US3727093A - Electron beam apparatus - Google Patents

Electron beam apparatus Download PDF

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Publication number
US3727093A
US3727093A US00108039A US3727093DA US3727093A US 3727093 A US3727093 A US 3727093A US 00108039 A US00108039 A US 00108039A US 3727093D A US3727093D A US 3727093DA US 3727093 A US3727093 A US 3727093A
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United States
Prior art keywords
cathode
bolt
assembly
electron beam
high temperature
Prior art date
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Expired - Lifetime
Application number
US00108039A
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English (en)
Inventor
J Fink
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CBS Corp
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Westinghouse Electric Corp
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Publication date
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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
    • H01J37/30—Electron-beam or ion-beam tubes for localised treatment of objects
    • H01J37/301—Arrangements enabling beams to pass between regions of different pressure
    • 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
    • H01J37/065—Construction of guns or parts thereof

Definitions

  • a high energy electron beam apparatus having a cathode assembly for operation within a high temperature environment.
  • the assembly associated with the cathode is subjected to high temperature generated by the cathode and associated excitation source. More specifically, this invention is directed to the support assembly associated with and about the cathode which includes sealed conductors with insulation means provided thereabout and also means for supporting and positioning a bolt type cathode accurately with respect to the assembly.
  • FIG. 1 A first figure.
  • cathodes must operate at high temperatures to minimize emission poisoning effects of the residual gases.
  • a tungsten bolt type cathode may in the design of the support assembly.
  • the insulating" material provided between conductors must be relatively free from evaporation or sublirn ation of materials from the structure so as to limit the surface leakage.
  • the insulating material utilized must be capable of withstanding this high temperature without breakdown or any substantial reduction in insulating properties.
  • the components must not warp as a result of the high temperature gradients, because such distortions will modify the characteristics of the device or destroy its operability.
  • the bolt cathode has-been mounted within a sleeve-like member-and held in position by a set screw bearing on the side of the cathode.
  • Another attempted solution to the mounting of the bolt cathode is to utilize a pin vice arrangement.
  • One problem found with these two arrangements was that a welding effect caused sticking and that made it difi'icult to modify the position of the cathode after some operation. It was also found with the set screw configuration that on occasion the screw might become loose within the threaded hole or sometimes might bind after a small amount of operation.
  • the cathode assembly comprises a plurality of conducting members passing through a header and mounted therein by means ofan insulating sleeve provided about the ocnductor and a glass frit material providedbetween the insulating sleeve and the conductor and between the insulating sleeve and the header.
  • the bolt type cathode is mounted in such a manner as to be spring loaded.
  • FIG. 1 is a schematic showing of an electron beam welding apparatus designed for operation in the atmosphere incorporating the teachings of this invention
  • FIG. 2 is an enlarged sectional view illustrating the cathode and main supporting column and associated insulator
  • FIG. 3 is a top view of a cathode assembly
  • FIG. 4 is a sectional view taken along lines TV-IV of FIG. 3;
  • FIG. 5 is an enlarged sectional view of the conducting lead'in FIG. 4 and associated support structure.
  • an electron beam apparatus comprising three sections 10, 12 and 14.
  • the top section or chamber 10 is a high pressure section which is filled with a suitable insulating gas such as SF and where the high voltage supplies are located.
  • the middle section 12 is the section of the apparatus where the lowest vacuum is found.
  • a cathode assembly 16 is mounted in the middle section 12.
  • the succeeding or lower chamber 14 is where the electron Y beam generated by the cathode assembly 16 is directed and passes through succeeding pumping stages and finally to the'bottom orifice 18 where it goes on into the full atmosphere and bombards a workpiece 20.
