Abstract: An induction RF fluorescent lamp configuration provides reduced EMI, including a lamp envelope with a re-entrant cavity both covered on the partial vacuum side with phosphor and filled with a working gas mixture, a tubular ferromagnetic core on the non-vacuum side said re-entrant cavity wound directly on the said core with two windings having different numbers of turns, a first active winding having one end connected to an RF ballast and the other end connected to local ground, and a second passive winding having one end grounded and the other end free.

Abstract: A lamp includes a discharge vessel; electrodes spaced apart in the discharge vessel comprising tungsten or tungsten alloy; and a fill sealed within the vessel having a pressure between 50-200 mbar. The fill includes: a starting gas which comprises: xenon, krypton, argon or combinations thereof with the exception of pure argon; optionally radioactive Kr85 with a maximum activity level of 0.124 MBq/l as part of the starting gas; and a metal halide component. The lamp includes an active tungsten regeneration cycle wherein the fill comprises a species of the tungsten or tungsten alloy of material of the electrodes during lamp operation, wherein the solubility of tungsten or components of tungsten alloy in the tungsten or tungsten alloy species is lower in a gas phase adjacent to the electrodes than at close proximity of the wall of the discharge vessel.

Abstract: A lamp includes a discharge vessel; electrodes spaced apart in the discharge vessel comprising tungsten or tungsten alloy; and a fill sealed within the vessel having a pressure between 50-200 mbar. The fill includes: a starting gas which comprises: xenon, krypton, argon or combinations thereof with the exception of pure argon; optionally radioactive Kr85 with a maximum activity level of 0.124 MBq/l as part of the starting gas; and a metal halide component. The lamp includes an active tungsten regeneration cycle wherein the fill comprises a species of the tungsten or tungsten alloy of material of the electrodes during lamp operation, wherein the solubility of tungsten or components of tungsten alloy in the tungsten or tungsten alloy species is lower in a gas phase adjacent to the electrodes than at close proximity of the wall of the discharge vessel.

Abstract: A metal-halogenide filling for forming an ionisable filling comprises at least one inert gas, mercury and at least one halogen, the filling including at least the components Rb-halogenide and Mn-halogenide. This filling can in particular be contained in the discharge container of a metal-halogenide lamp.

Abstract: A high-pressure discharge lamp with an axial symmetry axis and metal halogenide filling has electrodes with shafts designed as pins with a diameter of 0.5 to 1.15 mm. The halogen for the halogenide is composed of iodine and possibly bromine components, iodine being used alone or in combination with bromine, and the bromine/iodine atomic ratio amounting to maximum 2.

Abstract: A low-pressure discharge lamp (1) is provided that includes a glass tube (2) having an inner diameter in a range of 1 to 5 mm and a pair of electrodes (3) disposed at end portions in the glass tube (2). The pair of electrodes (3) contain at least one transition metal selected from transition metals of Groups IV to VI. Mercury and a rare gas containing argon and neon are sealed in an inner portion of the glass tube (2). A relationship between a cathode glow discharge density J and a composition index ? of the sealed rare gas of the low-pressure discharge lamp (1) satisfies the following expression ??J=I/(S·P2)?1.5? (where S represents an effective discharge surface area (mm2) of an electrode, I represents a RMS lamp current (mA), P represents a pressure (kPa) of a sealed rare gas, and ? represents a composition index of a sealed rare gas that is a constant expressed by ?=(90.5A+3.4N)×10?3 when a total of a composition ratio A of argon and a composition ratio N of neon is expressed by A+N=1).

Abstract: The invention relates to a high-pressure mercury discharge lamp for DC operation at a nominal wattage of more than 1.5 kW. Said high-pressure mercury discharge lamp comprises an anode, at least some areas of which are made of a material containing at least some tungsten, said material having a grain number of more than 200 grains per mm2 and a density of more than 19.05 g/cm3.

Abstract: The present rare gas fluorescent lamp can prevent reduction of an effective light-emitting region by securely suppressing creeping discharge even when a conductive material is provided to improve starting performance. The rare gas fluorescent lamp having a light-emitting tube whose inner surface is coated by a fluorescent material and which is filled with a rare gas, a plurality of external electrodes which are provided on an outer surface of the light-emitting tube, a conductive material, which is provided at an end portion of the light-emitting tube that corresponds to a portion on which the external electrodes are arranged, the rare gas fluorescent lamp, and a creeping discharge prevention unit that is provided inward of the conductive material in an axial direction to prevent diffusion of creeping discharge occurring between the conductive material and electrical charges stored on the inner surface of the light-emitting tube.

