US3566184A - Cold cathode discharge devices - Google Patents

Cold cathode discharge devices Download PDF

Info

Publication number
US3566184A
US3566184A US745612A US3566184DA US3566184A US 3566184 A US3566184 A US 3566184A US 745612 A US745612 A US 745612A US 3566184D A US3566184D A US 3566184DA US 3566184 A US3566184 A US 3566184A
Authority
US
United States
Prior art keywords
cathode
aperture
enclosure
further electrode
electrode
Prior art date
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
Application number
US745612A
Other languages
English (en)
Inventor
Clifford William Alfre Maskell
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
UK Atomic Energy Authority
Original Assignee
UK Atomic Energy Authority
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Priority claimed from GB02766/66A external-priority patent/GB1154379A/en
Application filed by UK Atomic Energy Authority filed Critical UK Atomic Energy Authority
Application granted granted Critical
Publication of US3566184A publication Critical patent/US3566184A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J3/00—Details of electron-optical or ion-optical arrangements or of ion traps common to two or more basic types of discharge tubes or lamps
    • H01J3/02—Electron guns
    • H01J3/025—Electron guns using a discharge in a gas or a vapour as electron source
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J17/00—Gas-filled discharge tubes with solid cathode
    • H01J17/02—Details
    • H01J17/04—Electrodes; Screens
    • H01J17/06—Cathodes
    • H01J17/066—Cold cathodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2893/00—Discharge tubes and lamps
    • H01J2893/0064—Tubes with cold main electrodes (including cold cathodes)
    • H01J2893/0065—Electrode systems
    • H01J2893/0066—Construction, material, support, protection and temperature regulation of electrodes; Electrode cups

