Micro-channel plate type photomultiplier for eliminating saturation recovery overshoot

Abstract

The invention discloses a micro-channel plate type photomultiplier capable of eliminating saturation recovery overshoot, and solves the technical problem of saturation recovery overshoot of the existing micro-channel plate type photomultiplier at a high counting rate. The device comprises an outer shell, an entrance window is connected to an opening in one side face of the outer shell, a photoelectric cathode is arranged on the face, located in the outer shell, of the entrance window, a micro-channel plate assembly, an anode and a packaging disc are sequentially and oppositely arranged on the face, away from the entrance window, of the photoelectric cathode, and the device further comprises an anode output line with one end connected with the anode; a circuit board assembly is arranged in the outer shell, the circuit board assembly is connected with the micro-channel plate assembly through an electrode lead, connected with the photoelectric cathode through an electrode lead and connected with the packaging disc through an electrode lead, and the circuit board assembly is connected with a high-voltage connector; functional layers of a single channel of the micro-channel plate are respectively a conductive layer, a secondary electron emission layer and a metal oxide film layer. According to the invention, the elimination of saturation recovery overshoot of the micro-channel plate type photomultiplier at a high counting rate can be realized.

Description

Technical Field

[0001] The present invention relates to a photomultiplier tube, and more particularly to a microchannel plate type photomultiplier tube for eliminating saturation recovery overshoot. Background Art

[0002] A photomultiplier tube is a photoelectric detection device that can convert extremely weak optical signals into electrical signals and amplify them. A microchannel plate type photomultiplier tube (abbreviated as MCP-PMT) is a type of photomultiplier tube that uses a microchannel plate (abbreviated as MCP) as an electron multiplication component, and has the characteristics of small volume, fast time response, and high time resolution, and is mostly used for the measurement of ultrafast time courses such as sub-nanosecond to nanosecond.

[0003] The MCP is a plate-like structure composed of millions of microchannels with diameters ranging from a few micrometers to more than a dozen micrometers, and the inner surface of each channel is covered with a secondary electron emission material. When the photoelectrons emitted by the photocathode enter the microchannel, they will be accelerated through the microchannel under the action of an electric field and hit the inner wall of the microchannel to generate secondary electrons, and the number of electrons will increase with each collision, thereby realizing the amplification of the electronic signal. When the frequency of the pulsed light incident on the photocathode is high (the intensity of a single pulsed light remains unchanged), the electrons on the inner wall of the microchannel plate will be consumed in large quantities, and the external circuit is too late to supplement the consumed electrons. This causes the output of the MCP-PMT to saturate under high-frequency irradiation, the single-pulse output of the MCP-PMT becomes smaller, and the higher the irradiation rate, the greater the degree of reduction in the single-pulse output.

[0004] When the incident light switches from high frequency to low frequency, the single-pulse output of the MCP-PMT does not immediately return to the output under low-frequency light irradiation, but there is an obvious overshoot, and then it slowly drops back to the output state under the initial low-frequency light irradiation. That is to say, when the MCP-PMT recovers from the saturated state at a high counting rate to the non-saturated state at a low counting rate, there is an overshoot problem, that is, saturation recovery overshoot. This greatly limits the quantitative measurement of the microchannel plate type photomultiplier tube in certain specific scenarios. Summary of the Invention

[0005] The purpose of the present invention is to solve the technical problem that the existing microchannel plate type photomultiplier tube has saturation recovery overshoot at high counting rates, which further limits the quantitative measurement in certain specific scenarios, and to provide a microchannel plate type photomultiplier tube for eliminating saturation recovery overshoot.

