US3402314A - Gridded electron tube with dispenser cathode having coated surface portions - Google Patents

Gridded electron tube with dispenser cathode having coated surface portions Download PDF

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Publication number
US3402314A
US3402314A US534489A US53448966A US3402314A US 3402314 A US3402314 A US 3402314A US 534489 A US534489 A US 534489A US 53448966 A US53448966 A US 53448966A US 3402314 A US3402314 A US 3402314A
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United States
Prior art keywords
cathode
grid
portions
tube
dispenser
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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
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US534489A
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English (en)
Inventor
Vlaardingerbroek Marinu Teunis
Dorgelo Eduard Gerhardus
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US Philips Corp
North American Philips Co Inc
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US Philips Corp
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    • 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
    • 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
    • H01J1/14—Solid thermionic cathodes characterised by the material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J21/00—Vacuum tubes
    • H01J21/02—Tubes with a single discharge path
    • H01J21/06—Tubes with a single discharge path having electrostatic control means only
    • H01J21/065—Devices for short wave tubes

Definitions

  • FIG.3 GRIUUED ELECTRON TUBE WITH DISPENSER CATHODE HAVING COATED ,SURFACE PORTIONS Filed March 15, 1966 FIGJ FIG.3
  • the invention relates to an electric discharge tube cornprising a cathode having a metallic emissive surface opposite one or more grids, and in particular to a high power tube for use at frequencies in excess of 3000 mc./s.
  • Tubes operating at such high frequencies entail great diiiiculties due to excessive heating of the first grid.
  • Such constructions involve the difficulty that the barium of the active cathode portions will migrate over the cathode surface at its operating temperature and ultimately cover also the nonemissive portions, which are thereby rendered emissive as well.
  • Such an oxide emissive layer has further disadvantages at very high frequencies, it is preferred to use a so-called dispenser type cathode with a metallic emissive surface.
  • the operating temperature of such a dispenser cathode is much higher than that of barium oxide cathodes, e.g., 1050 C., as a result of which the difficulties in connection with the excessively high grid temperature are aggravated, since a dispenser cathode causes increased heating of the grid by radiation, and, moreover, the electron flow is ⁇ also increased.
  • the difficulties encountered in the construction of a high power, high frequency electron tube, as previously described. are sub- 3,402,314 Patented Sept. 17, 1968 ICC stantially completely avoided, by incorporating in the tube a dispenser cathode whose active portions located opposite the grid apertures are coated with a thin coating of metal of the group of rhenium, iridium, ruthenium or osmium as described in the copending application.
  • the cathode can be operated at a temperature at least C. lower than the conventional value of 1050 C. for the ordinary dispenser cathode. Owing to the lower operating temperature, the emission of the non-coated portions of the cathode surface is strongly reduced.
  • the non-coated cathode surface portions may be covered with a substance inhibiting electron emissivity, for example, a carbide as described' in U.S. Patent No. 2,972,078, or zirconium as described in U.S. Patent No. 2,895,070.
  • the lower cathode temperature has the advantage of reducing the heating energy required for the cathode and also reducing heating of the grid by cathode radiation; also the insulation of the filament wire is improved. Moreover, the lifetime of the cathode is considerably prolonged.
  • FIG. 1 is a cross-sectional View of one form of a discharge tube according to the invention
  • FIG. 2 is a plan view of the grid of such a tube
  • FIG. 3 is a plan View of the emissive surface of the cathode used in the tube of FIG. 1.
  • the discharge tube shown in FIG. 1 is a so-called discseal triode for very high frequencies and high power. It comprises a dispenser cathode 1, a grid electrode 2 and an anode 3 separated -by the usual insulators forming the tube enevelope.
  • the grid electrode 2 in the form of a terminal disc, has secured to it a metal plate or disc 4 having elongated apertures or slots 5, across which grid wires 6 are stretched (FIG. 2). These wires 6 are soldered or welded to the plate 4 so that a satisfactory thermal contact between the wires 6 and the plate 4 is established and the wires 6 are, consequently, cooled satisfactorily.
  • the dispenser cathode 1 comprises a porous tungsten body 7, and is constructed as described in the copending application as a cavity-type or impregnated type, with the exception that, instead of the whole emissive surface 9 of the cathode being coated with the high work function metal Rh, Ir, Ru, Os, only the surface areas 8 (FIG. 3) located opposite the slots 5 of the grid plate 4 are coated with the rhenium, irridium, ruthenium or osmium, The work function of the portions 8 of the cathode surface is thus reduced with respect to that of the initial tungsten surface 9 to an extent such that the Iportions 8 have a satisfactory emission already at a cathode temperature more than 100 C.
  • these portions may be covered with an inhibitor such as zirconium, which offer the additional advantage that this surface also possesses gas-binding properties. It is found with the use of osmium, rhenium, ruthenium or iridium, that the separation between the portions of good emission and those of poor emission of the cathode surface is maintained during operation, since the osmium, rhenium, ruthenium or iridium do not migrate but remain where deposited, and
  • the member 7 would be of porous tungsten with a density of the order of 80% with the pores filled by impregnation from the melt with barium-calcium aluminate, as described in the copending application.
  • the high work function coating is provided, also as described in the copending application, by cathode sputtering or spraying through a suitable mask to form the stripe pattern illustrated in FIG. 3.
  • the invention is also applicable to tubes containing other types of cathodes having a metallic emissive surface.
  • An electron tube comprising cathode, grid and anode electrodes, said grid having plural apertures located between the cathode and the anode for allowing electrons to fiow from the cathode to the anode, said cathode ⁇ being a dispenser type cathode having a metallic surface with portions located opposite the grid apertures separated by portions located opposite solid parts of the grid, and a coating of a metal selected from the group consisting of rhenium, iridium, ruthenium and osmium covering only those portions of the cathode surface opposite the grid apertures, whereby said coated portions exhibit an adequate electron emission at a cathode temperature lower than the temperature to which the uncoated portions would have to be raised to generate adequate electron emission.

