US3172007A - Folded filament beam generator - Google Patents

Folded filament beam generator Download PDF

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Publication number
US3172007A
US3172007A US166255A US16625562A US3172007A US 3172007 A US3172007 A US 3172007A US 166255 A US166255 A US 166255A US 16625562 A US16625562 A US 16625562A US 3172007 A US3172007 A US 3172007A
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US
United States
Prior art keywords
filament
emitters
electron
accelerating
electron beam
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
US166255A
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English (en)
Inventor
Charles W Hanks
Maurice E Tyler
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.)
Stauffer Chemical Co
Original Assignee
Stauffer Chemical Co
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 to NL287527D priority Critical patent/NL287527A/xx
Priority to BE627165D priority patent/BE627165A/xx
Application filed by Stauffer Chemical Co filed Critical Stauffer Chemical Co
Priority to US166255A priority patent/US3172007A/en
Priority to DEST20157A priority patent/DE1171097B/de
Priority to AT22863A priority patent/AT257183B/de
Priority to GB1677/63A priority patent/GB982669A/en
Priority to FR921515A priority patent/FR1348684A/fr
Priority to CH45263A priority patent/CH404011A/de
Application granted granted Critical
Publication of US3172007A publication Critical patent/US3172007A/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, ion-optical arrangement
    • H01J37/06—Electron sources; Electron guns
    • H01J37/063—Geometrical arrangement of electrodes for beam-forming
    • 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
    • H01J37/30—Electron-beam or ion-beam tubes for localised treatment of objects
    • H01J37/305—Electron-beam or ion-beam tubes for localised treatment of objects for casting, melting, evaporating or etching