[0006] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0007] The present invention provides a microchannel plate type photomultiplier tube for eliminating saturation recovery overshoot, which is characterized in that it includes an incident window, one side of the incident window is coated with a photocathode, and on the side of the photocathode away from the incident window, a microchannel plate assembly, an anode, and a packaging disk are sequentially arranged;

[0008] The incident window is encapsulated and connected within the housing, and the photocathode, microchannel plate assembly, anode, and encapsulation disk are all encapsulated within the housing;

[0009] The anode is connected to the anode output wire, and the anode output wire sequentially passes through the encapsulation disk and the housing and extends to the outside of the housing;

[0010] A circuit board assembly is provided within the housing. The circuit board assembly is connected to the microchannel plate assembly through a microchannel plate electrode lead, connected to the photocathode through a cathode electrode lead, and connected to the encapsulation disk through a sealing disk electrode lead. A high-voltage connector extending to the outside of the housing is connected to the circuit board assembly.

[0011] Further, both between the microchannel plate electrode lead and the microchannel plate assembly and between the cathode electrode lead and the photocathode are connected through an electrode ring assembly.

[0012] Further, a ceramic assembly is further included. The ceramic assembly includes a plurality of sequentially connected ceramic rings. A plurality of electrode ring assemblies are connected between the plurality of ceramic rings, and the plurality of ceramic rings are used to provide insulation support for the plurality of electrode ring assemblies.

[0013] Further, a potting assembly is further included. The potting assembly includes a potting shell with one end open and potting glue;

[0014] The open end of the potting shell is connected to the inner wall of the housing. The incident window, photocathode, microchannel plate assembly, anode, encapsulation disk, electrode ring assembly, ceramic assembly, and the end of the anode output wire connected to the anode are all encapsulated and connected within the potting shell;

[0015] The potting glue is potted within the potting shell, and the microchannel plate electrode lead, cathode electrode lead, and sealing disk electrode lead respectively pass through the potting glue and the potting shell to connect to the electrode ring assembly.

[0016] Further, the material of the incident window is one of magnesium fluoride crystal, quartz glass, and borosilicate glass.

[0017] Further, the material of the photocathode is an ultraviolet solar-blind type material or a visible light type material or an infrared band response type material.

[0018] Further, the microchannel plate assembly is a single-piece microchannel plate. The single-piece microchannel plate is connected to a microchannel plate electrode lead through an electrode ring assembly. Or, the microchannel plate assembly is a two-piece cascaded microchannel plate or a three-piece cascaded microchannel plate. Each microchannel plate is connected to a microchannel plate electrode lead through an electrode ring assembly, and between two adjacent microchannel plates, they are commonly connected to a microchannel plate electrode lead through an electrode ring assembly.

[0019] Further, the functional layer in the microchannel plate includes a conductive layer, a secondary electron emission layer, and a metal oxide film layer, which are sequentially arranged from outside to inside in the microchannels.

[0020] Further, both the conductive layer and the secondary electron emission layer are functional layers formed by a hydrogen reduction process on lead silicate glass, and the metal oxide film layer is a film layer with a nanoscale thickness deposited on the secondary electron emission layer by atomic layer deposition technology;

[0021] The metal oxide film layer is one of aluminum oxide film layer, magnesium oxide film layer, and zinc oxide film layer, and its thickness is between 1 nm and 10 nm.

[0022] Further, the circuit board assembly is a voltage-dividing circuit board, including an input terminal. The input terminal is connected to the positive plate of capacitor C1 and one end of n resistors connected in series in sequence. A positive plate of a filter capacitor Ci and an output terminal are connected between adjacent two resistors. The negative plates of each filter capacitor Ci and the negative plate of capacitor C1 are connected to the ground of the voltage-dividing circuit, where n≥3 and i = 2 to n;

[0023] The microchannel plate electrode lead, the cathode electrode lead, and the sealing disc electrode lead are respectively connected to an output terminal, and the high-voltage connector is connected to the input terminal.

