US2784123A - Secondary electron emitter and process of preparing same - Google Patents

Secondary electron emitter and process of preparing same Download PDF

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Publication number
US2784123A
US2784123A US285466A US28546652A US2784123A US 2784123 A US2784123 A US 2784123A US 285466 A US285466 A US 285466A US 28546652 A US28546652 A US 28546652A US 2784123 A US2784123 A US 2784123A
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United States
Prior art keywords
magnesium
oxygen
base member
alloy
emitter
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Expired - Lifetime
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US285466A
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English (en)
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Rappaport Paul
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RCA Corp
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RCA Corp
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Publication date
Priority to NL94756D priority Critical patent/NL94756C/xx
Priority to BE519545D priority patent/BE519545A/xx
Application filed by RCA Corp filed Critical RCA Corp
Priority to US285466A priority patent/US2784123A/en
Priority to FR1072940D priority patent/FR1072940A/fr
Priority to GB10362/53A priority patent/GB728181A/en
Priority to DER11506A priority patent/DE1012698B/de
Application granted granted Critical
Publication of US2784123A publication Critical patent/US2784123A/en
Anticipated expiration legal-status Critical
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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
    • 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
    • H01J1/32—Secondary-electron-emitting 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 Ian improved method of processing a secondary emitter electrode for use in an electron multiplier type electron tube, and to secondary electron emitters made by this process.
  • Figs. 1, 2 and 3 schematically show the various steps in the process of activating a AgMg alloy secondary emitter according to the invention and Fig. 4 is a graph showing the comparison of tests of secondary emission ratio of a AgMg secondary emitter processed according to the invention with a AgMg emitter processed by the previously used method.
  • the best secondary emitters are those that consists of an oxide film on a metal base member.
  • One of the most satisfactory ways to achieve this is by the use of a AgMg alloy of approximately 98.3 percent silver and 1.7 percent magnesium as the base member.
  • a magnesium oxide film is formed on this alloy base member when it is heated for a suitable time in an oxidizing atmosphere.
  • the magnesium atoms inside the AgMgalloy move around due to the increased temperature, and those arriving at the surface of the alloy become oxidized and stick, thus forming the MgO lm.
  • This type of surface has a number of d-istinct advantages over other secondary emitters.
  • the object of the present invention is to provide oxidized silver-magnesium alloy emitters which are not subject to magnesium evaporation.
  • oxygen-free atmosphere is a gas medium containing no appreciable oxygen gas.
  • the residual water vapor pressure can be as low as 10-22 mm./Hg and no noticeable change in the alloy takes place when baking except for a general outgassing and cleaning.
  • the alloy is baked in a commercial dry hydrogen furnace Where the probability of finding oxygen is very small, one still gets acceptably activated emitters, probably'dueV to the 8 i03 min/Hg water Vapor pressure present.
  • the magnesium when the alloy base member is initially baked in a substantially oxygen-free atmosphere including some other molecular oxidizer, such as water vapor, which does not diffuse into the alloy to any appreciable extent, the magnesium is allowed to diffuse to the surface before it is oxidized.
  • the magnesium arriving at the surface forms the oxide due to the action of water vapor and heat.
  • the process can take place in: a vacuum chamber containing a residual pressure of water vapor, as described above; a hydrogen atmosphere with residual water vapor; or an inert gas, such as helium, at atmospheric pressure containing a low partial pressure of water vapor.
  • water vapor other molecular oxidizing agents which will not diffuse freely into the AgMg alloy, such as alcohols, carbon dioxide and nitrogen pentoxide, may be used.
  • the emitter Since the molecular oxidizing agent cannot freely dif# fuse into the alioyfany magnesium that has -not arrivedl at the surface during the baking processit still present ⁇ in the metallic form in the alloy the emitter is later operated at high temperatures, asin the RF heating during outgasing and cathode breakdown,
  • Figs. l and 2 show, respectively, a portion of the surface of a AgMg strip or base member before any processing for 'use as a secondary emitter, and such a strip after preliminary processing with a low pressure of a molecular oxidizing gas to produce the golden MgO surface.
  • the free Mg atoms have been shown schematically by stippling in Figs. 1 and 2.
  • the formation of the MgO surface reduces the number of Mg atoms in the alloy to a small extent.
  • a silvermagnesium alloy secondary emitter in which the proportion of magnesium is small compared to the proportion -ofsilvery which has previously been heated in a suitable oxidizing atmosphere including a molecular oxidizing material which does not diffuse freely into the alloy, such as one containing water vapor to form a MgO secondary emitter surface, is reheated in an oxygen atmosphere, to render the emitter incapable of appreciable evaporation of magnesium, as shown schematically in Fig. 3.