Definitions

  • a cold cathode discharge device comprising an enclosure, having means to admit a gas to the interior of said enclosure and means to maintain the gas therein at a predetermined pressure-An anode is at least partly disposed within the enclosure and a hollow cathode of mesh material is mounted within the enclosure.
  • One wall of the cathode has an aperture in which is positioned a further electrode which, with the aperture, defines a gap.
  • a suitable operating potential is applied to the anode, cathode, and further electrode whereby a stream of electrons leave the hollow cathode through the gap to produce a beam having a cross-sectional shape substantially the same as the shape of the gap.
  • the beam is focused by varying the potential applied to the further electrode.
  • This invention relates to cold-cathode discharge devices which form electron sources.
  • the expression cold-cathode as used in this specification signifies that the cathode is nonthermionic.
  • the cold-cathode discharge device disclosed in the above cognate patent applications comprises an enclosure, means to maintain the enclosure at a low gas pressure, an anode mounted within the enclosure or forming part of an interior wall of the enclosure, a hollow cathode formed at least partly of wire mesh mounted within the enclosure, one wall of the cathode being of circular outline and part spherical shape with the concave side outwards and having a central circular aperture, a further electrode of circular outline positioned in said aperture to define with said aperture an annular gap, and means to apply suitable operating potentials to the anode, cathode and further electrode.
  • the resulting beam is of an annular cross-sectional shape and may be focused to impinge on an object over an annular region of the object or alternatively the beam may be brought to a point focus to impinge on the object at a
  • An object of the present invention is to provide a cold cathode discharge device capable of producing an electron beam of a noncircular cross-sectional shape.
  • a further object of the present invention is to provide a cold-cathode discharge device capable of producing an electron beam which may be focused to from an elongated beam.
  • a further object of the present invention is to provide a cold cathode discharge device capable of subjecting an object to an electron beam over a noncircular or a nonannular shaped area of the object in one operation without scanning the electron beam.
  • a cold-cathode discharge device comprises an enclosure, means to maintain the enclosure at a low gas pressure, an anode mounted within the enclosure or forming part of an interior wall of the enclosure, a hollow cathode formed at least partly of wire mesh mounted within the enclosure, one wall of the cathode having a central noncircular aperture, a further electrode of similar noncircular outline positioned in said aperture to define with said aperture a gap of substantially uniform width, and means to apply suitable operating potentials to the anode, cathode and further electrodes.
  • the operating potential applied to the further electrode may be the same as, or positive relative to, or negative relative to, that applied to the cathode.
  • the cathode may be of a cylindrical shape with the said aperture provided in an end wall of the cylindrical shape.
  • the end wall may be concave outwardly with respect to the cathode if desired.
  • the cathode may be of a cylindrical shape with the said aperture provided in a longitudinal wall of the cylindrical shape.
  • the aperture in the longitudinal wall of the cylindrical shape is provided in a portion of the wall which is concave outwardly with respect to the cathode.
  • the cathode need not be of a right circular cylindrical shape but may be of any desired cross-sectional shape, for example, it may be rectangular.
  • An earthed screening electrode may be provided to encompass part of said cathode if desired.
  • FIG. 1 shows a partly diagrammatic section through the device
  • FIG. 2 shows an underneath device of FIG. 1
  • FIG. 3 shows a modified form of the cathode shown in FIG.
  • the device comprises an enclosure formed by an approximately cylindrical tube 1 of heat resisting glass, about 22 cms. in diameter and 30 cms. long, closed at the ends by aluminum plates 2 and 3 with O-ring seals (not shown), and supported with its axis vertical.
  • the plates 2 and 3 are both earthed, and in operation of the device form anodes.
  • a cathode 4 is supported within the enclosure by a conducting tube 5 which extends downwards from a cathode connector 6 having a bore 7 for water cooling.
  • the cathode connector 6 is secured to a removable portion 8 of the plate 2 by way of an insulating cylinder 9. Extending through the portion 8, concentric with the tube 5, is a conducting tube 10 which forms an earthed shield.
  • the cathode 4 comprises a right circular cylindrical portion 11 with flat portions 12 and 13 at the top and bottom respectively.
  • the portion 13 of the cathode 4 has a central noncircular aperture.
  • a flat plate of similar noncircular outline which forms a further electrode 14 is supported in the aperture in the portion 13 of the cathode 4 by a conducting rod 15, so as to leave a gap 16 of uniform width between the electrode 14 and the portion 13.
  • the rod 15 passes through an insulating bush 17 in the portion 12 of the cathode 4.
  • the gap I6 is, in the particular embodiment of the device here described, of approximately square shape.
  • the edge of the aperture in the portion 13 of the cathode 4 and the edge of the further electrode 14 are rounded at the corners 17 so that the gap 16 is of substantially uniform width throughout. In some cases small alumina pegs may be pushed into the gap 16 at intervals around it for the purpose of maintaining the width unifonn.
  • the portion 11 of the cathode 4 is of stainless steel mesh or refractory wire mesh
  • the portions 12 and 13, and the electrode 14 are of refractory metal plate, for example, tantalum plate.
  • the portion 13 and the electrode 14 may also be formed of stainless steel mesh or refractory wire mesh.
  • the edges of the portion 13 and the electrode 14 defining thegap 16 may be made smooth by welding to them rings of the appropriate shape.
  • the rod 15 is of a refractory metal, although alternatively the rod 15 may be replaced by a support formed by a cylinder of stainless steel wire mesh, this alternative being possible because of the reduced heating effect on a mesh.
