A high collection efficiency large-area microchannel plate photomultiplier tube

Abstract

The application discloses a high-collection-efficiency large-area micro-channel plate photomultiplier, which comprises a vacuum glass container, a photoelectric cathode, a focusing electrode, a micro-channel plate electron multiplier, an anode and a power supply wire; the photoelectric cathode is covered on the inner surface of the vacuum glass container; the focusing electrode is arranged directly below the photoelectric cathode; the diameter of the top opening of the focusing electrode is larger than the diameter of the bottom opening and smaller than the diameter of the photoelectric cathode; a high secondary electron emission material layer is uniformly covered on the inner wall of the focusing electrode; the micro-channel plate electron multiplier is arranged at the bottom opening of the focusing electrode; the voltage of the focusing electrode is smaller than the input voltage of the micro-channel plate electron multiplier; the anode is arranged directly below the output end of the micro-channel plate electron multiplier; and the photoelectric cathode, the focusing electrode, the micro-channel plate electron multiplier and the anode are powered through the power supply wire. Under the high collection effect, the collection efficiency of the large-area micro-channel plate photomultiplier can be greatly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vacuum photoelectric detection, and particularly relates to a high-collection-efficiency large-area micro-channel plate photomultiplier. BACKGROUND

[0002] The photomultiplier is a vacuum photoelectric detection device based on the external photoelectron emission effect, the secondary electron emission effect and the electron optics theory, which can convert a weak light signal into a photoelectron and obtain a multiplication effect.

[0003] The large-area photomultiplier is a type of photomultiplier, which has a large light-sensitive area and a photon counting capability, and is widely used in high-energy physics experiments such as large-scale neutrino and cosmic ray detection.

[0004] The large-area photomultiplier includes a vacuum glass container, a photocathode, a focusing electrode, an electron multiplication electrode and an anode, and can be divided into a large-area dynode type and a micro-channel plate type according to the electron multiplication electrode. The main difference between the two is the electron multiplication electrode. The electron multiplication electrode of the large-area dynode photomultiplier is a dynode electron multiplication electrode, and the electron multiplication electrode of the large-area micro-channel plate photomultiplier is a micro-channel plate electron multiplication electrode.

[0005] The electron collection efficiency represents the ratio of the number of effectively multiplied photoelectrons to the number of photoelectrons emitted by the photocathode. The collection efficiency is an important parameter for characterizing the performance of the photomultiplier, and directly affects the detection efficiency and determines the detection capability of the photomultiplier for incident light signals.

[0006] In the large-area dynode photomultiplier, the dynode has a large opening area, and when used as the electron multiplication electrode, a high collection efficiency can be obtained. The literature Chen L, Wang X, He J, et al. A Large Area Dynode-MCP-PMT Design With High CE and Good Time Performance [J]. IEEE Transactions on Nuclear Science, 2022, 69(10): 2113-2117 reports that the collection efficiency of the large-area dynode photomultiplier product R12860 can reach 90%. In the micro-channel plate photomultiplier, the micro-channel plate (such as Figure 1) is a small glass disc with a honeycomb structure, which is composed of millions of microchannels, each channel is an independent electron multiplier, and the upper and lower surfaces are coated with nickel-chromium electrodes. According to the literature "GW Fraser. The electron detection efficiency of microchannel plates [J]. Nuclear Instruments and Methods in Physics Research, 1983, 206(3): 445-449", the secondary electron emission coefficient of the nickel-chromium electrode is not more than 1, and the electrons hitting the electrode will not excite new secondary electrons. Therefore, the collection efficiency of the large-area microchannel plate photomultiplier tube is only contributed by the photoelectrons entering the channel, which will not exceed the opening area ratio. According to the literature Chen L, Tian J, Zhao T, et al. Simulation of the electron collection efficiency of a PMT based on the MCP coated with high secondary yield material [J]. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2016, 835: 94-98, if no measures are taken, the highest collection efficiency of the large-area microchannel plate photomultiplier tube is only 74.8%, which is lower than that of the large-area dynode photomultiplier tube SUMMARY

[0007] The purpose of the present application is to solve the problem of low collection efficiency of large-area microchannel plate photomultiplier tubes, and to provide a design of a high-efficiency large-area microchannel plate photomultiplier tube.

