US3381157A - Annular hollow cathode discharge apparatus - Google Patents

Annular hollow cathode discharge apparatus Download PDF

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Publication number
US3381157A
US3381157A US417399A US41739964A US3381157A US 3381157 A US3381157 A US 3381157A US 417399 A US417399 A US 417399A US 41739964 A US41739964 A US 41739964A US 3381157 A US3381157 A US 3381157A
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US
United States
Prior art keywords
cathode
aperture
hollow
hollow cathode
electrons
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
US417399A
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English (en)
Inventor
Fernand J Ferreira
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Raytheon Technologies Corp
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United Aircraft Corp
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
Application filed by United Aircraft Corp filed Critical United Aircraft Corp
Priority to US417399A priority Critical patent/US3381157A/en
Priority to IL24630A priority patent/IL24630A/en
Priority to GB49176/65A priority patent/GB1121115A/en
Priority to DE19651514990 priority patent/DE1514990A1/de
Priority to FR39701A priority patent/FR1455620A/fr
Priority to CH1673865A priority patent/CH457631A/de
Priority to BE673420D priority patent/BE673420A/xx
Priority to NL6516051A priority patent/NL6516051A/xx
Priority to ES0320887A priority patent/ES320887A1/es
Application granted granted Critical
Publication of US3381157A publication Critical patent/US3381157A/en
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
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/02—Details
    • H01J37/04—Arrangements of electrodes and associated parts for generating or controlling the discharge, e.g. electron-optical arrangement or ion-optical arrangement
    • H01J37/06—Electron sources; Electron guns
    • H01J37/077—Electron guns using discharge in gases or vapours as electron sources
    • 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