  • a pre-oxidized AgMg sample is heated in oxygen, it becomes brittle, which means that the oxygen penetrates the already formed MgO film, and oxidizes free magnesium atoms left in the alloy, thus freezing them in place.
  • the inal emitter would be an alloy of silver and magnesium oxide having a magnesium oxide surface and having a composition of approximately 98.3 parts or 97.23 percent of silver, 1.7 parts or 1.68 percent of magnesium, and 1.1 parts or 1.09 percent of combined oxygen.
  • the small amount of free magnesium left in the emitter is indicated'by the sparse stippling in Fig. 3.
  • a significant increase in secondary emission ratio is observed by this treatment, probably because of the effect of the oxygen in the Mg() surface.
  • Some free Mg in the MgO surface may be oxidized which would increase the mean free path for secondary electrons and give rise to a greater yield of secondary electrons.
  • the oxygen itself may also act as a source of secondary electrons because of its valence band of six electrons.
  • the treatment of the pre-oxidized AgMg emitter with oxygen can be carried out at temperatures from about 500 C. almost up to the melting point of silver, i. e., approximately 960 C., for periods from tive minutes to a half hour or more, depending on the temperature and pressure.
  • the pressure of the oxygen is not critical, and may be as low as a few millimeters of mercury and as high as several atmospheres. In general, the lower the temperature and pressure are, the longer will be the time required to oxidize substantially all of the free magnesium in the alloy.
  • the diusion rate of oxygen into silver is proportional to the temperature and the external oxygen pressure.
  • the lower curve shows the secondary emission ratio of a AgMg alloy secondary emitter which had beenprocessed in water vapor to produce the desired mas I- MgO surface without any additional treatment.
  • the upper curve shows the secondary emission ratio of a second emitter which had been processed tirst in water vapor and then heated in oxygen at atmospheric pressure for a half hour at 600 C.
  • the two emitters were mounted in the same tube envelope and subjected to the same tube processing including cathode breakdown and exhaust.
  • the oxygen processing produces a considerable improvement in the secondary emis sion ratio, in addition to minimizing the evaporation of metallic magnesium onto various tube electrodes and the tube envelope during activation and operation of the tube.
  • the method of preparing a secondary emitter comprising the steps of: heating a base member of AgMg alloy, in which the proportion of magnesium is small compared to the proportion of silver, in a iirst oxidizing gas medium including a low partial pressure of a molecular oxidizing material selected from the group consisting of water vapor, alcohols, carbon dioxide and nitrogen pentoxide, to produce a secondary emissive surface of Mg() on said base member; and then heating said surface-oxidized base member in a second oxidizing gas medium the oxidizing agent of which is essentially oxygen for a period of time sutiicient to oxidize substantially all of the free magnesium left in said base member to minimizeevaporation of free magnesium from the emitter upon any subsequent heating thereof during use.
  • the method of preparing a secondary emitter oomprising the steps of: heating a base member of AgMg alloy, in which the proportion of magnesium is small compared to the proportion of silver, in a iirst oxidizing gas medium including a low partial pressure of water vapor, -to produce a secondary emissive surface of MgO on said base member; and then heating said surfaceoxidized base member in a second oxidizing gas medium the oxidizing agent of which is essentially oxygen for a period of time sufficient to oxidize substantially all of rthe free magnesium left in said base member, to minimize evaporation of free magnesium from the emitter upon any subsequent heating during use.
  • a secondary emitter electrode comprising a base consisting essentially of magneisum oxide and silverv andcontaining less than one tenth of one percent by weight of free magnesium, the proportion ot magnesium oxide being small comparedV to the proportion of silver-,lV
  • said base having a secondary emjssive surface of magnesium oxide.
  • a secondary emitter electrode comprising a base consisting essentially of about 3 percent magnesium oxide, 97 percent silver and less than one tenth ⁇ of one percent of free magnesium, by weight, and having a secondary emissive surface of magnesium oxide.
  • the method of preparing va secondary emitter comprising the steps of: heating a strip of AgMg alloy consisting of approximately 98.3 percent 'silver and 1.7 percent magnesium, by weight, at a temperature of about 550 C. for about one-half hour in an ⁇ oxygen-free gas medium including a partial pressure of water vapor at a vapor pressure of labout 5 104 mm. of mercury, to produce a golden surface of MgO on ysaid strip; ⁇ and then heating said oxidized strip with high frequency induction heating at about 700 C. in oxygen at atmospheric pressure for about five minutes, to oxidize substantially all of the free magnesium left in said alloy and thereby minimize evaporation of free magneisum from said emit lter on any subsequent heating thereof during use.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Electrodes For Compound Or Non-Metal Manufacture (AREA)
  • Cold Cathode And The Manufacture (AREA)
  • Manufacture And Refinement Of Metals (AREA)
US285466A 1952-05-01 1952-05-01 Secondary electron emitter and process of preparing same Expired - Lifetime US2784123A (en)

