US3658400A - Method of making a multialkali photocathode with improved sensitivity to infrared light and a photocathode made thereby - Google Patents

Method of making a multialkali photocathode with improved sensitivity to infrared light and a photocathode made thereby Download PDF

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Publication number
US3658400A
US3658400A US15742A US3658400DA US3658400A US 3658400 A US3658400 A US 3658400A US 15742 A US15742 A US 15742A US 3658400D A US3658400D A US 3658400DA US 3658400 A US3658400 A US 3658400A
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sensitivity
photocathode
maximum
until
evaporating
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Fred Anderson Helvy
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RCA Corp
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RCA Corp
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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

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  • a method for making a muliialkali photocathode includes simultaneous evaporation of sodium and antmony alternately with simultaneous evaporation of potassium and antimony.
  • the disclosure includes a photocathode made by the method 8 Claims, 3 Drawing Figures PATNTEDAPRZS 1912 Y 3,658,400 SHEET 10F 2 7447' MAX/MIM,- 7*//5/14 INVENTOR IBI/m19.
  • FIG. l is a flow chart of steps 1-18 used for practicing a preferred embodiment of the novel method.
  • a phototube 26 shown in FIG. 2 is provided with a photocathode surface 28 having improved sensitivity to infrared light.
  • the tube 26 has a tubular glass wall section 30 about inches long, 2 inches outside diameter and one-sixteenth inch thickness.
  • One end of the wall section 30 is closed by a glass faceplate 32, which is flat on the outside and concave on the inside with a radius of curvature of about l.9 inches.
  • the other end ofthe wall section 30 is closed by a stem 34 having a number of electrical lead-in pins 35.
  • a stem 34 having a number of electrical lead-in pins 35.
  • dynodes 36 Along the interior of the tube are spaced a series of dynodes 36. Near the dynodes 36 are spaced three channels 38,40, 42 of tantalum foil containing, respectively, substances for evaporating potassium, sodium, and cesium.
  • the potassium channel 38 contains potassium chromate, aluminum, and tungsten.
  • the sodium channel 40 contains sodium chromate, aluminum, and tungsten.
  • the cesium channel 42 contains cesium chromate, zirconium and tungsten.
  • a resistance filament situated near the faceplate has two antimony alloy beads 44 attached to it for evaporating antimony.l
  • the channels 38, 40, 42 and the filament 44 are suitably connected by internal leads to electrical current sources through the pins 35 so that they can be activated separately by electrical resistance heating.
  • Light transmission through the faceplate 32 is monitored by directing light from an incandescent tungsten filament at an angle through the faceplate 32 and Wall 30 to a light sensing tube.
  • Photoemissive sensitivity of the interior faceplate surface is monitored by collecting the emitted electrons with one or more of the internal electrodes, such as the electrode 46.
  • the electrode 46 is impressed with a voltage of between 50 and 150 volts positive with respect to the photocathode 28 through a lead 48 going from a lead-in pin 35 to ari aluminum coating on the wall 30 and in contact with the photocathode 28 and lead 50 also from a lead-in pin 35 to the electrode 46.
  • the sensitivity is expressed in terms of microamperes of emitted electron current per lumen of light incident on the photocathode 28.
  • the tube is continuously evacuated through exhausted tubulation 47 in the stem.
  • the tubulation is of about l inch inside diameter and about 2 inches long. It
  • the tube 26 is placed in an-oven which has been preheated to about 190 C.
  • the channels 38, 40, 42 are preheated to clean and degas them. Then the potassium channel 38 current is set so that the channel will release potassium vapor when the faceplate 32 temperature reaches about 180 C.
  • Potassium is evaporated on the antimony layer until maximum sensitivity is reached. The maximum is generally about l.5 l-5) microamperes per lumen.
  • the oven temperature is increased to about 220 (215- 230) C and the sodium channel 40 current adjusted so that sodium vapor willbe released when the faceplate 32 reaches about 210 (205220) C.
  • Sodium is evaporated until a maximum sensitivity is reached.
  • the maximum is generally about 20 (l5-80) microamperes per lumen.
  • Steps 7 through 10 are repeated at least several times until the maximum sensitivity in step l0 is about 30 percent (2S-35 percent) of the highest maximum sensitivity reached in any of the previous steps 5 through 10.