[0008] The present application is realized by the following technical solutions:

[0009] A high-efficiency large-area microchannel plate photomultiplier tube, comprising a vacuum glass container, a photocathode, a focusing electrode, a microchannel plate electron multiplier, an anode and a power supply line. The vacuum glass container is divided into upper and lower parts. The upper structure is a sphere, an ellipsoid or a cylinder with a curved top, and the photocathode is uniformly covered on the inner surface of the upper structure; the lower structure is a handle structure connected to the upper structure.

[0010] The photocathode is covered on the inner surface of the vacuum glass container and is used to receive light and generate photoelectrons.

[0011] The focusing electrode is placed right below the photocathode, and is used to accelerate, focus, collect and multiply the photoelectrons emitted from the photocathode. The top and bottom of the focusing electrode are both provided with openings, the diameter of the top opening is larger than that of the bottom opening and smaller than that of the photocathode. The inner wall of the focusing electrode is uniformly covered with a high secondary electron emission material layer.

[0012] The microchannel plate electron multiplier is composed of single or double microchannel plates in a V-shaped cascade, and is placed at the bottom opening of the focusing electrode, and is used to multiply the photoelectrons collected by the focusing electrode and the electrons multiplied by the focusing electrode. The voltage of the focusing electrode is smaller than the input voltage of the microchannel plate electron multiplier.

[0013] The anode is placed right below the output end of the microchannel plate electron multiplier, and is used to collect the multiplied electrons output by the microchannel plate electron multiplier, and the collected electrical signal is led out through a signal lead-out wire.

[0014] The photocathode, the focusing electrode, the microchannel plate electron multiplier and the anode are powered through a power supply wire.

[0015] The microchannel plate electron multiplier is composed of single or double microchannel plates in a V-shaped cascade.

[0016] The focusing electrode is a conical shell, and is provided with horizontal circular cross-section openings at the top and bottom of the conical shell, respectively forming the top and bottom openings of the focusing electrode.

[0017] The diameter of the bottom opening of the focusing electrode is smaller than or equal to the diameter of the microchannel plate electron multiplier.

[0018] The focusing electrode, the microchannel plate electron multiplier and the anode are fixed into an integrated body by an insulating frame, and are coaxial with the center line of the photocathode and the vacuum glass container.

[0019] The surface and the inner wall of the microchannel plate electron multiplier are uniformly covered with a high secondary electron emission material layer.

[0020] The material composition of the high secondary electron emission material layer is selected from one of Al2O3 or MgO materials.

[0021] The high secondary electron emission material layer is plated on the corresponding part by using an atomic layer deposition method (ALD).

[0022] Compared with the prior art, the beneficial effects of the present application are:

[0023] The application provides a high-collection-efficiency large-area micro-channel plate photomultiplier tube, which has the advantage of high collection efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is a micro-channel plate structure schematic diagram.

[0025] Figure 2 It is a structure schematic diagram of the high-collection-efficiency large-area micro-channel plate photomultiplier tube.

[0026] In the figure: 1, vacuum glass container; 2, photoelectric cathode; 3, focusing electrode; 4, micro-channel plate electron multiplier; 5, anode; 6, power supply electrode and signal lead-out wire; 7, insulating frame. DETAILED DESCRIPTION

[0027] The above content of the application is further explained in the form of examples, but this should not be understood as the range of the above subject matter of the application is limited to the following examples, and all the technologies realized based on the above content of the application belong to the range of the application.

[0028] The application provides a high-collection-efficiency large-area micro-channel plate photomultiplier tube, which has the advantage of high collection efficiency. Figure 2 As shown in the figure, it comprises a vacuum glass container 1, a photoelectric cathode 2, a focusing electrode 3, a micro-channel plate electron multiplier 4, an anode 5, a power supply electrode and a signal lead-out wire 6, and an insulating frame 7.

[0029] In the application, the above vacuum glass container 1 is in the shape of a sphere, an ellipsoid or a cylinder with a curved top.

[0030] The photocathode 2 is uniformly deposited and covers the inner surface of the upper hemisphere of the vacuum glass container to receive light and generate photoelectrons. The photocathode can be made of alkali or multialkali metal materials and is coated with a uniform thickness on the entire inner surface of the vacuum light-transmitting container. The thickness and structure are determined according to the specific application requirements. The photocathode potential is the lowest in the entire photomultiplier tube, generally 0V.

