Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
  • H01J9/02—Manufacture of electrodes or electrode systems
  • H01J9/022—Manufacture of electrodes or electrode systems of cold cathodes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
  • H01J1/02—Main electrodes
  • H01J1/025—Hollow cathodes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J61/00—Gas-discharge or vapour-discharge lamps
  • H01J61/02—Details
  • H01J61/04—Electrodes; Screens; Shields
  • H01J61/06—Main electrodes
  • H01J61/067—Main electrodes for low-pressure discharge lamps
  • H01J61/0672—Main electrodes for low-pressure discharge lamps characterised by the construction of the electrode
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J61/00—Gas-discharge or vapour-discharge lamps
  • H01J61/02—Details
  • H01J61/04—Electrodes; Screens; Shields
  • H01J61/06—Main electrodes
  • H01J61/067—Main electrodes for low-pressure discharge lamps
  • H01J61/0675—Main electrodes for low-pressure discharge lamps characterised by the material of the electrode
  • H01J61/0677—Main electrodes for low-pressure discharge lamps characterised by the material of the electrode characterised by the electron emissive material
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J61/00—Gas-discharge or vapour-discharge lamps
  • H01J61/02—Details
  • H01J61/04—Electrodes; Screens; Shields
  • H01J61/06—Main electrodes
  • H01J61/09—Hollow cathodes

Definitions

• the present invention relates to an electrode for gas discharges with an electrically conductive material.
• Cold electrodes are usually provided on the inside with a coating consisting of mixtures of alkaline earth oxides - hereinafter called activation - to reduce the work function (principle of Wehnelt i.J. 1907). Since the oxides are not stable under normal ambient conditions, the emission coatings in the form of carbonates are applied to the substrate of the electrode and at low pressures and high temperatures, e.g. with annealing of the carrier material, converted into the corresponding oxides.
• the photoelectric work function of the material of the emission coating (3) in the region of the working temperature of the electrode, which is below 570 K, preferably below 420 K, is lower than that of the carrier material (1).
• the essence of the solution according to the invention is therefore that the coating of the electrode which emits the electrons (“emission coating”) is chosen in a particular way with regard to its photoelectric work function.
• this work function should be lower than that of the carrier material of the electrode.
• the photoelectric work function in the temperature range from 0 to 500 K should be less than 5.6 * 10 "19 joules / electron.
• Specifically usable coating materials are yttrium, praseodymium or rubidium or mixtures thereof.
• the photoelectric work function is defined as the photoelectric quantum energy that has to be used per electron to release it from the electrode (measured in eV / electron or joule / electron).
• the electron-emitting layer can consist of metallic or semiconducting substances with a lower photo work function compared to the carrier material instead of the oxides which have a high photo work function at low temperatures, often with simultaneous use of the hollow cathode effect known in principle.
• the advantage of the invention is the avoidance of undesired chemical conversion on the electrode surface.
• the electrode is almost independent of the gas atmosphere during manufacture and conditioning; the activation mass cannot be poisoned, and an incompletely carried out reaction during the reaction can later release reaction products into the atmosphere of the gas discharge space.
• the electrode according to the invention is largely safe from incorrect treatment during manufacture and conditioning by e.g. untrained staff. Avoiding the previously necessary, very technically complex preparation process for carbonate mixtures can lead to considerable cost advantages.
• Oxide mixtures when thermally excited, have a low photo work function.
• thermal electron emission from inhomogeneous, multi-component, insulating solids the electronic band structure of which has indirect transitions, lattice vibrations (phonons) are involved in the excitation of the transitions in the minimum of the band gap (Lit .: eg Joseph Eichmeier, "Modern Vacuum Electronics”; Springer Verlag, Berlin 1981).
• the photo work function could be found as the decisive factor for the losses; under certain circumstances it differs from the thermally determined work function. Since the phonon energy in cold electrodes is considerably lower than in thermally emitting electrodes, indirect band transitions cannot be excited with cold electrodes.
• Coating materials according to the invention have only almost direct band transitions and a small band gap, which make it unnecessary for high-energy phonons to participate in the excitation process.
• the electrode is designed as a hollow body, in particular cup-shaped, and that the emission coating (3) is located on the inside of the hollow body.
• the hollow cathode effect can thus be used positively.
• the hollow body can in particular have the shape of a cup and the emission coating is located on the inside of the hollow body, where the emission of the electrons takes place.
• the emission coating (3) has a lower photoelectric work function than the remaining surface of the electrode, in particular the outer surface of the hollow body. In this way, a concentration of the electron emission on the emission coating is achieved.
• the carrier material (1) is provided on the outside of the hollow body with a coating (4), preferably made of nickel or platinum, which has a high photo work function, preferably higher than 8.0 * 10 "19 joules / electron. This advantageously allows the life of the electrode to be increased during operation by preventing the discharge from spreading to the outside of the carrier body and thus destroying it.
• the carrier material (1) has a low photoelectric work function, preferably less than 6.4 * 10 "19 joules / electron leads to the advantage that the special coating on the inside of the electrode space can be saved since the carrier - And coating material can be identical.
• the carrier material can preferably contain metal, in particular iron. It is particularly preferred in terms of content that the carrier material consists of the metal.
• the emission coating (3) can also contain dopants to reduce the photo work function compared to the pure substance, preferably with the dopants, for example calcium, cesium or barium in the concentrations 10 "5 at% to 1 at%. This can further reduce the work function and thus the losses are achieved by narrowing the band gap in the electronic band structure compared to the use of pure substances.
• dopants for example calcium, cesium or barium in the concentrations 10 "5 at% to 1 at%.
• a part of the surface of the carrier material (1) is provided with an electrically insulating coating (4) for suppressing an electron or ion current. This has the advantage of completely suppressing an electron current from the outside of the carrier material and thereby increases the service life of the electrode.
• the parts of the electrode directed towards gas discharge can be coated with an electrically insulating, temperature- and vacuum-resistant material, preferably ceramic. This has the advantageous effect that the atomization of the active or the carrier material of the electrode is prevented, starting from the edge facing the gas discharge.
• an electrically insulating sleeve (9), which is provided with a collar, can be arranged in the opening of the cavity formed by the electrode in such a way that the collar covers the edges of the opening in the direction of the gas discharge.
• the edge of the opening of the cavity formed by the electrode facing the gas discharge can moreover be shaped such that the electrical field gradient at the opening is reduced, preferably by bending or flanging. In this way, a partial reduction in the atomization rate can be achieved without the need for a further manufacturing element.
• the electrode can be surrounded by a glass body (8), which can preferably be cylindrical.
• the electrode in the glass body (8) can be centered with a ring (10) made of poorly heat-conducting insulating material, preferably ceramic or mica. This allows the electrode to be centered in a cylindrical glass body to avoid glass breakage in the event of mechanical stress (e.g. impact, impact) or one-sided thermal stress, as is the case e.g. could arise when conditioning the electrode.
• the at least partially field-free space is created in the interior of a metallic cup, hollow cylinder or hollow cone.
• the device according to the invention is therefore suitable for the use of existing production tools for producing the carrier bodies in a construction known per se.
• the device according to the invention can also be designed such that a reactive gas binding substance (getter) is attached to at least part of the surface of the carrier material (1) and is activated, for example, when the electrodes are conditioned.
• a reactive gas binding substance getter
• the materials for coating the carrier material (1) can be applied in the form of hydrides, preferably as yttrium hydride.
• the hydrides are converted into the metallic form with the liberation of hydrogen. This is advantageous because the oxidation of reactive substances located in the discharge space is avoided during the heating and glowing process, as can be found in the regeneration of discharge lamps containing mercury, for example high-voltage fluorescent tubes.
• the invention is described in more detail below with reference to the examples:
• FIG. 1 shows an exemplary embodiment of the invention.
• the electrode is shown in longitudinal section.
• the layer thicknesses are not shown to scale in the drawing for clarity.
• the electrode according to the invention consists of the carrier body (1), produced e.g. made of iron and, for example, in the form of a cup, with an opening (2) facing the gas discharge.
• the inside of the carrier body (1) is provided with a layer (3) of a material with a low photoelectric work function, e.g. Yttrium, which was applied by mechanical, chemical and / or physical coating processes (e.g. pressing, rolling, vapor deposition, sputtering, galvanizing, spraying), while the outer surface (4) is exemplarily made of material with high photoelectric work function, e.g. Nickel or platinum.
• a material with a low photoelectric work function e.g. Yttrium
• the outer surface (4) is exemplarily made of material with high photoelectric work function, e.g. Nickel or platinum.
• the power supply wires (5) are connected in a manner known per se, e.g. fixed by spot welding.
• Figure 2 shows an example of a longitudinal section through an electrode according to the invention, installed in a cylindrical glass body (8) in a design known per se, as part of a gas discharge vessel, for use e.g. in high-voltage fluorescent tubes.
• the power supply wires (5) in the crimp foot (6) are vacuum-tight with the
• a glass tube (7) additionally melted in the squeezing foot (6) can serve to evacuate the gas discharge vessel (not shown in FIG. 2).
• the electrode is usually attached to the gas discharge vessel by means of the glass body (8).
• Fig. 2 shows the opening (2) of the support body (1) with an insulating protective ring (9), for example made of ceramic, which is attached to the support body (1) in a known manner by squeezing, rolling, knurling, rolling, etc. .
• the centering ring (10) can deviate from the circular ring shape, for example with notches or the like, in order to to enable fluidically advantageous evacuation of the gas discharge vessel through the extension tube (7).
• FIG. 3 shows comparative results of measurements of the photoelectric work function of various commercially available electrodes compared to an embodiment according to the invention.