  • the photocathode will take on a light blue hue when the proper sensitivity for this step is reached.
  • the tube 26 is cooled gradually to about 160 (155 -l65) C over a period of about 5 (5-10) minutes.
  • the tube 26 is baked at 160 (l55-l65) C until a new maximum sensitivity is reached.
  • Antimony is evaporated until the sensitivity decreases to about IO percent (5-15 percent) of the maximum reached in step 14).
  • the tube is baked at (l55-l65) C until a new maximum sensitivity is reached.
  • Steps 15) and 16) are repeated until the maximum sensitivity of step 16) stabilizes and the infrared sensitivity is between 0.5 and I6 microamperes per lumen.
  • the tube 26 is slowly cooled to room temperature at a rate of about l0 C per minute and removed from the oven. After the exhaust tubulation 47 is sealed 0H, the tube 26 is operative.
  • Sensitivity of the evaporated layers is measured separately for visible light and infrared light. lt is desirable to be able to measure both visible and infrared sensitivity almost simultaneously so that the photocathode may be processed to give a favorable relative value of both sensitivities.
  • two separate incandescent tungsten light sources are used, each about 0.1 lumen in output. The sources are spaced apart a short distance from the faceplate. Interposed between one source and the faceplate is a glass light filter passing infrared light but no visible light. For instance, a filter passing less than 0.025 percent at 750 nanometers wavelength, percent at 900 nanometers and about 90 percent at about 1,250 nanometers is suitable.
  • the sensitivity of the photocathode to both visible and infrared light may be measured separately and almost simultaneously by manual switching from one light source to the other.
  • the rates of evaporation of the evaporated elements are limited by the speed and accuracy at which the sensitivity can be monitored. A relatively slow evaporation rate makes the monitoring less critical.
  • the novel method can be used to form photocathodes having improved red response in tubes, such as image tubes for which internal processing may not be as useful as external processing because of possible contamination of electrodes.
  • the novel method results in high reproducibility of photocathodes and is thus particularly well suited for automated fabrication of photocathodes. With present methods, complete automation is not feasible because of a relatively low degree of reproducibility in the absence of a highly skilled operator. Furthermore, by the novel method it takes considerably less time, as much as 50 percent less, to make a multialkali photocathode than by present methods.
  • present multialkali photocathodes have a thickness on the order of 30 nanometers, whereas photocathodes made by the novel method may have a thickness on the order of
  • the greater thickness accounts in part for an increase in the sensitivity of the photocathode to red light, as shown in FIG. 3.
  • the curve 52 in FIG. 3 represents the approximate response characteristic of a commonly used multialkali photocathode made by present methods. The response is seen to be quite low in the 700 nanometer wavelength region.
  • the curve 54 represents the approximate response characteristic of a photocathode made by the novel method.
  • the photocathode made by the novel method has a more nearly constant and higher sensitivity throughout the visual spectrum than present multialkali photocathodes.
  • novel photocathode is made by a series of evaporations, it is presently not possible to define precisely the actual finished structure, since there is an alloying of the evaporated substances.
  • the chemical compositions of the various thickness portions of the photocathode are not known. Therefore, the novel photocathode can presently be best described as the product of the novel method.
  • the novel photocathode may be used as a photoemitter on an opaque substrate or as a secondary electron emitting surface.
  • step a of forming said base layer includes:
  • sensitizing includes:
  • step 1 cooling said substrate from the temperature at which said evaporating of potassium is carried out to a temperature sitivity of step 1 stabilizes to a value of at least 0.1 microampere per lumen for infrared light. 5.
  • An electron emissive photocathode made by the method defined in claim l.
  • An electron emissive photocathode made by the method defined in claim 2.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Common Detailed Techniques For Electron Tubes Or Discharge Tubes (AREA)
  • Formation Of Various Coating Films On Cathode Ray Tubes And Lamps (AREA)
US15742A 1970-03-02 1970-03-02 Method of making a multialkali photocathode with improved sensitivity to infrared light and a photocathode made thereby Expired - Lifetime US3658400A (en)

