US3838304A - Method of making a bialkali photocathode with improved sensitivity and high temperature operating characteristics - Google Patents

Method of making a bialkali photocathode with improved sensitivity and high temperature operating characteristics Download PDF

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US3838304A
US3838304A US00378517A US37851773A US3838304A US 3838304 A US3838304 A US 3838304A US 00378517 A US00378517 A US 00378517A US 37851773 A US37851773 A US 37851773A US 3838304 A US3838304 A US 3838304A
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maximum
sensitivity
until
evaporating
method defined
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Donie A Mc
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Burle Technologies Inc
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RCA Corp
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Priority to GB3106674A priority patent/GB1476213A/en
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Assigned to BURLE INDUSTRIES, INC. reassignment BURLE INDUSTRIES, INC. MERGER (SEE DOCUMENT FOR DETAILS). PENNSYLVANIA, EFFECTIVE JULY 14, 1987 Assignors: NPD SUBSIDIARY, INC., 38
Assigned to BURLE TECHNOLOGIES, INC., A CORP. OF DE reassignment BURLE TECHNOLOGIES, INC., A CORP. OF DE ASSIGNMENT OF ASSIGNORS INTEREST. (SEE RECORD FOR DETAILS) Assignors: BURLE INDUSTRIES, INC., A CORP. OF PA
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Assigned to BARCLAYS BUSINESS CREDIT, INC. reassignment BARCLAYS BUSINESS CREDIT, INC. SECURITY INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: BURLE TECHNOLOGIES, INC., A DE CORP.
Assigned to BARCLAYS BUSINESS CREDIT, INC. reassignment BARCLAYS BUSINESS CREDIT, INC. SECURITY INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: BURLES TECHNOLOGIES, INC., A CORP. OF DE
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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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  • ABSTRACT A bialkali photocathode is made by a series of alternate evaporations of antimony, sodium and potassnrrn.
  • the disclosure includes a photocathode 'ifi'd'by the T method described.
  • This invention relates to the art of making photoemitting surfaces.
  • a previous type of photoemitting surface is a semitransparent multialkali photocathode such as described in US. Pat. Nos. 2,770,561 to A. 1-1. Sommer and 3,372,967 to F. R. Hughes.
  • photocathodes of this type which havebeen sensitized with cesium (cesiated photocathodes) have substantially higher sensitivities of response than non-cesiated photocathodes.
  • cesiated photocathodes have been found inadequate for certain applications.
  • photomultiplier tubes having cesiated photocathodes have been used for scintillation counting, in applications, such as, for example, geophysical exploration in which the ambient temperature of operation approaches 150C. At such temperatures, the cesiated photocathode appears to decompose and the expected useful life of the device is severely restricted.
  • FIG. 1 is a flow chart of the preferred embodiment of the novel method.
  • FIG. 2 is a' sectional view of a phototube having a photocathode made by themethod of FIG. 1.
  • FIG. 3 is a graph comparing the spectral response of the photocathode made by the present method.
  • FIG. 1 is a flow chart of the steps used for practicing a preferred embodiment of the novel method.
  • a phototube 26 shown in FIG. 2, is provided with an improved bialkali photocathode surface 28 having improved sensitivity and improved high temperature operating characteristics.
  • the tube 26 has a tubular glass wall section 30.
  • 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 1.9 inches.
  • the other end of the wall section 30 is closed by a stem 34 having a number of electrical lead-in pins 35.
  • a series of dynodes 36 are spaced two channels 38, 40 of tantalum foil containing,
  • the potassium channel 38 contains potassium chromate, ziroconium, and tungsten.
  • the sodium channel 40 contains sodium chromate, zirconium, and tungsten.
  • a resistance filament 42 situated near the faceplate has two antimony alloy beads 43 attached to it for evaporating antimony.
  • the channels 38, 40 and the tilament 42 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 44.
  • the electrode 44 is impressed with a voltage of between 50 and 150 volts positive with respect to the photocathode 28 through a lead 46 going from a lead-in pin 35 to the photocathode 28 and through lead 48, also from a lead-in pin 35, to the electrode 44.
  • 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 exhaust tubulation 50 in the stem and preferably maintained at a vacuum of 10 torr.
  • vacuums of 10 torr to 10 torr are considered suitable.
  • the tubulation leads directly to a titanium evaporation ion vacuum pump having a pumping speed of about 250 liters per second.
  • processing steps for preparing the photoemissive surface are as follows with ranges of parameters given in parentheses immediately after a preferred value:
  • the tube is baked for about 5 (3 to 6) hours at about 400C. to clean and degas the interior.
  • the filament 42 is heated and antimony is evaporated from the antimony leads 43 until the light transmission of the faceplate 32 is about percent (65 percent The transmission of the faceplate 32 before evaporation is defined as percent.
  • the tube 26 is placed in an oven which has been preheated to about'l90C. (C.200C.).
  • the channels 38, 40 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 C. 160C.-200C.
  • Potassium is evaporated on the antimony layer until maximum sensitivity is reached.
  • the maximum is generally about 1.5 (1-5) microamperes per lumen.
  • the oven temperature is increased to about 210 (200250)C. and the sodium channel 40 current adjusted so that sodium vapor will be released when the faceplate 32 reaches about 210 (200250)C.
