CN111261489B - Photocathode for photomultiplier, preparation method and photomultiplier - Google Patents
Photocathode for photomultiplier, preparation method and photomultiplier Download PDFInfo
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- CN111261489B CN111261489B CN202010077422.4A CN202010077422A CN111261489B CN 111261489 B CN111261489 B CN 111261489B CN 202010077422 A CN202010077422 A CN 202010077422A CN 111261489 B CN111261489 B CN 111261489B
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- 238000002360 preparation method Methods 0.000 title claims abstract description 16
- 239000011521 glass Substances 0.000 claims abstract description 43
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims abstract description 27
- 229910052593 corundum Inorganic materials 0.000 claims abstract description 27
- 229910001845 yogo sapphire Inorganic materials 0.000 claims abstract description 27
- 239000000758 substrate Substances 0.000 claims abstract description 24
- 230000003287 optical effect Effects 0.000 claims abstract description 8
- 239000002178 crystalline material Substances 0.000 claims abstract description 5
- 238000001704 evaporation Methods 0.000 claims description 59
- 230000008020 evaporation Effects 0.000 claims description 43
- 229910052787 antimony Inorganic materials 0.000 claims description 42
- WATWJIUSRGPENY-UHFFFAOYSA-N antimony atom Chemical compound [Sb] WATWJIUSRGPENY-UHFFFAOYSA-N 0.000 claims description 42
- 239000010408 film Substances 0.000 claims description 42
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 claims description 39
- 229910052700 potassium Inorganic materials 0.000 claims description 36
- 239000011591 potassium Substances 0.000 claims description 36
- 238000002310 reflectometry Methods 0.000 claims description 26
- 238000000034 method Methods 0.000 claims description 23
- 239000002585 base Substances 0.000 claims description 22
- 229910052751 metal Inorganic materials 0.000 claims description 19
- 239000002184 metal Substances 0.000 claims description 19
- 238000004519 manufacturing process Methods 0.000 claims description 15
- 230000003647 oxidation Effects 0.000 claims description 14
- 238000007254 oxidation reaction Methods 0.000 claims description 14
- 238000012544 monitoring process Methods 0.000 claims description 13
- TVFDJXOCXUVLDH-UHFFFAOYSA-N caesium atom Chemical compound [Cs] TVFDJXOCXUVLDH-UHFFFAOYSA-N 0.000 claims description 12
- 238000007872 degassing Methods 0.000 claims description 12
- 238000000137 annealing Methods 0.000 claims description 10
- 239000003513 alkali Substances 0.000 claims description 9
- 229910052792 caesium Inorganic materials 0.000 claims description 9
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 8
- 238000010438 heat treatment Methods 0.000 claims description 8
- 230000001590 oxidative effect Effects 0.000 claims description 8
- 239000001301 oxygen Substances 0.000 claims description 8
- 229910052760 oxygen Inorganic materials 0.000 claims description 8
- 230000008569 process Effects 0.000 claims description 7
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 6
- 238000007740 vapor deposition Methods 0.000 claims description 6
- 230000008021 deposition Effects 0.000 claims description 5
- 238000011049 filling Methods 0.000 claims description 5
- 238000005086 pumping Methods 0.000 claims description 5
- 230000008859 change Effects 0.000 claims description 4
- 238000002425 crystallisation Methods 0.000 claims description 4
- 230000008025 crystallization Effects 0.000 claims description 4
- 238000007747 plating Methods 0.000 claims description 4
- 238000004321 preservation Methods 0.000 claims description 4
- 238000006243 chemical reaction Methods 0.000 claims description 3
- 229910052757 nitrogen Inorganic materials 0.000 claims description 3
- 229920006395 saturated elastomer Polymers 0.000 claims description 3
- 239000010409 thin film Substances 0.000 claims description 2
- 230000000694 effects Effects 0.000 abstract description 5
- 239000013589 supplement Substances 0.000 abstract description 3
- 238000002834 transmittance Methods 0.000 description 6
- 239000013307 optical fiber Substances 0.000 description 3
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- TUOVKSNRKKDMIK-UHFFFAOYSA-N [O].[Ag].[Cs] Chemical compound [O].[Ag].[Cs] TUOVKSNRKKDMIK-UHFFFAOYSA-N 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- NSXHMNIAFHXYSD-UHFFFAOYSA-N cesium silver oxygen(2-) Chemical compound [O--].[Ag+].[Cs+] NSXHMNIAFHXYSD-UHFFFAOYSA-N 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 239000011365 complex material Substances 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 230000003595 spectral effect Effects 0.000 description 1
