US2190695A - Secondary electron emitter and method of making it - Google Patents
Secondary electron emitter and method of making it Download PDFInfo
- Publication number
- US2190695A US2190695A US195941A US19594138A US2190695A US 2190695 A US2190695 A US 2190695A US 195941 A US195941 A US 195941A US 19594138 A US19594138 A US 19594138A US 2190695 A US2190695 A US 2190695A
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- US
- United States
- Prior art keywords
- caesium
- carbon
- making
- secondary electron
- layer
- 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.)
- Expired - Lifetime
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Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
- H01J9/02—Manufacture of electrodes or electrode systems
- H01J9/12—Manufacture of electrodes or electrode systems of photo-emissive cathodes; of secondary-emission electrodes
- H01J9/125—Manufacture of electrodes or electrode systems of photo-emissive cathodes; of secondary-emission electrodes of secondary emission electrodes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J2201/00—Electrodes common to discharge tubes
- H01J2201/32—Secondary emission electrodes
Definitions
- This invention relates to a method of manufacturing secondary-emission electrodes, i. e.
- electrodes consisting, at least on part of their surface, of a material that readily emits secondary electrons when it is struck by primary electrons.
- the invention relates furthermore to electric discharge tubes comprising such an electrode.
- a secondary emission electrode which contains caesium consists in' that within an exhausted tube caesium is applied by vaporisation to an oxidised base or underlayer and then is oxidised and activated.
- a drawback of this method is that upon being vaporised the caesium deposits not only on the surface of the secondary-emission electrode but also at other points of the discharge tube, for example on a primary cathode, at which points the presence of caesium may have a harmful effect.
- caesium in a closed discharge tube caesium is vaporised and is precipitated on a layer of carbon provided on a base or underlayer and is 30 subsequently oxidised and is present in finely divided condition in and on the layer of carbon. It has been found that such an electrode possesses excellent properties for secondary emission and also that the manufacture thereof has no harm- 5 ful effect on other parts of the tube since owing to the adsorbing and combining action of the layer of carbon the caesium deposits at the desired place. This layer of carbon forms at the same time an underlayer having sufi'icient proper- 4o ties of conduction.
- FIG. 1 shows the steps of the method according to the invention and Figure 2 shows in greatly enlarged crosssection a portion of an electrode made in accordance with the invention.
- the finished electrode shown in Figure 2 comprises a base 4 on which is a conductive layer 5 of car- 50 .bon deposited on the base by any of various well known methods.
- the conductive layer of carbon has in and on it an oxide such as caesium oxide which is present in finely divided condition and the particles of which are indicated by the dots 6.
- the caesium is precipitated on the layer of carbon from caesium vapor in a closed discharge tube and the caesium oxide is produced by subsequently oxidizing the precipitated caesium.
- a secondary emission of 4 secondary electrons per primary electron may be obtained already at 150 volts.
- the method of making a surface having secondary electron emissivity several times unity which consists in providing a body with a conductive layer of carbon, depositing alkali metal from the vapor phase on the surface of said carbon layer and oxidizing the alkali metal deposited on the carbon surface.
- the method of making a surface having secondary electron emissivity several times unity which consists in exposing a body having a conductive surface layer of carbon to the vapor of an alkali metal, depositing said alkali metal from the vapor phase on said carbon surface, exposing the electrode to an oxidizing atmosphere and converting the deposited alkali metal into oxide.
- the method of making a surface having secondary electron emissivity several times unity which consists in enclosing an electrode having a carbon surface in an evacuated vessel, depositing caesium from the vapor phase on the carbon surface of said electrode, introducing an oxidizing atmosphere into said vessel, and converting the deposited caesium into caesiun oxide.
- An electrode having a/fatio of secondary electron emission of several times unity upon im-'- pact by primary electrons at several hundred volts and comprising a layer of carbon in and on which caesium oxide is present in finely divided condition.
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- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Discharge Lamp (AREA)
- Cold Cathode And The Manufacture (AREA)
Description
Feb. 20, 1940. H. BRUINING ET AL 2,190,695
SECONDARY ELECTRON EMITTER AND METHOD OF MAKING IT Fi led March 15, 1938 1 conr 543E wm/ ca/voucrwz LAYER 0F CARBUN l-XPOSE CARBON COATED 2 BASE r0 VAPOR/ZED CAES/UM nv 020550 VESSEL AND DEPOSIT CAESIUM o/v CARBON LA YER 3 OXIDIZE MES/UM 0N CARBON LAYER HVVENTORS HAJO BRl/INING, JAN HENDRIK DE BOERAND ARTEN CORNELL? TEVES ATTORNEY.
Patented Feb. 20, 1940 UNITED STATES PATENT OFFICE,
SECONDARY ELECTRON EMITTER AND METHOD OF MAKING IT Application March 15,
1938, Serial No. 195,941
In the Netherlands April 2, 1937 4 Claims.
This invention relates to a method of manufacturing secondary-emission electrodes, i. e.
electrodes consisting, at least on part of their surface, of a material that readily emits secondary electrons when it is struck by primary electrons.
The invention relates furthermore to electric discharge tubes comprising such an electrode.
Various materials have previously been proposed as coatings of such secondary emission electrodes; amongst them an important place is held by the metals and compounds, more particularly the oxides, of the alkali metals and in particular of caesium. A very customary method of manufacturing, for example, a secondary emission electrode which contains caesium consists in' that within an exhausted tube caesium is applied by vaporisation to an oxidised base or underlayer and then is oxidised and activated. A drawback of this method is that upon being vaporised the caesium deposits not only on the surface of the secondary-emission electrode but also at other points of the discharge tube, for example on a primary cathode, at which points the presence of caesium may have a harmful effect.
