US3883764A - Cathode structure for high current, low pressure discharge devices - Google Patents

Cathode structure for high current, low pressure discharge devices Download PDF

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Publication number
US3883764A
US3883764A US448018A US44801874A US3883764A US 3883764 A US3883764 A US 3883764A US 448018 A US448018 A US 448018A US 44801874 A US44801874 A US 44801874A US 3883764 A US3883764 A US 3883764A
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United States
Prior art keywords
envelope
approximately
cylinder
mercury
discharge
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US448018A
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English (en)
Inventor
Peter D Johnson
John M Anderson
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General Electric Co
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General Electric Co
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Filing date
Publication date
Application filed by General Electric Co filed Critical General Electric Co
Priority to US448018A priority Critical patent/US3883764A/en
Priority to AR255774A priority patent/AR202843A1/es
Priority to JP49121540A priority patent/JPS50120180A/ja
Priority to BR56/75A priority patent/BR7500056A/pt
Priority to DE19752502649 priority patent/DE2502649A1/de
Priority to NL7502365A priority patent/NL7502365A/xx
Priority to GB8511/75A priority patent/GB1505142A/en
Priority to BE153976A priority patent/BE826261A/xx
Application granted granted Critical
Publication of US3883764A publication Critical patent/US3883764A/en
Priority to JP1977170721U priority patent/JPS5394492U/ja
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • 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