- 230000009469 supplementation Effects 0.000 description 1
- 238000001429 visible spectrum Methods 0.000 description 1
Images
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J43/00—Secondary-emission tubes; Electron-multiplier tubes
- H01J43/04—Electron multipliers
- H01J43/06—Electrode arrangements
- H01J43/08—Cathode arrangements
-
- 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
- H01J1/34—Photo-emissive cathodes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
- H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
- H01J29/10—Screens on or from which an image or pattern is formed, picked up, converted or stored
- H01J29/36—Photoelectric screens; Charge-storage screens
- H01J29/38—Photoelectric screens; Charge-storage screens not using charge storage, e.g. photo-emissive screen, extended cathode
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J40/00—Photoelectric discharge tubes not involving the ionisation of a gas
- H01J40/02—Details
- H01J40/04—Electrodes
- H01J40/06—Photo-emissive cathodes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J43/00—Secondary-emission tubes; Electron-multiplier tubes
- H01J43/04—Electron multipliers
-
- 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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- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Formation Of Various Coating Films On Cathode Ray Tubes And Lamps (AREA)
Abstract
The invention relates to the technical field of photomultiplier tubes, and provides a photocathode for a photomultiplier tube, a preparation method and the photomultiplier tube. Preparing a basal layer on the inner side surface of a glass optical window of the photomultiplier, wherein the basal layer is made of Al2O3Forming a crystalline material of (a); a bi-alkaline photocathode is prepared on a base layer, wherein the base layer is in contact with both the bi-alkaline photocathode. Thus, the present invention employs Al in the photocathode2O3The basal layer is used as an antireflection film, so that the probability of light incidence to the photocathode is effectively increased, and the quantum efficiency of the photocathode is improved; at the same time, Al2O3The substrate layer has certain conductivity, and can rapidly supplement electrons of the photocathode which are lacked due to the photoelectric effect, so that the quantum efficiency is further improved.
Description
Technical Field
The invention relates to the technical field of photomultiplier tubes, in particular to a photocathode for a photomultiplier tube and a preparation method thereof.
Background
The photoelectric cathode converts an optical signal into an electric signal by utilizing an external photoelectric effect, the development of the photoelectric cathode is in a long process, the external photoelectric effect is discovered for the first time by Hertz in 1887 in electromagnetic wave experiments, and the phenomenon is explained by using a quantum theory for the first time by Einstein in 1905. The first practical photocathode, cesium silver oxide photocathode, was discovered in 1929 and is sensitive to both the visible spectrum and the near infrared, but the quantum efficiency of such photocathode is not high. With the advent of silver cesium oxide cathodes, research on photocathodes has focused on the search for other complex materials with higher quantum efficiency and different spectral response characteristics.
The quantum efficiency is an important characteristic of photocathodes, and is always the focus of research of researchers in various countries, and the quantum efficiency of photocathodes has a great relationship with the structure and components thereof, and the quantum efficiency of photocathodes is influenced by the transmittance, the electron supplementation mode and the like of transmissive photocathodes.
Disclosure of Invention
In view of the drawbacks and deficiencies of the prior art, a first aspect of the present invention provides a method for preparing a photocathode for a photomultiplier, comprising the steps of:
preparing a basal layer on the inner side surface of a glass optical window of the photomultiplier, wherein the basal layer is made of Al2O3Forming a crystalline material of (a);
a bi-alkaline photocathode is prepared on a base layer, wherein the base layer is in contact with both the bi-alkaline photocathode.
In a further embodiment, the preparing of the base layer comprises:
at a certain temperature, Al is firstly evaporated on the glass light windowForming a metal film, introducing oxygen, performing glow discharge, and oxidizing to Al2O3A base layer.