  • Sodium is evaporated until a substantially maximum sensitivity is reached.
  • the maximum is generally about 35 (20-60) microamperes per lumen.
  • Antimony is evaporated until a maximum sensitivity is passed at about 40 (30-60) microamperes per lumen and sensitivity has decreased to a substantially fixed value between 30 and 50 percent of that maximum.
  • Antimony is evaporated until a maximum sensitivity is passed and sensitivity has decreased to a substantially fixed value between 30 and 50 percent of that maximum.
  • Antimony is evaporated until a maximum sensitivity is passed and sensitivity decreases to a substantially fixed value between 30 and 50 percent of that maximum.
  • Potassium is evaporated until the sensitivity passes a maximum and decreases to about 60 to 70 percent of that maximum.
  • the tube 26 is baked at 220C. (2 l250) until a new maximum sensitivity is reached.
  • the tube is slowly cooled at a rate of about 4 (2-10)C. per minute.
  • step 13 is repeated.
  • step 13 is re- I peated.
  • step 13 is repeated.
  • step 13 is repeated.
  • the tube 26 is slowly cooled to room temperature at a rate of about 4C. (2l0) per minute and removed from the oven. After the exhaust tubulation 47 is sealed off, the tube 26 is operative.
  • GENERAL CONSIDERATIONS Techniques for monitoring sensitivity and light transmission during processing as well as for evaporating photocathode materials are further described, for instance in the US. Pats. to A. H. Sommer and F. R. Hughes, referenced above, and also in [1.8. Pat. Nos. 2,914,690 to A. H. Sommer and 2,676,282 J. J. Polkosky.
  • Light transmission of the faceplate, for the purpose of monitoring the thickness of the antimony layer, is measured by conventional means. lts measurement is not critical.
  • Sensitivity of the evaporated layers is measured separately for visible light and blue light. It is desirable to be able to measure both visible and blue 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 and operated at approximately 2,854K. The sources are spaced apart a short distance from the faceplate. Interposed between one source and the faceplate is a glass light filter apssing primarily blue light. For instance, a Corning CS5-58 bandpass filter passing approximately percent at 380 nanometers wavelength, 40 percent at 400 nanometers and about 20 percent at about 440 nanometers is suitable.
  • the sensitivity of the photocathode to both visible and blue 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.
  • Maximum sensitivity is determined from the first derivative of the increasing sensitivity function.
  • the first derivative takes a zero value at the peak of a sensitivity curve.
  • a computer can be used to continually calculate the derivative of the sensitivity function, or a human operator can simply observe a plotted curve of the sensitivity and note when its tangent is horizontal to indicate a peak.
  • spurious peaks in the sensitivity which are of lower values than a later highest maximum peak. In order to discriminate these spurious peaks from the maximum it is necessary to continue evaporation until the sensitivity has fallen to a value of about percent of the sensitivity at the peak in question.
  • a reference herein to evaporation of an alkali metal to a substantially maximum sensitivity means an evaporation past the maximum to at least 15 percent of the sensitivity at the maximum. Excess alkali metal evaporated after a maximum is reached generally evaporates off again during subsequent baking.
  • the magnitudes of sensitivities tend to change. Wherever such changes are critical and require reevaporation to establish a fixed percentage of sensitivity relative to the maximum sensitivity achieved, the terminology specifies a substantially fixed percentage.
  • a sensitivity is considered substantially fixed whenever its magnitude remains relatively stable, within the ranges specified, over a period of 5 to 10 seconds.
  • the novel method results in a bialkali photocathode having improved high temperature operating characteristics and improved sensitivity over similar photocathodes processed by conventional methods.
  • the curves 52 and 54 in FIG. 3 represent the approximate response characteristics of two competing photocathodes made by present methods for high temperature operation and utilizing the same materials (Sb, Na, and K).
  • Curve 56 represents the approximate response characteristic of a photocathode made by .the novel method. It is seen that the sensitivity is considerably higher over the entire response region and extends as far as 700 nanometers. Moreover, photomultipliers utilizing the novel photocathodes have been found to maintain stable response characteristics even at temperatures approaching C.
  • novel photocathode is made by a series of evaporations, it is presently not possibleto 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.
  • Method of making a photocathode comprising in order:
  • step i cooling said substrate from the temperature at which the above step i is carried out, said cooling being at a rate of about 4C. per minute to a plurality of intermediate temperatures between said temperature and C.
  • step I is performed at the intermediate temperatures of: 200C., 190C, 180C., and 170C.
  • An electron emissive photocathode made by the method defined in claim 1.
  • An electron emissive photocathode made by the method defined in claim 4.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Formation Of Various Coating Films On Cathode Ray Tubes And Lamps (AREA)
  • Common Detailed Techniques For Electron Tubes Or Discharge Tubes (AREA)
  • Image-Pickup Tubes, Image-Amplification Tubes, And Storage Tubes (AREA)
US00378517A 1973-07-12 1973-07-12 Method of making a bialkali photocathode with improved sensitivity and high temperature operating characteristics Expired - Lifetime US3838304A (en)

