Method for dynamically adjusting gain of micro-channel plate type photomultiplier and micro-channel plate type photomultiplier

Abstract

The invention relates to a micro-channel plate type photomultiplier, in particular to a method for dynamically adjusting the gain of the micro-channel plate type photomultiplier and the micro-channel plate type photomultiplier, and solves the technical problem of poor gain improvement effect caused by the space charge effect easily generated by the existing method for improving the gain of the micro-channel plate type photomultiplier. Based on structural parameters and electrical parameters of an existing micro-channel plate type photomultiplier, the modulation electrode is arranged between the micro-channel plate and the anode, a modulation electric field generated after working voltage is applied to the modulation electrode permeates into the output electrode and the micro-channel of the micro-channel plate, and therefore the number of multiplication electrons output by the micro-channel plate is modulated, and the photomultiplier efficiency is improved. The gain of the micro-channel plate type photomultiplier can be improved or reduced, so that the specific requirements of different application scenes and different moments on the gain can be met.

Description

Technical Field

[0001] The invention relates to a microchannel plate type photomultiplier tube, and in particular to a method for dynamically adjusting the gain of a microchannel plate type photomultiplier tube and the microchannel plate type photomultiplier tube. Background Art

[0002] The microchannel plate (MCP) photomultiplier tube (PMT) is an advanced photodetector device that combines MCP electron multiplication technology with the principles of traditional PMTs. It converts weak light signals into electrical signals, amplifies them highly, and outputs them, enabling effective detection of weak light signals. A MCP PMT primarily consists of a photocathode, a microchannel plate (MCP), and an anode. The MCP comprises a large number of microchannels, each with a secondary electron emission characteristic. When a light signal strikes the photocathode, electrons in the photocathode material absorb the photon energy. When the energy exceeds the work function of the photocathode material, the electrons escape from the photocathode surface, forming photoelectrons. After entering the microchannels of the MCP, the photoelectrons are accelerated by the electric field within the microchannels and collide with the microchannel walls, generating secondary electrons. These secondary electrons continue to accelerate and collide, generating more secondary electrons, thereby multiplying the electrons. After the electron beam has been multiplied by the MCP, it reaches the anode, which collects the electrons and converts them into an electrical signal for output. The magnitude of this electrical signal is proportional to the intensity of the incident light signal.

[0003] Microchannel plate photomultiplier tubes have the characteristics of high gain (up to 108), fast response (up to the order of ps), low noise (nA order) and wide dynamic range. They have been widely used in astronomy, high-energy physics, biomedical imaging, nuclear medicine, laser technology, environmental monitoring and other fields. Gain is an important indicator of microchannel plate photomultiplier tubes, which directly affects the breadth and depth of their application. In many application scenarios, the incident light signal is extremely weak, and microchannel plate photomultiplier tubes are required to generate more obvious electrical signal output for these weak light signals, thereby improving the detection sensitivity. In some special application fields, microchannel plate photomultiplier tubes are required to have the ability to accurately detect and count single photons. At present, the methods to improve the gain of microchannel plate photomultiplier tubes mainly include: optimizing the structure and materials of the microchannel plate, adjusting the operating voltage and electric field, and adopting advanced manufacturing processes.

[0004] In terms of optimizing the microchannel plate structure, the microchannel diameter is usually reduced or the microchannel length is increased to increase the number of collisions between electrons and between electrons and the microchannel walls, thereby generating more secondary electrons. At the same time, increasing the fill factor of the microchannel plate to increase the number of microchannels involved in electron multiplication is also a common means of improving gain. In terms of improving the microchannel plate material, materials with a high secondary electron emission coefficient are generally selected to make it easier for electrons to generate more secondary electrons when colliding with the inner walls of the microchannel, thereby increasing gain. In terms of adjusting the operating voltage and electric field, by optimizing the operating voltage and electric field distribution, the energy of the electrons is increased, so that more secondary electrons are generated when they collide with the inner walls of the microchannel, and the scattering and loss of electrons are reduced, thereby increasing gain. In terms of adopting advanced manufacturing processes, the inner surface of the microchannel is specially treated to improve its microstructure and chemical properties. This not only improves the secondary electron emission performance, but also reduces the adsorption and scattering of electrons on the channel walls, thereby increasing gain.

