EP0422451A1 - Tube à rayons électroniques - Google Patents

Tube à rayons électroniques Download PDF

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Publication number
EP0422451A1
EP0422451A1 EP90118545A EP90118545A EP0422451A1 EP 0422451 A1 EP0422451 A1 EP 0422451A1 EP 90118545 A EP90118545 A EP 90118545A EP 90118545 A EP90118545 A EP 90118545A EP 0422451 A1 EP0422451 A1 EP 0422451A1
Authority
EP
European Patent Office
Prior art keywords
cathode
grid
electron tube
tube according
anode
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Withdrawn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
EP90118545A
Other languages
German (de)
English (en)
Inventor
Giorgio Agosti
Hans-Günter Dr. Mathews
Werner Dr. Rohrbach
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.)
ABB Asea Brown Boveri Ltd
ABB AB
Original Assignee
ABB Asea Brown Boveri Ltd
Asea Brown Boveri AB
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 ABB Asea Brown Boveri Ltd, Asea Brown Boveri AB filed Critical ABB Asea Brown Boveri Ltd
Publication of EP0422451A1 publication Critical patent/EP0422451A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
    • H01J1/02—Main electrodes
    • H01J1/13—Solid thermionic cathodes
    • H01J1/20—Cathodes heated indirectly by an electric current; Cathodes heated by electron or ion bombardment
    • H01J1/28—Dispenser-type cathodes, e.g. L-cathode

Definitions

  • the invention relates to an electron tube with a cathode, an anode and at least one independent first grid between cathode and anode.
  • Electron tubes of the type mentioned have long been known and are commercially available.
  • the cathode of such an electron tube is completely covered with osmium in order to be able to achieve higher current densities.
  • the osmium has the task of reducing the work function of the electrons.
  • An osmium-coated dispenser cathode is e.g. from patent EP-0 156 454 or from Technical Bulletin # 116, "Osmium coated dispenser cathodes - 'M' Type", Spectra-Mat Inc., 1240 Highway 1, Watsonville, California CA 95076, USA.
  • a tungsten matrix cathode is covered with two layers.
  • An Os or Os / Ru layer serves as the first layer and a W / Os alloy serves as the second layer.
  • Impregnated dispenser cathodes which are coated with Os, an Os / Ru alloy or Ir (so-called M-type cathodes), have a longer service life than S-type cathodes without surface metallization because of their approximately 100 ° lower working temperature.
  • M-type cathodes Performance analysis of three different M-type dispenser cathodes
  • a problem with known electron tubes of high current density is the lattice load due to electron bombardment. It leads to an undesirable thermal emission of the lattice, which results from cathode material being deposited on the lattice during operation and thereby reducing the work function of the electrons.
  • the object of the invention is to provide an electron tube of the type mentioned at the outset, which has a low lattice load even at high currents.
  • the cathode has both strongly emitting and at most weakly emitting regions, the strongly emitting regions being arranged behind openings in the first grid and the at most weakly emitting regions corresponding to a shadow cast by the first grid adjacent to the cathode onto the cathode .
  • the advantage of the arrangement according to the invention lies in the fact that the stream of charged particles is only generated where it also comes into play. It is thus focused on the openings in the grille.
  • the preferably cylindrical cathode ensures the necessary stability and precision with the usually very small distances between the first grid and the cathode.
  • a sheet metal grid is preferably used. Such grids are easier to manufacture and are mechanically less sensitive than wire grids.
  • Graphite grids are particularly advantageous because they suffer only very low temperature-related mechanical deformations even when subjected to a greater current load.
  • Grid currents occur in an electron tube with a cathode structured according to the invention, which lead to temperature increases. If the grid is now very fine and close to the cathode, deformations of the grid can severely disrupt the geometric alignment in the tube.
  • the preferred graphite grids include, in particular, pyrographite and electrographite grids.
  • the invention is also suitable in connection with conventional wire grids.
  • the openings in the grid are diamond-shaped or rectangular.
  • the strongly emitting areas also have a regular, lattice-like shape.
  • a tetrode with a cathode designed according to the invention can switch high currents without showing the high load on the control grid which is present in the prior art.
  • the cathode there can preferably be coated with a layer, e.g. from Mo / Ru, passivated.
  • the cathode is preferably coated with a material from the following group: Sc2O3 / W, Os / Ir, Os / Ru, Os / W, Ir, Os, Os + W / Os, Os / Ru + W / Os.
  • Os, Os / Ru, Os / W are particularly preferred because of the strong increase in emissivity.
  • the double layers of Os + W / Os, Os / Ru + W / Os also represent a special group, because of their properties that prevent interdiffusion.
  • cathode a so-called matrix or dispenser cathode, which is known for its current capacity, as the cathode.
  • FIG. 1 shows a tetrode in longitudinal section according to a preferred embodiment of the invention.
  • a cylindrical cathode 1, a first grid 2 adjacent to the cathode 1, a second grid 3 and a cylindrical anode 4 are arranged coaxially with a common axis 5.
  • the first grid 2 is e.g. a sheet metal grid with openings 6.
  • the second grid is designed accordingly.
  • the cathode is constructed in the manner of a matrix cathode, as is e.g. is known from the cited patent specification EP-0 157 454.
  • a porous tungsten matrix is impregnated with a barium-containing substance.
  • the cathode 1 is selectively covered with a strongly emitting layer. It is preferably an osmium-containing, i.e. osmated layer.
  • strongly emitting regions 7.1, 7.2, 7.3 are located behind the openings 6 of the first grating 2. In between, one or more regions 8, which emit at most weakly, are provided. The at most weakly emitting regions 8 correspond to an imaginary shadow cast by the grid 2 on the cathode 1.
  • FIG. 2 shows a cross section through the tetrode of FIG. 1.
  • the (imaginary) shadow is created by projecting the first grating 2 in the radial direction (with respect to the axis 5).
  • the strongly emitting areas 7.1, 7.4, 7.7 are separated by the at most weakly emitting area 8.
  • the strongly emitting areas 7.1, 7.2, ..., 7.9 are in this case rectangles which form a regular pattern in two directions perpendicular to one another.
  • the at most weakly emitting region 8 separates the strongly emitting regions 7.1, 7.2, ..., 7.9 in the same way as the grating 2 and the openings 8.
  • the shape of the openings is of subordinate importance. In practice, however, are usually regular Grid used, for example diamond-shaped. have rectangular openings.
  • the advantage of the invention is that the flow of charged particles, which undesirably strikes the first grating 2, is largely prevented. Rather, the emitted electrons are guided very specifically through the openings 6 of the grid. As a result, the grid no longer heats up so much and it can no longer interfere with the electron tube in the manner of a parasitic cathode.
  • the osmized areas usually have two to three times higher emissivity than the non-osmotic areas. If the ratio is to be increased further, the non-osmized areas are preferably additionally passivated with an emission-inhibiting layer.
  • a layer consisting essentially of Mo and Ru (Mo / Ru layer) is particularly suitable for this. In such a case, the areas in the shadow of the first grating not only emit weakly, but essentially not at all.
  • a cathode according to the invention can be produced using known means. Especially in the case of dispenser cathodes, which were previously used in a final process step e.g. have been osmized over the entire area, it means only a small change to cover the cathode with a suitable mask before osmosis, so that an osmium layer structured according to the invention is formed.
  • the grid can also be designed as a graphite grid (e.g. pyrographite, electrographite). Such grids endure higher current loads and thus allow the electron tube to be operated at higher current densities as a whole.
  • graphite grid e.g. pyrographite, electrographite
  • the invention is in no way limited to tetrodes. It is used wherever at least one independent grid is arranged in front of a cathode. Accordingly, the invention can be used with triodes as well as with pentodes and even more complex electron tubes.
  • cylindrical symmetry is not a mandatory requirement, but only a preferred feature of the invention. Accordingly, the invention is also suitable for flat structures.
  • the invention provides electron tubes with large currents and at the same time a low lattice load.