In a further embodiment, the thickness of the base layer is monitored by reflectivity during deposition of the base layer.
In a further embodiment, the preparing of the base layer comprises:
and 4, step 4: repeating the step 2 and the step 3 to prepare Al2O3The basal layer reaches a certain thickness;
and 5: raising the temperature, for the prepared Al2O3And carrying out high-temperature annealing crystallization treatment on the substrate layer.
In a further embodiment, the deposition temperature of the Al metal film is 300-400 ℃.
In a further embodiment, in step 2-3, the oxidation time is 5-20 min/time, and the oxidation is stopped when the sum of the reflectivity reduction ratios reaches 20% -50% by reflectivity monitoring.
In a further embodiment, in step 5, Al is added2O3The annealing temperature of the substrate layer is 500-700 ℃, and the annealing time is 1-5 hours.
In a further embodiment, the preparation of the double-alkali photocathode comprises:
evaporating deposited Al2O3The glass housing of the substrate layer is mounted in a bell-type vacuum system,
extending a cathode assembly comprising a potassium source, a cesium source and antimony balls into the glass shell, and adjusting the position of the cathode assembly to enable the antimony balls to be positioned below the equatorial plane of the glass shell;
uniformly increasing the temperature at the speed of 2 ℃/min to reach the final baking degassing temperature, wherein the baking degassing temperature is more than 300 ℃; after reaching the baking degassing temperature, keeping the temperature unchanged and preserving the heat for three hours;
and when the temperature is reduced to below 200 ℃ after the heat preservation is finished, the cathode is manufactured, and the method specifically comprises the following steps:
firstly, adjusting the evaporation current of a potassium source, a cesium source and an antimony ball to be 3.5A, 2.0A and 0.5A, increasing the evaporation current of potassium at the rate of 0.2A/min until the evaporation current reaches 5.5A, and degassing; when the potassium evaporation current reaches 5.5A, the photocurrent curve of the photocurrent monitoring system begins to rise; then increasing the potassium evaporation current at the rate of 0.2A/10min, manufacturing a potassium layer, and ending the evaporation process of the potassium layer when the potassium content in the glass shell tends to be saturated until the photocurrent reaches a peak value and keeps constant;
keeping the potassium evaporation current unchanged at the moment, then increasing the antimony evaporation current at the rate of 0.2A/min until the reflectivity begins to decrease, keeping the current of the antimony balls at 1.7A at the moment, and keeping the current of the antimony balls unchanged for 3 min; then, the current of the antimony ball is increased by 0.5A, and the current is maintained for 5 min; then, increasing the current of an antimony ball by 0.3A, maintaining the current of an antimony source until the reflectivity begins to increase, and then maintaining the current of evaporation for 10min to obtain an antimony film;
closing the current of the antimony source;
ending the vapor deposition of the antimony film;
increasing the potassium evaporation current at 0.2A/10min to react the generated potassium layer with the vapor-deposited antimony film to form K3Sb；
And after the reaction of the potassium layer and the antimony film is finished, carrying out evaporation plating of the cesium source, wherein: the initial evaporation current is 4.5A, the evaporation current is increased to 7A according to 0.1A/min, the photocurrent is continuously increased, after 1 hour, the reflectivity is increased to 1.8 times of the initial value, namely, the cesium atoms fully replace potassium atoms from the surface of the cathode to form K2A CsSb photocathode structure;
and finishing the preparation process of the double-alkali photocathode.
According to a second aspect of the present invention, there is also provided a photocathode produced according to the foregoing method for producing a photocathode for a photomultiplier.
According to the scheme, the aluminum oxide base layer is prepared on the photocathode of the photomultiplier, and the double-alkali photocathode is prepared on the base layer, so that the effective light transmittance is enhanced, and the quantum efficiency of the photocathode is improved; meanwhile, the aluminum oxide substrate layer can quickly supplement electrons which are lacked by the photoelectric effect of the traditional photocathode, so that the quantum efficiency of the photocathode is improved. The quantum efficiency of the photomultiplier prepared by the invention is improved from 20% to more than 30% by adopting the photocathode.