Abstract: A device for operating a discharge lamp of the short arc type having a feed device which supplies a direct current to the discharge lamp when operation starts and an alternating current afterwards, in which the feed device supplies a direct current which is smaller than the rated current to the discharge lamp at the start of operation, and a direct current which is at least as large as the rated current, afterwards. A control which ascertains whether the discharge lamp at the start of operation is in a hot or cold start operating state, and which establishes one of the following parameters based on whether the hot or cold operating state ascertained to exist: the value of the direct current which is at least as great as the rated current; the feed duration of the direct current which is at least as great as the rated current.

Abstract: Metal halide lighting with good color during dimming may be obtained. An appropriate balance of commonly used metal halides (NaI, DyI3, CeI3, CaI2, TlI) is dosed in the lamp. No mercury is used. A higher than typical xenon fill pressure from 50 to 500 Kilopascals may be used to help control thermal properties and voltage. If necessary, modulation of the power at acoustic resonance frequencies may be used to straighten and center the arc. Efficient and pleasant white output is obtained. As the power is reduced, the chromaticity either (1) remains fairly constant or (2) drifts acceptably towards warm pinkish colors. Large factors of attenuation in output can be realized. The lumen output was reduced by at least a factor of twenty in one sample as the power was dimmed from 70 to 20 watts.

Abstract: An emission device for an ultra-high pressure mercury lamp which maintains an electrode tip shape by which a stable discharge can always be carried out is achieved for a short arc ultra-high pressure mercury lamp with silica glass arc tube containing a pair of opposed electrodes spaced apart a distance of at most 2 mm and in which the arc tube is filled with at least 0.15 mg/mm3 of mercury, a rare gas and a halogen in the range from 1×10?6 ?mole/mm3 to 1×10?2 ?mole/mm3; by providing an operating device which produces a current feed by which the surface of the tip of at least one of the electrodes is shifted into a molten state during lamp operation.

Abstract: In a discharge tube of the present invention, a filler gas is composed of a mixture of inert gas and hydrogen gas and an airtight cylinder 10 in which the filler gas is enclosed in an airtight manner is provided. A pair of first and second discharge electrodes 22 and 24 are opposed to each other within an internal space of the airtight cylinder, so that an electric discharge is generated between discharging surfaces of the first and second discharge electrodes. In the discharge tube, a concentration of the hydrogen gas in the filler gas is set in a range from 20 percent by volume to 80 percent by volume.

Abstract: There is provided an improved high-pressure discharge lamp which includes an arc tube encapsulating a halogen, and a pair of tungsten electrodes disposed in the arc tube. The oxygen content in the tungsten electrodes is not more than 15 ppm, while the amount of the encapsulated halogen lies in the range of 1×10?7 to 1×10?2 ?mol/mm3.

Abstract: A discharge lamp which maintains a high lumen maintenance factor even when operated for a long time is obtained in a discharge lamp which has a silica glass discharge vessel and a pair of opposed electrodes in the discharge vessel and in which the discharge vessel is filled with at least 0.15 mg/mm3 mercury, a rare gas with argon as the main component, and 2×10?4 ?mole/mm3 to 7×10?3 ?mole/mm3 bromine by meeting the following conditions when feeding a direct current of 5 mA between the electrodes and a glow discharge produced: 1.0×10?4?b/a?1.2×10?1??Condition (1) c/a?1.4×10?1??Condition (2) d/a?1.2×10?2??Condition (3) e/a?1.4×10?2??Condition (4) where a is the emission intensity of the argon with a wavelength of 668 nm, b is the emission intensity of OH with a wavelength of 309 nm, c is the emission intensity of hydrogen (H) with a wavelength of 656 nm, d is the emission intensity of C2 with a wavelength of 517 nm, and e is the emission intensity of CH with a wavelength of 431 nm.