Landscapes

  • Electrodes For Cathode-Ray Tubes (AREA)
  • Solid Thermionic Cathode (AREA)
  • Cold Cathode And The Manufacture (AREA)
EP90118545A 1989-10-10 1990-09-27 Tube à rayons électroniques Withdrawn EP0422451A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
CH368989 1989-10-10
CH3689/89 1989-10-10
CH454289 1989-12-19
CH4542/89 1989-12-19

Publications (1)

Publication Number Publication Date
EP0422451A1 true EP0422451A1 (fr) 1991-04-17

Family

ID=25693627

Family Applications (1)

Application Number Title Priority Date Filing Date
EP90118545A Withdrawn EP0422451A1 (fr) 1989-10-10 1990-09-27 Tube à rayons électroniques

Country Status (3)

Country Link
EP (1) EP0422451A1 (fr)
JP (1) JPH03171531A (fr)
CN (1) CN1050946A (fr)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1321431C (zh) * 2003-09-09 2007-06-13 卫军民 一种大功率四极电子管及其制作方法

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3843902A (en) * 1972-08-24 1974-10-22 Varian Associates Gridded convergent flow electron gun
US4230968A (en) * 1976-05-26 1980-10-28 Hitachi, Ltd. Cathode structure for magnetrons
GB2116356A (en) * 1982-03-10 1983-09-21 Hitachi Ltd Impregnated cathode
GB2139413A (en) * 1983-04-18 1984-11-07 Litton Systems Inc An electron gun

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3843902A (en) * 1972-08-24 1974-10-22 Varian Associates Gridded convergent flow electron gun
US4230968A (en) * 1976-05-26 1980-10-28 Hitachi, Ltd. Cathode structure for magnetrons
GB2116356A (en) * 1982-03-10 1983-09-21 Hitachi Ltd Impregnated cathode
GB2139413A (en) * 1983-04-18 1984-11-07 Litton Systems Inc An electron gun

Also Published As

Publication number Publication date
JPH03171531A (ja) 1991-07-25
CN1050946A (zh) 1991-04-24

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