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  • Solid Thermionic Cathode (AREA)
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US534489A 1965-04-07 1966-03-15 Gridded electron tube with dispenser cathode having coated surface portions Expired - Lifetime US3402314A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL6504397A NL6504397A (cs) 1965-04-07 1965-04-07

Publications (1)

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US3402314A true US3402314A (en) 1968-09-17

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US (1) US3402314A (cs)
AT (1) AT262459B (cs)
BE (1) BE679168A (cs)
CH (1) CH444976A (cs)
DE (1) DE1564397C3 (cs)
ES (1) ES325122A1 (cs)
GB (1) GB1100420A (cs)
NL (1) NL6504397A (cs)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3648096A (en) * 1968-09-26 1972-03-07 Gen Electric Electron beam focusing bipotential cathode
US3967150A (en) * 1975-01-31 1976-06-29 Varian Associates Grid controlled electron source and method of making same
US4031425A (en) * 1974-10-19 1977-06-21 U.S. Philips Corporation Dispenser cathode for a grid-controlled electron tube and method of manufacturing same
EP0004424A1 (en) * 1978-03-23 1979-10-03 Thorn Emi-Varian Limited Thermionic cathode
US4250428A (en) * 1979-05-09 1981-02-10 The United States Of America As Represented By The Secretary Of The Army Bonded cathode and electrode structure with layered insulation, and method of manufacture

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2535467C2 (de) * 1975-08-08 1985-06-05 Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt Verfahren zum Herstellen einer Kathode einer gittergesteuerten Leistungsröhre

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
None *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3648096A (en) * 1968-09-26 1972-03-07 Gen Electric Electron beam focusing bipotential cathode
US4031425A (en) * 1974-10-19 1977-06-21 U.S. Philips Corporation Dispenser cathode for a grid-controlled electron tube and method of manufacturing same
US3967150A (en) * 1975-01-31 1976-06-29 Varian Associates Grid controlled electron source and method of making same
EP0004424A1 (en) * 1978-03-23 1979-10-03 Thorn Emi-Varian Limited Thermionic cathode
US4250428A (en) * 1979-05-09 1981-02-10 The United States Of America As Represented By The Secretary Of The Army Bonded cathode and electrode structure with layered insulation, and method of manufacture

Also Published As

Publication number Publication date
DE1564397B2 (de) 1974-04-04
DE1564397A1 (de) 1970-02-12
CH444976A (de) 1967-10-15
DE1564397C3 (de) 1974-10-31
BE679168A (cs) 1966-10-06
NL6504397A (cs) 1966-10-10
ES325122A1 (es) 1967-01-01
GB1100420A (en) 1968-01-24
AT262459B (de) 1968-06-10

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