[0031] The focusing electrode 3 is positioned at the handle of the glass container directly below the photocathode 2, and is used to accelerate, focus, collect, and multiply the photoelectrons emitted from the photocathode 2. In this embodiment, the focusing electrode 3 is a conical shell with horizontally truncated openings at both the top and bottom. The diameter of the top opening is larger than the diameter of the bottom opening but smaller than the diameter of the photocathode 2, and the diameter of the bottom opening is equal to the diameter of the microchannel plate electron multiplier 4. The diameter, height, and placement of the bottom and top openings of the focusing electrode 3 need to be determined based on the actual engineering requirements for collection efficiency and transit time dispersion. To further achieve high collection efficiency, a layer of high secondary electron emission material is uniformly coated inside the focusing electrode 3; in this embodiment, Al2O3 material is used. The potential of the focusing electrode 3 is higher than the potential of the photocathode 2 but lower than the input voltage of the microchannel plate electron multiplier 4, and is adjustable from 100V to 1500V.

[0032] The microchannel plate electron multiplier 4 is composed of a single or double microchannel plate cascaded in a "V" shape and is placed at the bottom opening of the focusing electrode 3. It is used to multiply the photoelectrons collected by the focusing electrode 3 and the electrons multiplied by the focusing electrode 3. The number of microchannel plate electron multipliers 4 depends on the specific gain requirements of the engineering project; it can be a single microchannel plate or a double microchannel plate cascaded in a "V" shape. In this embodiment... Figure 2 The method employs two cascaded microchannel plate electron multipliers 4. The potential of the input electrode of the first microchannel plate is higher than that of the focusing electrode 3, with a potential difference between the two being between 100 and 1000V. To obtain an ideal multiplication effect, the bias voltage of a single microchannel plate electron multiplier 4 is between 600 and 1000V, and the gap voltage between the two microchannel plate electron multipliers 4 is between 50 and 500V. In a preferred embodiment, to obtain a good collection effect, the surface and channel of the microchannel plate electron multiplier 4 are covered with a high secondary electron emission material; in this embodiment, Al2O3 material is used.

[0033] The anode 5 is placed directly below the output terminal of the electron multiplier 4 of the microchannel plate to collect the multiplied electrons output from the electron multiplier 4 of the microchannel plate. The anode 5 is the same as that of a traditional photomultiplier tube and can be made of copper or other metal materials. The diameter of the anode 5 should be greater than or equal to the diameter of the electron multiplier 4 of the microchannel plate. The potential of the anode 5 should be the highest, and the potential difference with the output electrode of the last microchannel plate is generally between 50 and 500V.

[0034] In this embodiment, the focusing electrode 3, the microchannel plate electron multiplier 4, and the anode 5 are all coaxial with the center of the photocathode 2 and are fixed together by an insulating frame 7, such as a ceramic frame, and placed inside a vacuum glass container. The power supply line and signal lead-out line 6 are placed inside the insulating frame 7. The power supply line supplies power to the photocathode, focusing electrode 3, microchannel plate electron multiplier 4, and anode 5, and the signal lead-out line is used to extract the electrical signal collected by the anode 5.

[0035] Thus, when photoelectrons enter the opening at the top of the focusing electrode 3, they will have three possible paths: some will collide with the inner wall of the focusing electrode 3 and be effectively multiplied; a second part will collide with the non-opening area of ​​the microchannel plate electron multiplier 4 and also be effectively multiplied; and a third part will directly enter the channel of the microchannel plate electron multiplier 4 and be effectively multiplied. The input voltage of the microchannel plate electron multiplier 4 is greater than the voltage of the focusing electrode 3. Under the influence of the electric field, the first and second parts of electrons will eventually enter the channel of the microchannel plate electron multiplier 4. Therefore, as long as photoelectrons enter the opening area at the top of the focusing electrode 3, they will be effectively multiplied, i.e., considered collected. Due to the large opening at the top of the focusing electrode 3, this design can significantly improve the collection efficiency of large-area microchannel plate photomultiplier tubes.

