US3659135A - Electron gun having cathode with cylindrical extension and control grid with conical section - Google Patents

Electron gun having cathode with cylindrical extension and control grid with conical section Download PDF

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Publication number
US3659135A
US3659135A US88769A US3659135DA US3659135A US 3659135 A US3659135 A US 3659135A US 88769 A US88769 A US 88769A US 3659135D A US3659135D A US 3659135DA US 3659135 A US3659135 A US 3659135A
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United States
Prior art keywords
cathode
anode
grid
circular
control grid
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Expired - Lifetime
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US88769A
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English (en)
Inventor
Johannes Hendrikus T Roosmalen
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US Philips Corp
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US Philips Corp
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    • 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
    • H01J3/029—Schematic arrangements for beam forming
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/46—Arrangements of electrodes and associated parts for generating or controlling the ray or beam, e.g. electron-optical arrangement
    • H01J29/56—Arrangements for controlling cross-section of ray or beam; Arrangements for correcting aberration of beam, e.g. due to lenses

Definitions

  • the rotationally-symmetric electron gun of a cathode-ray tube device comprises successively a cathode, a disk-shaped control grid provided with a central control, grid aperture and a disk-shaped anode grid provided with a central circular-cylindrical anode grid aperture.
  • the cathode comprises a first conductive circular cylinder from the base of which a second conductive circular cylinder projects the base of which forms the emitting surface.
  • the control grid aperture on the side of the anode grid, has a circular-cylindrical part and, on the side of the cathode, has a conical part which narrows towards the circular-cylindrical part, the wall of which encloses substantially an angle of 45 with the axis of the electron gun.
  • the diameter of the said first conductive circular cylinder and the diameter of the said circular-cylindrical part are substantially six times as large as the diameter of the emitting surface, while the diameter of the anode grid aperture is substantially four times as large, the length of the said second conductive cylinder is substantially twice as large, the distance between the emitting surface and the said circular-cylindrical part is substantially equally large, the axial length of the said conical part is at least equally large and the distance between the control grid and the anode grid is substantially one and a half times as large as the diameter of the emitting surface.
  • the control grid is kept at a negative potential relative to the cathode.
  • the anode is kept at a positive potential which is substantially four and a half times as large, relative to the cathode, while the space on the side of the anode grid remote from the control grid is kept substantially field-free.
  • the invention relates to a device comprising a cathode-ray tube, which cathode-ray tube comprises a rotationally-symmetric electron gun, in which electron gun are present successively a cathode provided with a plane electron-emitting surface extending substantially at right angles to the axis of the electron gun, a disk-shaped control grid provided with a central control grid aperture, and a disk-shaped anode grid provided with a central circular-cylindrical anode grid aperture, the control grid being kept at a negative potential relative to the cathode and the anode being kept at a higher positive potential relative to the cathode, the space on the side of the anode grid remote from the control grid being kept substantially fieldfree.
  • the invention also relates to a cathode-ray tube for such a device.
  • Measures already proposed previously to restrict the spherical aberrations in the electron gun for example, the individual or combined deformation of the anode grid with the intention of eliminating the lens defects thereof, the use of extra electrodes between the cathode and the anode grid, and the use of a spherically emitting surface, for example, a spherically emitting surface the radium of curvature of which varies as a function of the radial distance to the axis, so that the curvature decreases when the radial distance to the axis increases, are less efficacious than would be desirable and/or less simple to carry out than would be desirable.
  • the cathode in a device of the type mentioned in the first paragraph comprises a first conductive circular cylinder from the base of which a second conductive circular cylinder projects the base of which forms the emitting surface and the control grid aperture, on the side of the anode grid, has a circular-cylindrical part and, on the side of the cathode, has a conical part which narrows towards the circular-cylindrical part, of which conical part the wall encloses substantially an angle of 45 with the axis of the electron gun, the diameter of the said first conductive circular cylinder and the diameter of the said circular-cylindrical part being substantially six times as large, the diameter of the anode grid aperture being substantially four times as large the length of the said second conductive cylinder being substantially twice as large, the distance between the emitting surface and the said circular-cylindrical parts and the axial length of the said circular-cylindrical part being substantially equally large, the axial length of the said conical part being at least substantially
  • anode voltage for example, at a voltage of the anode grid relative to the cathode of 300 volts, a particularly small cross-over, which is desirable notably in an electron microscope, is obtained owing to the small influence of the spreading as a result of thermal speeds of the electrons at said high potential.
  • the electrons leaving the cathode with the same energy but at different angles with the axis of the electron gun reach the cross-over while sharply separated.
  • a particularly favorable selection of electrons having a small transverse speed can be obtained, while by means of this the electrons can also be selected properly for axial speeds, which can be very favorable, notably in a television camera tube, to obtain both a particularly small spot size and a particularly small beam current inertia.
  • the invention therefore relates in particular to a device as described above, in which a diaphragm is present at the area of the beam cross-over.
  • the invention also relates to a cathode-ray tube for the device as described above.
