A large-area photomultiplier tube with a segmented pressure-applying support system

Abstract

The present invention discloses a large-area photomultiplier tube with a segmented pressure application support system, which includes a vacuum glass container and a photocathode, an electron multiplication system, an anode, a segmented pressure application support system, and a power supply electrode contained therein. The anode passes through the vacuum glass container and is connected to an external signal processing circuit, and the power supply electrode passes through the vacuum glass container and is connected to an external power supply circuit. The vacuum glass container is spherical or nearly spherical; the photocathode is uniformly covered on the inner surface of the upper hemisphere of the vacuum glass container; the support system is placed at the handle opening of the vacuum glass container; the electron multiplication system is placed at the top opening of the segmented pressure application support system; the anode is placed parallel to the rear of the electron multiplication system. The photomultiplier tube of the present invention has high time resolution, high photoelectron collection efficiency, high photocathode coverage rate, and strong anti-geomagnetic field interference ability.

Description

Technical Field

[0001] The present invention belongs to the technical field of vacuum photodetectors, and particularly relates to a large-area photomultiplier tube with a segmented pressure application support system. Background Art

[0002] A photomultiplier tube is a vacuum photodetector device that is based on the external photoelectron emission effect, the secondary electron emission effect, and electron optics theory, and can convert a weak optical signal into photoelectrons and obtain a multiplication effect. A large-area photomultiplier tube is a type of photomultiplier tube. Due to its large photocathode coverage area and photon counting ability, it is widely used in high-energy physics detection experiments such as large-scale neutrino and cosmic ray detections.

[0003] Traditional large-area photomultiplier tubes are of the dynode type, such as Figure 1As shown in the figure, the vacuum glass container adopts an ellipsoidal or nearly spherical glass shell. The photocathode covers less than half of the inner surface area of the spherical shell. A dynode electron multiplier system is placed at the center of the bottom. The number of dynodes is generally 8 - 16, and an anode is set at its end. When light irradiates the vacuum glass container, incident photons will generate photoelectrons through the external photoelectric effect at the photocathode. The photoelectrons are collected by the dynodes under the action of the internal electric field and are multiplied step by step under the action of the electric field force. Finally, the multiplied electrons are collected by the anode and output as signals. Literature: Hirota S, Nishimura Y, Suda Y, et al. New large aperture, hybrid photo-detector and photo multiplier tube for a gigantic water Cherenkov ring imaging detector[J]. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2014, 766: 152 - 155 involves a typical traditional large-area dynode type photomultiplier tube produced by Hamamatsu Corporation of Japan, with excellent performance: the collection efficiency reaches 90%, and the transit time spread (time resolution) is 2.7 ns. Unfortunately, its shape is an ellipsoid with a major axis of 508 mm, and the diameter of the photocathode is only 460 mm. The photocathode only covers a part of the upper hemisphere area. If it is placed in a detector to form an array, due to the limitation of the major axis of the ellipsoid, the coverage rate of the photocathode is less than 80%, resulting in a waste of the detection space. In addition, literature: Liao D H, Liu H B, Zhou Y X, et al. Study of TTS for a 20-inch dynode PMT[J]. Chinese Physics C, 2017, 41(7): 076001 reported the anti-geomagnetic field interference ability of this photomultiplier tube product: the transit time spread of the non-shielded (affected by the geomagnetic field) sample tube can reach 5 times that of the shielded sample tube, and the anti-geomagnetic field interference ability is weak.