Abstract: The invention relates to a high-pressure gas discharge lamp, particularly a motorcar lamp, comprising a bulb including at least two neck portions and a vacuum-tight discharge vessel of quartz glass, at least two electrodes projecting into the discharge vessel, and a filling in the discharge vessel which, in the operating state, is in a discharge state. Such lamps are used, in particular, in headlights of motorcars. In order to ensure that the arc of the high-pressure gas discharge lamp generates a higher luminescence in a small area, and the lamp can be used as a light source in motorcar headlights, the discharge vessel of the high-pressure gas discharge lamp in accordance with the invention encloses a discharge space having a width B below 4 mm and a length C below 8 mm, and the filling comprises NaI, ScI3, Xe, ZnI3 and is free of Hg. Surprisingly it has been found that the use ZnI2 in the filling causes the arc to generate a higher luminescence in the area of the arc axis per dimension of the arc.

Abstract: A short arc mercury discharge lamp including an arc tube filled with at least mercury and a rare gas, a cathode and an anode positioned opposite to each other within the arc tube, the cathode having an tapered area which tapers in a direction towards the anode and a projection which protrudes from the tapered area in a direction towards the anode. The amount of mercury to be added in the arc tube is in a range of 0.2≦n≦52, where n is the weight (mg/cm3) of the mercury per unit of volume, and a pressure of the rare gas to be added in the arc tube is in a range of 0.1≦p≦800, where p is the pressure (kPa) of the rare gas at an ambient temperature of 25° C.

Abstract: An alternating current driven type plasma display device includes a plurality of sustain electrodes having a spacing less than 5×10−5 m and a discharge gas in a discharge space where discharge takes place. The discharge gas consists of xenon gas alone having a pressure greater than or equal to 1.0×104 Pa and less than or equal to 3.0×104 Pa or the discharge gas consists of krypton gas alone having a pressure less than or equal to 6.6×104 Pa.

Abstract: A mercury-free metal halide lamp includes an arc tube including a pair of electrodes inside the tube. In the arc tube, a rare gas and a metal halide are contained, and no mercury is contained. The mercury-free metal halide lamp is horizontally operated such that the pair of electrodes is substantially horizontal. The mercury-free metal halide lamp further includes magnetic field applying means for applying a magnetic field including a component substantially perpendicular to a straight line connecting heads of the pair of electrodes in a substantially vertical direction. The density of halogen atoms evaporated during steady-state operation with respect to unit inner volume of the arc tube is 20 &mgr;mol/cc or more.

Abstract: A bulb for an electrodeless lamp comprises: an envelope through which the light can be permeated; a filled material filled in the envelope for emitting the light as being excited by high frequency energy; and buffer gas, wherein the buffer gas comprises first buffer gas, and second buffer gas having a partial pressure less than 1% of the partial pressure of the first buffer gas in order to reduce a discharging voltage and lighting time, and thereby, the re-lighting after putting out the light can be performed easily and the re-lighting time is reduced to improve the convenience of the user and the reliability of electrodeless lamp.

Abstract: The present invention provides a tungsten-halogen light bulb having an arc tube with a seal portion at one end. A filament is provided in the interior of the arc tube, and a basic gas mainly comprising at least either gaseous xenon or gaseous krypton is filled in the arc tube. When V (V) denotes a rated voltage of the tungsten-halogen light bulb, P(MPa) denotes a filling pressure of the basic gas at a room temperature, and Xe vol. % and Kr vol. % respectively denote composition ratios of the gaseous xenon and of the gaseous krypton, the following formulas (1) and (2) are satisfied simultaneously, in which ‘%’ means ‘volume %’. V≧100 (Volt)  (1) P≧0.7+{0.1×(Kr%/(Kr%+Xe%))}  (2) In these formulas, Kr %+Xe %=100(%), 0≦Kr %≦100, and 0≦Xe %≦100. Accordingly, a crack at the seal portion of the arc tube is prevented and the lifetime is improved.

Abstract: A high pressure, lamp may be made in a pressure vessel by using an induction coil to melt an edge portion of a sealing wafer pressed against the circumference of an opening in the body of the lamp envelope. The pressure vessel and the lamp envelope are filled with desired fill materials. Induction heating is carried out by the induction coil and induction receiver that presses against the wafer, the lamp envelope or both to hold the melting piece or pieces in contact. The induction receiver may be fused to the lamp body forming a functional part of the overall lamp structure. The preferred resulting lamp includes a bonded metal piece that can be conveniently used for electrical or mechanical coupling or positioning of the lamp with respect to a base.