  • ' Power is derived from a source 19 comprising an autotransformer which supplies a variable voltage to the primary winding of a high voltage transformer, the output of which is rectified by a full wave rectifier.
  • the connection to the cathode connector 6 is by way of resistors 20 and 21 in series, the resistor 21 being variable.
  • the junction of resistors 20 and 21 is connected to the rod 15.
  • the circuit also includes an ammeter and a voltmeter (not shown).
  • Evacuation of the enclosure is by means of an oil diffusion pump 22 backed by a rotary pump (not shown), connection to the pumps being by way of an outlet pipe 23 passing through a removable portion 24 of the plate 3.
  • a gas is supplied from a gas supply cylinder 25 through a two-stage pressure regulator and a needle valve 26 to an inlet pipe 27 which also passes through the portion 24 of the plate 3
  • the pressure in the enclosure is controlled by adjusting the flow of gas with the pumps working continuously.
  • the enclosure is evacuated to a pressure of approximately 5 X 10- with helium to a pressure of approximately 3 X 10- torr.
  • a negative potential of approximately 2.75 kilovolts is applied to the cathode 4, the resistor 21 bein set to zero, so that the same potential isapplied to the electrode 14 as to the cathode 4.
  • the helium pressure is allowed to rise slowly. This is done by adjustment of the valve 26.
  • a hollow cathode discharge develops, accompanied by a stream of electrons which passes through the gap 16. Due to the shape of the gap 16 the stream of electrons forms a beam 28 of hollow square cross section.
  • the beam 28 is particularly adapted for a welding operation in which the edges of a square metallic cap 29 are to be welded to a metallic base 30.
  • the cap 29 may form part of a can for a semiconductor device.
  • the base 30 is mounted on a metallic support 31 and is so connected as an anode. On directing the beam 28 at the cap 29 the whole of the edge of the cap 29 is welded in one operation without the need to move the cap 29 or cause the beam 28 to scan.
  • the operation is generally similar except that the gas used is argon, in which case the pressure to which the enclosure is initially evacuated and the operating pressures are lower.
  • the resistor 21 is set to a low value, so that the electrode 14 is at a negative potential relative to the cathode 4.
  • a beam 28 is obtained with the cathode 4 at a negative potential of 6 kilovolts and an argon pressure of IO torr.
  • the enclosure isevacuated and filled with helium as in the first case. With a helium pressure of 18 X torr, the resistor 21 set to zero, and a negative potential of approximately 2.75 kilovolts applied to the cathode 4 a glow discharge occurs. This is not accompanied by an electron beam and the result of the discharge is that the potential difference between the support 31 and the cathode 4 falls to approximately 300 volts. 5'
  • the device may be operated with other gases, for example, oxygen. In this case, however, it is-desirable, although not essential, to make the cathode 4 of an oxidation resistant materi-
  • the device may be used for various other purposes, such as heat treatment, melting or zone'refinement, in which heating, particularly the heating of a refractory material, is involved.
  • H6. 3 shows a cathode'32 as a generally right circular cylindrical shape having a portion 33 formed by a longitudinally extending indentation.
  • the cathode 32 is arranged in an enclosure similar to the enclosure shown in FlG. 1 such that the longitudinal axis of the cylindrical shape lies in a sub-.
  • the curved surface 34 of the cathode 32 is made of a mesh or perforated material such as for example tantalum,'and'the portion 33 is made from mesh material or perforated material or thin solid plate material such asfor example stainless steel, or tantalum or other refractorymetal.
  • the end plates 35 of the cathode 32 are made from thin sheet metal for example stainless steel tantalum or other refractory metal.
  • the portion 33 of the cathode 32 is provided with a noncircular aperture 36.
  • a further-electrode 37 Positioned in'or adjacent the aperture is a further-electrode 37 which with the aperture 36 defines a gap 38.
  • the cathode 32 may be attached to the tube 5 of F IG. 1 by means of a thin tubular boss 39 which is tack welded on to cathode 32.
  • the further electrode 37 is connected to the power supply by way of the connector 40.
  • the mode of operation of the cathode 32 and further electrode 37 is identical to that of the cathode 4 and further electrode of FIG. 1, and the potentials applied to the cathode 32 and further electrode 3 may be the same as that described above.
  • the only significant difference between the structure shown in FIG. 3 and the cathode 4 and further electrode 14 of FIG. 1 is in the shape and construction of the cathode and further electrode.
  • the gaps defined by the cathodes 4 and 32 and the further electrodes 14and 37 may be of any desired shape to produce a hollow electron beam of any desired cross-sectional shape, forexample of a substantially rectangular shape, an eliptical shape, an ogival shape a multi sided shape or an irregular shape.
  • the hollow beam may be brought to a point focus if desired or arranged to focus along a line.
  • the electrodes 14 or 37 may be provided so that they can be maintained at a positive or a negative potential relative to the cathode 4 or 32. In either case the glow discharge can be restricted if the potential relative to the cathode 4 is made large enough.
  • An earthed screening electrode may be arranged to encircle the cathode 4 to reduce the loss of electrons to the walls of the enclosure.
  • a cold-cathode discharge device comprising an enclosure, means to admit a gas to the interior of said enclosure,
  • anode at least partly disposed within the enclosure, a hollow cathode formed at least partly of a mesh material mounted within the enclosure, one wall of said cathode having a substantially rectangular aperture therein, a further electrode of a similar substantially rectangular outline to said aperture positioned in said aperture to define with said aperture a gap, and means to apply suitable operating potentials to the anode, cathode and further electrode.
  • the cathode is of a cylindrical shape with a longitudinally extending indentation portion in the longitudinal wall of the cathode, said indentation being such as to present a concave surface outwardly with respect to'the said cathode, and said aperture being provided in said indentation portion.
  • a device as claimed in claim 1 wherein said cathode is substantially right circular cylindrical.

