EP0578525A1 - Elektronenkanone mit reduzierter Erhitzung des Gitters - Google Patents

Elektronenkanone mit reduzierter Erhitzung des Gitters Download PDF

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Publication number
EP0578525A1
EP0578525A1 EP93401590A EP93401590A EP0578525A1 EP 0578525 A1 EP0578525 A1 EP 0578525A1 EP 93401590 A EP93401590 A EP 93401590A EP 93401590 A EP93401590 A EP 93401590A EP 0578525 A1 EP0578525 A1 EP 0578525A1
Authority
EP
European Patent Office
Prior art keywords
electron gun
gun according
cathode
active face
emissive
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.)
Withdrawn
Application number
EP93401590A
Other languages
English (en)
French (fr)
Inventor
Noel Santonja
Pierre-Yves Chabaud
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.)
Thales Electron Devices SA
Original Assignee
Thomson Tubes Electroniques
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 Thomson Tubes Electroniques filed Critical Thomson Tubes Electroniques
Publication of EP0578525A1 publication Critical patent/EP0578525A1/de
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J23/00—Details of transit-time tubes of the types covered by group H01J25/00
    • H01J23/02—Electrodes; Magnetic control means; Screens
    • H01J23/06—Electron or ion guns
    • H01J23/065—Electron or ion guns producing a solid cylindrical beam
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J23/00—Details of transit-time tubes of the types covered by group H01J25/00
    • H01J23/02—Electrodes; Magnetic control means; Screens
    • H01J23/04—Cathodes