Abstract: Low-pressure mercury discharge lamp (1) comprising an at least partly substantially cylindrical discharge vessel (3) having a diameter D, wherein two electrodes are present near respective ends of said discharge vessel (3), which discharge vessel (3) is filled with a mixture of inert gasses having a pressure P and which discharge vessel (3) contains an amount of mercury, wherein D×P is at least 5.2 mPa. The invention is based on the novel understanding that a higher filling pressure of the inert gas mixture causes a lower mercury consumption in the lamp (1).

Abstract: A mercury-free high pressure sodium vapor lamp is dosed with sodium, xenon and zinc as an elemental metal additive. The addition of the metal additive prevents an undesirable low-voltage operating mode of the sodium-xenon discharge associated with a mercury-free HPS lamp, which otherwise occurs when sodium is no longer available to participate in the arc discharge.

Abstract: Plasma display panel in which the fluorescent layer comprises non-saturating green phosphor(s). This improves the efficacy of UV-light generation and allows the use of higher sustain voltages, leading to further improvement of the efficacy and luminance. The display panel may include driver means for sustaining a generated plasma with a sustain voltage whose peak to peak voltage is at least 400V. This can be combined with existing red and blue phosphor to obtain a desired color.

Abstract: A fluoride-based fluorescent material designated by a composition formula of MFn:R, wherein M is at least one element selected from the group consisting of rare earth elements, Al and Bi, alkaline earth metals, and alkaline metals, and R is a rare-earth-based activator including at least either Tb or Tb and Ce and n=1, 2 or 3. The fluoride-based fluorescent materials efficiently emit white-light of a luminescent peak at 543 nm.

Abstract: A metal halide discharge lamp which essentially permits disusing mercury is provided. The metal halide discharge lamp comprises a refractory and transparent hermetic vessel, a pair of electrodes fixed to the hermetic vessel, and a discharge medium sealed in the hermetic vessel and containing a first halide, a second halide, and a rare gas. The first halide is a halide of a metal which achieves a desired light emission. The second halide has a relatively high vapor pressure, being at least one halide of a metal which is unlikely to emit a visible light compared with the metal of the first halide and acts as a buffer gas.

Abstract: A xenon arc lamp is provided with an improved cathode support. The improvements reduce the number of assembly procedures and parts needed to produce an arc lamp. Such reduces the overall cost of manufacturing. The cathode suspension system is made by starting with a single piece of sheet Kovar material that is formed into a cup. Pieces are cut from the bottom of the cup such that three webs connect the outside ring to the center. The three webs each have a flap that is then folded back 90° to form a rigid strut arm. A tungsten cathode electrode is brazed at the center and apex of the three struts with a sleeve that helps bridge the fillet area.

Abstract: A neon lamp including a sealed glass bulb, electrodes and leads connected to the electrodes has a flat head whose center region descends into the interior of the sealed glass bulb. A method of producing the neon lamp includes steps of charging neon gas into a glass tube through a fine glass tube at the head of the glass tube, sealing the fine glass tube to obtain a sealed glass bulb having a projecting tip portion, removing excess glass of the projecting tip portion, and shaping the projecting tip portion into a substantially flat or lenticular head portion. A system for producing the neon lamp includes a shaping head for accommodating the sealed glass bulb with its projecting tip portion exposed outside the shaping head, heating means for melting the projecting tip portion, a projecting tip cutter for removing excess glass of the projecting tip portion, and a head presser for shaping the projecting tip portion into a substantially flat or lenticular shape.

Abstract: A flat type fluorescent lamp, obtaining an improvement in efficiency of brightness and being adjustable in an emitted light amount thereof, while maintaining a uniform light emission across the surface thereof, and illuminating with no use of mercury therein, comprising a sealed container being defined between a front glass substrate and a rear glass substrate which are hermetically bonded to each other, so as to enclose a rare gas as discharge gas therein, edge electrodes, having width from 2.

Abstract: A rare gas illumination system and method are configured to provide a sweeping illumination effect. In one embodiment, the rare gas illumination system includes a tube containing a gas and having a first electrode at a first end and a second electrode at a second end. A first boot having a first transformer is coupled to the first end of the tube. A second boot having a second transformer is coupled to the second end of the tube. The system includes a controller having a microcontroller, a memory, and an output power driver. The memory is configured to store a plurality of control codes corresponding to a plurality of illumination patterns. The microcontroller controls the illumination pattern of the tube by executing the corresponding control code to selectively activate the output driver to provide a voltage signal to at least one of the first boot and the second boot.