[0005] The above methods all aim to increase the gain by making the microchannel plate generate more secondary electrons. However, as the number of electron multiplications increases, the number of electrons accumulated in the microchannel also increases significantly, resulting in a large number of electrons gathering in the space at the output electrode of the microchannel plate, causing a serious space charge effect. As a result, some electrons cannot be output due to the space charge effect, making it difficult to effectively increase the electron gain of the microchannel plate photomultiplier tube. Summary of the Invention

[0006] The purpose of the present invention is to solve the technical problem that the existing method of improving the gain of a microchannel plate type photomultiplier tube is prone to produce a space charge effect, resulting in poor gain improvement effect, and to provide a method for dynamically adjusting the gain of a microchannel plate type photomultiplier tube and a microchannel plate type photomultiplier tube.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] A method for dynamically adjusting the gain of a microchannel plate photomultiplier tube, wherein the microchannel plate photomultiplier tube includes a photocathode, a microchannel plate, and an anode, wherein the photocathode is arranged on the input electrode side of the microchannel plate, and the anode is arranged on the output electrode side of the microchannel plate;

[0009] Its special feature is that it includes the following steps:

[0010] Step 1: a modulation electrode is provided between the output electrode and the anode of the microchannel plate, and a voltage-gain curve is obtained showing how the gain of the microchannel plate photomultiplier tube changes with the working voltage of the modulation electrode. Then, a working voltage is applied to the modulation electrode according to the voltage-gain curve and the gain requirement.

[0011] Step 2: photons are incident on the surface of the photocathode, and the photocathode is excited to generate photoelectrons that enter the microchannel plate;

[0012] Step 3: Photoelectrons are accelerated and collided in the microchannel of the microchannel plate to generate multiplied electrons;

[0013] Step 4: The modulation electrode generates a modulation electric field under the action of the working voltage, and the modulation electric field penetrates into the output electrode and microchannel of the microchannel plate;

[0014] Step 5: Modulating the electric field to modulate the output electrode of the microchannel plate and the electric field distribution within the microchannel, changing the movement distance of the multiplied electrons, thereby adjusting the number of multiplied electrons output by the microchannel plate, and further adjusting the number of multiplied electrons moving to the anode, thereby achieving adjustment of the gain of the microchannel plate type photomultiplier tube;

[0015] Step 6: Adjust the amplitude of the operating voltage according to the voltage-gain curve and the gain requirement, and then return to step 4 to achieve dynamic adjustment of the gain of the microchannel plate photomultiplier tube.

[0016] Furthermore, step 1 is specifically as follows:

[0017] Step 1.1, set the initial distance between the modulation electrode and the microchannel plate output electrode to L0, where H≤L0≤0.5mm, and H is the thickness of the microchannel plate output electrode;

[0018] Set the working voltage of the modulation electrode to V0 = V MCP ×(1-L0 / H)+i×10≤V MCP , i is the operating voltage variation coefficient, i=1,2,3,…, V MCP is the operating voltage of the output electrode of the microchannel plate;

[0019] Step 1.2: At the initial distance between the modulation electrode and the output electrode of the microchannel plate, apply the operating voltage when i is 1, 2, 3, ... to the modulation electrode, and calculate the number of multiplied electrons collected by the anode when a single electron is incident on the microchannel plate, and then record the maximum number of multiplied electrons collected by the anode N max and the voltage-gain curve of the microchannel plate photomultiplier tube gain as the modulating electrode operating voltage changes;

[0020] Step 1.3, set the distance between the modulation electrode and the output electrode of the microchannel plate to L0+H / 20 and L0-H / 20 respectively, and then follow the method of step 1.2 to calculate the maximum number of multiplied electrons N collected by the anode. max+ 、N max- and the voltage-gain curve of the microchannel plate photomultiplier tube gain as the modulating electrode operating voltage changes;