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Application Number Priority Date Filing Date Title
US00378517A US3838304A (en) 1973-07-12 1973-07-12 Method of making a bialkali photocathode with improved sensitivity and high temperature operating characteristics
JP49080095A JPS5146582B2 (enrdf_load_stackoverflow) 1973-07-12 1974-07-11
DE19742433664 DE2433664C3 (de) 1973-07-12 1974-07-12 Verfahren zur Herstellung einer Fotokatode
GB3106674A GB1476213A (en) 1973-07-12 1974-07-12 Photocathodes

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US00378517A US3838304A (en) 1973-07-12 1973-07-12 Method of making a bialkali photocathode with improved sensitivity and high temperature operating characteristics

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JP (1) JPS5146582B2 (enrdf_load_stackoverflow)
GB (1) GB1476213A (enrdf_load_stackoverflow)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
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
US4306188A (en) * 1979-10-30 1981-12-15 Rca Corporation Photomultiplier tube having a photocurrent collector
US4376246A (en) * 1981-01-22 1983-03-08 Rca Corporation Shielded focusing electrode assembly for a photomultiplier tube
US4407871A (en) * 1980-03-25 1983-10-04 Ex-Cell-O Corporation Vacuum metallized dielectric substrates and method of making same
US4407857A (en) * 1981-06-30 1983-10-04 Rca Corporation Method for processing a lithium-sodium-antimony photocathode
US4431711A (en) * 1980-03-25 1984-02-14 Ex-Cell-O Corporation Vacuum metallizing a dielectric substrate with indium and products thereof
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
US4839511A (en) * 1988-01-29 1989-06-13 Board Of Regents, The U. Of Texas System Enhanced sensitivity photodetector having a multi-layered, sandwich-type construction
CN105140084A (zh) * 2015-07-24 2015-12-09 北方夜视技术股份有限公司 一种钠铯锑双碱光电阴极的制作方法

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS55112765A (en) * 1979-02-20 1980-08-30 Sabun Kogyosho:Kk Tip for barrel grinding
JPS59191251U (ja) * 1983-06-03 1984-12-19 株式会社東芝 研摩材
JPS60242960A (ja) * 1984-05-17 1985-12-02 Tipton Mfg Corp 多孔質樹脂メデイアおよびその製造方法
JPH0318128Y2 (enrdf_load_stackoverflow) * 1985-10-31 1991-04-17
JP5380258B2 (ja) * 2009-11-27 2014-01-08 学校法人光産業創成大学院大学 フォトカソードの製造方法

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3658400A (en) * 1970-03-02 1972-04-25 Rca Corp Method of making a multialkali photocathode with improved sensitivity to infrared light and a photocathode made thereby
US3753023A (en) * 1971-12-03 1973-08-14 Rca Corp Electron emissive device incorporating a secondary electron emitting material of antimony activated with potassium and cesium

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3658400A (en) * 1970-03-02 1972-04-25 Rca Corp Method of making a multialkali photocathode with improved sensitivity to infrared light and a photocathode made thereby
US3753023A (en) * 1971-12-03 1973-08-14 Rca Corp Electron emissive device incorporating a secondary electron emitting material of antimony activated with potassium and cesium

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
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
US4306188A (en) * 1979-10-30 1981-12-15 Rca Corporation Photomultiplier tube having a photocurrent collector
US4407871A (en) * 1980-03-25 1983-10-04 Ex-Cell-O Corporation Vacuum metallized dielectric substrates and method of making same
US4431711A (en) * 1980-03-25 1984-02-14 Ex-Cell-O Corporation Vacuum metallizing a dielectric substrate with indium and products thereof
US4376246A (en) * 1981-01-22 1983-03-08 Rca Corporation Shielded focusing electrode 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
US4839511A (en) * 1988-01-29 1989-06-13 Board Of Regents, The U. Of Texas System Enhanced sensitivity photodetector having a multi-layered, sandwich-type construction
CN105140084A (zh) * 2015-07-24 2015-12-09 北方夜视技术股份有限公司 一种钠铯锑双碱光电阴极的制作方法
CN105140084B (zh) * 2015-07-24 2017-04-19 北方夜视技术股份有限公司 一种钠铯锑双碱光电阴极的制作方法

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DE2433664B2 (de) 1976-05-06
GB1476213A (en) 1977-06-10
JPS5039870A (enrdf_load_stackoverflow) 1975-04-12
DE2433664A1 (de) 1975-01-30
JPS5146582B2 (enrdf_load_stackoverflow) 1976-12-09

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