Landscapes

• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Discharge Lamp (AREA)
• Gas-Filled Discharge Tubes (AREA)
• Glass Compositions (AREA)
• Vessels And Coating Films For Discharge Lamps (AREA)

Applications Claiming Priority (3)

Publications (2)

Family

ID=8036992

Family Applications (1)

Country Status (8)

Families Citing this family (11)

Family Cites Families (27)

• 1997
  • 1997-03-05 DE DE29703990U patent/DE29703990U1/de not_active Expired - Lifetime
• 1998
  • 1998-02-28 CN CNB988002426A patent/CN1152411C/zh not_active Expired - Fee Related
  • 1998-02-28 JP JP53805298A patent/JP4510941B2/ja not_active Expired - Fee Related
  • 1998-02-28 BR BR9805925-4A patent/BR9805925A/pt not_active Application Discontinuation
  • 1998-02-28 WO PCT/DE1998/000595 patent/WO1998039791A2/fr not_active Ceased
  • 1998-02-28 AT AT98916816T patent/ATE387008T1/de not_active IP Right Cessation
  • 1998-02-28 EP EP98916816A patent/EP0907960B1/fr not_active Expired - Lifetime
  • 1998-02-28 US US09/180,339 patent/US6417607B1/en not_active Expired - Fee Related
  • 1998-02-28 DE DE59814169T patent/DE59814169D1/de not_active Expired - Lifetime

Non-Patent Citations (1)

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