RU2079182C1 - Gas-discharge ultraviolet tube - Google Patents

Abstract

FIELD: illumination devices which are based on ionization and luminescence effects. SUBSTANCE: device has bulb with window which is transparent to ultraviolet light. Bulb is filled with gas which emits ultraviolet light. In addition bulb contains anode and cathode in insulator. Anode and cathode are located along bulb axis and are shaped as through cylinders and provide single discharge trunk. Anode cylinder is tightly mounted on insulator cylinder in which cathode is located. Insulator may be ended with capillary which enters into anode chamber. Light of discharge trunk is based on negative discharge in cathode chamber and plasma in insulator capillary (if it is present). In addition device has several trunks which are located in parallel to or at angle to bulb axis. In addition bulb is shielded from interaction with plasma and trunks are located in required position due to shared shielding cylinder and fixer with mounting holes. cathodes in each trunk has their own terminals and anodes are connected to fixer to which anode current pickup is attached. Shielding cylinder is neutral or has its own terminal or is connected to fixers and anodes of all trunks. EFFECT: decreased size, increased stability and intensity of emitter light, decreased cost. 5 cl, 5 dwg, 1 tbl

Description

 The invention relates to discharge lamps, emitting mainly in the short-wave vacuum UV region of the spectrum. High energy of lamp emission quanta (up to 11 eV), low power consumption allow developing portable devices based on the effect of photoionization, photoluminescence and optical absorption based on these lamps: these are gas analyzers, optical hygrometers, devices for astrophysics, etc.

 Known low-power UV lamp [1] which contains a flask with a transparent window in vacuum UV, filled with some inert gas and / or hydrogen, containing the anode and cathode in the form of metal washers soldered into the flask body, and a glass capillary for passage of discharge, built into a partition separating the anode and cathode chambers. The disadvantage of the lamp is that at a low pressure of the working gas (fractions of mm Hg), at which the maximum contribution of energy to the resonance lines is achieved, the gas in the lamp quickly disappears due to the "burning" of its ions by the glass of the bulb, which leads to a small lamp life. Therefore, such lamps, to increase the service life, are filled with gas up to several mmHg. Art. which unambiguously leads to an undesirable increase in the ignition voltage on the lamp to 1500 V. In addition, to weaken the effect of "stiffness", the diameter of the bulb of such a lamp with the most active hydrogen gas is usually increased to 25 mm, which limits its use in modern portable equipment.

 Also known is the design of a UV-hydrogen lamp [2] which consists of a bulb with a window transparent in vacuum UV, a cathode with a cavity for concentration of negative cathode glow, an insulator in which the cathode is enclosed, and an anode made in the form of a vitrified pin and mounted parallel to the cathode , and its free end reaching the outlet of the hollow cathode.

 Unlike classical hollow-cathode tubes emitting atomic lines of the evaporated cathode metal, the authors were interested in the glow of the filler-hydrogen gas itself, the pressure of which in the lamp was 3 mm Hg. Despite this pressure, the ignition voltage and the voltage drop across the lamp of this design does not exceed 600 and 400 V, respectively. However, the serious disadvantages of this lamp with a pin anode include radiation instability due to anisotropy of the electric field in the anode-cathode gap, gas “burning” due to intense plaque formation on the bulb near the discharge, which also prevents the bulb’s window from approaching the discharge and reducing its diameter that is, reduce the dimensions of the lamp.

 Closest to the proposed solution is the design of a lamp with a ring anode and a hollow cathode with a blind hole [3] In this lamp, the ring anode for eliminating light diaphragm is made in the form of a stepped hollow cylinder with a base in the inner cavity having a through axial hole into which a centering is inserted an insulator mounted on the basis of a hollow cathode with a blind hole. The shape of the anode creates a collecting electron lens in the space between the anode and cathode, which increases the electron density and the number of radiative transitions above the cathode zone. With dimensions: diameter 36 mm and length 140 mm, the anode in the lamp is removed from the window by a distance of 70 mm. With such dimensions, the lamp is designed on average for 20 mA of discharge current and 6 watts of power consumption for a service life of up to 500 hours.