[0004] The new large-area microchannel plate type photomultiplier tube (NNVT, Photomultiplier tubes, http: / / www.nvt.com.cn / art / 2020 / 3 / 23 / art_1235_25349.html) is produced by North Yashi Technology Co., Ltd. of China Ordnance Group. As Figure 2As shown in the figure, the photomultiplier tube has an ellipsoidal vacuum glass container; two microchannel plate assemblies are used to replace the traditional dynode electron multiplication system, and they are placed at the mouth of the glass handle in a central sunk manner. Compared with the dynode-type photomultiplier tube of the same size above, the collection efficiency of this large-area microchannel plate-type photomultiplier tube has been increased to 100%. The disadvantages are that the transit time dispersion is relatively large, reaching 15 ns; the major axis of the ellipsoidal shell is 508 mm, the diameter of the photocathode is 460 mm, and the coverage rate of the photocathode is not high; in addition, the ability to resist the interference of the geomagnetic field is not strong either. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a large-area photomultiplier tube with a segmented pressure-supplying support system aiming at the deficiencies of the above-mentioned existing technologies, which has high time resolution, high photoelectron collection efficiency, high photocathode coverage rate and strong ability to resist the interference of the geomagnetic field.

[0006] To achieve the above technical purpose, the technical solution adopted by the present invention is as follows:

[0007] A large-area photomultiplier tube with a segmented pressure-supplying support system, comprising a vacuum glass container, a photocathode for receiving light illumination and generating photoelectrons, an electron multiplication system for collecting the photoelectrons emitted from the photocathode and generating multiplied electrons, an anode for collecting the multiplied electrons output by the electron multiplication system, a segmented pressure-supplying support system for supporting the electron multiplication system and the anode and accelerating and focusing the photoelectrons emitted from the photocathode, and a power supply electrode for supplying power to the photocathode, the electron multiplication system, the anode and the segmented pressure-supplying support system;

[0008] The photocathode, the electron multiplication system, the anode and the segmented pressure-supplying support system are placed inside the vacuum glass container;

[0009] The anode is connected to an external signal processing circuit through a signal lead wire passing through the vacuum glass container, the power supply electrode is connected to an external power supply circuit through a power line passing through the vacuum glass container, and the vacuum glass container is spherical or nearly spherical;

[0010] The photocathode uniformly covers the inner surface of the upper hemisphere of the vacuum glass container, and the coverage diameter of the photocathode is equal to the diameter of the vacuum glass container;

[0011] The support system is placed at the mouth of the handle of the vacuum glass container;

[0012] The electron multiplication system is placed at the top opening of the segmented pressure-supplying support system;

[0013] The anode is placed parallel to the rear of the electron multiplication system, and its area is greater than or equal to the area of the output port of the electron multiplication system.

[0014] To optimize the above technical solution, the specific measures taken also include:

[0015] The main body of the above-mentioned segmented pressure application type support system is a tapered ceramic barrel with a narrower upper part and a wider lower part, and openings at both the upper and lower ends.

[0016] The surface of the above-mentioned tapered ceramic barrel is covered with a multi-stage segmented pressure application type electrode. The taper is determined according to the curvature of the photocathode, and in combination with the voltage of the segmented pressure application type electrode, the paths and the electric field distributions along the way that the photoelectrons generated at various positions of the photocathode reach the electron multiplication system are the same.

[0017] The above-mentioned segmented pressure application type electrode includes two or more stages, with a certain distance between each stage, and can be pressurized independently.

[0018] The diameter of the upper opening of the above-mentioned tapered ceramic barrel is less than or equal to the diameter of the electron multiplication system, the diameter of the lower opening does not exceed the diameter of the handle opening of the vacuum glass container, and the height is not less than the total thickness of the electron multiplication system and the anode.

[0019] The upper edge of the above-mentioned tapered ceramic barrel is not lower than the handle opening of the vacuum glass container.

[0020] The above-mentioned electron multiplication system is a dynode electron multiplication system or a multi-slice microchannel plate assembly.

[0021] The above-mentioned segmented pressure application type support system, electron multiplication system and anode are coaxial with the center of the photocathode.