Drawings
FIG. 1 is a schematic structural diagram of a photocathode prepared according to the present invention.
FIG. 2 shows Al of the present invention2O3The flow chart of the preparation method of the substrate layer is shown.
FIG. 3 shows Al of the present invention2O3The substrate layer manufacturing equipment is schematically shown in the structural diagram.
FIG. 4 is a flow chart of the method for preparing the double-alkali photocathode of the present invention.
Detailed Description
In order to better understand the technical content of the present invention, specific embodiments are described below with reference to the accompanying drawings.
In this disclosure, aspects of the present invention are described with reference to the accompanying drawings, in which a number of illustrative embodiments are shown. Embodiments of the present disclosure are not necessarily intended to include all aspects of the invention. It should be appreciated that the various concepts and embodiments described above, as well as those described in greater detail below, may be implemented in any of numerous ways, as the disclosed concepts and embodiments are not limited to any one implementation. In addition, some aspects of the present disclosure may be used alone, or in any suitable combination with other aspects of the present disclosure.
According to the embodiment of the invention, a method for improving the quantum efficiency of a photocathode is provided, namely, a novel photocathode of a photomultiplier is prepared, and particularly, a method for evaporating a layer of low-background high-transmittance glass shell on the inner surface of an optical window of the high-transmittance glass shell (such as a low-background high-transmittance glass shell)Layer of aluminum oxide (Al)2O3Crystalline material) and then a double-alkali cathode is vapor-plated on the substrate layer to prepare the photocathode with high quantum efficiency. The quantum efficiency of the photomultiplier using the photocathode is improved from 20% to more than 30%.
In combination with the illustration, the embodiment of the invention discloses a preparation method of a photocathode for a photomultiplier, which comprises the following steps: first, a base layer 20 is prepared on the inner surface of the glass window 10 of the photomultiplier tube, the base layer being made of Al2O3Forming a crystalline material of (a); a dibasic photocathode 30 is then prepared on the base layer, where the base layer is in contact with both the dibasic photocathode.
Thus, due to Al2O3The existence of the basal layer as an antireflection film effectively increases the probability of light incidence to the photocathode, thereby improving the quantum efficiency of the photocathode; at the same time, Al2O3The substrate layer has certain conductivity, and can rapidly supplement electrons of the photocathode which are lacked due to the photoelectric effect, so that the quantum efficiency is further improved.
In alternative embodiments, Al2O3The preparation of the substrate layer comprises:
at a certain temperature, evaporating Al on a glass light window to form a metal film, introducing oxygen, performing glow discharge, and oxidizing to Al2O3A base layer.
In a further embodiment, the thickness of the base layer is monitored by reflectivity during deposition of the base layer.
With reference to the illustrated examples, the preparation of the substrate layer in a preferred embodiment includes:
and 4, step 4: repeating the step 2 and the step 3 to prepare Al2O3The basal layer reaches a certain thickness;
and 5: raising the temperature, for the prepared Al2O3And carrying out high-temperature annealing crystallization treatment on the substrate layer.
Wherein the vapor deposition temperature of the Al metal film is 300-400 ℃.
In the step 2-3, the oxidation time is 5-20 min/time, and the oxidation is stopped when the sum of the reflectivity reduction ratios reaches 20% -50% through the reflectivity monitoring.
In step 5, for Al2O3The annealing temperature of the substrate layer is 500-700 ℃, and the annealing time is 1-5 hours.
FIG. 3 schematically shows Al2O3A system for base layer preparation. The preparation system as shown in the figure comprises a reflectivity film thickness monitoring system 1, a coating clamp 3, a table top 4, an optical fiber 5, a bell jar 6, a heating device 7, a flowmeter 8, a vacuum pumping system 9 and a pipeline 10.
The bell jar 6 is installed in a manner that it can be lifted up and down with respect to the table top 1. After the bell jar 6 is mounted and fixed on the table-board 1, a cavity is formed inside to form an implementation space of vapor deposition. The bottom of the cavity is communicated with a pipeline 10 and communicated with a vacuum-pumping system 9 through the pipeline 10. The glass housing 2 is disposed in a closed cavity formed by the bell jar by a jig or a fixing mechanism and is communicated with the pipe 10.