 The disadvantage of this design is the open anode and closed volumes inside the cavity of the cathode and insulator. This design is unsuitable for small lamps with a low content of emitting working gas, because while reducing the distance between the anode and the window to several mm and reducing the size of the observation lamp, a sharp darkening of the window from the spraying of the cathode cavity and the rapid disappearance of the working gas.

 The aim of this invention is the miniaturization of a gas discharge UV lamp while increasing the stability and intensity of its radiation.

 This goal is achieved by the fact that in a gas-discharge UV lamp containing a bulb filled with gas emitting predominantly in a vacuum ultraviolet, the window is transparent in this area, the anode and the through hollow cathode in the insulator, creating one discharge barrel, anode, cathode and insulator in accordance with the invention made in the form of through cylinders having a common axis, the anode at one end facing the window has a cover with a viewing hole and the other end is tightly mounted on the end of the insulator, inside of which the cathode is flush with it, and the lengths of the anode and insulator are at least twice the diameter and length of the cathode, respectively.

 Another difference of the proposed lamp is that the through cylindrical insulator ends with a capillary entering the anode cavity, the free end of which is at least twice the diameter of the capillary, and the hollow cathode is installed inside the insulator in front of the capillary.

 Another difference is the installation in the lamp of several discharge shafts made in accordance with the invention, parallel and / or located at a certain angle to the axis of the bulb, with a common electrically neutral screen cylinder and a latch covering all the discharge shafts, with the lid and bottom of the screen cylinder and the retainer has holes in the number of discharge shafts, and the anodes are in the form of open cylinders and fastened to the retainer.

 An additional difference is that the common screen cylinder has a separate output.

 An additional difference is that the common screen cylinder is connected to the anodes of all the discharge shafts.

 Figure 1 shows a UV discharge lamp in which the anode, hollow cathode and insulator are made in the form of through cylinders; figure 2 gas-discharge UV lamp in which a cylindrical insulator ends with a capillary entering the cavity of the anode; figure 3 gas-discharge UV lamp containing several discharge barrels with a common electric neutral screen cylinder and a latch, covering all the discharge trunks, and the anodes are fastened with a latch; in FIG. 4 multi-barrel gas-discharge UV lamp, in which the common screen cylinder has a separate output; in Fig.5 multi-barrel gas-discharge UV lamp with a common screen cylinder connected to the anodes of all the discharge barrels, and the barrels themselves are installed at an angle to the axis of the bulb.

 The gas discharge lamp shown in Fig. 1 consists of a glass bulb 11 with a sealed window 2 of material transparent in the vacuum UV region, through cathodes 3, insulator 4 and anode 5, made in the form of cylinders. The cathode 3, the insulator 4 and the anode 5 are located on the same axis and form the discharge tube of the lamp. The anode 5 at the end facing the window 2 has a cover 6 with an inspection hole 7, and the other end of its anode 5 is tightly mounted on the end of the insulator 4, inside of which the cathode 3 is flush with it. The lengths of the anode 5 and insulator 4 are at least twice the diameter and length of the hollow cathode 3, respectively. These dimensions were established empirically and determined from the condition that there is no breakdown between the cathode 3 and the anode 5 at the time of ignition through the open end of the insulator, as well as the absence of deposits on window 2 at the maximum approximation (up to 3-5 mm) of the anode 5 to the lamp window. The insulator 4 has a bulge 8 for mounting it with a metal clamp 9 to the vitrified anode current lead 10. The cathode is attached to the vitrified cathode current lead 11. The bulb 1 is filled with gas emitting in the vacuum UV region of the spectrum.

 The lamp operates as follows.

 When a constant voltage lamp is applied to electrodes 3 and 5, a glow discharge arises between them with a concentration of negative cathode glow in the cavity of cathode 3. This glow at low discharge current (several mA) and power consumption belongs to the excited filler gas.