[0022] The present invention has the following beneficial effects:

[0023] The present invention evenly covers the photocathode on the inner surface of the upper hemisphere of the vacuum glass container. The coverage diameter of the photocathode is equal to the diameter of the vacuum glass container. After placing it in the detector to form an array, the photocathode coverage rate is effectively improved;

[0024] By using the design of the segmented pressure application type support system, the main body of the support system is a tapered ceramic barrel with a narrower upper part and a wider lower part, and openings at both the upper and lower ends. The surface of the ceramic barrel is covered with a segmented electrode of two or more stages. There is a certain distance between each electrode and can be pressurized independently. The electron multiplication system is placed at the top opening of the support system. Under the appropriate pressure matching between the support system and the electron multiplication system, effective focusing and collection of photoelectrons to the electron multiplication system can be achieved;

[0025] The distance between the electron multiplication system and the photocathode, the taper of the support system and the voltage configuration are reasonably designed. The linear distances from the electron multiplication system to each latitude of the photocathode are basically the same; the taper of the segmented pressure application type support system is determined according to the curvature of the photocathode, and in combination with the appropriate voltage of the segmented electrode, the paths and the electric field distributions along the way that the photoelectrons generated at various positions of the photocathode reach the electron multiplication system are basically the same, so as to ensure the minimum transit time spread and improve the time resolution;

[0026] By designing the placement position of the support system at a relatively high level, the placement height of the support system should not be too low, and its upper edge should not be lower than the handle opening of the vacuum glass container, so that the movement path of the photoelectrons from the photocathode to the electron multiplication system is shorter and the magnetic field interference they receive is smaller, enabling this photomultiplier tube to have strong anti-geomagnetic field interference ability. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a schematic structural diagram of a large-area dynode photomultiplier tube in the conventional technology;

[0028] Figure 2 is a schematic structural diagram of a new large-area microchannel plate photomultiplier tube;

[0029] Figure 3 is a schematic structural diagram of an embodiment of the photomultiplier tube of the present invention;

[0030] Figure 4 is a schematic diagram of the electric field simulation result of the photomultiplier tube of the present invention.

[0031] Figures 1-4 The reference numerals in are: 1, vacuum glass container; 2, photocathode; 3, dynode electron multiplication system; 4, anode; 5, incident photon; 6, photoelectron; 7, microchannel plate assembly; 8, segmented pressure application support system; 81, primary segmented electrode; 82, secondary segmented electrode; 83, final-stage segmented electrode; 9, power supply electrode and signal lead-out wire. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0033] A large-area photomultiplier tube based on a segmented pressure application support system, as Figure 3 shown, mainly includes a vacuum glass container 1, a photocathode 2 covering the inside of the vacuum glass container 1, an electron multiplication system, an anode 4, a segmented pressure application support system 8, and a power supply electrode and signal lead-out wire 9 placed in the vacuum glass container 1.

[0034] The photocathode 2 is used to receive light illumination and generate photoelectrons 6;

[0035] The electron multiplication system is used to collect the photoelectrons 6 emitted from the photocathode 2 and generate multiplied electrons;

[0036] The segmented pressure application support system 8 is used to support the electron multiplication system and the anode 4 and accelerate and focus the photoelectrons 6 emitted from the photocathode 2; the anode 4 is used to collect the multiplied electrons output by the electron multiplication system, and the anode 4 is placed parallel to the rear of the electron multiplication system, and its area is greater than or equal to the area of the output port of the electron multiplication system;

[0037] The power supply electrode is used to supply power to the photocathode 2, the electron multiplication system, the anode 4, and the segmented pressure support system 8;

[0038] The vacuum glass container 1 is spherical or nearly spherical, and the specific shape depends on the requirements for the transit time dispersion of the photoelectrons 6 in the project. Here, an ellipsoidal vacuum transparent container is used to describe the present invention in detail, but it does not limit the protection scope of the present invention.

[0039] The photocathode 2 is covered on the inner surface of the upper hemisphere of the ellipsoidal vacuum glass container 1. The covering diameter of the photocathode 2 is equal to the diameter of the vacuum glass container 1. When this photomultiplier tube is placed in a detector to form an array, the distance between the photocathodes 2 of adjacent tubes is closer, and the cathode coverage rate can be improved to a certain extent.

[0040] The segmented pressure support system 8 is coaxially placed with the center of the photocathode at the handle opening of the glass container directly below the photocathode 2. The placement height should not be too low. In this embodiment, the upper edge of the segmented pressure support system 8 is higher than the handle opening of the vacuum glass container 1, so that the movement path of the photoelectrons 6 from the photocathode to the electron multiplication system is shorter and the magnetic field interference received is smaller.

