circuit 6 makes the impedance matching between the high-frequency power circuit 3 and the induction coil 4 to reduce reflection and efficiently feeds the high-frequency power to the electrodeless discharge lamp 5. The DC power circuit 2 and the high-frequency power circuit 3 are stored in a first metal case 9, and the matching circuit 6 is stored in a second metal case 10. The high-frequency power circuit 3 and the matching circuit 6 are electrically connected via a double shield coaxial cable 11, and an electric conductor 11 electrically connected to the first and second metal cases 9, 10 respectively is provided around the double shield coaxial cable 11.

Ballast with lamp sensor and method therefor

Abstract: A ballast circuit is provided having an input, an output for coupling to an electric discharge lamp and an oscillation circuit for illuminating the lamp. A circuit may be included for sensing when a voltage on an input to the oscillation circuit exceeds desired levels. The ballast circuit may be shut down, limited or otherwise controlled to reduce the possibility of ballast failure.

Methane conversion using a high‐frequency pulsed plasma: Discharge features

Abstract: The pulsed plasma of methane was experimentally characterized using single and sequential pulse modes. At a single pulse mode, only pulsed corona and streamer discharges occurred at a low pulse voltage. A pulsed spark discharge developed afrer the pulsed streamer discharge at a high pulse voltage. An image analysis indicated that the weak luminescence could be found in the latter period of the pulsed corona discharge. The pulsed streamer and spark discharges bridged the discharge gap and emitted a relatively strong light. At a sequential pulse mode, the streamer or spark discharge developed easily and evenly at a low pulse voltage, as the pulse frequency increased in comparison with that at the single pulse mode. The high-frequency pulsed plasma was more practical than other plasmas due to its relatively high energy efficiency at room temperature and atmospheric pressure.

High-pressure discharge lamp, and manufacturing method, lighting method, and lighting device for the same

Abstract: A high pressure discharge lamp having a pair of electrodes with a space of 0.5 mm to 2.0 mm inclusive between them and disposed in an arc tube. An electrical discharge takes place between the electrodes. Each of the electrodes has an electrode rod and a head that is provided at the discharge side end of the electrode rod and having a larger diameter than the electrode rod. A surface of the head being opposite to the other electrode is convexly curved and a protruding part is formed in the vicinity of the center portion of the end of the head.

Electric discharge laser with acoustic chirp correction

Abstract: The invention incorporates methods and structural changes in gas discharge lasers for minimizing wavelength chirp at high pulse rates. The major cause of wavelength chirp in high pulse rate gas discharge lithography lasers as pressure waves from a discharge reflecting back to the discharge region coincident with a subsequent discharge. During burst mode operation, the laser gas temperature in prior art lasers changes. This in turn changes the location of the coincident pressure waves from pulse to pulse, which ultimately alters the beam direction, causing the grating in the LNP to reflect back to the discharge region light at a slightly different wavelength. A solution to the problem is to include in the laser chamber structural elements to moderate or disperse the pressure waves and to maintain a constant laser gas temperature. One embodiment has a laser gas discharge chamber with baffles (70), heat exchanger (40), and a fan (38).

IGBT module technology with high partial discharge resistance

Abstract: The high operating voltages of 6.5 kV IGBT modules place additional demands on the insulation and partial-discharge resistance. The most important component affected here is the metallized aluminum nitride ceramic which is embedded in a silicone gel. A high electric field strength can cause a local electric discharge in the silicone gel known as partial discharge, leading ultimately to electric insulation failure and reducing the reliability of the IGBT module. For a 6.5 kV IGBT module, the insulation test must be performed up to a voltage of 10.5 kV rms. Technological steps have been carried out to reduce the maximum electric field strength along the edge of the copper metallization. The edge of the ceramic was coated with a high-impedance layer of doped amorphous silicon. The electric current along the edge of the ceramic homogenizes the electric field strength. The partial discharge was determined up to 11 kV and a considerable reduction was observed compared to standard modules. Without an a-Si:H coating, the partial discharge already increases strongly at low voltages of 3-4 kV. At high voltages, the interface between the silicone gel and the substrate is a major source of partial discharge. The a-Si:H coating reduces electric field peaks and the partial discharge does not exceed 10 pC up to a voltage of 10 kV.