  • FIG. 1 Several pumping stages and several pumping orifices are shown in FIG. 1.
  • the pressure increases stage by stage from the cathode assembly 16 on out to the worka Torr, and the final stage is at about 200 Torr.
  • a magnetic lens 24 is utilized for focusing the electron beam.
  • the electron beam generated at the cathode assembly 16 in the low pressure region is accelerated by an anode member 17.
  • the anode member 17 is at substantially ground potential.
  • the cathode assembly 16 is at a negative potential of 150,000 volts while the succeeding stages of the system are all actually at about ground potential.
  • the electron beam proceeds through an aperture in the anode member 17 and is focused by the magnetic lens 24 and passes on through several orifices separating differential pressures which are maintained by the various pumps located progressively along a tubular housing 26.
  • the housing 26 maybe of a suitable metal such as non-magnetic stainless steel.
  • the cathode assembly 16 is shown mounted within a socket portion 30.
  • the socket portion 30 is mounted on one end of a column assembly 32 that is supported at the other end by a conical insulator 34.
  • the conical insulator 34 is made of a suitable material such as alumina.
  • the column assembly 32 may be of suitable material such as a Kovar alloy.
  • the conical insulator 34 provides insulation and mechanical support for the cathode assembly 16 within the system.
  • the cathode assembly 16 plugs ito the socket 30 at the bottom of the column 32 and is held in place by a retaining member 36 which has an aperture 38 and forms a part of the electron optics.
  • the cathode assembly 16 is shown in detail in FIGS. 3 and 4.
  • the assembly 16 comprises a cathode housing member 41 which includes cup shaped housing portions 43 and 45.
  • the portion 43 includes a transverse portion 47 and most of the cathode assembly is attached to the portion 47 by suitable means such as screws.
  • An insulating ring assembly 49 is positioned within the housing portion 43 and is secured to the transverse portion 47.
  • the ring assembly 49 includes a ring 51 of a suitable material such as a Kovar alloy.
  • a plurality of electrical conductive support leads 46 are supported in apertures 53 positioned about the ring 51.
  • FIG. 5 shows in detail the mounting of one of the support leads 46 in the aperture 53.
  • a suitable insulating sleeve 55 surrounds the support lead 46.
  • a glass frit seal 57 secures the sleeve 55 to the support lead 46 and a glass frit seal 59 secures the sleeve 55 within the aperture 53 of the ring 51.
  • the support leads 46 extend through apertures in the transverse member 47.
  • the bolt cathode 40 is mounted in a housing 61 which is made predominantly of a suitable metal such as Kovar.
  • the housing 61 is secured to the transverse member 47 with an insulating disc 63 mounted therebetween.
  • the bolt cathode 40 projects beyond the I housing 61 and through an aperture in the transverse member 47
  • the extended and free end of the bolt cathode 40 is surrounded by a heater member 42.
  • the bolt cathode 40 is made of suitable refractory material such as tungsten and has a diameter of about 0.060 inch and about 2 inches long.
  • the heater 42 emits electrons which bombard the bolt 40 thus providing the bolt 40 with sufficient energy to heat it up to electron emitting temperature about 2,500C.
  • a tubular heat shield member 44 surrounds the heater 42 and provides better thermal efficiency.
  • One leg of the heater 42 is supported by the heat shield 44 which in turn is supported by three of the support leads 46.
  • the other leg of the heater 42 is supported by a member 79 which is in turn supported by an insulated lead 46.
  • a cap member 48 Above the heat shield 44 is a cap member 48 which is designed to reflect the energy back into the bolt 40 and make the system more thermally efficient.
  • the bolt cathode 40 is provided at one end with a lock washer 50 which is retained in a suitable notch.52 provided in the bolt 40.
  • the retaining washer 50 is confined in a recess portion 54 of a bearing assembly 56.
  • the bearing assembly 56 is comprised of a fixed sleeve member 58, a movable sleeve member 60 and a spring member 62.
  • the bearing assembly 56 is positioned within a hollow portion 64 of the housing 61.
  • the fixed member 58 of graphite is seated in the hollow portion 64.
  • the movable member 60 is also of graphite and the spring member 62 applies pressure on the movable member 60 so that the bolt 40 is pressed against a bearing surface 66.
  • the bolt 40 is located by two holes, one in the movable member 60 where the lockingwasher 50 is held and the other in the fixed member 58.