[0021] Step 1.4: Compare N max 、N max+ and N max-, if N max+ >N max , then the distance between the modulation electrode and the microchannel plate output electrode is increased in steps of H / 20, and then the method of step 1.2 is used to obtain the maximum number of multiplied electrons collected by the anode and the voltage-gain curve of the microchannel plate type photomultiplier tube gain as a function of the modulation electrode operating voltage, until the maximum number of multiplied electrons collected by the anode no longer increases, and the distance between the modulation electrode and the microchannel plate output electrode and the voltage-gain curve of the microchannel plate type photomultiplier tube gain as a function of the modulation electrode operating voltage at this distance are obtained;

[0022] If N max- >N max , then the distance between the modulation electrode and the microchannel plate output electrode is reduced in steps of H / 20, and then the method of step 1.2 is used to obtain the maximum number of multiplied electrons collected by the anode and the voltage-gain curve of the microchannel plate type photomultiplier tube gain as a function of the modulation electrode operating voltage, until the number of multiplied electrons collected by the anode no longer increases, and the distance between the modulation electrode and the microchannel plate output electrode and the voltage-gain curve of the microchannel plate type photomultiplier tube gain as a function of the modulation electrode operating voltage at this distance are obtained;

[0023] Step 1.5: According to the distance between the modulation electrode and the microchannel plate output electrode obtained in step 1.4, a modulation electrode is set between the microchannel plate output electrode and the anode, and an operating voltage is applied to it according to the voltage-gain curve and gain requirements at this distance.

[0024] Furthermore, in step 1.1, the working voltage of the modulation electrode adopts a DC stable modulation voltage or a pulse modulation voltage.

[0025] The present invention also provides a microchannel plate type photomultiplier tube for implementing the above-mentioned method for dynamically adjusting the gain of a microchannel plate type photomultiplier tube, comprising a photocathode, a microchannel plate, and an anode, wherein the photocathode is arranged on the input electrode side of the microchannel plate, and the anode is arranged on the output electrode side of the microchannel plate; the special feature of the microchannel plate is that:

[0026] Also included is a modulation electrode disposed between the microchannel plate output electrode and the anode;

[0027] The distance L between the modulation electrode and the microchannel plate output electrode satisfies: H≤L≤D / 10, where H is the thickness of the microchannel plate output electrode and D is the distance between the microchannel plate output electrode and the anode;

[0028] The modulation electrode generates a modulation electric field after applying an operating voltage. The modulation electric field modulates the output electrode of the microchannel plate and the electric field distribution in the microchannel, thereby modulating the number of multiplied electrons output by the microchannel plate, thereby adjusting the gain of the microchannel plate type photomultiplier tube. Dynamic adjustment of the gain of the microchannel plate type photomultiplier tube is achieved by adjusting the amplitude of the operating voltage.

[0029] Furthermore, the distance between the modulation electrode and the output electrode of the microchannel plate is 10 μm-0.5 mm.

[0030] Furthermore, the modulation electrode is a mesh electrode with a duty cycle greater than 90% or a conductive material film with an electron transmittance greater than 90%.

[0031] Furthermore, the modulation electrode is a metal material thin film with 100% electron transmittance.

[0032] Furthermore, the microchannel pore size of the microchannel plate is 6 μm and the thickness is 0.38 mm;

[0033] The distance between the photocathode and the input electrode of the microchannel plate is 0.16 mm, the distance between the output electrode of the microchannel plate and the modulation electrode is 0.2 mm, and the distance between the modulation electrode and the anode is 1.15 mm.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. The method for dynamically adjusting the gain of a microchannel plate-type photomultiplier tube provided by the present invention is based on the structural and electrical parameters of existing microchannel plate-type photomultiplier tubes. A modulation electrode is provided between the microchannel plate and the anode. When an operating voltage is applied to the modulation electrode, a modulation electric field is generated that penetrates into the output electrode and microchannel of the microchannel plate, thereby modulating the number of multiplied electrons output by the microchannel plate. This can increase or decrease the gain of the microchannel plate-type photomultiplier tube to meet the specific gain requirements in different application scenarios and at different times.