[0041] The main body of the segmented pressure support system 8 is a tapered ceramic barrel with a narrow upper part and a wide lower part and openings at both ends, and the surface is covered with multi-stage segmented electrodes. The taper is determined according to the curvature of the photocathode 2, and in combination with the voltage of the segmented pressure electrodes, the movement paths and the electric field distributions along the way of the photoelectrons 6 generated at various positions of the photocathode 2 to reach the electron multiplication system are the same.

[0042] In this embodiment, a three-stage segmented electrode is used to cover the surface of the tapered support barrel, which are the primary segmented electrode 81, the secondary segmented electrode 82, and the final segmented electrode 83 respectively.

[0043] The design of the segmented pressure support system 8 can form an accelerating and focusing electric field inside the photomultiplier tube, effectively focus the photoelectrons 6 into the electron multiplication system, and obtain high time resolution and high photoelectron 6 collection efficiency.

[0044] The electron multiplication system is placed at the top of the segmented pressure support system 8 and is coaxially centered with it. It can be a dynode electron multiplication system 3 or a microchannel plate assembly 7. In this embodiment, 2 microchannel plate assemblies 7 are used, but it does not limit the protection scope of the present invention.

[0045] The straight-line distances from the microchannel plate assembly 7 to each latitude of the photocathode 2 are basically the same. The taper of the segmented pressure support system 8 is designed in cooperation with the curvature of the photocathode 2, so that the distances of the photoelectrons 6 generated at various positions of the photocathode 2 to reach the microchannel plate assembly 7 are not very different, and the electric field distributions passed through are basically the same, thereby ensuring the minimum transit time dispersion.

[0046] The anode 4 is placed behind the microchannel plate and is coaxial with its center. It is used to collect the photoelectrons 6 multiplied by the microchannel plate assembly 7 and supply the electrode and the signal lead-out wire 9 to output the electron current signal collected by the anode. Figure 3 In Figure 3 , the electrode and the signal lead-out wire 9 are represented by a straight line. On the one hand, as a signal lead-out wire, it can output the electron current signal collected by the anode. On the other hand, as an electrode, it is connected to an external power supply circuit through a power line to supply power to the photocathode 2, the segmented pressure support system 8, the microchannel plate assembly 7, and the anode 4, so as to form a potential difference between them in turn to ensure the normal operation of the photomultiplier tube.

[0047] The above-mentioned photocathode 2 is made of an appropriate photocathode material and is uniformly coated on the inner hemispherical surface of the vacuum glass container 1. The material of the photocathode 2 can be a double-alkali or multi-alkali metal material, and its thickness and structure are determined according to specific usage requirements during the coating process. In this embodiment, the diameter of the photocathode 2 is equal to the inner major axis of the vacuum glass container 1, which is 500 mm. The potential of the photocathode 2 is the lowest in the entire photomultiplier tube, generally 0 V.

[0048] The above-mentioned photomultiplier tube adopts a segmented pressure support system 8, the main body of which is a conical ceramic barrel. The ceramic barrel is narrow at the top and wide at the bottom. The opening diameter at the upper end is less than or equal to the diameter of the electron multiplication system, and the opening diameter at the lower end does not exceed the diameter of the handle of the vacuum glass container, and the diameters are quite the same. The height is not less than the total thickness of the electron multiplication system and the anode 4.

[0049] The surface of the conical ceramic barrel is covered with a three-stage segmented electrode. The heights of each stage are equal and there is a certain distance between them, and they can be independently pressurized. The potential of the first-stage segmented electrode 81 is equal to or slightly less than the potential of the last-stage segmented electrode 83, which is adjustable from 10 to 1000 V. The potential of the secondary segmented electrode 82 is higher than the potentials of the first stage and the secondary stage, which is adjustable from 200 to 2000 V.