  • the cathode-ray tube comprises a rotationally-symmetric electron gun in which are present successively a cathode which is provided with a plane electronemitting surface extending substantially at right angles to the axis of the electron gun, a disk-shaped control grid provided with a central control grid aperture and a disk-shaped anode grid provided with a central circular-cylindrical anode grid aperture, and which is characterized in that the cathode comprises a first conductive circular cylinder from the base of which a second conductive circular cylinder projects the base of which forms the emitting surface and the control grid aperture comprises, on the side of the anode grid, a circular cylindrical part and, on the side of the cathode, has a conical part which narrows towards the circular-cylindrical part, of which conical part the wall encloses substantially an angle of 45 with the axis of the electron gun, the diameter of the said first
  • FIG. 1 is a cross-sectional view of the electrode configuration of the electron gun in the cathode-ray tube of a known device, through the axis of the electron gun.
  • FIG. 2 shows the potential field and electron paths for electrons which leave the electron-emitting surface without initial speed in the known device shown in FIG. 1, in the half of the same cross-section,
  • FIG. 3 is a cross-sectional view of the electrode configuration of the electron gun in the cathode-ray tube of an embodiment of the device according to the invention through the axis of the electron gun.
  • FIG. 4 shows the potential field and the electron paths for electrons which leave the electron-emitting surface without initial speed in the device shown in FIG. 3, in the half of the same cross-section,
  • FIGS. 5 and 6 show the same electrode configuration and the same potential field as FIG. 4 with electron paths for electrons which leave the emitting surface with an initial speed in the plane of the drawing at different angles with the axis of the electron gun.
  • the cathode 1 has the emitting surface 2 which extends at right angles to the axis 3 of the electron gun.
  • the disk-shaped control grid 4 Opposite to the emitting surface 2 is arranged the disk-shaped control grid 4, in front of which the disk-shaped anode grid 5 is present which forms one assembly with the conductive anode cylinder which ensures that the space on the side remote from the control grid is kept field-free.
  • the control grid has a circular-cylindrical aperture 7 and the anode grid has a circular-cylindrical aperture 8.
  • A (the diameter of the control grid aperture 7) 600 ,u..
  • B (The diameter of the anode grid aperture 8) 400 LL.
  • C (The distance between the emitting surface 2 and the control grid aperture 7) 100 u.
  • the voltages are, for example, chosen to be so that the negative control grid voltage V i.e. the voltage of the control grid relative to the cathode, is substantially threetenths of the positive anode voltage V i.e. the voltage of the anode grid relative to the cathode.
  • FIG. 2 shows the electrostatic field in the electron gun shown in FIG. 1 for the following electrode voltages:
  • the potential field is denoted by the equipotential lines, the potential values in volts being indicated in brackets.
  • 9 is assumed to be the terminating equipotential plane, and linearly increasing potentials are assumed along 10 and 11.
  • the figure shows electron paths which extend from the emitting surface 2 to the surface 9. These are electron paths for the electrons which start from the emitting surface at initial speed zero. As shown in the Figure, said paths intersect the axis of the gun at far divergent places.
  • the cathode body consists of a conductive circular cylinder 12, from the base 13 of which the second conductive circular cylinder 14 projects the base of which forms the emitting surface 15.
  • the control grid 16 has a control grid aperture which has a circular-cylindrical part 17 and a narrowing conical part 18.
  • the wall 19 ofthe conical part 18 encloses an angle of 45 with the axis 20 of the gun.
  • the diskshaped anode grid 21 forms one assembly with the anode cylinder 22, and has a circular-cylindrical aperture 23.
  • anode potential V is used which is substantially 4.5 X the negative control grid voltage V for example, an anode potential V 10 volts, and a control grid potential V 2.2 volts, the result illustrated in FIGS. 4, 5 and 6 being obtained.
  • FIG. 2 shows the potential field and electron paths for electrons which start from the emitting surface at initial speed zero in the known electron gun shown in FIG. 1
  • FIG. 4 shows the same in the electron gun shown in FIG. 3.
  • Reference numeral 24 denotes a terminating equipotential plane, and linearly increasing voltages are assumed along 25 and 26.
  • the electron paths shown intersect in this case the axis 20 of the gun substantially at the same place.
  • FIGS. 5 and 6 show the same field as FIG. 4 while in FIGS. 5 and 6 electron paths are shown for electrons, which leave the emitting surface at an initial speed corresponding to 0.2 eV. at different angles a with the axis of the electron gun.
  • FIG. 5 it relates to paths for electrons which start at an initial speed having a component upwards in the figure.
  • FIG. 6 it relates to paths for electrons which start at an initial speed having a component downwards in the figure.
  • said electron paths intersect the plane 24 substantially at the same place.
  • the Figures show separate target places for different values of a as a result of which a particularly favourable selection by means of a diaphragm is possible.
  • a device comprising a cathode-ray tube, which cathoderay tube has a rotationally-symmetric electron gun, in which electron gun are present successively a cathode provided with a plane electron-emitting surface extending substantially at right angles to the axis of the electron gun, a disk-shaped control grid provided with a central control grid aperture, and a disk-shaped anode-grid provided with a central circular-cylindrical anode grid aperture, the control grid being at a negative potential relative to the cathode and the anode being at a higher positive potential relative to the cathode, the space on the side of the anode grid remote from the control grid being substantially field-free, characterized in that the cathode comprises a first conductive circular cylinder from the base of which a second conductive circular cylinder projects the base of which forms the emitting surface and the control grid aperture, on the side of the anode grid, having a circular-cylindrical part and, on the side of the catho
  • a device as claimed in claim 2 characterized in that a diaphragm is provided at the area of the cross-over of the electron beam produced in the cathode-ray tube.