Priority Applications (6)

Application Number Priority Date Filing Date Title
NL94756D NL94756C (fr) 1952-05-01
BE519545D BE519545A (fr) 1952-05-01
US285466A US2784123A (en) 1952-05-01 1952-05-01 Secondary electron emitter and process of preparing same
FR1072940D FR1072940A (fr) 1952-05-01 1953-03-13 émetteur d'électrons secondaires
GB10362/53A GB728181A (en) 1952-05-01 1953-04-15 Secondary electron emitter
DER11506A DE1012698B (de) 1952-05-01 1953-04-23 Verfahren zur Herstellung von Sekundaeremissionskathoden mit einer Magnesiumoxydoberflaeche

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US285466A US2784123A (en) 1952-05-01 1952-05-01 Secondary electron emitter and process of preparing same

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US2784123A true US2784123A (en) 1957-03-05

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US (1) US2784123A (fr)
BE (1) BE519545A (fr)
DE (1) DE1012698B (fr)
FR (1) FR1072940A (fr)
GB (1) GB728181A (fr)
NL (1) NL94756C (fr)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2902417A (en) * 1956-09-19 1959-09-01 Ibm Application of solid lubricant coatings to surfaces
US2922906A (en) * 1956-12-26 1960-01-26 Gen Electric Target electrode assembly
US2934670A (en) * 1956-11-05 1960-04-26 Columbia Broadcasting Syst Inc Electron tubes and method of making same
US3216824A (en) * 1961-07-03 1965-11-09 Commissariat Energie Atomique Preparation of materials of composite structure
US3284256A (en) * 1960-10-10 1966-11-08 Commissariat Energie Atomique Method of manufacturing a composite, heat-insulating material of the type formed by stacking foils of oxidisable metal
US3450574A (en) * 1966-11-14 1969-06-17 Northern Electric Co Method of coating refractory wares with magnesia
US4017952A (en) * 1973-11-09 1977-04-19 Hitachi, Ltd. Method for disassembling and repairing a sodium-handling apparatus
US4088510A (en) * 1976-02-19 1978-05-09 Rca Corporation Magnesium oxide dynode and method of preparation
US4478648A (en) * 1982-04-23 1984-10-23 Man Maschinenfabrik Augsburg-Nurnberg Ag Method of producing protective oxide layers
US5630886A (en) * 1994-08-29 1997-05-20 Mitsubishi Materials Corporation Corrosion-resistant film for protecting surfaces of Ag and corrosion-resist composite structures
CN109346390A (zh) * 2018-08-31 2019-02-15 湖北汉光科技股份有限公司 铯束管用电子倍增器的二次发射体的制作方法