  • This invention relates toa novel annular hollow cath ode and particularly to a perforated cathode which emits a disc-like beam of electrons radially inward lfrom a slit aperture around its entire inner periphery.
  • Electron beams liberate electrons from the surface of a heated cathode by thermionic emission. Electron beams are produced in a hollow cathode by the release of electrons as a result of the impact of high energy electrons with background gas molecules within the hollow cathode itself.
  • Previous conventional hollow cathodes comprise closed hollow cylinder-s [fabricated from wire mesh or perforated metal with -a circular aperture in one end.
  • a glow discharge is initiated.
  • a well-collimated pencil beam of high current density, high-energy electrons emanates from the hollow cathode aperture.
  • the beam can be -focused by conventional electromagnetic lenses to power densities comparable with those of convention-al electron beamY Welders.
  • the annular cathode may be used for applications such as welding, brazng, zone melting, fibre drawing and vapor deposition.
  • the annular hollow cathode is preferably a hollow toroid or similar shape fabricated from wire mesh, usually Ia. refractory metal.
  • the surrounding pressure is lowered to the range of generally 0.1 micron of mercury.
  • the substantially evacuated chamber is then rback lled with an inert ⁇ gas such :as helium or argon, or any gas compatible with the workpiece at the temper-a-J tures employed.
  • a hollow cathode discharge can then be initiated and maintained with a pon tential difference of several thousand volts between the cathode and anode or workpiece.
  • a well-focused beam of electrons is emitted from the annular slot 'and bombards the workpieceuniformly around its circumference.
  • Modified cathode shapes -and arrangements may be used, for example, inverted cathodes with beams directed radially outward, cathodes with laxially directed beams, multiple or stacked cathodes, and cathodes with irregular cross-sectional areas, geometries or shapes to weld irregu larly shaped pieces.
  • Another object of this invention is a novel annular hollow cathode having solid or perforated walls which may be used with nonconductor as well as with metallic workpieces.
  • a further object of this invention is a novel annular hollow cathode which may be used for welding, brazing, zone melting, fibre drawing and vapor deposition.
  • Another object of this invention is a novel annular hollow cathode having an irregular shape for operating upon irregular workpieces..
  • FIGURE 1 shows a perforated wall hollow cathode of the prior art
  • FIGURE 2 is a schematic of a typical annular hollow cathode system
  • FIG. 1 shows the detail of the preferred annular hollow cathode
  • FIGURE 4 shows schematically the operation of the :annular cathode
  • FIGURE 1 there is shown the prior air hollow cathode comprising a closed hollow cylinder 10, the cylinder being fabricated from thev wire mesh.
  • a circular aperture 12 is cut in one end of the cylindrical cathode 10.
  • the cathode is biased negatively with respect to the anode, which may be the surroundings or the workpiece, a glow discharge is initiated and a high energy electron beam 14 is generated.
  • the cathode Because of the special geometry of the cathode 10, most of the electrons in the portion of the plasma within the cylinder emerge from the aperture as beam 14. Furthermore, these electrons are accelerated through approximately the full potential drop across the discharge in a region very close to the aperture 12.
  • any small electric fields which exist in the ambient plasma filling the enclosure have a negligible elect on the energy or direc tiohfof the beam 14.
  • a workpiece 16 positioned in the path of the beam 14 may be heated, welded or otherwise acted upon by the electron beam 14. While not shown, the beam 14 can be focused by electromagnetic lenses. Likewise, discharge will generally only take place at a pressure level below 1000 microns.
  • FIGURE 2 shows schematically an annular hollow cath ode beam discharge system of this invention
  • FIGAv URE 3 shows the structure of the novel hollow cathode.
  • the annular hollow cathode 20 may be fabricated from stainless steel from a 10 mil, 40 mesh wire cloth or similar substance. Cathodes thus far fabricated have had an outer diameter, D0, typically from 1.3 tp 4times the inner diameter D1, but are obviously notlimited thereto.
  • the height H of the cathode assembly does not appear to be a critical factor; however, the size of the aperture A may well be critical as will be explained subsequently. Nor does it appear that the wall thickness or the mesh size have an appreciable effect upon the electron beam output.
  • the cathode 20, workpiece 22 and associated supports are enclosed .in .an air-tight enclosure 24 which may be of glass or other suitable material.
  • the cathode is supported by arm 26 which may also be the negative potenL tial lead to the cathode.
  • Workpiece 22 may be held in place by a metallic arm 30 on which are positioned two adjustable clamping structures 28 and 28. If the work piece 22 is metallic, it may be grounded to act as the anode. If the workpiece 22 is a nonconductor, the workpiece support structures 28 and 30 may act as the anodec
  • a separate anode 32 as shown in FIGURE 3, may be provided at any location within the enclosure 24 with a positive potential lead and anode support 34.
  • FIG- URE 5 shows in cross section the beam as generated by cathode 20 and focused upon workpiece 22.
  • the enclosure 24 may be initially evacuated by means of vacuum pump 36. After evacuation to the proper pressure level, a supply of gas 38 may be used to produce a gas atmosphere within the enclosure.
  • the gas may be helium, hydrogen, nitrogen or argon, or any gas suitable for the workpiece.
  • the desira ble mode of operation that is the electron beam mode, is similar to abnormal glow discharge in that it has a positive voltage-current characteristic and undergoes a transition into an arc-like mode of operation, sometimes called the fountain mode, as the power level is increased.
  • the voltage or current at which this transition occurs depends upon the cathode geometry, gas type and gas pressure.
  • the operation of the discharge modes may be compared with the operation of conventional glow discharges.
  • a conventional glow discharge practically all the potential drop across the discharge occurs in a region quite close to the cathode, this drop being known as the cathode fall.
  • the characteristic thickness, dc, of the cathode fall depends on the gas pressure, gas type, cathode material and applied voltage.
  • the high potential end of this region can be identified visually by a sharp demarcation between a dark portion of a discharge near the cathode, called the cathode dark space, and a bright region called the negative glow.
  • the aperture perturbs the potential distribution and a portion of the cathode fall occurs inside the Cathoder FIGURE 4 shows these conditions.
  • the potential drop inside the cathode usually com# prises a small fraction of the total cathode fall.
  • the special shape of the cathode makes it highly improbable for electrons formed by ionization in the cavity to escape from the cathode cavity through any of the holes except the aperture. Electrons emitted from the inside of the wire screen 44 by secondary emission processes also have a high probability of being trapped in the inc ternal potential well.
  • the perturbed potential dis tribution in vicinity the aperture A resembles a Y concave flens.
  • the electric field lines normal to the equiu potential lines converge in the vicinity of the aperture. Electrons inside the cavity drift toward the aperture in the relatively weak electric field within. In the aperture region they are accelerated through the full cathode fall and thus acquire a highly directed velocity approximately along the iluid lines. In this manner the perforated wall hollow cathode forms a highly collimated energetic elec tron beam. Therefore, it is quite desirable to keep the potential drop which occurs inside the cathode to a small fraction of the total cathode fall.. For this reason it apa pears that the aperture A should be held somewhat less than dc. However, A cannot be made too small or no electron beam will form as explained previously.
  • the operation ofthe perforated wall hollow cathode in the electron beam mode is analagous to an abnormal glow discharge.
  • the secu ondary discharge that occurs inside the lhollow cathode and the associated production of ion electron pairs prou vides it with an additional source of electrons and a higher current capability than a glow discharge.
  • Most eicient operation is achieved when the current ⁇ from the aperture greatly exceeds the outward current emanating from the exterior surface of the cathode. The outward current represents losses since it does not contribute in any way to the electron beam current.
  • a perforated wall annular hollow cathode has a positive-voltage curl rent characteristic
  • the measured beam power as well as the input power of the perforated wall cathodes is slightly higher for the larger cathodes,
  • the solid wall cathode operates at significantly lower power than any of the perforated wall cathodes regardless of size. Beam power efficiency is comparable for all per-1 forated wall cathodes, Efficiencies of the annular cathE ode of 75% have been achieved, Shielding around the solid wall annular hollow cathode is an effective means for increasing the efiiciency of this cathode to this level,
  • FIGURE 6 shows additional modifications of the cathode assembly.
  • the cathode 70 is not plane, but at an angle so that the beam focuses on the workpiece 72 at a point other than the plane of the cathode, The beam would therefore be conical in shape
  • FIGURE 6C illustrates the use of multiple or stacked cathodes 70 and 70V which may operate upon a workpiece 72 simultaneously.
  • FIGURE 6D shows the use of a cathode 70 having an axially directed beam which forms a circular pattern upon workpiece 72, y
  • Other modifications are obvious to those skilled in the art, such as cathodes of various geometries such as triangular or trapezoidal, cathodes with varying width apertures or with. irregularly shaped apertures, or with a portion of the aperture blocked,
  • annular hollow cathode Other applications of the annular hollow cathode are brazing, sputtering, and zone heating,
  • the feature of the annular hollow cathode which allows it to heat insulators as well as conductors produces a high po tential for such applications as zone refining of ceramics and growing crystals' of materials such as alumina
  • Theuse of the annular hollow cathode in a cusped magnetic field provides a mechanism for spreading the heated zone
  • the catha ode may be used to heat both tungsten and fused silica or other substrates in chemical vapor deposition.
  • cathode configurations shown are not the only possible configurations, and that a. wide range of regular and irregular cathode geometries may be derived from this teaching. It is also obvious that various modifications and substitutions may be made without departing from the scope of the invention as hereinafter claimed,
  • a cathode structure comprising a hollow metallic element containing a continuous elongated aperture along at least a portion of the surface thereof,
  • said aperture being curved in the plane containing said sheet of electrons
  • said aperture extending continuously about the inside surface of said element whereby said sheet of elec trons converges at the center of said element.
  • a hollow cathode device as in claim 12 in which the cross section of said hollow metallic element varies on area. with azimuthal locations about the center of said elementa 14n
  • a hollow cathode device as in claim 12 in which said slot varies in orientation with. azimuthal locations about the center of said clementL 16.
  • a hollow cathode device as in claim 12 in which said slot varies in width with azimuthal locations about the center of said element.