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  • Electron Sources, Ion Sources (AREA)
  • Solid Thermionic Cathode (AREA)
US88769A 1969-11-22 1970-11-12 Electron gun having cathode with cylindrical extension and control grid with conical section Expired - Lifetime US3659135A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL6917641A NL6917641A (xx) 1969-11-22 1969-11-22

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US3659135A true US3659135A (en) 1972-04-25

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Country Status (7)

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US (1) US3659135A (xx)
AU (1) AU2244270A (xx)
BE (1) BE759247A (xx)
DE (1) DE2054709A1 (xx)
FR (1) FR2069602A5 (xx)
GB (1) GB1271589A (xx)
NL (1) NL6917641A (xx)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3831058A (en) * 1971-08-30 1974-08-20 Roosmalen J Van Device comprising a television camera tube and television camera
US3925706A (en) * 1973-02-23 1975-12-09 Hitachi Ltd Field emission electron gun device of the automatic control type
EP0247470A2 (de) * 1986-05-23 1987-12-02 Nokia (Deutschland) GmbH Elektronenstrahlerzeugungssystem
US4910442A (en) * 1985-01-25 1990-03-20 National Institute For Researches In Inorganic Materials Field emission type electron gun

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS54129871A (en) * 1978-02-13 1979-10-08 Philips Nv Device having camera tube

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2508346A (en) * 1945-06-22 1950-05-16 Gen Electric Ultra high frequency electron discharge device
US3013171A (en) * 1953-08-14 1961-12-12 Int Standard Electric Corp Thermionic cathodes
GB891984A (en) * 1958-06-25 1962-03-21 Varian Associates Linear particle accelerator apparatus
US3130340A (en) * 1959-10-16 1964-04-21 Tesla Np Electron gun for generating a hollow beam

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2508346A (en) * 1945-06-22 1950-05-16 Gen Electric Ultra high frequency electron discharge device
US3013171A (en) * 1953-08-14 1961-12-12 Int Standard Electric Corp Thermionic cathodes
GB891984A (en) * 1958-06-25 1962-03-21 Varian Associates Linear particle accelerator apparatus
US3130340A (en) * 1959-10-16 1964-04-21 Tesla Np Electron gun for generating a hollow beam

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3831058A (en) * 1971-08-30 1974-08-20 Roosmalen J Van Device comprising a television camera tube and television camera
US3925706A (en) * 1973-02-23 1975-12-09 Hitachi Ltd Field emission electron gun device of the automatic control type
US4910442A (en) * 1985-01-25 1990-03-20 National Institute For Researches In Inorganic Materials Field emission type electron gun
EP0247470A2 (de) * 1986-05-23 1987-12-02 Nokia (Deutschland) GmbH Elektronenstrahlerzeugungssystem
EP0247470A3 (en) * 1986-05-23 1989-04-19 Nokia Graetz Gesellschaft Mit Beschrankter Haftung Electron beam generating device

Also Published As

Publication number Publication date
AU2244270A (en) 1972-05-25
DE2054709A1 (de) 1971-06-03
NL6917641A (xx) 1971-05-25
GB1271589A (en) 1972-04-19
BE759247A (fr) 1971-05-21
FR2069602A5 (xx) 1971-09-03

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