Definitions

  • the present invention relates to an improved electron beam generator for high energy application, wherein very high current electron beams are required such as, for example, in electron beam furnaces.
  • the present invention provides for initially directing emitted electrons in a desired direction away from the emission area so that the emitter itself co-operates with accelerating means in the establishment of a desired beam geometry, and furthermore, provides for materially simplifying the control over very high current beams.
  • the foregoing is accomplished herein through the utilization of a double or folded filament configuration, wherein a pair of electron emissive elements are disposed in close parallelism with electrical currents flowing in opposite directions in these two elements.
  • Thermionic emission thus produced from the elements is caused to proceed in the particular direction therefrom in part by the magnetic fields established by these two portions of the folded filament hereof.
  • the folded filament beam source of the present invention has proven to be highly advantageous in electron beam furnaces employed in the melting of refractory metals and is, of course, applicable to other high energy beam applications.
  • FIGURE 1 is a perspective view of an electron beam generator in accordance with this invention.
  • FIGURE 2 is a representation of magnetic field lines about the emitters of the source of the present invention.
  • FIGURE 3 is a schematic illustration of an electron beam furnace including the electron beam generator of FIGURE 1;
  • FIGURE 4 is a transverse sectional view through a modified version of the electron beam generator of this invention.
  • FIGURE 5 is a schematic illustration of alternative electrical connections to separate electron emitters in accordance with this invention.
  • the present invention in brief, comprises a backing electrode defining an elongated emission chamber having an opening to the exterior of the electrode. Within this chamber there are disposed a pair of spaced parallel electron emitters which are joined together at one end thereof to form a U-shaped filament. An electric current is passed serially through these emitters of the filament to raise same to a sufficient temperature for electron emis sion and this current produces magnetic fields surrounding the emitters. Inasmuch as the current passes in oppo-,
  • This magnetic field configuration establishes a virtual source of electrons along the line half way between and parallel to the two emitters, with electrons traveling from such line in the direction of the lines of force of the combined magnetic fields.
  • the above-described filament is disposed within the emission chamber of the backing electrode with the direction of electron emission pointed toward an opening in such chamber. Exteriorly of the chamber there is provided electronic accelerating means establishing an electric field attracting electrons emitted from the filament. It is found that with this configuration substantially all electrons leaving the filament area travel in the same direction, as constrained by the magnetic fields about the filament emitters, and consequently, the formation of the emission into an electron beam is greatly facilitated.
  • FIGURE 1 a broken perspective view of a preferred embodiment of the present invention and including a backing electrode 11 defining a generally cylindrical emission chamber 12 therein.
  • This chamber communicates with the exterior of the backing member at a relatively large opening longitudinally of the member and chamber.
  • a filament 14 comprising first and second parallel emitters 16 and 17.
  • the emitters 16 and 17 of the fila-' ment may, for example, be formed of 70 mil tungsten Wire and are joined together at one end thereof to thereby form a U-shaped configuration, as illustrated.
  • the two emitters of the filament are arranged in closely spaced parallelism with the separation between emitter wires being of the order of the diameter of an individual wire.
  • Suitable insulating supporting means are provided for mounting the filament in the position shown and described.
  • an electron accelerating electrode 19 which extends longitudinally of the element with a leading edge of such electrode adjacent and below the lip 13 upon the backing element. Electron emission from the filament 14 is accomplished by energization of this filament, and such is illustrated schematically by the power supply 21 connected across the free ends of the two emitters 16 and 17. An electronic accelerating field is established by suitable energization of the accelerating electrode 19, and this is schematically illustrated by the battery 22, shown in FIG- j URE l as having the positive side thereof electrically connected to the electrode and the negative side thereof returned to the backing electrode and filament as through ground connections.
  • the passage of a current through the emitters of the filament 14 produces a magnetic field encircling each of these emitters.
  • the present invention is directed to the production of very high energy electron beams and, consequently, there is employed a very high heating current which is passed through the emitters in order to achieve the desired quantity of electron emission. Consequently, the strength of the magnetic fields encircling the emitters is actually many orders of magnitude greater than is normally encountered in electron sources.
  • the magnetic field configuration about the emitters of the filament is schematically illustrated in FIGURE 2, wherein the separate emitter wires 15 and 17 are shown as being encircled by magnetic field lines, indicated by the dashed lines thereabout.
  • the magnetic field lines extend, for example, in a clockwise direction about the lower emitter 1'7 and in a counter clockwise direction about the upper emitter 16. This produces an addition of magnetic fields between the emitters, and as illustrated, the magnetic field lines are directed from left to right between the emitters.
  • Electrons thermionically emitted from the emitters 16 and 17 are acted upon by an accelerating electric field established between the accelerating electrode 19 and the filament and backing electrode so as to be attracted away from the filament.
  • these emitted electrons travel away from the emitters they cross lines of magnetic forces shown in FIGURE 2, and consequently, are acted upon by forces at right angles to the direction of travel and to the direction of the magnetic field lines.
  • the overall magnetic envelope about the filament is seen to resemble the magnetic field configuration about an individual wire, the actual fields existing within this envelope differ quite materially from that about a single wire.
  • Emitted electrons are urged toward the area of lower field strength and trapped.
  • electrons are constrained to travel in a plane which is perpendicular to the plane of the two emitters and equal distance between these emitters. This is indicated by the large black arrow 31 in FIGURE 2, wherein it is assumed that an electron accelcrating field from acceleration means urges electrons to the right in this figure.
  • This magnetic collimation of emitted electrons is highly desirable and advantageous inasmuch as it materially simplifies the direction of electrons into a beam.
  • Generation of an actual beam of electrons is highly desirable and important in many applications and particularly with regard to the present invention, wherein it is desired that the electron energy shall be 4 most fully utilized as for the heating and melting of materials such as refractory metals, for example.
  • the present invention prevents this occurrence by the limitation of emission direction, and experimentation has shown that substantially no electrons are emitted at large angles to the plane extending through the emitters of the filament.
  • the very high energy and high density electron beam generated by the present invention is particularly useful in electron beam furnaces such as illustrated in FIGURE 3.
  • an enclosure 41 is evacuated to a very low pressure, as indicated by the block arrows 42, and a melt stock 43 is arranged to be lowered in the enclosure above a mold 44.
  • the electron beam generator of the present invention as indicated at 46, is disposed to direct a very high energy electron beam 47 into the open top of the mold 44 and the melt stock 43 is fed into this beam so that the beam bombards a portion of the melt stock, and consequently, melts it so that it drips downwardly into the mold.
  • this molten material is further bombarded and heated by the electron beam focused to generally bombard all of the open top' of the mold.
  • This mold 44 may be formed, for example, of copper with cooling tubes therein for the passage of water in order to prevent damage to the mold itself and also in order to remove heat from the lower portion of the material dripping into the mold so that a solidified ingot 48 is formed beneath the molten pool of material at the top of the mold.
  • This ingot 48 may be continuously removed or pulled downwardly from the bottom of the mold.