The glass housing 2 as shown is an ellipsoidal high-permeability glass housing (also referred to as a glass container) with a narrowed connection at its lower portion. In other embodiments, other shapes of glass housings are possible.
An optical fiber 5 is arranged above the glass shell 2, and the optical fiber 5 passes through the bell jar to be connected with an external reflectivity film thickness monitoring system 1 and is used for monitoring the film thickness through the reflectivity change in the evaporation process.
In the inner wall of the bell jar 6, a heating device 7, such as a heating wire or a thermocouple, is further arranged for heating the internal environment of the bell jar, so as to realize temperature regulation and control in the process. The flow meter 8 is provided in the line 10 and performs gas flow control.
In one exemplary implementation, with reference to the examples shown in fig. 2 and 3, the glass housing is first evacuated to a vacuum of 10 degrees f-3Under the condition of (1), starting heating; raising the temperature to 300-400 ℃ at the speed of 10 ℃/min, and baking and preserving the heat after the temperature is reached, wherein the time duration is more than 1 hour; recording the reflectivity value at the moment after the constant condition of heat preservation (more than 1 hour to 3 hours) is achieved; rapidly increasing the current of an evaporated Al source to enable an Al metal film to be rapidly evaporated, monitoring the reflectivity, and stopping evaporation when the reflectivity is reduced by 2-5%; filling a certain amount of high-purity oxygen into the glass shell to maintain the vacuum degree at 1Pa-100Pa, oxidizing for 5-20min, recording the reflectivity value, stopping filling oxygen, and continuing to vacuumize;
repeating the evaporation and oxidation processes of the Al metal film until the sum of the reflectivity reduction ratios reaches 20-50 percent, and finishing the oxidation.
At this time, due to the evaporated Al2O3The layer is still in an amorphous state, and needs to be annealed for crystallization treatment, the temperature of the bell jar is raised to 500-700 ℃, and evaporated Al is treated2O3The layer is subjected to high-temperature baking annealing treatment for 1-5 hours, so that Al is formed2O3The layer is transformed into a crystalline state. Thus, crystalline Al is obtained2O3The basal layer has less dislocation and interface, and improves the light transmittance, thereby increasing the quantum efficiency.
Al2O3 is used as an antireflection film for a photocathode in the present invention because of its low refractive index and wide light transmission range. Al vapor deposition by traditional resistance evaporation method2O3The film is mostly formed by evaporating an Al film and then oxidizing the Al film into Al by an oxidation mode2O3A film. However, in the actual production process of the photomultiplier, it has been found that the intensity of glow is weakened as the thickness of the Al thin film increases, and it is difficult to oxidize the Al inside to Al2O3. In this way, in order to make the deposited Al completeReact to Al2O3The invention adopts a mode of evaporating an Al metal film for multiple times, and carries out the Al oxidation by multiple times of glow discharge2O3And preparing the substrate layer, so that a uniform and crystalline substrate layer is formed on the surface of the glass light window.