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US1574270A 1970-03-02 1970-03-02

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US (1) US3658400A (enExample)
JP (1) JPS5032194B1 (enExample)
CA (1) CA930256A (enExample)
DE (1) DE2109903C2 (enExample)
FR (1) FR2083948A5 (enExample)
GB (1) GB1345778A (enExample)
NL (1) NL174098C (enExample)

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3838304A (en) * 1973-07-12 1974-09-24 Rca Corp Method of making a bialkali photocathode with improved sensitivity and high temperature operating characteristics
US3858955A (en) * 1973-01-15 1975-01-07 Rca Corp Method of making a iii-v compound electron-emissive cathode
US3884539A (en) * 1972-12-11 1975-05-20 Rca Corp Method of making a multialkali electron emissive layer
US3992071A (en) * 1975-04-01 1976-11-16 The United States Of America As Represented By The Secretary Of The Army Processes for activating S-1 cathode
US4002735A (en) * 1975-06-04 1977-01-11 Rca Corporation Method of sensitizing electron emissive surfaces of antimony base layers with alkali metal vapors
US4198106A (en) * 1978-02-21 1980-04-15 Varo, Inc. Method of manufacturing a photocathode for an image intensifier tube
US4305972A (en) * 1980-06-30 1981-12-15 Rca Corporation Method for expeditiously processing a sodium-potassium-cesium-antimony photocathode
US4306188A (en) * 1979-10-30 1981-12-15 Rca Corporation Photomultiplier tube having a photocurrent collector
US4333031A (en) * 1979-03-30 1982-06-01 Rca Corporation Photomultiplier tube having directional alkali metal vapor evaporation means
US4357368A (en) * 1978-12-26 1982-11-02 Rca Corporation Method of making a photosensitive electrode and a photosensitive electrode made thereby
US4370585A (en) * 1980-08-29 1983-01-25 Rca Corporation Evaporator support assembly for a photomultiplier tube
US4407857A (en) * 1981-06-30 1983-10-04 Rca Corporation Method for processing a lithium-sodium-antimony photocathode
US4568567A (en) * 1984-10-09 1986-02-04 Rca Corporation Method of removing trace quantities of alkali metal impurities from a bialkali-antimonide photoemissive cathode
US4585935A (en) * 1984-02-10 1986-04-29 Rca Corporation Electron discharge device having a substantially spherical electrostatic field lens
US4671778A (en) * 1986-03-19 1987-06-09 Rca Corporation Imaging device having an improved photoemissive cathode appendage processing assembly
US4682021A (en) * 1986-01-29 1987-07-21 Rca Corporation Header assembly for an intensified charge coupled image sensor
CN1052811C (zh) * 1996-11-06 2000-05-24 南京理工大学 多碱光电阴极的制造方法
CN115125491A (zh) * 2022-06-15 2022-09-30 北方夜视技术股份有限公司 一种多碱光电阴极制备用碱源的蒸发特性测量的方法

Citations (6)

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Publication number Priority date Publication date Assignee Title
US2431401A (en) * 1940-06-25 1947-11-25 Rca Corp Method of manufacturing photoelectric tubes
US2770561A (en) * 1954-03-08 1956-11-13 Rca Corp Photoelectric cathode and method of producing same
US2914690A (en) * 1955-12-05 1959-11-24 Rca Corp Electron-emitting surfaces and methods of making them
US3179835A (en) * 1960-11-22 1965-04-20 Rca Corp Pickup tube having a cesiated photocathode and a substantially leakagefree target, and method of making the same
US3372967A (en) * 1966-07-06 1968-03-12 Rca Corp Method of making a multi-alkali cathode
US3498834A (en) * 1967-02-03 1970-03-03 Weston Instruments Inc Photoelectric surfaces and methods for their production