[0024] Advantages of the present invention:

[0025] A microchannel plate type photomultiplier tube for eliminating saturation recovery overshoot in the present invention adopts a microchannel plate with functional layers being a conductive layer, a secondary electron emission layer, and a metal oxide film layer respectively, and realizes the elimination of saturation recovery overshoot of the microchannel plate type photomultiplier tube at high counting rates. Description of the drawings

[0026] Figure 1 It is a schematic structural diagram of an embodiment of a microchannel plate type photomultiplier tube for eliminating saturation recovery overshoot in the present invention;

[0027] Figure 2 It is a schematic structural diagram of the microchannels in the microchannel plate in an embodiment of a microchannel plate type photomultiplier tube for eliminating saturation recovery overshoot in the present invention;

[0028] Figure 3 It is a schematic circuit structural diagram of the circuit board assembly in an embodiment of a microchannel plate type photomultiplier tube for eliminating saturation recovery overshoot in the present invention;

[0029] Figure 4 It is a schematic diagram showing the change of the single-pulse output charge amount of the MCP-PMT with the pulse light irradiation frequency in an embodiment of the present invention;

[0030] Figure 5Schematic diagram of the measured saturation recovery of a microchannel plate type photomultiplier tube prepared by using a conventional microchannel plate;

[0031] Figure 6 In an embodiment of a microchannel plate type photomultiplier tube for eliminating saturation recovery overshoot according to the present invention, it is a schematic diagram of the measured saturation recovery of the microchannel plate type photomultiplier tube.

[0032] In the figure, 1 - incident window, 101 - cathode electrode lead, 102 - microchannel plate electrode lead, 103 - sealing disk electrode lead; 2 - photocathode; 3 - microchannel plate assembly, 301 - conductive layer, 302 - secondary electron emission layer, 303 - metal oxide film layer; 4 - anode; 5 - encapsulation disk; 6 - electrode ring assembly; 7 - ceramic assembly; 8 - potting assembly; 9 - circuit board assembly; 10 - outer housing; 11 - high - voltage connector; 12 - anode output line. Detailed implementation manners

[0033] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the accompanying drawings and embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0034] A microchannel plate type photomultiplier tube for eliminating saturation recovery overshoot, as Figure 1 shown, includes an incident window 1. One side of the incident window 1 is coated with a photocathode 2. Opposite to the side of the photocathode 2 away from the incident window 1 are arranged a microchannel plate assembly 3, an anode 4, and an encapsulation disk 5 in sequence. The incident window 1 is hermetically connected within the outer housing 10, and the photocathode 2, the microchannel plate assembly 3, the anode 4, and the encapsulation disk 5 are all encapsulated within the outer housing 10. The anode 4 is connected to the anode output line 12, and the anode output line 12 passes through the encapsulation disk 5 and the outer housing 10 in sequence and extends to the outside of the outer housing 10. Light in the wavelength range to be measured passes through the incident window 1 and irradiates onto the photocathode 2. The material of the incident window 1 can be selected from magnesium fluoride crystal, quartz glass, borosilicate glass, etc. The photocathode 2 is a semiconductor compound attached to the inner side of the incident window 1, and its function is to convert incident light into photoelectrons. According to the different wavelength ranges to be measured, the type of the photocathode 2 can be an ultraviolet solar - blind type material, a visible - light type material, or a material responsive to the infrared wavelength range.

[0035] The function of the microchannel plate assembly 3 is to multiply and amplify the photoelectrons emitted by the photocathode 2 to form a detectable electron flow signal. The microchannel plate assembly 3 can be a single-piece microchannel plate, a two-piece cascaded microchannel plate, or a three-piece cascaded microchannel plate, which is selected according to the required multiplication degree. For a single-piece microchannel plate, a two-piece cascaded microchannel plate, or a three-piece cascaded microchannel plate, each microchannel plate is connected to a microchannel plate electrode lead through an electrode ring assembly 6.

[0036] In this embodiment, the microchannel plate assembly 3 is a two-piece cascaded microchannel plate. The functional layer structure of a single channel of the microchannel plate is as Figure 2 shown, which are a conductive layer 301, a secondary electron emission layer 302, and a metal oxide film layer 303 respectively. Among them, the conductive layer 301 and the secondary electron emission layer 302 are functional layers formed by the hydrogen reduction process of lead silicate glass, and the metal oxide layer 303 is a film layer with a nanometer-level thickness plated on the secondary electron emission layer 302 by atomic layer deposition technology. The metal oxide film layer 303 can be an aluminum oxide film layer, a magnesium oxide film layer, a zinc oxide film layer, etc., and the thickness of the metal oxide film layer 303 is between 1 nm and 10 nm.