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Plasma Technology (AREA)
  • Electron Sources, Ion Sources (AREA)
  • Welding Or Cutting Using Electron Beams (AREA)
  • Arc Welding In General (AREA)
US417399A 1964-12-10 1964-12-10 Annular hollow cathode discharge apparatus Expired - Lifetime US3381157A (en)

Priority Applications (9)

Application Number Priority Date Filing Date Title
US417399A US3381157A (en) 1964-12-10 1964-12-10 Annular hollow cathode discharge apparatus
IL24630A IL24630A (en) 1964-12-10 1965-11-16 Annular hollow cathode discharge apparatus
GB49176/65A GB1121115A (en) 1964-12-10 1965-11-19 Improvements in and relating to annular hollow cathode discharge apparatus
DE19651514990 DE1514990A1 (de) 1964-12-10 1965-11-23 Hohllathode
FR39701A FR1455620A (fr) 1964-12-10 1965-11-25 Cathode creuse annulaire et appareil à décharge en comportant application
CH1673865A CH457631A (de) 1964-12-10 1965-12-03 Hohlkathode zur Erzeugung eines Elektronenbündels durch Stossionisation
BE673420D BE673420A (xx) 1964-12-10 1965-12-08
NL6516051A NL6516051A (xx) 1964-12-10 1965-12-09
ES0320887A ES320887A1 (es) 1964-12-10 1965-12-10 Perfeccionamientos en los aparatos para generar heces de electrones.