  • Electron beam furnaces of the type generally described above are known in the art, and it is quite important that electron beams employed therein shall have a very high energy in order to melt the melt stock and to further heat the molten pool of material within the mold. It is also quite necessary for the electron beam to be rather sharply defined in order that it shall only bombard the melt stock as it is moved into the beam, rather than providing a variable or a random bombardment of it. Likewise it is necessary for the beam definition to be adequate to prevent undue bombardment of the top of the mold, for quite clearly this would then destroy the mold itself.
  • the electron beam generator of the present invention does provide for the generation of an electron beam having the above-noted requirements.
  • Extremely dense electron beams are produced in accordance with the present invention, and the electron beam appears to be generated at a point or line between the parallel emitters of the filament.
  • a divergence of the beam during its traverse from the generator to the area of bombardment will be seen to be illustrated in FIGURE 3, and this is a natural consequence of the repulsion existing between the electrons of the beam.
  • This beam divergence is not only acceptable herein but is also highly desirable, for an expanded beam focus at the top of the mold then serves to properly heat all of the molten pool of material therein.
  • FIGURE 4 a transverse sectional view of an electron beam generator in accordance with the present invention and including an additional element in the form of a movable front plate 51.
  • This plate is physically and electrically connected to the backing electrode 11 in extension in part across the opening of the emission chamber 12 therein.
  • the front plate 51 may be mounted as by means of bolts 52 upon the front of the backing member, and slots 53 provided in this front plate allow for vertical control over the position of this front plate. Consequently, it will be seen that the electric field configuration at the entrance to the emission chamber 12 is controllable by varying the position of the front plate 51.
  • ions may be slightly curved in passage through this accelerating field, they will not be acted upon sufliciently to curve them into impingement with the emitters of the filament. Instead ions will at most enter the emission chamber and bombard the rear portion thereof. For this reason the backing electrode 11 may be formed of a relatively massive structure to readily accommodate any such ion bombardment.
  • the folded filament structure of the present invention has been described above with respect to particular preferred embodiments thereof and in connection with a preferred application thereof, wherein sufiicient electron beam energy is produced to rapidly melt even refractory metals in large quantities. Attainment of electron emission of this order may be accomplished by the passage of a current of the order of 115 to 125 amperes through a 70 mil tungsten filament including two parallel emitters as described above. Application of a kilovolt accelerating voltage, for example, produces an extremely energetic electron beam highly suitable for utilization in electron beam furnaces.
  • a very close spacing of the filament emitters is desirable in order to achieve maximum direction of the emitted electrons, and as above noted, a separation of the filaments by a distance of the order of the filament diameter has proven advantageous.
  • With the magnitude of heating current employed there are produced magnetic fields of the order of hundreds of gauss immediately adjacent the emitters, and consequently, there results a strong repulsive force between the separate parallel emitters of the filament.
  • the electron beam generator hereof may be elongated in the form of an annulus, preferably with an opening in the backing electrode directed outwardly of same, and this configuration is quite advantageous in certain electron beam furnace applications wherein it is desired to direct electrons into the open top of a casting mold from a plurality of directions. It is also possible to employ externally generated magnetic fields for additional direction of the electron beam generated hereby.
  • An improved electron beam source comprising a backing element defining a chamber therein with a longitudinal opening to the exterior of said backing element, a pair of electron emitters disposed in spaced parallel relation within said chamber along said opening and in a plane across said opening, means connecting said emitters together at one end of each, means passing a current through said emitters in such a direction as to establish thereby a magnetic field having field lines extending toward said opening between said emitters, and electron accelerating means disposed exteriorly of said backing element adjacent the longitudinal opening therein, whereby eleetrons emitted from said emitters are directed through said opening.
  • An improved electron beam generator comprising a pair of electron emitters disposed in closely spaced parallel relationship and electrically joined together at one end of each to form a U-shaped electron source, means passing current serially through said emitters to establish electron emission therefrom, said current further establishing magnetic fields having field lines extending in opposite directions about said emitters to thereby add together between the emitters, a backing member defining an emission chamber opening to the exterior thereof and disposed about said emitters in position to direct said adding magnetic field lines outwardly of the member through the chamber opening, and electron acceleration means adjacent said member outside said chamber for establishing an electron accelerating field whereby electrons emitted from said emitters substantially all travel along said adding magnetic field lines for establishing an electron beam.
  • An improved electron source for emitting very large quantities of electrons comprising first and second elongated electron emitters disposed in closely spaced parallel relationship, means passing a very large current through one of said emitters and a like very large current in an opposite direction through the other emitter for establishing thermionic emission therefrom, said current establishing magnetic fields encircling said emitters with lines of force of the fields adding between the emitters, and elongated electron accelerating means disposed longitudinally of said emitters in spaced parallel relation thereto adjacent the space therebetween, whereby the establishment of an electron accelerating field withdraws emitted electrons along a plane intermediate the emitters and perpendicular to a common plane of the emitters.
  • An electron source as set forth in claim 3 further defined by said emitters having the configuration of straight wires joined together at one of the adjacent ends of each, and said means passing electric current serially through said emitters to thereby establish said magnetic fields.
  • An improved electron beam generator adapted for disposition in an evacuated chamber and comprising a filament having two parallel emitting wires in closely spaced and insulated relationship, connections for the passage of a heating current through the filament to raise at least the emitter wires to a temperature for thermionic emission and to establish a strong magnetic field about said wires which adds together between same, and means establishing an electron accelerating field adjacent said filament for attracting electrons therefrom in a plane between the wires and parallel thereto.
  • An improved electron beam generator comprising a folded filament having two elongated electron emissive portions disposed in closely spaced parallel relation, connections to said filament for passing a large heating current through said filament along one filament portion in a direction opposite to heating current flow in the other portion, an accelerating electrode adapted to establish an electron accelerating field extending to said filament for attracting emitted electrons therefrom, and means at least in part extending between said filament and accelerating electrode longitudinally thereof,- said means being adapted to be maintainedat substantially the potential of said filament for bowing said accelerating field about said means whereby emitted electrons are withdrawn in quantity from said filament only along lines of force of said accelerating field.
  • An improved electron source for emitting very large quantities of electrons comprising an electron emitter including a single U-shaped emitter wire having a pair of elongated parallel legs disposed in closely spaced parallel relationship and separated by a distance substantially equal to the diameter of the wire, and means passing a very large current through the wire of said electron emitter to establish electron emission therefrom, said current establishing magnetic fields encircling the wire of said emitter with the lines of force of the fields adding between the legs of the emitter, whereby the establishment of an electron accelerating field withdraws emitted electrons along a plane intermediate the emitters and perpendicular to a common plane of the emitters.