[0037] In this example, the metal oxide film layer is an aluminum oxide film layer with a thickness of 1 nm.

[0038] In this example, the anode 4 is made of metal, receives the electrons multiplied by the microchannel plate assembly 3, and outputs them backward. The anode 4 can be a single anode or a multi-anode. As Figure 1 shown, the anode 4 is a single anode.

[0039] The sealing disc 5 is made of kovar alloy, provides a sealed vacuum environment for the normal operation of the microchannel plate type photomultiplier tube, and serves as a grounding point. The anode 4 passes through the sealing disc 5 by means of ceramic-metal sealing and outputs the electron flow to the outside through the anode output wire 12.

[0040] The microchannel plate electrode lead 102 and the microchannel plate assembly 3, as well as the cathode electrode lead 101 and the photocathode 2, are all connected through the electrode ring assembly 6; the electrode ring assembly 6 provides high-voltage contacts for the photocathode 2 and the microchannel plate assembly 3, and provides a sealed vacuum environment.

[0041] It further includes a ceramic component 7. The ceramic component 7 includes a plurality of sequentially connected ceramic rings. The plurality of ceramic rings connect a plurality of electrode ring assemblies 6. The plurality of ceramic rings are used to provide insulating support for the plurality of electrode ring assemblies 6 and are welded to the electrode ring assemblies 6 by means of ceramic-metal sealing.

[0042] As Figure 1As shown, the potting assembly 8 includes a potting shell with an open end and potting glue; the open end of the potting shell is connected to the inner wall of the outer housing 10, and the incident window 1, the photocathode 2, the microchannel plate assembly 3, the anode 4, the encapsulation disc 5, the electrode ring assembly 6, the ceramic assembly 7, and part of the anode output wire 12 are all located inside the potting shell; the potting glue is potted inside the potting shell. The cathode electrode lead 101, the microchannel plate electrode lead 102, and the sealing disc electrode lead 103 are wires with insulating layers, used to provide a path for the DC high voltage. One end of them is connected to the corresponding electrode ring assembly 6, and the other end passes through the potting glue and the potting shell and is welded to the circuit board assembly 9; the potting assembly 8 provides an insulating and moisture-proof environment for the tube body of the microchannel plate type photomultiplier tube and is composed of a potting shell and potting glue.

[0043] A circuit board assembly 9 is arranged inside the outer housing 10. The circuit board assembly 9 is connected to the microchannel plate assembly 3 through the microchannel plate electrode lead 102, connected to the photocathode 2 through the cathode electrode lead 101, and connected to the encapsulation disc 5 through the sealing disc electrode lead 103. A high-voltage connector 11 extending to the outside of the outer housing 10 is connected to the circuit board assembly 9. One end of the high-voltage connector 11 is welded to the circuit board assembly 9, and the other end is used to connect an external high-voltage DC power supply. The function of the circuit board assembly 9 is to provide a voltage-dividing circuit for each electrode and is composed of a circuit board and resistors and capacitors welded thereon.

[0044] Among them, the circuit board assembly 9 is a voltage-dividing circuit board, including an input terminal. The input terminal is connected to the positive plate of the capacitor C1 and 4 resistors connected in series in sequence. A positive plate of a filter capacitor Ci and an output terminal are connected between two adjacent resistors. The negative plates of each filter capacitor Ci and the negative plate of the capacitor C1 are connected to the ground of the voltage-dividing circuit board; the microchannel plate electrode lead 102, the cathode electrode lead 101, and the sealing disc electrode lead 103 are respectively connected to an output terminal, and the high-voltage connector 11 is connected to the input terminal.