Definitions

  • the present invention relates to electric discharge devices, and more particularly to improved cathode structures for high current, low pressure discharge devices useful for enhanced photochemical stimulation, high intensity fluorescent lamps and high output gas lasers.
  • High current, low pressure discharges in mercury and other metal vapors and inert gases have been found to be efficient and intense sources of ultraviolet radiation useful in photochemistry and numerous other applications.
  • Ordinary fluorescent lamp electrodes for example, are capable of delivering currents of up to 3 or 4 amperes for short periods of time, such as those required for experimental work.
  • two or more filaments are generally employed at each electrode where such current densities are required. These filaments, however, are not adequate for higher currents and longer life required for recently developed practi cal applications.
  • a plurality of filaments occupy so much space that the electrode section of the discharge tube must generally be of larger diameter than the section occupied by the positive column of gases.
  • other externally heated cathodes such as the barium aluminate dispenser type cathode or the massive tungsten-thorium filaments used for high current gas laser applications, while providing the de sired arc current, exhibit a reduced overall efficiency because they require on the order of 50 watts or more to maintain the temperature of the filament at a useful value.
  • Electric lamps emitting ultraviolet radiation generally utilize a gaseous discharge including mercury as the emitting species.
  • the lamp parameters for low current density generally less than 0.2 ampere/cm
  • low pressure of emitting species generally below one Torr
  • the lamp parameters for low current density generally less than 0.2 ampere/cm
  • low pressure of emitting species generally below one Torr
  • the use of such electric lamps for photochemical reactions, such as cross-linking of polymers and breaking of polymeric bonds is very inefficient.
  • other ultraviolet emitting lamps when operated at high pressures and high currents still only emit useful ultraviolet radiation at wavelengths longer than 2300 A.U..
  • an object of this invention to provide an improved electrode structure for an electric discharge device which overcomes the aforementioned disadvantages and exhibits a low voltage drop thereby providing low power loss at the electrode.
  • the cathode structure comprises an oxide emissive mix coated on a filament mounted axially inside a hollow cylinder of refractory metal.
  • the cathode structure comprises an oxide emissive mix coated on a filament mounted axially inside a hollow cylinder of refractory metal.
  • FIG. 1 is a horizontal view, with parts broken away of a lamp constructed in accord with the present invention and suitable for operation for the production of high intensity ultraviolet radiation;
  • FIG. 2 is a partial perspective view of one embodiment of an improved electrode structure in accord with the present invention.
  • FIG. 1 illustrates, by way of example of one embodiment of our invention, a far ultraviolet lamp including an evacuable envelope, represented generally at 10.
  • the evacuable envelope 10 is preferably formed of an ultraviolet transmissive material, such as fused quartz, for example, so that ultraviolet radiation freely passes through the envelope.
  • the evacuable envelope 10 includes end members 11 and 12, respectively, which each support an electrode assembly 13.
  • the electrode assemblies include lead-in and support members 14 and 15 substantially parallel to each other and extending through the end members 11 and 12, respectively.
  • the end members 11 and 12 provide a graded seal at the ends of the evacuable envelope 10.
  • FIG. 1 illustrates generally a current regulating transformer 16 including a primary winding 17 and a secondary winding 18.
  • the primary winding 17 is connected to a suitable source of current and voltage and the secondary winding 18 is connected to electrodes 15 at each end of the evacuable envelope 10.
  • FIG. 2 illustrates the electrode assembly 13 particularly useful as a cathode as comprising an open-ended cylinder 21 and an oxide emissive coated filament 23.
  • the cylinder 21 is preferably formed of a refractory metal material, such as molybdenum, tantalum, tungsten, rhenium, or any other metal having negligible vapor pressures at temperatures of approximately l,200 to l,300C.
  • the refractory metal cylinder 21 may have a wall thickness of between 1 and .mils, a diameter of approximately 0.5 to 2.0 centimeters, and an axial dimension approximately 2 or 3 times the diameter.
  • FIG. 2 also illustrates the lead-in and support member extending into the cylinder 21 and attached to the inner surface of the cylinder wall by suitable means, such as spot welds.
  • the lead-in and support member 15 has at one end thereof a support rod 22 extending orthogonally from the support member 15 for supporting one end of the filament 23, illustrated in the form of a helix.
  • the other end of the filament is supported by lead-in and support member 14.
  • the helical filament 23 is mounted coaxially in the cylinder 21 and includes a coating 24 of an emissive mix such as those used in high output fluorescent lamps.
  • These emissive mixes generally include one or more of the alkaline earth oxides or one or more of the rare earth oxides, or one or more of the oxides of thorium, yttrium, zirconium, hafnium, or tantalum.
  • the filament material itself is also not critical and may include materials such as tungsten, tantalum or rhenium, for example.
  • the inner wall of the cylinder 21 Prior to operation of the lamp, it is necessary to coat the inner wall of the cylinder 21 with emissive mix. This may be achieved, for example, by providing a sufficient current flow through the emissive coated filament 23 to achieve a higher-than-normal temperature, e.g., about l,l00C, for the alkaline earth emissive mix referred to above. As a result of this heating, the emissive mix diffuses to the inner wall of the cylinder 21 and provides a coating thereon. After the coating is applied, the lead-in and support members 14 and 15 are electrically connected together, as illustrated in FIG. 1.