Abstract: A gas recovery and reuse/recycle method is disclosed which can readily and economically recover valuable and/or environmentally hazardous gases from a manufacturing or chemical process and then return the gas to the process for reuse, and repeat this many times without significant contamination or degradation of the gas or the produced products. All gas transport, compression and storage equipment is designed and maintained so that it is non-contaminating to the process gas. Commonly the process gas will be a Group VIII gas, preferably He, Ne, Kr or Xe, or a gas which comprises a hazard to the ambient environment or beings therein, such as a carbon oxide gas, a halocarbon gas, an acid-precursor gas, a biologically hazardous gas, or a radioactive gas.

Abstract: A fluorescent cavity backlight system that provides a high efficiency light source suitable for rear illumination of transmissive electronic display devices. The inventive fluorescent cavity backlight system can be adapted to a wide variety of flat panel display applications. The invention takes a complete system approach towards designing a high efficiency backlight source. The backlight system comprises three major subassemblies: a phosphor illuminator, a fluorescent cavity, and improved control/driver electronics. Each of the subassemblies has been optimized internally, and with respect to each of the other subassemblies.

Abstract: A discharge device for operation in a gas at a prescribed pressure includes a cathode having a plurality of micro hollows therein, and an anode spaced from the cathode. Each of the micro hollows has dimensions selected to produce a micro hollow discharge at the prescribed pressure. Preferably, each of the micro hollows has a cross-sectional dimension that is on the order of the mean free path of electrons in the gas. Electrical energy is coupled to the cathode and the anode at a voltage and current for producing micro hollow discharges in each of the micro hollows in the cathode. The discharge device may include a discharge chamber for maintaining the prescribed pressure. A dielectric layer may be disposed on the cathode when the spacing between the cathode and the anode is greater than about the mean free path of electrons in the gas. Applications of the discharge device include fluorescent lamps, excimer lamps, flat fluorescent light sources, miniature gas lasers, electron sources and ion sources.

Abstract: There is presented a cold cathode subminiature fluorescent lamp comprising a glass envelope, a pair of lead wires sealed to the envelope and extending through the envelope at an entry location to the interior thereof, an electrode mounted on the lead wires in the envelope, and a ceramic-glass bead formed on and around the lead wires in the envelope between the electrode and the entry location. The electrode includes a plurality of metal wire tabs. The envelope contains a fill gas comprising neon and argon.

Abstract: A metal halide lamp in which rare earth halides are encapsulated and the occurrence of milky cloudiness is suppressed to achieve a prolongation of the service life of the lamp. To achieve this result, inert gas, mercury, indium halide, cesium halide, and rare earth halides are encapsulated in an emission part, with the encapsulation amount of the indium halide being from 0.8 micromole to 8.0 micromole/cm.sup.3 of tube volume, and the lamp is operated with an essentially horizontal arc axis using a direct current. Furthermore, iodine and bromine are contained in the halogen which forms the halides, and there is a ratio of the iodine atom number to the total halogen atom number is greater than or equal to 50%.

Abstract: An method of operating a neon stop lamp for a vehicle is described. By adjusting the lamp pressure, the then controlling the frequency and pulse width of the power, the lamp efficiency can be increased, while also shifting the chromaticity for the lamp to comply with automotive standards. The result is a small, efficient light source whose light may be reflected and focused, and whose color is correct for vehicle warning lights.

Abstract: A nearly pure neon is described along with a method of operating the lamp. A phosphor is coated on the lamp wall. By properly stimulating the neon, ultraviolet light may be emitted, that can stimulate the phosphor to a first light emission. The lamp may then be operated to produce a visible light emission that is the result of neon emission or of intermediate combinations of the neon and phosphor emissions. A single neon lamp may then produce in one instance, an amber color, or in other instance, a red color without the cold environment problems typical of a mercury based lamp. The output efficiency is enhanced when the lamp is formed as an aperture lamp. The narrow source is also useful as a source in reflector and lens systems. High pressure neon lamps offer a small source size, direct color with no filtering, good tolerance of impact and jarring, moderate cost, and increased vehicle styling potential.