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US417399A US3381157A (en) 1964-12-10 1964-12-10 Annular hollow cathode discharge apparatus

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US3381157A true US3381157A (en) 1968-04-30

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US417399A Expired - Lifetime US3381157A (en) 1964-12-10 1964-12-10 Annular hollow cathode discharge apparatus

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US (1) US3381157A (xx)
BE (1) BE673420A (xx)
CH (1) CH457631A (xx)
DE (1) DE1514990A1 (xx)
ES (1) ES320887A1 (xx)
FR (1) FR1455620A (xx)
GB (1) GB1121115A (xx)
IL (1) IL24630A (xx)
NL (1) NL6516051A (xx)

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3452179A (en) * 1967-04-12 1969-06-24 Us Air Force Electron optical system
US3492525A (en) * 1968-03-11 1970-01-27 United Aircraft Corp Sectional hollow cathode discharge apparatus
US3614510A (en) * 1968-06-04 1971-10-19 United Ekingdom Atomic Energy Nonthermionic cathode discharge devices
US3769008A (en) * 1971-05-19 1973-10-30 B Borok Method for sintering workpieces of pressed powdered refractory metal or alloy and vacuum furnace for performing the same
DE2455001A1 (de) * 1973-11-21 1975-10-02 Hitachi Ltd Wicklung fuer eine elektrische maschine
US4377773A (en) * 1980-12-12 1983-03-22 The United States Of America As Represented By The Department Of Energy Negative ion source with hollow cathode discharge plasma
US4760238A (en) * 1986-01-21 1988-07-26 The Welding Institute Charged particle beam generation
US4886992A (en) * 1987-07-22 1989-12-12 Centre National De La Recherche Scientifique Electron source with magnetic means
US5552675A (en) * 1959-04-08 1996-09-03 Lemelson; Jerome H. High temperature reaction apparatus
US20110318498A1 (en) * 2009-02-24 2011-12-29 University Of Virginia Patent Foundation Coaxial Hollow Cathode Plasma Assisted Directed Vapor Deposition and Related Method Thereof
US20140216343A1 (en) 2008-08-04 2014-08-07 Agc Flat Glass North America, Inc. Plasma source and methods for depositing thin film coatings using plasma enhanced chemical vapor deposition
US9721764B2 (en) 2015-11-16 2017-08-01 Agc Flat Glass North America, Inc. Method of producing plasma by multiple-phase alternating or pulsed electrical current
US9721765B2 (en) 2015-11-16 2017-08-01 Agc Flat Glass North America, Inc. Plasma device driven by multiple-phase alternating or pulsed electrical current
US10242846B2 (en) 2015-12-18 2019-03-26 Agc Flat Glass North America, Inc. Hollow cathode ion source
US10573499B2 (en) 2015-12-18 2020-02-25 Agc Flat Glass North America, Inc. Method of extracting and accelerating ions
US10586685B2 (en) 2014-12-05 2020-03-10 Agc Glass Europe Hollow cathode plasma source
US10755901B2 (en) 2014-12-05 2020-08-25 Agc Flat Glass North America, Inc. Plasma source utilizing a macro-particle reduction coating and method of using a plasma source utilizing a macro-particle reduction coating for deposition of thin film coatings and modification of surfaces

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3466487A (en) * 1967-06-16 1969-09-09 United Aircraft Corp Device for moving a beam of charged particles
GB2194673B (en) * 1986-08-30 1990-10-24 English Electric Valve Co Ltd Apparatus for forming an electron beam sheet

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2084172A (en) * 1930-12-13 1937-06-15 Rca Corp Electron tube
GB888609A (en) * 1957-07-31 1962-01-31 Cie Francaise Thomsom Houston Improvements in and relating to electron emitting devices
US3210518A (en) * 1962-12-21 1965-10-05 Alloyd Electronics Corp Hollow cathode device
US3218431A (en) * 1962-12-27 1965-11-16 Gen Electric Self-focusing electron beam apparatus
US3262013A (en) * 1962-02-02 1966-07-19 Martin Marietta Corp Perforated hollow cathode discharge device

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2084172A (en) * 1930-12-13 1937-06-15 Rca Corp Electron tube
GB888609A (en) * 1957-07-31 1962-01-31 Cie Francaise Thomsom Houston Improvements in and relating to electron emitting devices
US3262013A (en) * 1962-02-02 1966-07-19 Martin Marietta Corp Perforated hollow cathode discharge device
US3210518A (en) * 1962-12-21 1965-10-05 Alloyd Electronics Corp Hollow cathode device
US3218431A (en) * 1962-12-27 1965-11-16 Gen Electric Self-focusing electron beam apparatus