[0045] As Figure 3 shown, the resistors R1, R2, R3, R4, and R5 are used to divide the voltage for each electrode, and their values are 30 kΩ, 820 kΩ, 3 MΩ, 3 MΩ, and 2 MΩ respectively. The capacitor C1 and R1 form an RC filter circuit, used to filter the DC high voltage fed into the high-voltage connector 11. The value of the capacitor C1 is 1 nF. The capacitors C2, C3, C4, and C5 are all capacitors connected to each electrode, used for dynamically grounding each electrode to reduce high-frequency noise interference. The values of the capacitors C1, C2, C3, and C4 are 330 pF, 330 pF, 330 pF, and 470 pF respectively. The outer housing 10 is made of metal, used for the overall strength support of the microchannel plate type photomultiplier tube and also for the shielding of the electromagnetic environment.

[0046] Figure 4It is a graph showing the variation of the single-pulse output charge of a microchannel plate photomultiplier tube with the pulse light irradiation frequency. When the incident light frequency is less than 1 kHz, the single-pulse charge output by the microchannel plate photomultiplier tube remains basically unchanged. As the incident light frequency increases (the intensity of a single pulse light remains unchanged), due to the saturation effect of the microchannel plate, the output of a single pulse gradually decreases.

[0047] Among them, Figure 4 In it, the pulse light irradiation frequency at point A is 10 Hz, and the pulse light irradiation frequency at point B is 500 kHz. Figure 5 It is the measured results of the saturation recovery of two microchannel plate photomultiplier tubes prepared with a conventional microchannel plate. The microchannel plate photomultiplier tube operates stably at an incident light frequency of 10 Hz for a period of time, and then the incident light frequency is increased to 500 kHz. The output of the microchannel plate photomultiplier tube decreases due to the saturation effect. Finally, the incident light frequency is decreased to 10 Hz again. Compared with the microchannel plate used in the conventional microchannel plate photomultiplier tube, the functional layer of a single channel only has a conductive layer 301 and a secondary electron emission layer 302 in the microchannel plate of the present invention.

[0048] According to Figure 5 it can be known that at the moment when the incident light frequency is decreased from 500 kHz to 10 Hz, that is, at the moment when the microchannel plate photomultiplier tube recovers from the saturated state at a high counting rate to the non-saturated state at a low counting rate, compared with the initial non-saturated state, there is an overshoot in the output of a single pulse, and the overshoot amplitude exceeds 20%.

[0049] Figure 6 They are two microchannel plate photomultiplier tubes prepared by the present invention that eliminate the overshoot of saturation recovery. According to Figure 6 it can be known that when the incident light frequency is decreased from 500 kHz to 10 Hz, there is no overshoot at the moment of saturation recovery.

[0050] As described above, it is only the specific implementation manner of the present invention, as well as the effect comparison between the relevant specific implementation manner and the related comparative examples. However, the protection scope of the present invention is not limited thereto. Any change or replacement within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claimed rights.

Claims

1. A microchannel plate photomultiplier tube for eliminating saturation recovery overshoot, characterized in that: It comprises an incident window (1), one side of the incident window (1) is plated with a photocathode (2), and the side of the photocathode (2) away from the incident window (1) is provided with a microchannel plate assembly (3), an anode (4), and a packaging disk (5) in sequence; The incident window (1) is packaged and connected in an outer shell (10), and the photocathode (2), the microchannel plate assembly (3), the anode (4), and the packaging disk (5) are all packaged in the outer shell (10); The anode (4) is connected to an anode output line (12), and the anode output line (12) passes through the packaging disk (5) and the outer shell (10) in sequence, and extends to the outside of the outer shell (10); A circuit board assembly (9) is arranged in the outer shell (10); the circuit board assembly (9) is connected to the microchannel plate assembly (3) via a microchannel plate electrode lead, connected to the photocathode (2) via a cathode electrode lead, and connected to the packaging disk (5) via a sealing disk electrode lead; the circuit board assembly (9) is connected to a high-voltage connector (11) extending to the outside of the outer shell (10).