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Electron Sources, Ion Sources (AREA)
US166255A 1962-01-15 1962-01-15 Folded filament beam generator Expired - Lifetime US3172007A (en)

Priority Applications (8)

Application Number Priority Date Filing Date Title
NL287527D NL287527A (it) 1962-01-15
BE627165D BE627165A (it) 1962-01-15
US166255A US3172007A (en) 1962-01-15 1962-01-15 Folded filament beam generator
DEST20157A DE1171097B (de) 1962-01-15 1963-01-10 Elektronenstrahl-Generator fuer einen Elektronenstrahl-Ofen
AT22863A AT257183B (de) 1962-01-15 1963-01-11 Elektronenstrahl-Generator
GB1677/63A GB982669A (en) 1962-01-15 1963-01-14 Improvements in or relating to electron beam generators
FR921515A FR1348684A (fr) 1962-01-15 1963-01-15 Générateur de faisceau à filament plié
CH45263A CH404011A (de) 1962-01-15 1963-01-15 Elektronenstrahlgenerator

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US166255A US3172007A (en) 1962-01-15 1962-01-15 Folded filament beam generator

Publications (1)

Publication Number Publication Date
US3172007A true US3172007A (en) 1965-03-02

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US166255A Expired - Lifetime US3172007A (en) 1962-01-15 1962-01-15 Folded filament beam generator

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US (1) US3172007A (it)
AT (1) AT257183B (it)
BE (1) BE627165A (it)
CH (1) CH404011A (it)
DE (1) DE1171097B (it)
GB (1) GB982669A (it)
NL (1) NL287527A (it)

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3303320A (en) * 1962-09-25 1967-02-07 Heraeus Gmbh W C Vapor-coating apparatus
US3383541A (en) * 1965-11-17 1968-05-14 United Aircraft Corp Glow discharge cathode having a large electron beam emitting aperture
US3392304A (en) * 1965-10-19 1968-07-09 Air Reduction Power supply for an electron beam furnace gun
US3400243A (en) * 1964-08-10 1968-09-03 Mech Tronics Corp Electron beam welding machine
US3432709A (en) * 1965-10-23 1969-03-11 Atomic Energy Commission Calutron ion source with magnetic field inducing coil within arc chamber
US3433923A (en) * 1964-08-10 1969-03-18 Mech Tronics Corp Electronic beam welding machine
US3433922A (en) * 1964-08-10 1969-03-18 Mech Tronics Corp Electron beam welding machine
US3483423A (en) * 1967-12-12 1969-12-09 Air Reduction Apparatus for producing an electron beam
DE1764177B1 (de) * 1967-05-26 1971-01-28 David Sciaky Elektronenstrahlerzeugungssystem,insbesondere fuer Schweisszwecke
US3748365A (en) * 1972-05-26 1973-07-24 Airco Inc Electron beam heating system
US3852560A (en) * 1972-05-31 1974-12-03 Cockerill Continuous electronic heating device for metallic wire and sheet metal
US4251709A (en) * 1978-12-29 1981-02-17 Schumacher Berthold W Process for joining metals
US6196889B1 (en) 1998-12-11 2001-03-06 United Technologies Corporation Method and apparatus for use an electron gun employing a thermionic source of electrons
US6455990B1 (en) 1998-12-11 2002-09-24 United Technologies Corporation Apparatus for an electron gun employing a thermionic electron source
EP1830382A2 (en) * 2006-02-24 2007-09-05 The Boc Group, Inc. Electron beam gun