Definitions

  • the present invention relates to grid electron guns, in particular those intended to equip high power electronic tubes.
  • These tubes are mainly of the linear beam type such as klystrons or traveling wave tubes. They could also be of triode or tetrode type.
  • Linear beam tube cannons include a cathode of emissive material and an anode brought to a more positive potential than that of the cathode.
  • the cathode provides, when heated, an electron beam directed towards the anode.
  • a control grid is used which is arranged between the cathode and the anode. It is brought to a potential intermediate between that of the cathode and that of the anode.
  • the control grid is bombarded by electrons. There is an interception of the electron beam which is very troublesome in high power tubes. In addition the control grid heats up strongly which limits the duration of use of the barrel. It has been proposed to suppress the bombardment of the control grid, to place a mask grid near or in contact with the cathode.
  • This mask grid has the same design as the control grid and is often brought to the potential of the cathode.
  • this mask-grid when heated like the cathode, itself becomes emissive as a result of migration of emissive material from the cathode.
  • the electrons emitted by the mask grid have aberrant trajectories and the electron beam converges poorly.
  • a mask grid has been associated with circular openings and a cathode, the emissive surface of which, opposite each opening of the mask grid, has the shape of a spherical cup.
  • the electron beam emitted is less disturbed but the production of such a gun is more complicated and more expensive.
  • the present invention proposes to remedy these drawbacks. It proposes to remove the mask grid and to dig grooves deep enough in the cathode so that their bottom does not emit electrons. The absence of the mask grid removes pollution.
  • the non-emissive grooves form a virtual mask grid. The grooves are arranged so as to be directly opposite the solid parts of the control grid. The electrons emitted by the cathode do not bombard the control grid.
  • the present invention provides an electron gun comprising a cathode of emissive material with an active face emitting electrons through a control grid.
  • the control grid is opposite but without contact with the active face.
  • the cathode and the control grid help to create an electric field in their vicinity.
  • the active face has emissive zones and non-emissive zones, the latter are grooves dug in the emissive material.
  • the intensity of the electric field is substantially zero and the control grid has solid parts which coincide and are directly opposite the grooves.
  • the grooves have two opposite sides spaced at a distance one to five times smaller than the distance between the bottom and the active face.
  • At least one groove has on its sides an area treated against electronic emission, this area being contiguous with the active face. This area is approximately the width of the space between the two sides.
  • the active face includes at least one area treated against electronic emission around the grooves. This area is approximately one-tenth the width of the space between the sides of the groove.
  • the pores can be blocked by crushing in the tralted area against electronic emission.
  • the emissive material can also be melted by laser in the area treated against electronic emission, whether porous or not. It can also be covered with a protective layer in as strong an output working material as possible.
  • the protective layer has a thickness of the order of a micrometer.
  • Figure 1 shows in longitudinal section an electron gun with a known type of grid. It comprises a cathode 1 which has a concave active face. Cathode 1 is often brought to a negative high voltage. The active face emits an electron beam when the cathode is heated.
  • the cathode can be of the type impregnated with a porous matrix 2 (often made of tungsten) impregnated with a thermoemissive material (often barium aluminates).
  • the matrix 2 is mounted on a skirt 3 of refractory metal.
  • a heating filament 10 is provided for heating the porous matrix 2.
  • the electron beam is emitted to an anode 4 open at its center so that the electron beam can pass through.
  • the electrons enter a user device 5 in the form of a tunnel which can be the body of a microwave tube.
  • This device is not part of the barrel.
  • This device 5 is generally brought to ground and ends in a collector (not shown) which collects the electrons.
  • the anode 4 can be brought to the potential of the user device 5 as in FIG. 1 or has a potential intermediate between the potential of the cathode 1 and that of the user device 5.
  • Grids and a focusing or wehnelt electrode can be inserted between cathode 1 and anode 4. In FIG. 1, between cathode 1 and anode 4, there are successively two grids 6,7 and a wehnelt 8.
  • the wehnelt 8 helps to focus the electron beam.
  • One of the grids 6 is a mask grid, it is in contact with the active face of the cathode 1. It is brought to the same potential as the cathode.
  • the mask grid 6 is pierced with openings. Electrons are emitted at these openings in the form of elementary beams.
  • Between the mask grid 6 and the wehnelt 8 is a control grid 7.
  • the control grid 7 is brought to a potential intermediate between that of the cathode 1 and that of the anode 4.
  • This control grid 7 includes openings which are aligned with those of the mask grid 6. However, the openings of the control grid 7 are often slightly wider than those of the mask grid 6.
  • the control grid 7 can be used to pulse pulse the beam of electrons when the gun is intended to operate in pulses or to adjust the current of the gun when it is intended to operate continuously.
  • the two grids 6,7 are substantially parallel and follow the curvature of the active face of the cathode 1.
  • the mask grid 6 introduces aberrations at the level of the electron beam because it ends up being polluted by the emissive material and by starting to emit electrons. Electrons emitted by it bombard the control grid 7 which heats up in turn and others have disturbed trajectories.
  • FIG. 2 shows in front view, an active face 20 of a cathode of a gun according to the invention. It is assumed that the cathode is formed from a matrix of emissive material.
  • the active face 20 has hatched emissive zones 22 and non-emissive zones 21 without hatching.
  • the non-emissive zones 21 are grooves dug in the emissive material.
  • FIG 3 we see in cross section the cathode of Figure 2 associated with a control grid 30 placed near the active face 20 of the cathode.
  • the control grid 30 has bars 31, the design of which corresponds to that of the grooves 21.
  • the grooves 21 are directly opposite the bars 31 of the control grid 30.
  • the control grid 30 is brought to a more positive potential than that of the cathode.
  • the control grid and the cathode help create an electric field in their vicinity.
  • Figure 4 shows in detail a groove 21. It is formed of a bottom 40 and two sides 41 which face each other. The two sides 41 preferably make a right angle with the bottom 40.
  • the grooves are non-emissive areas because the bottom 40 of the grooves does not emit electrons.
  • the grooves are dimensioned and positioned relative to the control grid 30 so that the intensity of the electric field is substantially zero at the bottom 40 of the grooves. On the sides 41 of the grooves, the intensity of the electric field is much lower than that existing at the active face 20 of the cathode. There is practically no electronic emission at the sides 41 of the grooves 21.
  • the grooves 21 will preferably be given a depth p of the order of once to five times the distance e separating their two sides 41.
  • This distance e corresponds substantially to the dimension of the cross section of the bars 31 of the control grid 30, dimension measured parallel to the active face 20 of the cathode.
  • the cathode is formed of a porous matrix impregnated with thermoemissive material, the pores can be blocked by crushing the porous material.
  • the porous matrix is often made of tungsten and is fragile. Attacking the tungsten with an appropriately shaped tool closes the pores and eliminates the emission of electrons in the treated area.
  • the areas treated against electronic emission can also be melted by laser whether the material is porous or not.
  • the laser beam is moved along the areas to be treated. If the cathode has pores they are plugged by fusion.
  • a third variant consists in covering the areas to be treated against electronic emission with a protective layer.
  • the protective layer will be in as strong an output working material as possible.
  • a material with strong output work can emit electrons only in the presence of a strong electric field.
  • This material can for example be tungsten, molybdenum disilicide or a carbide of a refractory metal or one of their alloys or mixtures.
  • the refractory metals are for example tungsten, molybdenum or tantalum.
  • the thickness of the deposited layer will advantageously be of the order of a micrometer.
  • the deposition can be done by evaporation or by a physicochemical process under a controlled atmosphere, for example, vapor deposition or vacuum deposition.
  • a mask can be used having openings corresponding to the areas to be treated against the emission. electronics and solid parts corresponding to the areas to be protected.
  • areas 43 of the active face 20 of the cathode located at the edge of the grooves 21. These areas 43 at the edge of the grooves are normally emissive. However, they can be geometrically ill-defined due to the fragility of the porous matrix. The trajectories of electrons from these areas could be disturbed.
  • the zones 42 treated against the electronic emission from the sides of the grooves 21 will have approximately a width l2 from the active face 20, this width l2 being substantially equal to the distance e separating the two sides 41 of the grooves.
  • the zones 43 treated against the electronic emission of the active face 20 will have a width l1 from the edge of the groove substantially equal to one tenth of the distance e .
  • FIG. 5 represents a section of a cannon according to the invention. It is comparable to that of FIG. 1. There is a cathode 1 facing an anode 4, a wehnelt 8 and a control grid 30 but in accordance with the invention the mask grid has been eliminated.
  • the active face 20 of the cathode has emissive zones 22 and non-emissive zones formed by grooves 21, the bottom of which is subjected to a substantially zero electric field.
  • the control grid 30 has bars 31 which are in direct face-to-face contact with the grooves 21 since there is no longer a mask grid. The risk of bombardment of the control grid 30 is considerably reduced by virtue of the non-emissive grooves 21.