[0050] The design of the segmented pressure support system 8 has three functions:

[0051] 1. Support the electron multiplication system and the anode;

[0052] 2. Cooperate with the electron multiplication system to achieve the acceleration and focusing of electrons, and obtain high time resolution and high collection efficiency;

[0053] 3. Play a shielding role, shielding the electric field generated by the microchannel plate assembly 7 and the anode 4 assembly inside the barrel to prevent the performance of the photomultiplier tube from deteriorating due to the overflow of this electric field.

[0054] The electron multiplication system is a dynode electron multiplication system 3 or a multi-chip microchannel plate assembly 7. The number of stages is determined according to the requirements for gain in the actual project. According to the need for gain, the electron multiplication system is composed of 8 to 16 stages of dynodes or 2 to 3 "V"-type cascaded microchannel plates, and the applied voltage increases gradually.

[0055] In this embodiment, a "V"-type cascade method of two microchannel plates is adopted. The input electrode of each microchannel plate faces the vacuum spherical cavity, and the output electrode faces the anode 4.

[0056] The potential of the input electrode of the first microchannel plate should be higher than that of the first-stage segmented electrode 81, and it is adjustable from 100 V to 2000 V.

[0057] In order to obtain an ideal multiplication effect and enable the photomultiplier tube to obtain sufficient electron amplification when detecting weak light or performing single-photon measurement counting, the bias voltage of the microchannel plate assembly 7 is adjustable from 600 V to 1000 V, and the gap voltage between the two microchannel plates is adjustable from 100 V to 800 V.

[0058] The above-mentioned anode 4 is a collector for multiplying electrons and receives the electron flow from the microchannel plate assembly 7. The anode 4 can be made of a copper sheet or other metal materials, and its area should be greater than or equal to the area of the microchannel plate assembly 7 to better collect the electron flow from the microchannel plate assembly 7. The potential of the anode 4 should be the highest, and generally the potential difference from the output electrode of the last microchannel plate is adjustable from 50 V to 500 V.

[0059] The supply electrodes and signal lead-out wires 9 required for the photocathode 2, the segmented pressure-applying support system 8, the electron multiplication system, and the anode 4 are placed in the segmented pressure-applying support system 8. A fusion welding process can be used to maintain vacuum sealing between the metal lead and the ceramic bracket.

[0060] In this way, when working voltages are applied to the photocathode 2, the segmented pressure-applying support system 8, the electron multiplication system, and the anode 4, an accelerating and focusing electric field is formed between the photocathode 2, the segmented pressure-applying support system 8, and the electron multiplication system, and a collection electric field is formed between the electron multiplication system and the anode 4. The light vacuum glass container 1 irradiates the photocathode 2 to generate photoelectrons 6, which are collected by the electron multiplication system under the acceleration and focusing of the focusing electric field. The electron flow after multiplication and amplification of the electrons enters the anode 4 under the acceleration of the collection electric field, and the collected current signal is output as the final signal.

[0061] According to the above embodiment, the structural performance of this large-area microchannel plate photomultiplier tube was simulated using the finite integration method, and the results of the electric field distribution are as Figure 4 shown, which indicates that:

[0062] 1. The electric field shows obvious focusing properties. The electrons emitted from the cathode surface will move along the direction of the electric field lines towards the microchannel plate.

[0063] 2. The electric field distribution between the cathode and the microchannel plate is highly consistent, which means that the electric field distribution along the path that the photoelectrons 6 pass from the cathode to the microchannel plate is approximately the same, resulting in a small electron transit time spread.

[0064] According to the statistical simulation results, the collection efficiency of photoelectrons 6 on the entire photocathode surface of this photomultiplier tube can reach 100%;

[0065] The transit time spread of electrons on the entire photocathode surface can reach 3.0 ns, and this result is 5 times higher than that of the above-mentioned mass-produced large-area microchannel plate photomultiplier tube;

[0066] When this photomultiplier tube is placed perpendicular to the direction of the geomagnetic field, it is most affected by the geomagnetic field. At this time, the collection efficiency is slightly reduced to 94.4%, which is still 4.4% higher than the collection efficiency of the dynode-type photomultiplier tube in the shielded state (ideal situation, not affected by the geomagnetic field interference);

[0067] The transit time spread value is shortened by 0.05 ns. Compared with the shielded state, the performance is improved instead. This photomultiplier tube has strong anti-geomagnetic field interference ability.