Abstract: The invention provides a rare gas discharge fluorescent lamp device which is long in life and high in brightness and efficiency. The lamp device comprises a rare gas discharge fluorescent lamp including a glass bulb having xenon, argon or krypton gas enclosed therein, a fluorescent layer formed on an inner face of the bulb, and a pair of electrodes located at the opposite ends of the bulb. A pulse-like voltage wherein the ratio of an energization period with respect to one cycle is higher than 5% but lower than 70% (xenon or krypton gas) or 80% (argon gas) and the energization period is shorter than 150 .mu.sec is applied between the electrodes of the lamp. Such pulse-like voltage is produced from a circuit including a dc power source, a pulse signal source, and a switching element for controlling application of a voltage of the dc power source or such voltage boosted by a boosting transformer or a resonance circuit.

Abstract: A discharge lamp comprises an HPS discharge device within an outer envelope filled with inert gas. A normally nonconductive spark gap device within the outer envelope is connected across conductors used to apply a voltage to the HPS discharge device. The spark gap breaks down when the applied voltage exceeds a certain value to prevent breakdown through the inert gas within the outer envelope.

Abstract: A rare-gas arc lamp includes a pair of coil filaments disposed at the opposite ends of an elongated bulb for increasing an area of a positive column produced between the coil filament pair in a direction perpendicular to the elongated axis of the bulb, and a rare-gas mainly including xenon gas and having substantially no mercury therein sealed in the bulb at a prescribed pressure selected from the range between 20 Torr and 200 Torr. The combination of the coil filament pair and the xenon gas sealed in the bulb at a prescribed pressure in the range of 20 Torr to 200 Torr may reduce visible changes in a luminance distribution of the lamp when the positive column fluctuates during the operation of the lamp.

Abstract: A high-pressure sodium discharge lamp provided with a solid electrode consisting mainly of tungsten plus a small quantity of rhenium, and free of alkaline earth metals. The addition of rhenium suppresses sodium attack which caused the tip end of the electrode to break off before the desired lamp life was reached.

Abstract: A gas discharge lamp for emitting vacuum UV radiation, comprising a lamp body filled at low pressure with a gas capable of emitting radiation in the vacuum UV range (e.g., argon), electrodes within the lamp body for passing an electric field across the gas, a crystalline window (e.g., lithium fluoride) in the body for transmitting the vacuum UV radiation emitted by the gas, wherein the crystalline window is constructed of a material that, when exposed to the vacuum UV radiation emitted by the gas, forms color centers that block transmission of the radiation through the window, and a bleaching element located within the lamp body for emitting color-center bleaching radiation in response to the electric field degrading emission of the vacuum UV radiation, the bleaching radiation being in a frequency band (e.g., 5-6 eV) lower than the vacuum UV radiation.

Abstract: An array of microelectronic tubes is shown which includes a plate-like substrate upon which an array of sharp needle-like cathode electrodes is located. Each tube in the array includes an anode electrode spaced from the cathode electrode. The tubes each contain gas at a pressure of between about 1/100 and 1 atmosphere, and the spacing between the tip of the cathode electrodes and anode electrodes is equal to or less than about 0.5 .mu.m. The tubes are operated at voltages such that the mean free path of electrons travelling in the gas between the cathode and anode electrodes is equal to or greater than the spacing between the tip of the cathode electrode and the associated anode electrode. Both diode and triode arrays are shown.

Abstract: A low-pressure mercury vapor discharge lamp comprises a tubular bulb having an inside diameter of from 22 mm to 35 mm, an electrode-to-electrode distance of from 400 mm to 1,200 mm, and an inner surface coated with a phosphor. A rare gas including Kr and a mercury vapor source are sealed in the bulb, which is energized by an igniting device having a high-frequency power supply connected to a DC power supply for generating a substantially sinusoidal high-frequency output voltage, and a quiescent period generator connected to the high-frequency power supply and including a switch 17 turned on and off at least once during each half cycle to provide a quiescent period and thereby produce a substantially square wave high-frequency output voltage having rise and fall times of 2 .mu.s or less.

Abstract: A high pressure discharge lamp comprising a discharge vessel in which an electrode comprising a resistive element is present, said resistive element consisting of two parallel arranged branches having substantially the same electrical resistance. With such an electrode construction it is achieved that the starting point of the discharge on the electrode is stabilized.