In a further embodiment, the preparation of the double-alkali photocathode comprises:
evaporating deposited Al2O3The glass housing of the substrate layer is mounted in a bell-type vacuum system,
extending a cathode assembly comprising a potassium source, a cesium source and antimony balls into the glass shell, and adjusting the position of the cathode assembly to enable the antimony balls to be positioned below the equatorial plane of the glass shell;
uniformly increasing the temperature at the speed of 2 ℃/min to reach the final baking degassing temperature, wherein the baking degassing temperature is more than 300 ℃; after reaching the baking degassing temperature, keeping the temperature unchanged and preserving the heat for three hours;
and when the temperature is reduced to below 200 ℃ after the heat preservation is finished, the cathode is manufactured, and the method specifically comprises the following steps:
firstly, adjusting the evaporation current of a potassium source, a cesium source and an antimony ball to be 3.5A, 2.0A and 0.5A, increasing the evaporation current of potassium at the rate of 0.2A/min until the evaporation current reaches 5.5A, and degassing; when the potassium evaporation current reaches 5.5A, the photocurrent curve of the photocurrent monitoring system begins to rise; then increasing the potassium evaporation current at the rate of 0.2A/10min, manufacturing a potassium layer, and ending the evaporation process of the potassium layer when the potassium content in the glass shell tends to be saturated until the photocurrent reaches a peak value and keeps constant;
keeping the potassium evaporation current unchanged at the moment, then increasing the antimony evaporation current at the rate of 0.2A/min until the reflectivity begins to decrease, keeping the current of the antimony balls at 1.7A at the moment, and keeping the current of the antimony balls unchanged for 3 min; then, the current of the antimony ball is increased by 0.5A, and the current is maintained for 5 min; then, increasing the current of an antimony ball by 0.3A, maintaining the current of an antimony source until the reflectivity begins to increase, and then maintaining the current of evaporation for 10min to obtain an antimony film;
closing the current of the antimony source;
ending the vapor deposition of the antimony film;
increasing the potassium evaporation current at 0.2A/10min to react the generated potassium layer with the vapor-deposited antimony film to form K3Sb；
And after the reaction of the potassium layer and the antimony film is finished, carrying out evaporation plating of the cesium source, wherein: the initial evaporation current is 4.5A, the evaporation current is increased to 7A according to 0.1A/min, the photocurrent is continuously increased, after 1 hour, the reflectivity is increased to 1.8 times of the initial value, namely, the cesium atoms fully replace potassium atoms from the surface of the cathode to form K2A CsSb photocathode structure;
and finishing the preparation process of the double-alkali photocathode.
According to a second aspect of the present invention, there is also provided a photocathode prepared according to the foregoing method for preparing a photocathode for a photomultiplier, having a structural composition as shown in fig. 1.
The invention adopts non-evaporated Al in the implementation process2O3Method of the substrate layer 3 sample tubes were made (as an antireflection film and photocathode prepared on this basis and photomultiplier assembled under the same conditions, as in sample groups 2 and 3) as sample group 1; 3 sample tubes are manufactured by adopting a traditional one-time evaporation Al metal film and then an oxidation method to be used as a sample group 2; and 3 sample tubes are manufactured as a sample group 3 by adopting the method of evaporating an Al metal film for multiple times and oxidizing for multiple times. And respectively testing the quantum efficiency of the three groups of samples.
The results of the control tests are shown in the following table.
Visible, vapor deposited Al2O3The basal layer can obviously improve the quantum efficiency of the sample, and the quantum efficiency of the sample prepared by the method for evaporating the Al metal film for multiple times and oxidizing the Al metal film for multiple times is obviously higher than that of the sample prepared by the traditional one-time evaporating Al film. The invention adopts the method of evaporating and plating Al film for multiple times and oxidizing for multiple times2O3The substrate layer can be used as a photocathode, and the prepared photomultiplier tubeThe quantum efficiency is remarkably improved.
Although the present invention has been described with reference to the preferred embodiments, it is not intended to be limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, the protection scope of the present invention should be determined by the appended claims.
Claims (10)
1. A preparation method of a photocathode for a photomultiplier is characterized by comprising the following steps:
preparing a basal layer on the inner side surface of a glass optical window of the photomultiplier, wherein the basal layer is made of Al2O3Forming a crystalline material of (a);
a bi-alkaline photocathode is prepared on a base layer, wherein the base layer is in contact with both the bi-alkaline photocathode.
2. The method of producing a photocathode for a photomultiplier according to claim 1, wherein the production of the base layer comprises:
at a certain temperature, evaporating Al on a glass light window to form a metal film, introducing oxygen, performing glow discharge, and oxidizing to Al2O3A base layer.
3. The method for producing a photocathode for a photomultiplier according to claim 2, wherein the thickness of the base layer is monitored by reflectance during deposition of the base layer.