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2825668A (en) * 1956-03-20 1958-03-04 Jack F Koons Jr Process of making a plate oxide rectifier
FR2506518A1 (fr) * 1981-05-20 1982-11-26 Labo Electronique Physique Structure multiplicatrice d'electrons comportant un multiplicateur a galettes de microcanaux suivi d'un etage amplificateur a dynode, procede de fabrication et utilisation dans un tube photoelectrique
CN104278230A (zh) * 2014-09-05 2015-01-14 兰州空间技术物理研究所 一种高能粒子轰击用Ag-Mg合金型MgO膜层的制备方法

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2156262A (en) * 1932-12-27 1939-05-02 Colin G Fink Process of treating metal articles to alloy constituent metals
US2233276A (en) * 1938-03-25 1941-02-25 Rca Corp Secondary electron emissive electrode
US2266595A (en) * 1937-07-14 1941-12-16 Gen Electric Electric discharge device
US2373937A (en) * 1940-03-21 1945-04-17 Magnesium Elektron Ltd Process of coating magnesium and magnesium alloys
US2393803A (en) * 1945-01-27 1946-01-29 Rca Corp Method of making long life secondary electron emitters
US2447038A (en) * 1945-10-31 1948-08-17 Raytheon Mfg Co Cathode structure
US2477279A (en) * 1946-09-11 1949-07-26 Hanovia Chemical & Mfg Co Electrical discharge device
US2586771A (en) * 1946-04-06 1952-02-26 Int Standard Electric Corp Process for making secondary emission electrodes
US2620287A (en) * 1949-07-01 1952-12-02 Bramley Jenny Secondary-electron-emitting surface

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2156262A (en) * 1932-12-27 1939-05-02 Colin G Fink Process of treating metal articles to alloy constituent metals
US2266595A (en) * 1937-07-14 1941-12-16 Gen Electric Electric discharge device
US2233276A (en) * 1938-03-25 1941-02-25 Rca Corp Secondary electron emissive electrode
US2373937A (en) * 1940-03-21 1945-04-17 Magnesium Elektron Ltd Process of coating magnesium and magnesium alloys
US2393803A (en) * 1945-01-27 1946-01-29 Rca Corp Method of making long life secondary electron emitters
US2447038A (en) * 1945-10-31 1948-08-17 Raytheon Mfg Co Cathode structure
US2586771A (en) * 1946-04-06 1952-02-26 Int Standard Electric Corp Process for making secondary emission electrodes
US2477279A (en) * 1946-09-11 1949-07-26 Hanovia Chemical & Mfg Co Electrical discharge device
US2620287A (en) * 1949-07-01 1952-12-02 Bramley Jenny Secondary-electron-emitting surface

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2902417A (en) * 1956-09-19 1959-09-01 Ibm Application of solid lubricant coatings to surfaces
US2934670A (en) * 1956-11-05 1960-04-26 Columbia Broadcasting Syst Inc Electron tubes and method of making same
US2922906A (en) * 1956-12-26 1960-01-26 Gen Electric Target electrode assembly
US3284256A (en) * 1960-10-10 1966-11-08 Commissariat Energie Atomique Method of manufacturing a composite, heat-insulating material of the type formed by stacking foils of oxidisable metal
US3216824A (en) * 1961-07-03 1965-11-09 Commissariat Energie Atomique Preparation of materials of composite structure
US3450574A (en) * 1966-11-14 1969-06-17 Northern Electric Co Method of coating refractory wares with magnesia
US4017952A (en) * 1973-11-09 1977-04-19 Hitachi, Ltd. Method for disassembling and repairing a sodium-handling apparatus
US4088510A (en) * 1976-02-19 1978-05-09 Rca Corporation Magnesium oxide dynode and method of preparation
US4478648A (en) * 1982-04-23 1984-10-23 Man Maschinenfabrik Augsburg-Nurnberg Ag Method of producing protective oxide layers
US5630886A (en) * 1994-08-29 1997-05-20 Mitsubishi Materials Corporation Corrosion-resistant film for protecting surfaces of Ag and corrosion-resist composite structures
CN109346390A (zh) * 2018-08-31 2019-02-15 湖北汉光科技股份有限公司 铯束管用电子倍增器的二次发射体的制作方法

Also Published As

Publication number Publication date
DE1012698B (de) 1957-07-25
NL94756C (fr)
FR1072940A (fr) 1954-09-16
GB728181A (en) 1955-04-13
BE519545A (fr)

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