Treatment of liquids

Abstract: The present invention provides an apparatus (1) suitable for use in the treatment of liquid (31). The apparatus (1) comprises a high voltage electric discharge device (8) with a first electrode (24) and a second electrode (25) spaced apart from the first electrode (24) and an electrical power supply control (13) for applying a series of high voltage pulses across said first and second electrodes (24, 25) so as to produce an extended area electrical discharge in an electric discharge zone (37) extending between the first and second electrodes (24, 25). The apparatus (1) includes a gas delivery means (14, 29, 32, 33) for feeding a series of bubbles (36) of gas (2) into the liquid (31) in said electric discharge zone (37). The first and second electrodes (24, 25), and any secondary electrodes (28) therebetween, have opposed portions (103, 104), only said opposed portions of the electrodes (24, 25) and any secondary electrodes (28) present therebetween, being covered in solid dielectric insulator material (102).

Decomposition of CO2 into CO and O in a Microwave-Excited Discharge Flow of CO2/He or CO2/Ar Mixtures

Abstract: Decomposition of CO2 in a fast electric discharge flow of CO2/He or CO2/Ar mixtures was studied by observing UV and visible emission spectra The decomposition efficiency of CO2 in CO2/Ar mixtures was higher than that in CO2/He mixtures More than 90% of CO2 in CO2/Ar mixtures was selectively decomposed into CO and O at a microwave power of 100-200 W, and CO2 and Ar flow rates of 25 and 1000 sccm, respectively, at a total pressure of 05 Torr

Pressure effects on the development of an electric discharge in non-uniform fields

Abstract: Discharges at several atmospheres are widely used for triggering combustion in cars. However, their properties are not well understood since the size and duration of the discharges become very small at high pressures, which makes the experimental approach more difficult. One possibility should be to infer the discharge properties at high pressures from those at atmospheric pressure, provided that the so-called discharge similarity rules work correctly. Thus, an attempt to check this validity is provided in this paper. Then, after establishing the exact conditions which preserve pressure similarity rules in non-uniform gaps, an example is given of two discharges under similar conditions. A departure from similarity is quite clearly observed. At several atmospheres, the streamer induced plasma channel, instead of developing the usual streamer filaments seen at atmospheric pressure, demonstrates a leader structure, i.e. the formation of a hot channel before the whole gap is bridged. Finally, reasons are given explaining that such a fast rise in temperature with pressure is indeed to be expected.

Comparative study on electrochemical techniques for determination of hydrogen diffusion coefficients in metal hydride electrodes

Abstract: The constant potential discharge technique, constant current discharge technique and electrochemical impedance spectroscopy were employed to determine the hydrogen diffusion coefficient in a metal hydride electrode of MlNi365Co075Mn04Al02 alloy with various depth of discharge (DOD) at room temperature and with a specific DOD at various temperatures The results were compared and the advantages and disadvantages of these techniques were also discussed

Method and device for plasma treatment of moving metal substrates

Abstract: The invention concerns a method for treatment, in particular for cleaning and/or heating, a metal substrate (1) moving substantially continuously in a vacuum chamber (3) having a treatment zone wherein an electric discharge (10), that is a plasma, and a magnetic field are produced in a gas maintained at a pressure lower than atmospheric pressure between at least the substrate (1) forming an electrode, and at least a counter electrode (9) so that the substrate (1) is bombarded with ions produced in the electric discharge (10). Said method is characterised in that a magnetic confinement induction field is generated all around the substrate (1) in the treatment zone so that the electric discharge (10) is likewise confined all around the substrate (1) in said treatment zone by the confinement of the electrons released in the electric discharge (10).

Waveform Monitoring of Electric Discharge Machining by Wavelet Transform

Abstract: The waveform affects the quality and mechanical performance of a workpiece during electric discharge machining (EDM). This study uses the wavelet transform to process the waveform of EDM. The data of the waveform are obtained from the voltage and current between the workpiece and the electrode of the electric discharge machine, and are then calculated by the wavelet transform. The outcome shows that after the transformation, the original data can easily identify the different machining condition, thus, providing clear and useful information for the on-line control of EDM.

Scanning electron microscope

Abstract: PROBLEM TO BE SOLVED: To realize a scanning electron microscope, in which secondary electrons can be detected even under a low vacuum, and an observation of a secondary electron image can be performed. SOLUTION: By a differential evacuation of a sample room and a corona ring room 16, where a corona ring 10 has been positioned, to make a degree of vacuum in a corona ring room higher, a sufficient voltage to accelerate the secondary electrons can be applied to the corona ring 10 without generating an electrical discharge. As a result, the secondary electrons that are generated by their radiation of an electron beam EB to the sample are collected by a collector 9 where voltage of 300 V has been applied, and they are collected in the vicinity of a central opening of a collector throttling 17 by an electric field of the collector throttling 17 where higher voltage than the collector potential has been applied. The collected secondary electrons are accelerated by the corona ring 10, and they collide with a scintillator 21.