Cited By (28)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5552675A (en) * 1959-04-08 1996-09-03 Lemelson; Jerome H. High temperature reaction apparatus
US5628881A (en) * 1959-04-08 1997-05-13 Lemelson; Jerome H. High temperature reaction method
US3452179A (en) * 1967-04-12 1969-06-24 Us Air Force Electron optical system
US3492525A (en) * 1968-03-11 1970-01-27 United Aircraft Corp Sectional hollow cathode discharge apparatus
US3614510A (en) * 1968-06-04 1971-10-19 United Ekingdom Atomic Energy Nonthermionic cathode discharge devices
US3769008A (en) * 1971-05-19 1973-10-30 B Borok Method for sintering workpieces of pressed powdered refractory metal or alloy and vacuum furnace for performing the same
DE2455001A1 (de) * 1973-11-21 1975-10-02 Hitachi Ltd Wicklung fuer eine elektrische maschine
US4377773A (en) * 1980-12-12 1983-03-22 The United States Of America As Represented By The Department Of Energy Negative ion source with hollow cathode discharge plasma
US4760238A (en) * 1986-01-21 1988-07-26 The Welding Institute Charged particle beam generation
US4886992A (en) * 1987-07-22 1989-12-12 Centre National De La Recherche Scientifique Electron source with magnetic means
US9478401B2 (en) 2008-08-04 2016-10-25 Agc Flat Glass North America, Inc. Plasma source and methods for depositing thin film coatings using plasma enhanced chemical vapor deposition
US10438778B2 (en) 2008-08-04 2019-10-08 Agc Flat Glass North America, Inc. Plasma source and methods for depositing thin film coatings using plasma enhanced chemical vapor deposition
US20150004330A1 (en) 2008-08-04 2015-01-01 Agc Flat Glass North America, Inc. Plasma source and methods for depositing thin film coatings using plasma enhanced chemical vapor deposition
US20150002021A1 (en) 2008-08-04 2015-01-01 Agc Flat Glass North America, Inc. Plasma source and methods for depositing thin film coatings using plasma enhanced chemical vapor deposition
US10580624B2 (en) 2008-08-04 2020-03-03 Agc Flat Glass North America, Inc. Plasma source and methods for depositing thin film coatings using plasma enhanced chemical vapor deposition
US20140216343A1 (en) 2008-08-04 2014-08-07 Agc Flat Glass North America, Inc. Plasma source and methods for depositing thin film coatings using plasma enhanced chemical vapor deposition
US10580625B2 (en) 2008-08-04 2020-03-03 Agc Flat Glass North America, Inc. Plasma source and methods for depositing thin film coatings using plasma enhanced chemical vapor deposition
US9640369B2 (en) * 2009-02-24 2017-05-02 University Of Virginia Patent Foundation Coaxial hollow cathode plasma assisted directed vapor deposition and related method thereof
US20110318498A1 (en) * 2009-02-24 2011-12-29 University Of Virginia Patent Foundation Coaxial Hollow Cathode Plasma Assisted Directed Vapor Deposition and Related Method Thereof
US10586685B2 (en) 2014-12-05 2020-03-10 Agc Glass Europe Hollow cathode plasma source
US10755901B2 (en) 2014-12-05 2020-08-25 Agc Flat Glass North America, Inc. Plasma source utilizing a macro-particle reduction coating and method of using a plasma source utilizing a macro-particle reduction coating for deposition of thin film coatings and modification of surfaces
US11875976B2 (en) 2014-12-05 2024-01-16 Agc Flat Glass North America, Inc. Plasma source utilizing a macro-particle reduction coating and method of using a plasma source utilizing a macro-particle reduction coating for deposition of thin film coatings and modification of surfaces
US20170309458A1 (en) 2015-11-16 2017-10-26 Agc Flat Glass North America, Inc. Plasma device driven by multiple-phase alternating or pulsed electrical current
US9721765B2 (en) 2015-11-16 2017-08-01 Agc Flat Glass North America, Inc. Plasma device driven by multiple-phase alternating or pulsed electrical current
US10559452B2 (en) 2015-11-16 2020-02-11 Agc Flat Glass North America, Inc. Plasma device driven by multiple-phase alternating or pulsed electrical current
US9721764B2 (en) 2015-11-16 2017-08-01 Agc Flat Glass North America, Inc. Method of producing plasma by multiple-phase alternating or pulsed electrical current
US10242846B2 (en) 2015-12-18 2019-03-26 Agc Flat Glass North America, Inc. Hollow cathode ion source
US10573499B2 (en) 2015-12-18 2020-02-25 Agc Flat Glass North America, Inc. Method of extracting and accelerating ions

Also Published As

Publication number Publication date
ES320887A1 (es) 1966-09-01
NL6516051A (xx) 1966-06-13
GB1121115A (en) 1968-07-24
IL24630A (en) 1969-11-30
BE673420A (xx) 1966-04-01
CH457631A (de) 1968-06-15
DE1514990A1 (de) 1970-07-23
FR1455620A (fr) 1966-10-14

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