  • the position of the bolt 40 is determined by the position of an adjustable bearing surface 66.
  • the bearing surface or stop 66 is the end of a set screw 68 which thus allows adjustment of the position of the bolt 40.
  • the lock washer 50 may be of any suitable metal with the relatively low coefficient of expansion such as a Kovar alloy.
  • the seating of the lock washer 50 in the graphite cylindrical piece 64 is such that the fit of the washer 50 in the graphite member 64 determines the maximum allowable coefficient expansion of the washer 50. In some designs, the fit of the washer 50 in the receiving space in the graphite member 64 has confined the washer to the groove in the bolt thereby holding the bolt in place.
  • the set screw 68 which positions the bolt 40 is not too critical in terms of the coefficient expansion because of its short length and because it fits in a relatively massive metal housing 61 for which the temperature rise is not excessive.
  • the two graphite members 58 and 60 that support the bolt 40 provide two positions for bolt location. The design is such that if the back cover 65 of the housing 61 is removed, the bolt 40 can be withdrawn from the back of the assembly without disturbing the heater structure in the front.
  • the choice of graphite material for the bearing assembly 56 is important in that it provides an assembly which does not stick in the housing 61, nor to which the bolt 40 will stick after repeated use. Hence the bolt 40, or if need be the bolt 40 and the bearing assembly 56 may be removed and if necessary replaced in subsequent operations.
  • the bolt cathode 40 is provided with a potential of a negative 150,000 volts by a high voltage supply 69 in the chamber 10.
  • the electron beam is generated and maintained by system of electron optics so that the position of the emitting face of the bolt cathode 40 relative to the other members of the structure is critical.
  • the location of the bolt cathode 40 can greatly alter the shape of the beam. For this reason, the location of emitting face of the bolt cathode 40 is important and the set screw 68 in the back provides a precise location. After initial assembly the height of the cathode with respect to the cap is checked and measured and held within a half a thousand of an inch.
  • the heat shields 44 and 48 and heater 42 are supported by the support lead 46 which are in turn mounted in a low coefficient of expansion metal ring 51.
  • the insulation between the lead 46 and the ring 51 is provided by means of the ceramic cylinder 55.
  • the cylinder 55 may be of alumina of high purity or of any material which has the property having a high electrical 'resistance at a relatively high temperature.
  • a solder glass material 57 is provided between the lead 46 and the sleeve 55 and solder glass material 59 is provided between the sleeve 55 and the ring member 51.
  • the solder glass may be of any suitable type such as Pyroceram No. 7574 and may be purchased from Corning Glass Company of Coming, New York.
  • the assembly is made by means of the appropriate gluing material 57 and 59 while the insulation is provided by the sleeve 55.
  • This structure is assembled by means of the solder glass 57 and 59 and thereby held in place.
  • the insulation is provided by means of the alumina sleeve 55 so that excellent high temperature properties of insulation are maintained.
  • the surface leakage is minimized by extending che insulator 55 above and below the ring member 51 and by suitable shielding provided by the surrounding members.
  • the use of devitrifying solder glass as the glueing materials 57 and 59 permits the fabrication of such an assembly from aprts which need not be made with any great precision. This comes about by virtue of the fact that the devitrifying glass solidifies while still hot.
  • the glass is in the form of a suitable devitrifying solder glass such as Pyroceram No. 7574 mixed with nitro-cellulose and butyl-cellosolve in a suspension of catsup-like consistency that is painted upon the lead 46.
  • the frit is painted on the metal portion of the ring 51 that is going to be in contact with the ceramic sleeve 55,
  • the three pieces 46, 55 and 51 are put together in a suitable jig which must be made of a low expansion metal.
  • the assembly is then fired at approximately 800C for about 1 hour.
  • the lead 46 has a diameter of about 0.080 inch andis made of a low coefficient expansion material of electrical conducting such as a Kovar alloy.
  • a high current density electron beam source commeans is of a high temperature spring material and secures saidbolt cathode against said adjustable stop.