[0036] 2. The method for dynamically adjusting the gain of a microchannel plate-type photomultiplier tube provided by the present invention modulates the number of multiplied electrons output by the microchannel plate by dynamically adjusting the amplitude of the working voltage applied to the modulation electrode, while maintaining the total number of multiplied electrons generated by the microchannel plate itself. This achieves dynamic adjustment of the photomultiplier tube's electronic gain.

[0037] 3. The method for dynamically adjusting the gain of a microchannel plate type photomultiplier tube provided by the present invention maintains the gain characteristics of the microchannel plate itself. Not only can the electron beam at the output electrode of the microchannel plate be quickly pulled out of the microchannel plate through the modulation electrode, effectively reducing the influence of the space charge effect in the microchannel plate, thereby significantly improving the gain of the microchannel plate type photomultiplier tube on the original basis; at the same time, the electron output in the microchannel of the microchannel plate can be suppressed through the modulation electrode, thereby achieving the purpose of reducing the electron gain of the microchannel plate type photomultiplier tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a schematic structural diagram of a microchannel plate photomultiplier tube according to an embodiment of the present invention;

[0039] Figure 2 is a graph showing how the gain of a microchannel plate photomultiplier tube according to an embodiment of the present invention changes with the operating voltage of the modulation electrode;

[0040] The following are the descriptions of the reference numerals:

[0041] 1-photocathode, 2-microchannel plate, 3-modulation electrode, 4-anode. DETAILED DESCRIPTION

[0042] To make the objects, advantages and features of the present invention more clear, a microchannel plate photomultiplier tube with dynamically adjustable gain and a gain adjustment method thereof proposed by the present invention are further described in detail below with reference to the accompanying drawings and specific embodiments.

[0043] A method for dynamically adjusting the gain of a microchannel plate photomultiplier tube, wherein the microchannel plate photomultiplier tube includes a photocathode 1, a microchannel plate 2, and an anode 4, wherein the photocathode 1 is arranged on the input electrode side of the microchannel plate 2, and the anode 4 is arranged on the output electrode side of the microchannel plate 2. The method comprises the following steps:

[0044] Step 1: Figure 1 As shown, a modulation electrode 3 is set between the microchannel plate 2 and the anode 4, and a voltage-gain curve is obtained to show how the gain of the microchannel plate type photomultiplier tube changes with the working voltage of the modulation electrode 3. Then, an operating voltage is applied to the modulation electrode 3 according to the voltage-gain curve and the gain requirement, wherein the working voltage of the modulation electrode 3 adopts a DC stable modulation voltage or a pulse modulation voltage. Step 1 is specifically as follows:

[0045] Step 1.1, set the initial distance between the modulation electrode 3 and the output electrode of the microchannel plate 2 to L0, where H≤L0≤0.5mm, and H is the thickness of the output electrode of the microchannel plate 2;

[0046] Set the working voltage of the modulation electrode 3 V0 = V MCP ×(1-L0 / H)+i×10≤V MCP, i is the operating voltage variation coefficient, i=1,2,3,…, V MCP The working voltage of the output electrode of the microchannel plate 2;

[0047] Step 1.2: At the initial distance between the modulation electrode 3 and the output electrode of the microchannel plate 2, apply the operating voltages of 1, 2, 3, ... to the modulation electrode 3, respectively, and calculate the number of multiplied electrons collected by the anode 4 when a single electron is incident on the microchannel plate 2, and then record the maximum number N of multiplied electrons collected by the anode 4. max and a voltage-gain curve showing that the gain of the microchannel plate photomultiplier tube varies with the operating voltage of the modulation electrode 3;