This drawback may be avoided by utilising a method according to the present invention which consists in that in a closed discharge tube caesium is vaporised and is precipitated on a layer of carbon provided on a base or underlayer and is 30 subsequently oxidised and is present in finely divided condition in and on the layer of carbon. It has been found that such an electrode possesses excellent properties for secondary emission and also that the manufacture thereof has no harm- 5 ful effect on other parts of the tube since owing to the adsorbing and combining action of the layer of carbon the caesium deposits at the desired place. This layer of carbon forms at the same time an underlayer having sufi'icient proper- 4o ties of conduction.
In the accompanying drawing Figure 1 shows the steps of the method according to the invention and Figure 2 shows in greatly enlarged crosssection a portion of an electrode made in accordance with the invention.
In Figure 1 the rectangles numbered I, 2, and 3 represent the successive steps of the method. The finished electrode shown in Figure 2 comprises a base 4 on which is a conductive layer 5 of car- 50 .bon deposited on the base by any of various well known methods. The conductive layer of carbon has in and on it an oxide such as caesium oxide which is present in finely divided condition and the particles of which are indicated by the dots 6.
The caesium is precipitated on the layer of carbon from caesium vapor in a closed discharge tube and the caesium oxide is produced by subsequently oxidizing the precipitated caesium.
Although the invention has been described with reference to one of the alkali metals it may be applied as well to the other alkali metals viz. sodium, potassium, lithium and rubidium. Caesium is, however, particularly suitable for being applied with the aid of the method according to the invention since this metal is most readily adsorbed and taken up by carbon. It has proved to be possible to obtain in this way secondaryemission electrodes of which the secondary emission ratio varies between 3 and 4 at 500 volts. In some cases, more particularly when operating with a comparatively large quantity of caesium,
a secondary emission of 4 secondary electrons per primary electron may be obtained already at 150 volts.
What we claim is:
1. The method of making a surface having secondary electron emissivity several times unity which consists in providing a body with a conductive layer of carbon, depositing alkali metal from the vapor phase on the surface of said carbon layer and oxidizing the alkali metal deposited on the carbon surface.
2. The method of making a surface having secondary electron emissivity several times unity which consists in exposing a body having a conductive surface layer of carbon to the vapor of an alkali metal, depositing said alkali metal from the vapor phase on said carbon surface, exposing the electrode to an oxidizing atmosphere and converting the deposited alkali metal into oxide.
3. The method of making a surface having secondary electron emissivity several times unity which consists in enclosing an electrode having a carbon surface in an evacuated vessel, depositing caesium from the vapor phase on the carbon surface of said electrode, introducing an oxidizing atmosphere into said vessel, and converting the deposited caesium into caesiun oxide.
4. An electrode having a/fatio of secondary electron emission of several times unity upon im-'- pact by primary electrons at several hundred volts and comprising a layer of carbon in and on which caesium oxide is present in finely divided condition.
HAJO BRUINING. JAN HENDRIK nr: BOER. MARTEN CORNELIS TEVES.
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
NL207265X | 1937-04-02 |
Publications (1)
Publication Number | Publication Date |
---|---|
US2190695A true US2190695A (en) | 1940-02-20 |
Family
ID=19778619
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US195941A Expired - Lifetime US2190695A (en) | 1937-04-02 | 1938-03-15 | Secondary electron emitter and method of making it |
Country Status (6)
Country | Link |
---|---|
US (1) | US2190695A (en) |
BE (1) | BE427303A (en) |
CH (1) | CH207265A (en) |
FR (1) | FR836016A (en) |
GB (1) | GB492025A (en) |
NL (1) | NL50264C (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2472189A (en) * | 1941-07-03 | 1949-06-07 | Hartford Nat Bank & Trust Co | Thermionic tube having a secondary-emission electrode |
US2637002A (en) * | 1953-04-28 | Television pickup tube | ||
US3632442A (en) * | 1967-04-21 | 1972-01-04 | Philips Corp | Photocathodes |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2530167A (en) * | 1944-12-14 | 1950-11-14 | Hartford Nat Bank & Trust Co | Discharge tube |
-
0
- BE BE427303D patent/BE427303A/xx unknown
- NL NL50264D patent/NL50264C/xx active
-
1938
- 1938-03-15 US US195941A patent/US2190695A/en not_active Expired - Lifetime
- 1938-03-30 GB GB9752/38A patent/GB492025A/en not_active Expired
- 1938-03-31 CH CH207265D patent/CH207265A/en unknown
- 1938-04-01 FR FR836016D patent/FR836016A/en not_active Expired
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2637002A (en) * | 1953-04-28 | Television pickup tube | ||
US2472189A (en) * | 1941-07-03 | 1949-06-07 | Hartford Nat Bank & Trust Co | Thermionic tube having a secondary-emission electrode |
US3632442A (en) * | 1967-04-21 | 1972-01-04 | Philips Corp | Photocathodes |
Also Published As
Publication number | Publication date |
---|---|
GB492025A (en) | 1938-09-13 |
FR836016A (en) | 1939-01-09 |
CH207265A (en) | 1939-10-15 |
BE427303A (en) | |
NL50264C (en) |
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