[0068] In the description of the present invention, it should be understood that the terms "opening", "upper", "lower", "thickness", "top", "middle", "length", "inner", "periphery", etc. indicating the orientation or position relationship are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the components or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention.

[0069] The above is only the preferred implementation manner of the present invention. The protection scope of the present invention is not limited to the above embodiments. All technical solutions falling within the idea of the present invention belong to the protection scope of the present invention. It should be pointed out that for those of ordinary skill in the art in this technical field, several improvements and refinements made without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A large-area photomultiplier tube with a segmented pressure application support system, characterized in that, It includes a vacuum glass container (1), a photocathode (2) for receiving light illumination and generating photoelectrons (6), an electron multiplication system for collecting the photoelectrons (6) emitted from the photocathode (2) and generating multiplied electrons, an anode (4) for collecting the multiplied electrons output by the electron multiplication system, a segmented pressure support system (8) for supporting the electron multiplication system and the anode (4) and accelerating and focusing the photoelectrons (6) emitted from the photocathode (2), and a power supply electrode for supplying power to the photocathode (2), the electron multiplication system, the anode (4), and the segmented pressure support system (8); The photocathode (2), the electron multiplication system, the anode (4), and the segmented pressure support system (8) are placed inside the vacuum glass container (1); The anode (4) is connected to an external signal processing circuit through a signal lead wire passing through the vacuum glass container (1), and the power supply electrode is connected to an external power supply circuit through a power line passing through the vacuum glass container (1), and it is characterized in that: The vacuum glass container (1) is spherical or nearly spherical; The photocathode (2) uniformly covers the inner surface of the upper hemisphere of the vacuum glass container (1), and the covering diameter of the photocathode (2) is equal to the diameter of the vacuum glass container (1); The support system (8) is placed at the handle opening of the vacuum glass container (1); The electron multiplication system is placed at the top opening of the segmented pressure support system (8); The anode (4) is placed parallel to the rear of the electron multiplication system; The main body of the segmented pressure support system (8) is a tapered ceramic barrel with a narrow upper part and a wide lower part and openings at both the upper and lower ends; The surface of the tapered ceramic barrel is covered with a multi-stage segmented pressure electrode, and the taper is determined according to the curvature of the photocathode (2). Cooperating with the voltage of the segmented pressure electrode, the paths and the electric field distributions along the way of the photoelectrons (6) generated at various positions of the photocathode (2) to reach the electron multiplication system are the same.

2. The large-area photomultiplier tube with a segmented pressure application support system according to claim 1, characterized in that, The segmented pressure electrode includes two or more stages, and there is a certain distance between each stage and they can be independently pressurized.

3. A large-area photomultiplier tube having a segmented pressure application support system according to claim 1, wherein, The diameter of the upper opening of the tapered ceramic barrel is less than or equal to the diameter of the electron multiplication system, the diameter of the lower opening does not exceed the diameter of the handle opening of the vacuum glass container (1), and the height is not less than the total thickness of the electron multiplication system and the anode (4).

4. A large-area photomultiplier tube with a segmented pressure application support system according to claim 1, characterized in that, The upper edge of the tapered ceramic barrel is not lower than the handle opening of the vacuum glass container.

5. A large-area photomultiplier tube with a segmented pressure application support system according to claim 1, characterized in that, The electron multiplication system is a dynode electron multiplication system (3) or a multi-slice microchannel plate assembly (7).

6. The large-area photomultiplier tube with a segmented pressure application support system according to claim 5, characterized in that, The anode (4) is placed parallel to the rear of the electron multiplication system, and the area is greater than or equal to the area of the output port of the electron multiplication system.

7. A large-area photomultiplier tube with a segmented pressure application support system according to claim 1, characterized in that, The segmented pressure support system (8), the electron multiplication system, and the anode (4) are coaxial with the center of the photocathode (2).

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