US2189636A - Long life cathode for electron tubes - Google Patents

Long life cathode for electron tubes Download PDF

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Publication number
US2189636A
US2189636A US176852A US17685237A US2189636A US 2189636 A US2189636 A US 2189636A US 176852 A US176852 A US 176852A US 17685237 A US17685237 A US 17685237A US 2189636 A US2189636 A US 2189636A
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Prior art keywords
barium
cathode
casing
long life
electron tubes
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Expired - Lifetime
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US176852A
Inventor
Dewey D Knowles
George S Evans
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CBS Corp
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Westinghouse Electric and Manufacturing Co
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Priority to US176852A priority Critical patent/US2189636A/en
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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
    • H01J37/32—Gas-filled discharge tubes
    • H01J37/34—Gas-filled discharge tubes operating with cathodic sputtering
    • 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
    • H01J41/00—Discharge tubes for measuring pressure of introduced gas or for detecting presence of gas; Discharge tubes for evacuation by diffusion of ions
    • H01J41/12—Discharge tubes for evacuating by diffusion of ions, e.g. ion pumps, getter ion pumps
    • H01J41/14—Discharge tubes for evacuating by diffusion of ions, e.g. ion pumps, getter ion pumps with ionisation by means of thermionic cathodes

Definitions

  • the invention relates to cathodes, and especially to cathodes for gaseous discharge devices.
  • An object of the invention is to provide a cathode having a reserve supply of emissive 5 material to supplement the regular supply,
  • the electron emission from any of the thin film cathodes and from the latest type of oxidecoated cathodes is known to be either directly or indirectly due to free barium in or on the surface of the cathode.
  • This barium is ordinarily made available by difiusion from the core material either by decomposition of the coating due to heat or by electrolysis.
  • the life of such a cathode is, therefore, limited to the length of time that this barium supply can be maintained. There are various factors which limit the amount of barium supply that can be provided in the ordinary type of oxide-coated cathode structure.-
  • the invention concerns the idea of providing a reservoir of tree barium that will provide an auxiliary supply of electrons especially when the usual supply is not sumcient.
  • the cathode comprises a casing 28, preferably in the form of a thimble of metal, such as nickel or iron, having at the upper end a porous metallic block 24 having an opening 25.
  • This block or top is preferably of sintered tungsten or of a .metal having a porosity of the order of sintered tungsten.
  • is placed in the bottom of this casing or thimble.
  • the porous top 20 has electron-emissive material in its pores such as barium and strontium oxide and a suitable heater 22 maintains the porous top or block at a suitable electron emitting temperature which may be of the order or 900 C.
  • the top 24 has an opening 25 therein exposing the free barium 2
  • the advantage of the cathode structure shown is that the adjustment of additional electron emission is always instantaneous because there is no delay caused by the necessity of some part changing its temperature.
  • Cathode structure comprising a casing, a top on said casing having a porosity of the order of sintered tungsten, electron emitting material in said porous top, and barium within said casing, said top having an opening therethrough whereby said barium may be bombarded by ions from outside said casing having sufllcient velocity.
  • a cathode for an electrical discharge device comprising a casing enclosed except on the top side, the top side beingof material having pores of the order of those characterizing sintered tungsten and having an opening through it which has a diameter many times larger than said pores, a supply of an alkaline-earth, metal within said casing positioned so as to be bombarded by ions entering said casing through said opening.