[0048] Step 1.3, set the distance between the modulation electrode 3 and the output electrode of the microchannel plate 2 to L0+H / 20 and L0-H / 20 respectively, and then follow the method of step 1.2 to calculate the maximum value N of the multiplied electrons collected by the anode 4. max+ 、N max- and a voltage-gain curve showing that the gain of the microchannel plate photomultiplier tube varies with the operating voltage of the modulation electrode 3;

[0049] Step 1.4: Compare N max 、N max+ and N max- , if N max+ >N max , then the distance between the modulation electrode 2 and the output electrode of the microchannel plate 2 is increased in steps of H / 20, and then the maximum number of multiplied electrons collected by the anode 4 and the voltage-gain curve of the microchannel plate type photomultiplier tube gain as a function of the operating voltage of the modulation electrode 3 are obtained according to the method of step 1.2, until the maximum number of multiplied electrons collected by the anode 4 no longer increases, and the distance between the modulation electrode 3 and the output electrode of the microchannel plate 2 and the voltage-gain curve of the microchannel plate type photomultiplier tube gain as a function of the operating voltage of the modulation electrode 3 at this distance are obtained;

[0050] If N max- >N max , then the distance between the modulation electrode 2 and the output electrode of the microchannel plate 2 is reduced in steps of H / 20, and then the maximum number of multiplied electrons collected by the anode 4 and the voltage-gain curve of the microchannel plate type photomultiplier tube gain as a function of the operating voltage of the modulation electrode 3 are obtained according to the method of step 1.2, until the maximum number of multiplied electrons collected by the anode 4 no longer increases, and the distance between the modulation electrode 3 and the output electrode of the microchannel plate 2 and the voltage-gain curve of the microchannel plate type photomultiplier tube gain as a function of the operating voltage of the modulation electrode 3 at this distance are obtained;

[0051] Step 1.5: According to the distance between the modulation electrode 3 and the output electrode of the microchannel plate 2 obtained in step 1.4, the modulation electrode 3 is set between the output electrode of the microchannel plate 2 and the anode 4, and then the operating voltage is applied to the modulation electrode 3 according to the voltage-gain curve and gain requirements at this distance.

[0052] Step 2: photons are incident on the surface of the photocathode 1 , and the photocathode 1 is excited to generate photoelectrons that enter the microchannel plate 2 .

[0053] Step 3: Photoelectrons are accelerated and collided in the microchannel on the microchannel plate 2 to generate multiplied electrons.

[0054] Step 4: The modulation electrode 3 generates a modulation electric field under the action of the working voltage, and the modulation electric field penetrates into the output electrode and microchannel of the microchannel plate 2.

[0055] Step 5: Modulate the electric field to modulate the output electrode of the microchannel plate 2 and the electric field distribution in the microchannel, change the movement distance of the multiplied electrons, thereby adjusting the number of multiplied electrons output by the microchannel plate 2, and then adjust the number of multiplied electrons moving to the anode 4, thereby achieving adjustment of the gain of the microchannel plate type photomultiplier tube.

[0056] Step 6: Adjust the amplitude of the operating voltage according to the voltage-gain curve and the gain requirement, and then return to step 4 to achieve dynamic adjustment of the gain of the microchannel plate photomultiplier tube.

[0057] This embodiment also provides a microchannel plate type photomultiplier tube, which is used to implement the above-mentioned method of dynamically adjusting the gain of the microchannel plate type photomultiplier tube. Figure 1 As shown, the device includes a photocathode 1, a microchannel plate 2, and an anode 4, which are arranged in sequence. The photocathode 1 is arranged on the input electrode side of the microchannel plate 2, and the anode 4 is arranged on the output electrode side of the microchannel plate 2. A modulation electrode 3 is arranged between the output electrode of the microchannel plate 2 and the anode 4. The modulation electrode 3 is arranged close to the output electrode of the microchannel plate 2, and the distance L between the modulation electrode 3 and the output electrode of the microchannel plate 2 satisfies the following: H≤L≤D / 10, where H is the thickness of the output electrode of the microchannel plate 2, and D is the distance between the output electrode of the microchannel plate 2 and the anode 4.