Landscapes

  • Electron Sources, Ion Sources (AREA)
  • Discharge Lamp (AREA)
US745612A 1965-12-30 1968-07-17 Cold cathode discharge devices Expired - Lifetime US3566184A (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
GB02766/66A GB1154379A (en) 1965-12-30 1965-12-30 Improvements in or relating to Cold-Cathode Discharge Devices
GB5520665 1965-12-30
GB3305367 1967-07-18

Publications (1)

Publication Number Publication Date
US3566184A true US3566184A (en) 1971-02-23

Family

ID=10347901

Family Applications (1)

Application Number Title Priority Date Filing Date
US745612A Expired - Lifetime US3566184A (en) 1965-12-30 1968-07-17 Cold cathode discharge devices

Country Status (4)

Country Link
US (1) US3566184A (enrdf_load_stackoverflow)
DE (1) DE1764684A1 (enrdf_load_stackoverflow)
FR (1) FR95369E (enrdf_load_stackoverflow)
GB (1) GB1238451A (enrdf_load_stackoverflow)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3638061A (en) * 1970-07-15 1972-01-25 Hughes Aircraft Co Magnetically controlled crossed-field interrupter and switch tube with pressure control for long duration pules
US3903891A (en) * 1968-01-12 1975-09-09 Hogle Kearns Int Method and apparatus for generating plasma
US4163889A (en) * 1974-05-27 1979-08-07 U.S. Philips Corporation Device for the simultaneous operation of a number of gas discharge electron guns
US4647818A (en) * 1984-04-16 1987-03-03 Sfe Technologies Nonthermionic hollow anode gas discharge electron beam source
US5465030A (en) * 1995-01-20 1995-11-07 The United States Of America As Represented By The Secretary Of The Army Trigger apparatus for spark gap dischargers
US20100314540A1 (en) * 2009-06-14 2010-12-16 Adler David L Electron microscope with an emitter operating in medium vacuum
US9840765B2 (en) 2013-10-16 2017-12-12 General Electric Company Systems and method of coating an interior surface of an object

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5216690A (en) * 1992-03-11 1993-06-01 Hanks Charles W Electron beam gun with grounded shield to prevent arc down

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3903891A (en) * 1968-01-12 1975-09-09 Hogle Kearns Int Method and apparatus for generating plasma
US3638061A (en) * 1970-07-15 1972-01-25 Hughes Aircraft Co Magnetically controlled crossed-field interrupter and switch tube with pressure control for long duration pules
US4163889A (en) * 1974-05-27 1979-08-07 U.S. Philips Corporation Device for the simultaneous operation of a number of gas discharge electron guns
US4647818A (en) * 1984-04-16 1987-03-03 Sfe Technologies Nonthermionic hollow anode gas discharge electron beam source
US5465030A (en) * 1995-01-20 1995-11-07 The United States Of America As Represented By The Secretary Of The Army Trigger apparatus for spark gap dischargers
US20100314540A1 (en) * 2009-06-14 2010-12-16 Adler David L Electron microscope with an emitter operating in medium vacuum
US8729470B2 (en) * 2009-06-14 2014-05-20 DLA Instruments Electron microscope with an emitter operating in medium vacuum
US9840765B2 (en) 2013-10-16 2017-12-12 General Electric Company Systems and method of coating an interior surface of an object

Also Published As

Publication number Publication date
FR95369E (fr) 1970-09-11
DE1764684A1 (de) 1971-09-30
GB1238451A (enrdf_load_stackoverflow) 1971-07-07

Similar Documents

Publication Publication Date Title
EP0158970B1 (en) Nonthermionic hollow anode gas discharge electron beam source
US3566184A (en) Cold cathode discharge devices
US3320475A (en) Nonthermionic hollow cathode electron beam apparatus
US3411035A (en) Multi-chamber hollow cathode low voltage electron beam apparatus
US3243570A (en) Automatic gas pressure control for electron beam apparatus
GB1329228A (en) Electron beam apparatus
DE1514990A1 (de) Hohllathode
US3518484A (en) Hollow cathode discharge device with control electrode for electron beam focusing
US2433813A (en) Electric discharge tube
EP1151456A4 (en) DEVICE AND METHOD FOR REDUCING OPERATING VOLTAGE IN GAS DISCHARGE APPARATUS
US3262003A (en) Perforated hollow cathode discharge device
US4019091A (en) Gas discharge electron gun for generating an electron beam by means of a glow discharge
US4163172A (en) Sliding spark source cold cathode electron gun and method
US3286187A (en) Ion source utilizing a spherically converging electric field
GB730920A (en) Improvements in or relating to high-vacuum electric discharge tubes of the kind comprising cold electrodes
US1970532A (en) Electric discharge tube
US2245998A (en) Grid-controlled gas or vapor-filled discharge vessel for high operating voltages
US3099762A (en) Cathode ray tube using replaceable cathode
US2170034A (en) Rectifier tube
EP0231303B1 (de) Leuchtstofflampe für unipolaren betrieb
GB1017248A (en) Improvements in or relating to lasers
US2203452A (en) Electronic discharge tube
DE564295C (de) Dampfentladungsroehre fuer Lichtbogenentladung mit Kathodendruckkammer
GB2254185A (en) A surface discharge corona plasma cathode assembly.
US2238712A (en) Production of high frequency electrical oscillations