 According to plasma physics, when the discharge current flows, the electron stream rushes to the anode, and the ion stream to the cathode. Therefore, any gas discharge lamp operating on a direct current, a stream is installed that transfers the mass of ionized gas into the cathode chamber. The through design of the electrodes 3 and 5 and the insulator 4 provides a stable direction of this flow from the window 2 towards the open end of the insulator 4 and helps to reduce the settling of particles. Sprayed from cathode 3 on the window and on the walls of the insulator. The closed anode 5 in combination with the through cylindrical design of the discharge barrel create conditions for minimal gas stiffness during lamp operation.

 The high degree of screening of the walls of the bulb of the lamp of the proposed design from gas ions in combination with the purging of the ion current by the gas flow through the through insulator are factors that significantly reduce its dimensions by reducing the diameter of the bulb and the distance from the end of the anode to the window to several mm. The proposed design ensures the operation of a small lamp up to several thousand hours even at a working gas pressure of hundredths of a millimeter of mercury. at which minimal self-absorption of resonant radiation of gases emitting in the vacuum UV region is achieved.

 The gas discharge lamp shown in Fig. 2, in addition to the design in Fig. 1, has an insulator 4 ending in a capillary 12 located inside the cylindrical anode 5 so that its opening is opposite the viewing hole 7 in the anode cover 6, and the distance between the end of the capillary 12 and the cover of the anode 6 at least twice the inner diameter of the capillary 12. The proposed distance is selected empirically and optimally from the point of view of protecting window 2 from air raids from the discharge zone in the capillary 12. Hollow through to Todd 3 is installed inside the cylindrical insulator 4 through a capillary 12 immediately before.

 The device operates as follows.

 When a constant voltage lamp is supplied to the current leads 10 and 11, a glow discharge arises between the cathode 3 and the anode 5 with a concentration of negative cathode glow in the cavity of the cathode 3 and a positive plasma column in the glass capillary 12. Due to the additional plasma glow in the glass capillary 12, the radiation intensity of the lamp is higher. compared to that shown in FIG. 1. The radiation intensity, ignition voltage and lamp power depend on the length and diameter of the capillary 12. The greater the length and the smaller the diameter of the capillary 12, the higher the brightness, ignition voltage and power consumed by the lamp.

 At the same time, there is an increase in the stability of the radiation of the lamp. So in such a lamp there is no radiation pulsation, since in the proposed design there are no conditions for establishing a gas current that is counter to the ion current. In lamps with a dull cathode and insulator design, such conditions are created (especially in pulsed mode) due to a small pressure drop that arises as the discharge current flows between the anode and cathode chambers separated by a capillary and the gas accumulates in the cathode chamber.

 In FIG. 3 shows the design of a multi-barrel discharge lamp, in which several discharge barrels containing all the elements of one discharge lamp barrel in FIG. 1 are enclosed in bulb 1.

 An additional feature of the design is the presence of one common electrically neutral screen cylinder 13, covering all the trunks, and a latch 14, fastened through vitrified insulators 17 with all anodes 5, made in the form of open cylinders. The latch 14 is connected in one common current lead 10. The cover 15 and the bottom 16 of the screen cylinder 13, as well as the latch 14 have holes in the number of discharge shafts in the lamp. The screen cylinder 13 together with the cover 15 and the bottom 16 protects the walls of the bulb and the window from contact with the plasma. In addition, using the holes in the latch 14 and the bottom 16, as well as thickening 8, the position of the insulators 4 and the cathodes 3 of all the trunks is fixed.

 The device operates as follows.

 When applying constant current voltage to the current leads 10 and 11 of each barrel between the cathodes 3 of the anodes 5, discharges occur in each barrel. The radiation from each barrel through the inspection holes 18 in the cover 15 of the screen cylinder 13 enters the window 2 of the lamp. Thus, four independent light spots appear outside the window 2 of the lamp, as if four separate lamps were shining.

 In FIG. 4 shows a multi-barrel discharge lamp, in which, unlike the structure shown in FIG. 3, the screen cylinder 13 has its own output 19.

 In this case, a negative potential can be applied to the screen cylinder relative to the anode when the voltage difference between them is 10-20 V. A weak braking field in space arises in this case, the anode-screen cylinder can increase the degree of protection of the window from fast electrons from plasma accumulation on its inner surface of a negative charge, contributing to the deposition of positive metal ions on it, sprayed by the walls of the hollow cathode. This design is especially effective for lamps with high current load, for example, when operating in pulsed mode.