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  • Microwave Tubes (AREA)
EP93401590A 1992-06-26 1993-06-22 Elektronenkanone mit reduzierter Erhitzung des Gitters Withdrawn EP0578525A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9207888 1992-06-26
FR9207888A FR2693028A1 (fr) 1992-06-26 1992-06-26 Canon à électrons à échauffement réduit de la grille.

Publications (1)

Publication Number Publication Date
EP0578525A1 true EP0578525A1 (de) 1994-01-12

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Family Applications (1)

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EP93401590A Withdrawn EP0578525A1 (de) 1992-06-26 1993-06-22 Elektronenkanone mit reduzierter Erhitzung des Gitters

Country Status (3)

Country Link
US (1) US5399935A (de)
EP (1) EP0578525A1 (de)
FR (1) FR2693028A1 (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1996035219A1 (fr) * 1995-05-05 1996-11-07 Thomson Tubes Electroniques Canon a electrons a grille
WO1998054744A1 (en) * 1996-04-20 1998-12-03 Eev Limited Electron gun with a diamond grid

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2775118B1 (fr) * 1998-02-13 2000-05-05 Thomson Tubes Electroniques Grille pour tube electronique a faisceau axial a performances ameliorees
JP2002260522A (ja) * 2000-12-26 2002-09-13 Sony Corp 陰極構体とその製造方法及び電子銃並びに陰極線管

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3558967A (en) * 1969-06-16 1971-01-26 Varian Associates Linear beam tube with plural cathode beamlets providing a convergent electron stream
US3967150A (en) * 1975-01-31 1976-06-29 Varian Associates Grid controlled electron source and method of making same
GB2139413A (en) * 1983-04-18 1984-11-07 Litton Systems Inc An electron gun
US4873468A (en) * 1988-05-16 1989-10-10 Varian Associates, Inc. Multiple sheet beam gridded electron gun

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3914651A (en) * 1970-09-24 1975-10-21 Clayton A Washburn Cathode, ray tube structures
US4107570A (en) * 1973-03-12 1978-08-15 Washburn Clayton A Cathode ray tube indexing structures
GB1507544A (en) * 1975-12-29 1978-04-19 English Electric Valve Co Ltd Linear beam tubes
US4994709A (en) * 1989-03-22 1991-02-19 Varian Associates, Inc. Method for making a cathader with integral shadow grid

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3558967A (en) * 1969-06-16 1971-01-26 Varian Associates Linear beam tube with plural cathode beamlets providing a convergent electron stream
US3967150A (en) * 1975-01-31 1976-06-29 Varian Associates Grid controlled electron source and method of making same
GB2139413A (en) * 1983-04-18 1984-11-07 Litton Systems Inc An electron gun
US4873468A (en) * 1988-05-16 1989-10-10 Varian Associates, Inc. Multiple sheet beam gridded electron gun

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1996035219A1 (fr) * 1995-05-05 1996-11-07 Thomson Tubes Electroniques Canon a electrons a grille
FR2733856A1 (fr) * 1995-05-05 1996-11-08 Thomson Tubes Electroniques Cathode pour canon a electrons a grille, grille destinee a etre associee avec une telle cathode et canon a electrons comportant une telle cathode
WO1998054744A1 (en) * 1996-04-20 1998-12-03 Eev Limited Electron gun with a diamond grid

Also Published As

Publication number Publication date
US5399935A (en) 1995-03-21
FR2693028A1 (fr) 1993-12-31

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