[0058] The modulation electrode 3 generates a modulation electric field after applying the working voltage. The modulation electric field modulates the output electrode of the microchannel plate 2 and the electric field distribution in the microchannel, thereby modulating the number of multiplied electrons output by the microchannel plate 2, thereby realizing the adjustment of the gain of the microchannel plate type photomultiplier tube. The dynamic adjustment of the gain of the microchannel plate type photomultiplier tube is achieved by adjusting the amplitude of the working voltage.

[0059] This embodiment is based on a conventional microchannel plate photomultiplier tube structure. A modulation electrode 3 is disposed between the output electrode of the microchannel plate 2 and the anode 4, with the modulation electrode being located near the output electrode of the microchannel plate 2. Because the microchannel plate 2 has a microporous structure, the electric field generated by the modulation electrode 3 penetrates into the microchannels of the microchannel plate 2, thereby changing the electric field distribution at the output electrode of the microchannel plate 2 and within the microchannels near the output electrode. This in turn micro-modulates the electrons in the aforementioned region, allowing multiplied electrons that would otherwise only move to the output electrode to move to the anode 4, increasing the number of multiplied electrons output by the microchannel plate 2 and thereby improving the gain of the microchannel plate 2. Conversely, by adjusting the operating voltage amplitude of the modulation electrode 3, the electric field generated by the modulation electrode 3 forces multiplied electrons that would otherwise move to the anode 4 to move only to the output electrode, increasing the number of multiplied electrons that move to the output electrode while reducing the number of multiplied electrons that ultimately move to the anode 4, thereby reducing the gain of the microchannel plate 2.

[0060] The distance between the modulation electrode 3 and the output electrode of the microchannel plate 2 is 10μm-0.5mm. The modulation electrode 3 is a mesh electrode with a duty cycle greater than 90% or a conductive material film with an electron transmittance greater than 90%. The operating voltage applied by the modulation electrode 3 can be a DC stable modulation voltage or a pulse modulation voltage. The amplitude of the applied modulation voltage needs to be determined based on the structural parameters of the microchannel plate 2 and the structural parameters between the microchannel plate 2 and the modulation electrode 3. The greater the voltage difference between the modulation electrode 3 and the output electrode of the microchannel plate 2, the deeper the electric field generated by the modulation electrode 3 penetrates into the microchannel of the microchannel plate 2; the larger the aperture of the microchannel of the microchannel plate 2, the deeper the electric field generated by the modulation electrode 3 penetrates into the microchannel of the microchannel plate 2. The gain of the microchannel plate type photomultiplier tube changes with the depth of the electric field penetrating into the microchannel of the microchannel plate 2.

[0061] In this embodiment, the modulation electrode 3 uses a metal material film with an electron transmittance of 100%, the microchannel aperture of the microchannel plate 2 is 6 μm, the thickness is 0.38 mm, the distance between the photocathode 1 and the input electrode of the microchannel plate 2 is 0.16 mm, the distance between the output electrode of the microchannel plate 2 and the modulation electrode 3 is 0.2 mm, and the distance between the modulation electrode 3 and the anode 4 is 1.15 mm.

[0062] When the working voltage applied to the photocathode 1 is -1500V, the working voltage applied to the input electrode of the microchannel plate 2 is -1200V, the working voltage applied to the output electrode of the microchannel plate 2 is 400V, and the working voltage applied to the anode 4 is 0V, an electron is vertically emitted from the center of the photocathode 1 and enters a microchannel of the microchannel plate 2 for electron multiplication. When the microchannel plate type photomultiplier tube is not provided with the modulation electrode 3, the gain is 8115. The gain of the microchannel plate type photomultiplier tube of this embodiment varies with the working voltage of the modulation electrode 3, as shown in FIG. Figure 2As shown, when the operating voltage of the modulation electrode 3 is higher than -200V, the gain of the microchannel plate type photomultiplier tube shows a downward trend. When the operating voltage of the modulation electrode 3 is -150V, the gain of the microchannel plate type photomultiplier tube is reduced by 50% compared with the gain without the modulation electrode 3. When the operating voltage of the modulation electrode 3 is -220V, the gain of the microchannel plate type photomultiplier tube is 8870, which is 9.3% higher than the gain without the modulation electrode 3. It can be seen that in this embodiment, the modulation electrode 3 is provided between the output electrode and the anode of the microchannel plate 2, and the gain of the microchannel plate type photomultiplier tube can be dynamically adjusted by changing the operating voltage of the modulation electrode 3.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present invention.