 In FIG. 5 shows the design of a multi-barrel lamp, in which, unlike the structures shown in FIG. 3 and 4, the anodes 5 of all the discharge shafts are attached to the bottom 16 of the screen cylinder 13, which is welded through metal ties 20 to the latch 14. The discharge shafts are accumulated at a certain equal angle to the axis of the lamp bulb due to the same displacement of the centers of the holes in the bottom 16 and the latch 14 relative to the center of the holes 18 in the cylinder cover 15.

 The device operates as follows.

 When a constant voltage is applied to all cathode current leads 11 and anode current leads 10 in each trunk, an independent discharge flashes, the radiation from which crosses at a certain distance from the window in the region of intersection of the axes of the discharge trunks, creating a spot in this zone with a brightness equal to the total brightness of all trunks .

 The designs of multi-barrel lamps, in addition to those shown in FIG. 3, 4 and 5, can be made with cylindrical insulators ending in capillaries entering the cavity of the anodes in accordance with claim 2. In this case, the brightness of the radiation of each barrel, the ignition voltage and the power consumed by the lamp will accordingly increase.

 The general advantages of the proposed multi-barrel discharge lamps are as follows.

 Thanks to independent cathodes and anodes, it is possible to turn on or off part of the trunks, or turn them on sequentially in time depending on the requirements of the equipment. The combination of several discharge barrels in one bulb, that is, the actual replacement of several lamps with expensive windows with transparent windows in the vacuum UV region, a lamp many times reduces not only the volume occupied by the lamps in the equipment, but also their cost. The table shows the main parameters of single-barrel lamps made according to the claimed design in comparison with the California lamp 0701-02, used in analytical instruments with photoionization detection, and multi-barrel lamps, in comparison with the domestic spectral hydrogen lamp VMF-25, capable of creating at a given distance from windows (6-7 cm) equal to the proposed multi-barrel lamp, the radiation spot used in devices operating on the effect of photoluminescence.

 Comparative data of the table show that in all basic parameters the lamps made according to the proposed technical solution are superior to lamps traditionally used in environmental and spectral instruments. So single-barrel lamps made according to claims 1, 2, with the same radiation energy, are 3 times less in the ignition voltage and 12 times in size, compared with the lamp 0701-02 California. Multi-barrel lamps made according to claim 3, 4, 5, at a comparable or 2 times higher brightness, compared with the spectral lamp VMF-25, consume an order of magnitude less power depending on the number of barrels, operate at lower currents from 50 to 25 times and less in size from 6 to 3 times. Thus, the achieved miniaturization and efficiency of the lamps will make it possible to create on their basis a new class of portable, actually pocket-sized equipment.

Claims (5)

 1. A gas discharge ultraviolet lamp containing a bulb filled with gas emitting predominantly in a vacuum ultraviolet, a window transparent in this region, an anode and a through hollow cathode in the insulator, creating one discharge barrel, characterized in that the anode, cathode and insulator are made in the form end-to-end cylinders having a common axis, the anode at one end facing the window has a cover with a viewing hole, the other end is tightly mounted on the end of the insulator, inside of which the cathode is flush with it, and the lengths of the anode and insulator are yney least twice the diameter and length respectively of the cathode.  2. The lamp according to claim 1, characterized in that the through cylindrical insulator terminates in a capillary entering the cavity of the anode, the length of which is at least two times its diameter, and the hollow cathode is installed inside the insulator in front of the capillary.  3. The lamp according to paragraphs. 1 and 2, characterized in that it is equipped with additional discharge shafts, all the discharge shafts are parallel and / or at a certain angle to the axis of the bulb and are surrounded by a common electrically neutral screen cylinder and lock, and the cover and bottom of the screen cylinder and lock have holes in the number bit trunks, and the anodes are in the form of open cylinders and fastened with a latch.  4. The lamp according to paragraphs. 1 3, characterized in that the common screen cylinder has a separate output.  5. The lamp according to paragraphs. 1 to 3, characterized in that the common screen cylinder is connected to the anodes of all the discharge shafts.

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