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB892504A (en) * 1957-06-26 1962-03-28 Emi Ltd Improvements in or relating to a method of forming a photoemissive surface
US3434876A (en) * 1965-11-23 1969-03-25 Rca Corp Photosensitive cathodes

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2431401A (en) * 1940-06-25 1947-11-25 Rca Corp Method of manufacturing photoelectric tubes
US2770561A (en) * 1954-03-08 1956-11-13 Rca Corp Photoelectric cathode and method of producing same
US2914690A (en) * 1955-12-05 1959-11-24 Rca Corp Electron-emitting surfaces and methods of making them
US3179835A (en) * 1960-11-22 1965-04-20 Rca Corp Pickup tube having a cesiated photocathode and a substantially leakagefree target, and method of making the same
US3372967A (en) * 1966-07-06 1968-03-12 Rca Corp Method of making a multi-alkali cathode
US3498834A (en) * 1967-02-03 1970-03-03 Weston Instruments Inc Photoelectric surfaces and methods for their production

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3884539A (en) * 1972-12-11 1975-05-20 Rca Corp Method of making a multialkali electron emissive layer
US3858955A (en) * 1973-01-15 1975-01-07 Rca Corp Method of making a iii-v compound electron-emissive cathode
US3838304A (en) * 1973-07-12 1974-09-24 Rca Corp Method of making a bialkali photocathode with improved sensitivity and high temperature operating characteristics
US3992071A (en) * 1975-04-01 1976-11-16 The United States Of America As Represented By The Secretary Of The Army Processes for activating S-1 cathode
US4002735A (en) * 1975-06-04 1977-01-11 Rca Corporation Method of sensitizing electron emissive surfaces of antimony base layers with alkali metal vapors
US4198106A (en) * 1978-02-21 1980-04-15 Varo, Inc. Method of manufacturing a photocathode for an image intensifier tube
US4357368A (en) * 1978-12-26 1982-11-02 Rca Corporation Method of making a photosensitive electrode and a photosensitive electrode made thereby
US4333031A (en) * 1979-03-30 1982-06-01 Rca Corporation Photomultiplier tube having directional alkali metal vapor evaporation means
US4306188A (en) * 1979-10-30 1981-12-15 Rca Corporation Photomultiplier tube having a photocurrent collector
US4305972A (en) * 1980-06-30 1981-12-15 Rca Corporation Method for expeditiously processing a sodium-potassium-cesium-antimony photocathode
US4370585A (en) * 1980-08-29 1983-01-25 Rca Corporation Evaporator support assembly for a photomultiplier tube
US4407857A (en) * 1981-06-30 1983-10-04 Rca Corporation Method for processing a lithium-sodium-antimony photocathode
US4585935A (en) * 1984-02-10 1986-04-29 Rca Corporation Electron discharge device having a substantially spherical electrostatic field lens
US4568567A (en) * 1984-10-09 1986-02-04 Rca Corporation Method of removing trace quantities of alkali metal impurities from a bialkali-antimonide photoemissive cathode
US4682021A (en) * 1986-01-29 1987-07-21 Rca Corporation Header assembly for an intensified charge coupled image sensor
US4671778A (en) * 1986-03-19 1987-06-09 Rca Corporation Imaging device having an improved photoemissive cathode appendage processing assembly
CN1052811C (zh) * 1996-11-06 2000-05-24 南京理工大学 多碱光电阴极的制造方法
CN115125491A (zh) * 2022-06-15 2022-09-30 北方夜视技术股份有限公司 一种多碱光电阴极制备用碱源的蒸发特性测量的方法

Also Published As

Publication number Publication date
DE2109903A1 (de) 1971-09-30
GB1345778A (en) 1974-02-06
NL7102696A (enExample) 1971-09-06
DE2109903C2 (de) 1986-03-27
CA930256A (en) 1973-07-17
FR2083948A5 (enExample) 1971-12-17
NL174098B (nl) 1983-11-16
JPS5032194B1 (enExample) 1975-10-18
NL174098C (nl) 1984-04-16

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