  • the lamp is also charged with a low pressure of an inert gas such as krypton, argon or neon and a sufficient quantity of mercury 25.
  • the quantity of vaporizable mercury present as the charge 25 is sufficient to produce a mercury vapor pressure of 2 X 10' to 0.1 Torr at operating wall temperatures of 25 to 80C.
  • the inert gas is at a low pressure, as for example 0.5 25 and preferably approximately 2 5 Torr of krypton.
  • the excitation of the emitting mercury is greatly enhanced by interactions with a partial pressure of krypton gas. The enhanced excitation results in greatly enhanced emission intensity.
  • the lamp is started by the application of a line voltage, which may be of any desired voltage, but may conveniently be 120 or 240 volts, to the primary of the excitation transformer 16.
  • a line voltage which may be of any desired voltage, but may conveniently be 120 or 240 volts.
  • the initial application of the voltage causes excitation of the krypton, which immediately ionizes the mercury atoms initiating the discharge.
  • the establishment of a sufficient pressure of mercury permits ionization thereof and causes transfer of the discharge to mercury, as the conducting specie.
  • an efficient emission of photochemically useful radiation less than 2,000 A.U. and specifically at 1849 A.U. and 1942 A.U. radiation is obtained.
  • the bulb wall temperature i.e., the minimum temperature of the interior of the bulb wall exists during steady-state operation
  • This preferred temperature yields an operating pressure of mercury within the envelope within the range of approximately 2 X 10 Torr to 0.1 Torr.
  • the current density within the lamp is also maintained in the desired range by appropriately adjusting the total current through the discharge and the diameter of the narrow, U.V. transmissive portion of the lamp envelope.
  • the total current is controlled by external impedances, and is adjusted to obtain maximum output from the radiating spectroscopic states of the radiant species.
  • lamps having the novel electrode structure in accord with our invention may readily operate at voltages from 20 to 200 volts A.C. at current densities of between approximately 2 and 50 amperes/cm and within a preferred range of between approximately 5 and 25 amperes/cm
  • a typical lamp configuration for the attainment of such operation namely at a current density of approximately 10 amperes/cm and a pressure of approximately 3 X 10 Torr, may readily be obtained within a lamp envelope having an interior diameter within the ultraviolet transmissive region of approximately 14 mm and a length of approximately 15 cm between the cathode structures.
  • Lamps operated with the electrode structure in accord with the present invention exhibit numerous ad- -vantages over prior art electroded lamps. For example,
  • lamps constructed with our improved electrode structure have unusually high intensity of emission of the 1942 A.U. line.
  • Another advantage of lamps constructed with electrode structures in accord with the present invention is that at current densities above approximately 3 amperes/cm the discharge occupies the cylindrical electrode member 21 in a completely diffuse (hollow cathode) mode providing high current output and low electrode damage. This is believed to be attributable to the emissive mix evaporated onto the inside of the cylinder during activation which permits the entire electrode structure to function as a cathode, Still another advantage of our invention is an additional function provided by the cylinder 21; namely, the cylinder intercepts any subsequently evaporated or sputtered emissive mix thereby preventing darkening of the walls of the envelope. For example, a lamp similar to that illustrated in FIG. 1 operated at 10 amperes discharge current exhibited negligible darkening of the envelope with no discernible loss of UV output after 500 hours of operation.
  • the cathode fall (voltage drop) when operating in the hollow cathode mode is only a few volts, i.e., under 4 volts.
  • Conventional electrodes exhibit voltage drops in excess of 7 volts.
  • discharge lamps having electrodes constructed in accord with our invention have reduced power loss at the electrodes which results in lower cathode temperatures, i.e., on the order of 1000C at a current of IO amperes, for example.
  • the electrodes in accord with our invention are operated in a hollow cathode mode, a more diffuse discharge from a much larger effective surface area (substantially the entire electrode structure) is provided, thereby minimizing electrode deterioration and discharge tube wall darkening.
  • the invention can also be used in other applications such as very high intensity fluorescent lamps and high output gas lasers.
  • the novel electrode structure may be operated on direct current, if desired.
  • other chemically inert gases besides krypton may be used, if desired. Accordingly, the appended claims are intended to cover all such modifications, changes and uses as fall within the sphere and scope of the foregoing disclosure.
  • a high current, low pressure discharge device including anevacuable envelope having a partial pressure of an ionizable material therein and electrode structures for establishing an electric discharge therein, said electrode structures including an improved cathode structure comprising:
  • said evacuable envelope includes a partial pressure of a material selected from the group consisting of krypton, xenon and argon within the range of approximately 0.5 to 5 Torr and a quantity of mercury sufficient under lamp operating conditions to maintain a partial pressure of mercury of approximately 2 X 10 to 0.] Torr.
  • the device of claim 2 wherein the operating conditions include maintaining the coldest portion of the envelope at a temperature of approximately 25 to C.
  • said discharge comprises ionized mercury which when excited by current densities of approximately 2 to 50 amperes/cm emits ultraviolet radiation at wavelengths shorter than 2000 A.U.
  • said refractory metal is selected from the group consisting of molybdenum, tantalum, tungsten, and rhenium.
  • said evacuable envelope comprises an ultraviolet transmissive material.