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2090722A (en) * 1934-11-09 1937-08-24 Philips Nv X-ray tube
US2471298A (en) * 1943-10-02 1949-05-24 Gen Electric X Ray Corp Cathode cup construction
US2880483A (en) * 1957-06-11 1959-04-07 Stauffer Chemical Co Vacuum casting
DE1100200B (de) * 1959-09-26 1961-02-23 Heraeus Gmbh W C Elektronenschmelzanlage
US2994801A (en) * 1959-06-05 1961-08-01 Stauffer Chemical Co Electron beam generation

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2090722A (en) * 1934-11-09 1937-08-24 Philips Nv X-ray tube
US2471298A (en) * 1943-10-02 1949-05-24 Gen Electric X Ray Corp Cathode cup construction
US2880483A (en) * 1957-06-11 1959-04-07 Stauffer Chemical Co Vacuum casting
US2994801A (en) * 1959-06-05 1961-08-01 Stauffer Chemical Co Electron beam generation
DE1100200B (de) * 1959-09-26 1961-02-23 Heraeus Gmbh W C Elektronenschmelzanlage

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3303320A (en) * 1962-09-25 1967-02-07 Heraeus Gmbh W C Vapor-coating apparatus
US3400243A (en) * 1964-08-10 1968-09-03 Mech Tronics Corp Electron beam welding machine
US3433923A (en) * 1964-08-10 1969-03-18 Mech Tronics Corp Electronic beam welding machine
US3433922A (en) * 1964-08-10 1969-03-18 Mech Tronics Corp Electron beam welding machine
US3392304A (en) * 1965-10-19 1968-07-09 Air Reduction Power supply for an electron beam furnace gun
US3432709A (en) * 1965-10-23 1969-03-11 Atomic Energy Commission Calutron ion source with magnetic field inducing coil within arc chamber
US3383541A (en) * 1965-11-17 1968-05-14 United Aircraft Corp Glow discharge cathode having a large electron beam emitting aperture
DE1764177B1 (de) * 1967-05-26 1971-01-28 David Sciaky Elektronenstrahlerzeugungssystem,insbesondere fuer Schweisszwecke
US3483423A (en) * 1967-12-12 1969-12-09 Air Reduction Apparatus for producing an electron beam
US3748365A (en) * 1972-05-26 1973-07-24 Airco Inc Electron beam heating system
US3852560A (en) * 1972-05-31 1974-12-03 Cockerill Continuous electronic heating device for metallic wire and sheet metal
US4251709A (en) * 1978-12-29 1981-02-17 Schumacher Berthold W Process for joining metals
US6196889B1 (en) 1998-12-11 2001-03-06 United Technologies Corporation Method and apparatus for use an electron gun employing a thermionic source of electrons
US6455990B1 (en) 1998-12-11 2002-09-24 United Technologies Corporation Apparatus for an electron gun employing a thermionic electron source
EP1830382A2 (en) * 2006-02-24 2007-09-05 The Boc Group, Inc. Electron beam gun
US20070210691A1 (en) * 2006-02-24 2007-09-13 Kroneberger Cris K Electron beam gun
EP1830382A3 (en) * 2006-02-24 2008-01-23 Edwards Vacuum, Inc. Electron beam gun
US7764008B2 (en) 2006-02-24 2010-07-27 Ferrotec (Usa) Corporation Electron beam gun

Also Published As

Publication number Publication date
GB982669A (en) 1965-02-10
CH404011A (de) 1965-12-15
BE627165A (it)
DE1171097B (de) 1964-05-27
NL287527A (it)
AT257183B (de) 1967-09-25

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