Claims

1. A method for dynamically adjusting the gain of a microchannel plate type photomultiplier tube, wherein the microchannel plate type photomultiplier tube comprises a photocathode (1), a microchannel plate (2) and an anode (4), wherein the photocathode (1) is arranged on the input electrode side of the microchannel plate (2), and the anode (4) is arranged on the output electrode side of the microchannel plate (2); characterized in that: The following steps are involved: Step 1: a modulation electrode (3) is provided between the output electrode and the anode (4) of the microchannel plate (2), and a voltage-gain curve is obtained in which the gain of the microchannel plate type photomultiplier tube changes with the working voltage of the modulation electrode (3), and then a working voltage is applied to the modulation electrode (3) according to the voltage-gain curve and the gain requirement; Step 2: allowing photons to be incident on the surface of the photocathode (1), and the photocathode (1) is excited to generate photoelectrons that enter the microchannel plate (2); Step 3: Photoelectrons are accelerated and collided in the microchannel of the microchannel plate (2) to generate multiplied electrons; Step 4: The modulation electrode (3) generates a modulation electric field under the action of the working voltage, and the modulation electric field penetrates into the output electrode and microchannel of the microchannel plate (2); Step 5: Modulating the electric field to modulate the output electrode of the microchannel plate (2) and the electric field distribution in the microchannel, changing the movement distance of the multiplied electrons, thereby adjusting the number of multiplied electrons output by the microchannel plate (2), and further adjusting the number of multiplied electrons moving to the anode (4), thereby achieving adjustment of the gain of the microchannel plate type photomultiplier tube; Step 6: Adjust the amplitude of the operating voltage according to the voltage-gain curve and the gain requirement, and then return to step 4 to achieve dynamic adjustment of the gain of the microchannel plate photomultiplier tube.

2. The method for dynamically adjusting the gain of a microchannel plate photomultiplier tube according to claim 1, wherein: Step 1 is as follows: Step 1.1, setting the initial distance between the modulation electrode (3) and the output electrode of the microchannel plate (2) to L0, wherein H≤L0≤0.5mm, and H is the thickness of the output electrode of the microchannel plate (2); The working voltage of the modulation electrode (3) is set to V0 = V MCP ×(1-L0 / H)+i×10≤V MCP , where i is the operating voltage variation coefficient, i=1,2,3,…,V MCP The operating voltage of the output electrode of the microchannel plate (2); Step 1.2: At the initial distance between the modulation electrode (3) and the output electrode of the microchannel plate (2), apply a working voltage of 1, 2, 3, ... to the modulation electrode (3), and calculate the number of multiplied electrons collected by the anode (4) when a single electron is incident on the microchannel plate (2), and then record the maximum value N of the number of multiplied electrons collected by the anode (4). max and a voltage-gain curve of the microchannel plate type photomultiplier tube gain as the working voltage of the modulation electrode (3) changes; Step 1.3, set the distance between the modulation electrode (3) and the output electrode of the microchannel plate (2) to L0+H / 20 and L0-H / 20 respectively, and then obtain the maximum value N of the multiplied electrons collected by the anode (4) according to the method of step 1.