4. The method of producing a photocathode for a photomultiplier according to claim 2, wherein the production of the base layer comprises:
step 1, carrying out vacuum pumping and heating treatment on a photomultiplier glass shell;
step 2, evaporating an Al metal film on the inner side surface of a glass optical window of the glass shell of the photomultiplier at a certain temperature;
step 3, filling oxygen into the glass shell, performing glow discharge oxidation treatment on the evaporated Al metal film under the protection of nitrogen, and monitoring the thickness change of the substrate layer through the reflectivity;
and 4, step 4: repeating the step 2 and the step 3 to prepare Al2O3The basal layer reaches a certain thickness;
and 5: raising the temperature, for the prepared Al2O3And carrying out high-temperature annealing crystallization treatment on the substrate layer.
5. The method for producing a photocathode for a photomultiplier according to claim 4, wherein the deposition temperature of the Al metal thin film in step 2 is 300 ℃ to 400 ℃.
6. The method for producing a photocathode for a photomultiplier according to claim 4, wherein in the step 2 to 3, the oxidation time is 5 to 20 min/time, and the oxidation is stopped when the sum of the ratios of the reflectance drops to 20% to 50% by reflectance monitoring.
7. The method for producing a photocathode for a photomultiplier according to claim 4, wherein in step 5, Al is added2O3The annealing temperature of the substrate layer is 500-700 ℃, and the annealing time is 1-5 hours.
8. The method for producing a photocathode for a photomultiplier according to any one of claims 1 to 7, wherein the production of the double-alkali photocathode comprises:
evaporating deposited Al2O3The glass housing of the substrate layer is mounted in a bell-type vacuum system,
extending a cathode assembly comprising a potassium source, a cesium source and antimony balls into the glass shell, and adjusting the position of the cathode assembly to enable the antimony balls to be positioned below the equatorial plane of the glass shell;
uniformly increasing the temperature at the speed of 2 ℃/min to reach the final baking degassing temperature, wherein the baking degassing temperature is more than 300 ℃; after reaching the baking degassing temperature, keeping the temperature unchanged and preserving the heat for three hours;
and when the temperature is reduced to below 200 ℃ after the heat preservation is finished, the cathode is manufactured, and the method specifically comprises the following steps:
firstly, adjusting the evaporation current of a potassium source, a cesium source and an antimony ball to be 3.5A, 2.0A and 0.5A, increasing the evaporation current of potassium at the rate of 0.2A/min until the evaporation current reaches 5.5A, and degassing; when the potassium evaporation current reaches 5.5A, the photocurrent curve of the photocurrent monitoring system begins to rise; then increasing the potassium evaporation current at the rate of 0.2A/10min, manufacturing a potassium layer, and ending the evaporation process of the potassium layer when the potassium content in the glass shell tends to be saturated until the photocurrent reaches a peak value and keeps constant;
keeping the potassium evaporation current unchanged at the moment, then increasing the antimony evaporation current at the rate of 0.2A/min until the reflectivity begins to decrease, keeping the current of the antimony balls at 1.7A at the moment, and keeping the current of the antimony balls unchanged for 3 min; then, the current of the antimony ball is increased by 0.5A, and the current is maintained for 5 min; then, increasing the current of an antimony ball by 0.3A, maintaining the current of an antimony source until the reflectivity begins to increase, and then maintaining the current of evaporation for 10min to obtain an antimony film;
closing the current of the antimony source;
ending the vapor deposition of the antimony film;
increasing the potassium evaporation current at 0.2A/10min to react the generated potassium layer with the vapor-deposited antimony film to form K3Sb；
And after the reaction of the potassium layer and the antimony film is finished, carrying out evaporation plating of the cesium source, wherein: the initial evaporation current is 4.5A, the evaporation current is increased to 7A according to 0.1A/min, the photocurrent continuously rises, and after 1 hour, the reflectivity rises to 1.8 times of the initial value, namely, the cesium atoms fully replace potassium atoms from the surface of the cathode to form K2A CsSb photocathode structure;
and finishing the preparation process of the double-alkali photocathode.
9. A photocathode produced by the method for producing a photocathode for a photomultiplier according to any one of claims 1 to 8.
10. A photomultiplier tube having the photocathode of claim 9.
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