Experimental investigation of an electric arc air-spike with and without blunt body in hypersonic flow

Abstract: The effects of an arc discharge in a hypersonic flow are currently being studied in the Rensselaer Polytechnic Institute 24-inch Hypersonic Shock Tunnel (RPI HST) and modeled computationally. The arc is a high current car battery array-driven, 75-kilowatt peak, self-sustaining electrical discharge in a Mach 10, 260 psia stagnation pressure, and 560 K stagnation temperature flow. In this low enthalpy, "ideal gas," condition, schlieren photographs were taken of the apparatus with and without a downstream blunt body, with varying arc powers. The computational effort employed the Euler gasdynamic equations to represent a heat source in flow conditions and geometries identical to those tested in the RPI HST. These two results are then compared to qualitatively validate the code and gain a better perspective on the loss mechanisms involved in the experiment.

Treating method of liquid and device therefor

Abstract: PROBLEM TO BE SOLVED: To provide a method and a device for effectively treating liquid by electric discharge of the liquid by reducing the electric energy used for securing an electric discharge path. SOLUTION: In the method and the device for forming an electric discharged state between electrodes by applying a high voltage pulse and treating the liquid to be treated existing in the range of a high voltage pulse application, gas is fed into the liquid prior to introducing into the range of high voltage pulse application.

Discharge lamp operating apparatus

Abstract: A discharge lamp operating apparatus includes a discharge lamp and a driving circuit of the discharge lamp The driving circuit can vary power to be supplied to the discharge lamp and has a function to turn off the discharge lamp at a supplied power value above a supplied power value at which unstable discharge occurs in the discharge lamp

Control of low velocity airflow along a flat plate with a DC electrical discharge

Abstract: Ability of a DC electrical discharge to control low velocity airflow along a flat plate is analyzed. Specifically, the electrodes are flush mounted on the insulating surface of the plate creating a tangential corona discharge at close vicinity of the wall. In this paper, visualizations of the low velocity airflow (up to 1.4 m/s corresponding to Re=16,000) along the flat plate are presented. They show that the ionic wind induced by the corona discharge modifies the original airflow considerably, resulting in the airflow reattachment to the wall and reduction of the wake size. Velocity measurements by particle imaging velocimetry and by Pitot tube are conducted in a wind tunnel loop for higher airflow velocities (up to 11 m/s corresponding to 117,800). Results show that the corona discharge at such high airflow velocities does affect significantly the velocity profile within the viscous boundary layer.

Control apparatus for wire cut electric discharge machine

Abstract: In a wire cut electric discharge machine, a correction block is inserted into a corner of a movement path where the wire electrode is moved by the electrode moving device. The correction block does not correspond to the contour of the workpiece to be machined. When it is necessary to change machining condition such as the voltage to be applied to the wire electrode before and after the corner, a changing position to change the machining condition is set on the correction block.

Electric field in inductively coupled gas discharges

Abstract: The electric field in a low-pressure electrodeless discharge has been determined from discharge voltage measurements at constant discharge current as a function of gas pressure. Measurements have been made in neon, argon, and xenon at discharge currents of 1, 3, and 10 A with a driving frequency of 0.45 MHz. The behavior of the electric field as a function of gas pressure has been found to be qualitatively similar for all three gases. At the lowest gas pressures at which a discharge can be sustained, the electric field is relatively high. With increasing gas pressure the field reaches a local minimum, followed by a local maximum and another local minimum. Above 1 Torr, the electric field increases monotonically with gas pressure.

Gas mixtures and ozone production in an electrical discharge

Abstract: The quantitative production of ozone (O3) with N2, O2, and Ar gas mixtures in an atmospheric pressure corona discharge (CD) is investigated. A five-part model is presented that explores the discharge conditions needed for optimum ozone production. One part of the model is the well-known relationship that correlates the discharge's voltage, frequency, gap, dielectric material, etc with the generator's yield. The four other parameter's revolve around the correct selection of the gas mixture, which subsequently effect's the discharge's ionization potential, continuum background, excitation of atomic and molecular species, and gas cooling efficiency. Varying the ratios of the three basic components of air (N2, O2) and Ar) is demonstrated to have a pronounced effect on ozone production in a modified CD.

Two-dimensional spatial distribution of electric-discharge plasma around a frictional interface between dielectric surfaces

Abstract: Electric-discharge plasma and thermal radiation were directly observed in measuring two-dimensional spatial distributions of photon emission during friction between a diamond spherical surface and crystalline Al2O3 surface in ambient air. By using spectral filters, a clear difference was observed between the spatial distribution of the radiation from the plasma about the frictional point and that of the thermal radiation. This report elucidates the spatial distribution of the electric-discharge plasma on the interface between dielectric surfaces during friction, which then allows one to estimate the potential difference between the two dielectric surfaces at the discharge sites.