2. max+ 、N max- and a voltage-gain curve of the microchannel plate type photomultiplier tube gain as the working voltage of the modulation electrode (3) changes; Step 1.4: Compare N max 、N max+ and N max- , if N max+ >N max , then the distance between the modulation electrode (3) and the output electrode of the microchannel plate (2) is increased in steps of H / 20, and then the maximum value of the number of multiplied electrons collected by the anode (4) and the voltage-gain curve of the microchannel plate type photomultiplier tube gain as the modulation electrode (3) working voltage are obtained according to the method of step 1.2, until the maximum value of the number of multiplied electrons collected by the anode (4) no longer increases, and the distance between the modulation electrode (3) and the output electrode of the microchannel plate (2) and the voltage-gain curve of the microchannel plate type photomultiplier tube gain as the modulation electrode (3) working voltage is obtained at this distance; If N max- >N max , then the distance between the modulation electrode (3) and the output electrode of the microchannel plate (2) is reduced in steps of H / 20, and then the maximum value of the number of multiplied electrons collected by the anode (4) and the voltage-gain curve of the microchannel plate type photomultiplier tube gain as the modulation electrode (3) working voltage are obtained according to the method of step 1.2, until the maximum value of the number of multiplied electrons collected by the anode (4) no longer increases, and the distance between the modulation electrode (3) and the output electrode of the microchannel plate (2) and the voltage-gain curve of the microchannel plate type photomultiplier tube gain as the modulation electrode (3) working voltage is obtained at this distance; Step 1.5: According to the distance between the modulation electrode (3) and the output electrode of the microchannel plate (2) obtained in step 1.4, the modulation electrode (3) is set between the output electrode of the microchannel plate (2) and the anode (4), and then an operating voltage is applied thereto according to the voltage-gain curve at the distance and the gain requirement.

3. The method for dynamically adjusting the gain of a microchannel plate photomultiplier tube according to claim 2, wherein: In step 1.1, the working voltage of the modulation electrode (3) adopts a DC stable modulation voltage or a pulse modulation voltage.

4. A microchannel plate type photomultiplier tube, used to implement the method for dynamically adjusting the gain of a microchannel plate type photomultiplier tube according to any one of claims 1 to 3, comprising a photocathode (1), a microchannel plate (2) and an anode (4), wherein the photocathode (1) is arranged on the input electrode side of the microchannel plate (2), and the anode (4) is arranged on the output electrode side of the microchannel plate (2); characterized in that: It also includes a modulation electrode (3) disposed between the output electrode of the microchannel plate (2) and the anode (4); The distance L between the modulation electrode (3) and the output electrode of the microchannel plate (2) satisfies the following conditions: H≤L≤D / 10, where H is the thickness of the output electrode of the microchannel plate (2), and D is the distance between the output electrode of the microchannel plate (2) and the anode (4); The modulation electrode (3) generates a modulation electric field after applying an operating voltage. The modulation electric field modulates the output electrode of the microchannel plate (2) and the electric field distribution in the microchannel, thereby modulating the number of multiplied electrons output by the microchannel plate (2), thereby achieving adjustment of the gain of the microchannel plate type photomultiplier tube. Dynamic adjustment of the gain of the microchannel plate type photomultiplier tube is achieved by adjusting the amplitude of the operating voltage.

5. The microchannel plate photomultiplier tube according to claim 4, wherein: The distance between the modulation electrode (3) and the output electrode of the microchannel plate (2) is 10 μm-0.5 mm.

6. The microchannel plate photomultiplier tube according to claim 5, wherein: The modulation electrode (3) is a mesh electrode with a duty cycle greater than 90% or a conductive material film with an electron transmittance greater than 90%.

7. The microchannel plate photomultiplier tube according to claim 6, characterized in that: The modulation electrode (3) is a metal material thin film with an electron transmittance of 100%.

8. The microchannel plate photomultiplier tube according to any one of claims 4 to 7, characterized in that: The microchannel plate (2) has a microchannel pore size of 6 μm and a thickness of 0.38 mm; The distance between the photocathode (1) and the input electrode of the microchannel plate (2) is 0.16 mm, the distance between the output electrode of the microchannel plate (2) and the modulation electrode (3) is 0.2 mm, and the distance between the modulation electrode (3) and the anode (4) is 1.15 mm.

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