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Electron Sources, Ion Sources (AREA)
  • Particle Accelerators (AREA)
US00108039A 1971-01-20 1971-01-20 Electron beam apparatus Expired - Lifetime US3727093A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US10803971A 1971-01-20 1971-01-20

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US3727093A true US3727093A (en) 1973-04-10

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US00108039A Expired - Lifetime US3727093A (en) 1971-01-20 1971-01-20 Electron beam apparatus

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US (1) US3727093A (de)
JP (1) JPS5332239Y2 (de)
BE (1) BE778211A (de)
CA (1) CA953435A (de)
DE (1) DE2201832A1 (de)
GB (1) GB1373103A (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3928783A (en) * 1972-12-08 1975-12-23 Hitachi Ltd Thermionic cathode heated by electron bombardment
US4687964A (en) * 1985-05-09 1987-08-18 The United States Of America As Represented By The Administrator National Aeronautics & Space Administration Apparatus for mounting a field emission cathode
US20140091702A1 (en) * 2011-07-04 2014-04-03 Tetra Laval Holdings & Finance S.A. Cathode housing suspension of an electron beam device

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4496881A (en) * 1982-09-29 1985-01-29 Tetra Pak Developpement Sa Method of cold cathode replenishment in electron beam apparatus and replenishable cold cathode assembly

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1520674A (en) * 1922-04-10 1924-12-23 Eldridge Francis Layton Sparking plug
US1794950A (en) * 1922-11-07 1931-03-03 Westinghouse Electric & Mfg Co Vacuum-tube device
US2208406A (en) * 1938-08-17 1940-07-16 Westinghouse Electric & Mfg Co Cathode ray tube
US2455381A (en) * 1947-10-01 1948-12-07 Bell Telephone Labor Inc Cathode assembly for electron discharge devices
US2509053A (en) * 1947-11-08 1950-05-23 Bell Telephone Labor Inc Space current device employing mutually bombarded electrodes
US2602907A (en) * 1949-01-14 1952-07-08 Bell Telephone Labor Inc Filament mounting for high power electron discharge devices
US3268305A (en) * 1964-08-17 1966-08-23 Sylvania Electric Prod Composite wire
US3462635A (en) * 1966-10-24 1969-08-19 Ibm Holder for highly reactive cathodes of rare-earth borides such as lanthanum hexaboride,the holder provided with a cooling means opposite to the emissive end of the cathode in order to reduce tendency of holder deterioration

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1520674A (en) * 1922-04-10 1924-12-23 Eldridge Francis Layton Sparking plug
US1794950A (en) * 1922-11-07 1931-03-03 Westinghouse Electric & Mfg Co Vacuum-tube device
US2208406A (en) * 1938-08-17 1940-07-16 Westinghouse Electric & Mfg Co Cathode ray tube
US2455381A (en) * 1947-10-01 1948-12-07 Bell Telephone Labor Inc Cathode assembly for electron discharge devices
US2509053A (en) * 1947-11-08 1950-05-23 Bell Telephone Labor Inc Space current device employing mutually bombarded electrodes
US2602907A (en) * 1949-01-14 1952-07-08 Bell Telephone Labor Inc Filament mounting for high power electron discharge devices
US3268305A (en) * 1964-08-17 1966-08-23 Sylvania Electric Prod Composite wire
US3462635A (en) * 1966-10-24 1969-08-19 Ibm Holder for highly reactive cathodes of rare-earth borides such as lanthanum hexaboride,the holder provided with a cooling means opposite to the emissive end of the cathode in order to reduce tendency of holder deterioration

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3928783A (en) * 1972-12-08 1975-12-23 Hitachi Ltd Thermionic cathode heated by electron bombardment
US4687964A (en) * 1985-05-09 1987-08-18 The United States Of America As Represented By The Administrator National Aeronautics & Space Administration Apparatus for mounting a field emission cathode
US20140091702A1 (en) * 2011-07-04 2014-04-03 Tetra Laval Holdings & Finance S.A. Cathode housing suspension of an electron beam device
US9142377B2 (en) * 2011-07-04 2015-09-22 Tetra Laval Holdings & Finance S.A. Cathode housing suspension of an electron beam device

Also Published As

Publication number Publication date
JPS5332239Y2 (de) 1978-08-10
DE2201832A1 (de) 1972-08-03
JPS52106418U (de) 1977-08-13
CA953435A (en) 1974-08-20
BE778211A (fr) 1972-07-19
GB1373103A (en) 1974-11-06

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