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  • Discharge Lamp (AREA)
  • Vessels And Coating Films For Discharge Lamps (AREA)
US448018A 1974-03-04 1974-03-04 Cathode structure for high current, low pressure discharge devices Expired - Lifetime US3883764A (en)

Priority Applications (9)

Application Number Priority Date Filing Date Title
US448018A US3883764A (en) 1974-03-04 1974-03-04 Cathode structure for high current, low pressure discharge devices
AR255774A AR202843A1 (es) 1974-03-04 1974-09-26 Dispositivo de descarga de baja presion y alta corriente
JP49121540A JPS50120180A (pt) 1974-03-04 1974-10-23
BR56/75A BR7500056A (pt) 1974-03-04 1975-01-06 Estrutura aperfeicoada de eletrodo para dispositivos de descarga de alta corrente e baixa pressao
DE19752502649 DE2502649A1 (de) 1974-03-04 1975-01-23 Verbesserte elektrodenstruktur fuer hochstrom-niederdruck-entladungsvorrichtungen
NL7502365A NL7502365A (nl) 1974-03-04 1975-02-27 Elektrode voor een ontladingsinrichting met lage druk voor hoge stroom.
GB8511/75A GB1505142A (en) 1974-03-04 1975-02-28 High current low pressure discharge device
BE153976A BE826261A (fr) 1974-03-04 1975-03-04 Dispositif a decharge basse pression et courant eleve
JP1977170721U JPS5394492U (pt) 1974-03-04 1977-12-20

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US448018A US3883764A (en) 1974-03-04 1974-03-04 Cathode structure for high current, low pressure discharge devices

Publications (1)

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US3883764A true US3883764A (en) 1975-05-13

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US448018A Expired - Lifetime US3883764A (en) 1974-03-04 1974-03-04 Cathode structure for high current, low pressure discharge devices

Country Status (8)

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US (1) US3883764A (pt)
JP (2) JPS50120180A (pt)
AR (1) AR202843A1 (pt)
BE (1) BE826261A (pt)
BR (1) BR7500056A (pt)
DE (1) DE2502649A1 (pt)
GB (1) GB1505142A (pt)
NL (1) NL7502365A (pt)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4093893A (en) * 1976-11-22 1978-06-06 General Electric Company Short arc fluorescent lamp
US4117374A (en) * 1976-12-23 1978-09-26 General Electric Company Fluorescent lamp with opposing inversere cone electrodes
US4523125A (en) * 1981-07-13 1985-06-11 General Electric Company Fluorescent lamp electrodes
EP0560063A1 (de) * 1992-02-28 1993-09-15 Patent-Treuhand-Gesellschaft für elektrische Glühlampen mbH Niederdruckentladungslampe
US5675214A (en) * 1994-09-21 1997-10-07 U.S. Philips Corporation Low-pressure discharge lamp having hollow electrodes
US5856726A (en) * 1996-03-15 1999-01-05 Osram Sylvania Inc. Electric lamp with a threaded electrode
US6034768A (en) * 1997-09-26 2000-03-07 Physical Sciences Inc. Induced breakdown spectroscopy detector system with controllable delay time
US6552489B2 (en) * 2000-02-29 2003-04-22 Toshiba Lighting & Technology Corporation Fluorescent lamp and a method of making same, and a lighting fixture
US20080185951A1 (en) * 2007-02-06 2008-08-07 Deeder Aurongzeb Highly emissive cavity for discharge lamp and method and material relating thereto
US20100277051A1 (en) * 2009-04-30 2010-11-04 Scientific Instrument Services, Inc. Emission filaments made from a rhenium alloy and method of manufacturing thereof
US20160158400A1 (en) * 2013-09-27 2016-06-09 Zhiming He Ultraviolet sterilization and disinfection device and configuration method thereof

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3225327A1 (de) * 1982-07-07 1984-01-12 Institut optiki atmosfery Sibirskogo otdelenija Akademii Nauk SSSR, Tomsk Stoffdampfimpulslaser und verfahren zur speisung desselben
DE3225328A1 (de) * 1982-07-07 1984-01-12 Institut optiki atmosfery Sibirskogo otdelenija Akademii Nauk SSSR, Tomsk Gasentladungsroehre fuer einen gasimpulslaser