Description

1940- D. D. KNOWLES ET'AL 2,139,636
LONG LIFE CATHODE FOR ELECTRON TUBES Filed Nov. 27, 1937 WITNESSES: INVENTORS flewey D. Knowles and t George Evans.
A ATTORNEY Patented Feb. 6, 1940 LONG LIFE CATHODE FOR ELECTRON TUBES Dewey D. Knowles, Wilkinsburg, and George S.
Evans, Turtle Creek,
Pa., assignors to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application November 27, 1937, Serial No. 176,852
2 Claims.
The invention relates to cathodes, and especially to cathodes for gaseous discharge devices. An object of the invention is to provide a cathode having a reserve supply of emissive 5 material to supplement the regular supply,
especially when the regular supply is not sumcient for the load current being conducted through the discharge device.
Other objects and advantages of the invention will be apparent from the following description and drawing, in which the drawing shows a cross-section through a tube disclosing a preferred cathode therein.
The electron emission from any of the thin film cathodes and from the latest type of oxidecoated cathodes is known to be either directly or indirectly due to free barium in or on the surface of the cathode. This barium is ordinarily made available by difiusion from the core material either by decomposition of the coating due to heat or by electrolysis. The life of such a cathode is, therefore, limited to the length of time that this barium supply can be maintained. There are various factors which limit the amount of barium supply that can be provided in the ordinary type of oxide-coated cathode structure.-
If a thick coating of oxide is used to obtain more barium, the resistance becomes too high to be practical.
The invention concerns the idea of providing a reservoir of tree barium that will provide an auxiliary supply of electrons especially when the usual supply is not sumcient.
In the drawing, we have disclosed a tube I0 35 having usually a gaseous filling ll therein and an anode l2.
The cathode comprises a casing 28, preferably in the form of a thimble of metal, such as nickel or iron, having at the upper end a porous metallic block 24 having an opening 25. This block or top is preferably of sintered tungsten or of a .metal having a porosity of the order of sintered tungsten. A piece of metallic barium 2| is placed in the bottom of this casing or thimble. The porous top 20 has electron-emissive material in its pores such as barium and strontium oxide and a suitable heater 22 maintains the porous top or block at a suitable electron emitting temperature which may be of the order or 900 C.
It will be noted that the top 24 has an opening 25 therein exposing the free barium 2| to possible bombardment. It is desired that a temperature of approximately 400 C. be applied to the free barium 2| in the bottom of the casing while the top of the casing is operated at a temperature of approximately 900 C. If the emission of the electrons from the top of the crater cathode is sufficiently good, the voltage drop will be less and not many positive ions will project to the bottom of the casing and bombard the barium. If the emission decreases, however, the drop will increase and consequently, the number of high speed ions striking the barium pellet will increase. These ions sputter of! the barium and replenish the supply of barium at the crater opening 25. The advantage of the cathode structure shown is that the adjustment of additional electron emission is always instantaneous because there is no delay caused by the necessity of some part changing its temperature.
Many modifications may be made in the form, number and arrangement of the various elements disclosed and their application to other types of tubes. Accordingly, no limitations should be imposed upon the following claims except as necessitated by the prior art.
We claim as our invention:
1. Cathode structure comprising a casing, a top on said casing having a porosity of the order of sintered tungsten, electron emitting material in said porous top, and barium within said casing, said top having an opening therethrough whereby said barium may be bombarded by ions from outside said casing having sufllcient velocity.
2. A cathode for an electrical discharge device comprising a casing enclosed except on the top side, the top side beingof material having pores of the order of those characterizing sintered tungsten and having an opening through it which has a diameter many times larger than said pores, a supply of an alkaline-earth, metal within said casing positioned so as to be bombarded by ions entering said casing through said opening.
DEWEY D. KNOWLES. GEORGE S. EVANS.
US176852A 1937-11-27 1937-11-27 Long life cathode for electron tubes Expired - Lifetime US2189636A (en)

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2825839A (en) * 1951-01-16 1958-03-04 Int Standard Electric Corp Grids for electric discharge devices
US2845324A (en) * 1954-12-03 1958-07-29 Itt Gas discharge tube
US2928013A (en) * 1954-12-23 1960-03-08 Siemens Ag Electrical discharge device
US4476413A (en) * 1978-05-22 1984-10-09 Commonwealth Scientific And Industrial Research Organization Atomic spectral lamp
US5063324A (en) * 1990-03-29 1991-11-05 Itt Corporation Dispenser cathode with emitting surface parallel to ion flow

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2825839A (en) * 1951-01-16 1958-03-04 Int Standard Electric Corp Grids for electric discharge devices
US2845324A (en) * 1954-12-03 1958-07-29 Itt Gas discharge tube
US2928013A (en) * 1954-12-23 1960-03-08 Siemens Ag Electrical discharge device
US4476413A (en) * 1978-05-22 1984-10-09 Commonwealth Scientific And Industrial Research Organization Atomic spectral lamp
US5063324A (en) * 1990-03-29 1991-11-05 Itt Corporation Dispenser cathode with emitting surface parallel to ion flow

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