[0036] Example:

[0037] The present invention is described using the finite integration method. Figure 2 The performance of the photomultiplier tube structure shown was simulated. The vacuum glass container 1 is ellipsoidal in shape, with an outer diameter of 508 mm and an inner diameter of 500 mm, and has a handle at the bottom; the photocathode 2 has a diameter of 500 mm; the focusing electrode 3 has a top opening diameter of 247 mm and a bottom opening diameter of 56 mm; the diameter of the anode 5 and the diameter of the microchannel plate electron multiplier electrode 4 are both 56 mm; the simulation results are as follows:

[0038] Neither the focusing electrode nor the microchannel plate was coated with an Al2O3 film, and the photoelectron collection efficiency was 51.9%.

[0039] The focusing electrode is a conventional electrode without coating, and the microchannel plate is coated with an Al2O3 film, with a photoelectron collection efficiency of 74.2%.

[0040] The focusing electrode is coated with an Al2O3 film, while the microchannel plate is uncoated, resulting in a photoelectron collection efficiency of 77.7%.

[0041] The focusing electrode is coated with an Al2O3 film, and the microchannel plate is coated with an Al2O3 film, achieving a photoelectron collection efficiency of 100%.

[0042] The above merely describes preferred embodiments of the present application, and is not intended to limit the present application in any form. Any modification, equivalent replacement, and improvement of the above embodiments made by any person skilled in the art, without departing from the technical solution of the present application, according to the technical essence of the present application, are still within the protection scope of the present application.

Claims

1. A high collection efficiency large area microchannel plate photomultiplier tube characterized by: The vacuum glass container, the photocathode, the focusing electrode, the microchannel plate electron multiplier, the anode and the power supply wire; the vacuum glass container is divided into upper and lower two parts; the upper structure is a sphere, an ellipsoid or a cylinder with a curved top, and the photocathode is uniformly covered on the inner surface of the upper structure; the lower structure is a handle structure connected with the upper structure; The photocathode is covered on the inner surface of the vacuum glass container, and is used for receiving light and generating photoelectrons; The focusing electrode is arranged directly below the photocathode, and is used for accelerating, focusing, collecting and multiplying the photoelectrons emitted from the photocathode; the top and bottom of the focusing electrode are both provided with openings, the diameter of the top opening is greater than that of the bottom opening and smaller than that of the photocathode; The inner wall of the focusing electrode is uniformly covered with a high secondary electron emission material layer; The microchannel plate electron multiplier is composed of single or double microchannel plates in "V" type cascade, and is arranged at the bottom opening of the focusing electrode, and is used for multiplying the photoelectrons collected by the focusing electrode and the electrons multiplied by the focusing electrode; the voltage of the focusing electrode is less than the input voltage of the microchannel plate electron multiplier; The anode is arranged directly below the output end of the microchannel plate electron multiplier, and is used for collecting the multiplied electrons output by the microchannel plate electron multiplier, and the collected electrical signal is led out through the signal lead-out wire; The photocathode, the focusing electrode, the microchannel plate electron multiplier and the anode are powered by the power supply wire. The focusing electrode is a conical shell, and the top and bottom of the conical shell are both provided with horizontal circular cross-section openings, which form the top and bottom openings of the focusing electrode respectively; the surface and the inner wall of the microchannel plate electron multiplier are uniformly covered with a high secondary electron emission material layer.

2. The high collection efficiency large area microchannel plate photomultiplier tube of claim 1, wherein: The focusing electrode is a conical shell, and the top and bottom of the conical shell are both provided with horizontal circular cross-section openings, which form the top and bottom openings of the focusing electrode respectively.

3. The high collection efficiency large area microchannel plate photomultiplier tube of claim 1, wherein: The focusing electrode, the microchannel plate electron multiplier and the anode are fixed into an integrated body by the insulating frame, and are coaxial with the center line of the photocathode and the vacuum glass container.

4. The high collection efficiency large area microchannel plate photomultiplier tube of claim 1, wherein: The material composition of the high secondary electron emission material layer is selected from one of Al2O3 or MgO materials.

5. The high collection efficiency large area microchannel plate photomultiplier tube of claim 1, wherein: The high secondary electron emission material layer is plated on the corresponding part by using atomic layer deposition method.

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