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2692350A (en) * 1948-01-15 1954-10-19 Westinghouse Electric Corp Discharge lamp and electrode
US2935637A (en) * 1957-03-05 1960-05-03 Thomas M Cortese Fluorescent lamp
US3121184A (en) * 1960-12-30 1964-02-11 Gen Electric Discharge lamp with cathode shields
US3215882A (en) * 1962-12-31 1965-11-02 Sylvania Electric Prod Fluorescent lamp with noble metal amalgamated electrode
US3657591A (en) * 1970-06-26 1972-04-18 Gen Electric High intensity far u.v. radiation source

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2692350A (en) * 1948-01-15 1954-10-19 Westinghouse Electric Corp Discharge lamp and electrode
US2935637A (en) * 1957-03-05 1960-05-03 Thomas M Cortese Fluorescent lamp
US3121184A (en) * 1960-12-30 1964-02-11 Gen Electric Discharge lamp with cathode shields
US3215882A (en) * 1962-12-31 1965-11-02 Sylvania Electric Prod Fluorescent lamp with noble metal amalgamated electrode
US3657591A (en) * 1970-06-26 1972-04-18 Gen Electric High intensity far u.v. radiation source

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4093893A (en) * 1976-11-22 1978-06-06 General Electric Company Short arc fluorescent lamp
US4117374A (en) * 1976-12-23 1978-09-26 General Electric Company Fluorescent lamp with opposing inversere cone electrodes
US4523125A (en) * 1981-07-13 1985-06-11 General Electric Company Fluorescent lamp electrodes
EP0560063A1 (de) * 1992-02-28 1993-09-15 Patent-Treuhand-Gesellschaft für elektrische Glühlampen mbH Niederdruckentladungslampe
US5675214A (en) * 1994-09-21 1997-10-07 U.S. Philips Corporation Low-pressure discharge lamp having hollow electrodes
US5856726A (en) * 1996-03-15 1999-01-05 Osram Sylvania Inc. Electric lamp with a threaded electrode
US6034768A (en) * 1997-09-26 2000-03-07 Physical Sciences Inc. Induced breakdown spectroscopy detector system with controllable delay time
US6552489B2 (en) * 2000-02-29 2003-04-22 Toshiba Lighting & Technology Corporation Fluorescent lamp and a method of making same, and a lighting fixture
US20080185951A1 (en) * 2007-02-06 2008-08-07 Deeder Aurongzeb Highly emissive cavity for discharge lamp and method and material relating thereto
US7786660B2 (en) 2007-02-06 2010-08-31 General Electric Company Highly emissive cavity for discharge lamp and method and material relating thereto
US20100277051A1 (en) * 2009-04-30 2010-11-04 Scientific Instrument Services, Inc. Emission filaments made from a rhenium alloy and method of manufacturing thereof
US8134290B2 (en) * 2009-04-30 2012-03-13 Scientific Instrument Services, Inc. Emission filaments made from a rhenium alloy and method of manufacturing thereof
US8226449B2 (en) 2009-04-30 2012-07-24 Scientific Instrument Services, Inc. Method of manufacturing rhenium alloy emission filaments
US20160158400A1 (en) * 2013-09-27 2016-06-09 Zhiming He Ultraviolet sterilization and disinfection device and configuration method thereof
US10322204B2 (en) * 2013-09-27 2019-06-18 Zhiming He Ultraviolet sterilization and disinfection device and configuration method thereof

Also Published As

Publication number Publication date
JPS50120180A (pt) 1975-09-20
AR202843A1 (es) 1975-07-24
BE826261A (fr) 1975-06-30
GB1505142A (en) 1978-03-30
JPS5394492U (pt) 1978-08-01
NL7502365A (nl) 1975-09-08
BR7500056A (pt) 1975-12-02
DE2502649A1 (de) 1975-09-11

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