2. A microchannel plate photomultiplier tube for eliminating saturation recovery overshoot according to claim 1, characterized in that: The microchannel plate electrode lead and the microchannel plate assembly (3), as well as the cathode electrode lead and the photocathode (2) are connected via an electrode ring assembly (6).

3. A microchannel plate photomultiplier tube for eliminating saturation recovery overshoot according to claim 2, characterized in that: It also comprises a ceramic assembly (7), the ceramic assembly (7) comprising a plurality of ceramic rings connected in sequence, a plurality of electrode ring assemblies (6) being connected between the plurality of ceramic rings, and the plurality of ceramic rings being used to provide insulating support for the plurality of electrode ring assemblies (6).

4. A microchannel plate photomultiplier tube for eliminating saturation recovery overshoot according to claim 3, characterized in that: It also includes a potting assembly (8), which includes a potting shell with an open end and a potting glue; The open end of the potting shell is connected to the inner wall of the outer shell (10), and the incident window (1), the photocathode (2), the microchannel plate assembly (3), the anode (4), the packaging disk (5), the electrode ring assembly (6), the ceramic assembly (7), and one end of the anode output line (12) connected to the anode (4) are all packaged and connected in the potting shell; The potting glue is potted in the potting shell, and the microchannel plate electrode lead, cathode electrode lead, and sealing disk electrode lead respectively pass through the potting glue and the potting shell to connect to the electrode ring assembly (6).

5. A microchannel plate photomultiplier tube for eliminating saturation recovery overshoot according to claim 1, characterized in that: The material of the incident window (1) is one of magnesium fluoride crystal, quartz glass and borosilicate glass.

6. A microchannel plate photomultiplier tube for eliminating saturation recovery overshoot according to claim 1, characterized in that: The material of the photocathode (2) is an ultraviolet solar-blind material, a visible light material, or an infrared band responsive material.

7. A microchannel plate photomultiplier tube for eliminating saturation recovery overshoot according to claim 2, characterized in that: The microchannel plate assembly (3) is a single-piece microchannel plate, which is connected to a microchannel plate electrode lead via an electrode ring assembly (6); or, the microchannel plate assembly (3) is a double-piece cascaded microchannel plate or a triple-piece cascaded microchannel plate, each microchannel plate is connected to a microchannel plate electrode lead via an electrode ring assembly (6), and two adjacent microchannel plates are connected to a microchannel plate electrode lead via an electrode ring assembly (6).

8. A microchannel plate photomultiplier tube for eliminating saturation recovery overshoot according to claim 7, characterized in that: The functional layers in the microchannel plate include a conductive layer (301), a secondary electron emission layer (302), and a metal oxide film layer (303) which are arranged in sequence from outside to inside in the microchannel.

9. A microchannel plate photomultiplier tube for eliminating saturation recovery overshoot according to claim 8, characterized in that: The conductive layer (301) and the secondary electron emission layer (302) are both functional layers formed by a hydrogen reduction process of lead silicate glass, and the metal oxide film layer (303) is a film layer with a thickness of nanometers plated on the secondary electron emission layer (302) using an atomic layer deposition technique; The metal oxide film layer (303) is one of an aluminum oxide film layer, a magnesium oxide film layer, and a zinc oxide film layer, and has a thickness between 1 nm and 10 nm.

10. The microchannel plate photomultiplier tube for eliminating saturation recovery overshoot according to claim 1, characterized in that: The circuit board assembly (9) is a voltage divider circuit board, comprising an input terminal, the input terminal is connected to the positive plate of the capacitor C1 and one end of n resistors connected in series, a positive plate of a filter capacitor Ci and an output terminal are connected between two adjacent resistors, and the negative plate of each filter capacitor Ci and the negative plate of the capacitor C1 are connected to the ground of the voltage divider circuit, wherein n≥3, i=2-n; The microchannel plate electrode lead, the cathode electrode lead, and the sealing disk electrode lead are respectively connected to an output terminal, and the high-voltage connector (11) is connected to an input terminal.

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