Optimization Method Based on Microchannel Plate Position-Sensitive Anode Photon Counting Imaging Detector

Abstract

This invention relates to an optimization method for a microchannel plate position-sensitive anode photon counting imaging detector, comprising: modeling the space charge behavior within the MCP, modeling the space charge behavior between the MCP output end and the sensing layer film, modeling the space charge diffusion behavior within the sensing layer film, and modeling charge-segmented anode crosstalk. The results of the previous step are used as inputs for the next step, thus establishing a correlation between the design parameters or output characteristics of each step and the system output image. This completes the overall optimization design of the MCP position-sensitive anode photon counting imaging detector. This optimization method can comprehensively and systematically analyze the impact of space charge behavior within the detector on image quality, establish a correlation between the design parameters or output characteristics of each step and the system output image, and provide a corresponding theoretical basis for the overall detector design optimization. It is highly efficient, low-cost, and widely applicable.

Description

Technical Field

[0001] This invention relates to the field of photodetector technology, and in particular to an optimization method for a microchannel plate position-sensitive anode photon counting imaging detector. Background Technology

[0002] Space-based ultraviolet detection and astronomical observation targets exhibit weak radiation intensity, approaching a single-photon state. Traditional detection methods cannot meet the requirements in terms of detection sensitivity and imaging speed. Microchannel plate (MCP) position-sensitive anode photon counting imaging detectors detect photons in a two-dimensional manner and achieve imaging through integration over a certain time. They possess extremely high detection efficiency and extremely low dark noise, and are currently the only widely used array imaging detector in space science. The quality of their imaging directly restricts the development of space astronomical observations.

[0003] my country's deep-space ultraviolet exploration has gone through a process of "from scratch," but there is still a significant gap between China and foreign countries in the development of MCP-based position-sensitive anode photon counting imaging detectors and imaging system performance. Currently, the only wedge-shaped (WSZ) anode used in my country for deep-space ultraviolet exploration has a spatial resolution of around 88 μm, and the images exhibit nonlinear phenomena. Facing the future needs of space development, the demand for higher-performance photon counting imaging detectors is inevitable, making the optimized design of such detectors essential. In the field of photoelectric detector technology, there are also some studies on the influence of MCP on the behavior of space charge within the detector. For example, in 1989, Andy Smith et al. used charge clouds from the MCP that followed uniform and Gaussian distributions to simulate the distortion problem of the WSZ anode, concluding that the MCP gain, the distance between the MCP and the WSZ anodes all affect the image nonlinearity. Subsequently, M. Saito and G. J. Price et al. conducted extensive research on the emitted charge cloud of the MCP, primarily testing the effects of the distance between the MCP and the anode, the accelerating voltage between the MCP and the anode, and the operating voltage of the MCP on the size of the charge cloud, thereby causing distortion in the decoded image. In 2004, J. S. Lapington proposed that when electrons emitted from the MCP bombard the charge-segmented anode, a large number of secondary electrons are generated on the anode metal surface, altering the original spatial charge distribution of the electron cloud, thus causing positional nonlinearity and image instability. He proposed using a resistive anode to directly collect the emitted electron cloud from the MCP, thereby improving imaging quality by generating induced charges. In 2010, He Lingping et al. established a two-dimensional WSZ anode photon counting detector imaging model, simulating the influence of the relationship between the electron cloud size and the anode electrode period length on imaging quality. These studies show that many factors affect the imaging performance of MCP-based position-sensitive anode photon counting imaging detectors. However, whether it is the MCP aperture size, accelerating voltage, distance between MCP and anode, or detector charge readout method, all factors ultimately affect the behavior of space charge within the detector. Fundamentally, the behavior of space charge determines the imaging performance of this type of detector.

[0004] Currently, there is no integrated simulation model for the behavior of space charge within a MCP-based position-sensitive anode photon counting imaging detector. Existing models lack comprehensiveness, either missing behavioral aspects or focusing on the impact of individual device parameters on imaging performance. Much of the research concentrates on MCP electronic gain and the diffusion of the sensing layer film. The former lacks research on the behavior of MCP emitted charges within the vacuum chamber, neglecting the influence of the energy distribution and trajectory of the emitted charges on the original electrostatic field (particle-field interaction) and the restriction of space charge movement by the vacuum chamber walls, especially the issues of charge accumulation and charge scattering (particle-matter interaction) caused by the interaction of high-energy emitted charges with the vacuum chamber walls. The latter lacks research on charge-segmented anode crosstalk caused by the diffused sensing layer film charge. These shortcomings demonstrate the inadequacy of existing models, which cannot comprehensively and realistically reflect the behavior of space charge within the detector. The lack of an integrated model severely restricts further optimization and improvement of detector performance. Summary of the Invention

[0005] One objective of this invention is to provide an optimization method for a microchannel plate position-sensitive anode photon counting imaging detector. This method can comprehensively and systematically analyze the impact of space charge behavior within the detector on image quality, establish the correlation between design parameters or output characteristics of each component and the system output image, provide a corresponding theoretical basis for overall detector design optimization, and is highly efficient, low-cost, and widely applicable.

[0006] An optimization method for a microchannel plate position-sensitive anode photon counting imaging detector includes the following steps:

[0007] S1. The space charge behavior within the microchannel plate position-sensitive anode photon counting imaging detector is decomposed into the charge distribution within the microchannel plate, the charge distribution between the microchannel plate and the sensing layer film, the charge distribution on the sensing layer film, and the charge distribution of the position-sensitive anode. Based on the charge distribution within the microchannel plate, the charge distribution between the microchannel plate and the sensing layer film, the charge distribution on the sensing layer film, and the charge distribution of the position-sensitive anode, an integrated simulation model of the microchannel plate position-sensitive anode photon counting imaging detector is constructed, consisting of a microchannel plate space charge behavior model, a microchannel plate emission end and sensing layer film space charge behavior model, a sensing layer film space charge diffusion behavior model, and a charge segmentation type anode crosstalk model.

[0008] S2. Calculate the amount of charge on the position-sensitive anode panel, and substitute the amount of charge collected by the position-sensitive anode into the centroid decoding algorithm to obtain a simulated image;

[0009] S3. Compare the image resolution and nonlinearity of the input image and the simulated image to determine whether the input image meets the set accuracy; and

[0010] S4. When the input image does not meet the set accuracy, iteratively optimize the parameters of the integrated simulation model based on the microchannel plate position-sensitive anode photon counting imaging detector.

[0011] In one embodiment of the present invention, step S1 includes the following steps:

[0012] S11. Construct a model of space charge behavior within a microchannel plate;

[0013] S12. Using the results of the space charge distribution of the space charge behavior model in the microchannel plate as input, construct a space charge behavior model between the microchannel plate emission end and the sensing layer film.

[0014] S13. Using the results of the space charge distribution model between the microchannel plate emission end and the sensing layer film as input, construct a space charge diffusion behavior model within the sensing layer film; and

[0015] S14. Using the results of the space charge distribution model of the space charge diffusion behavior model in the sensing layer film as input, construct a charge segmentation type anode crosstalk model.

[0016] In one embodiment of the present invention, step S11 includes the following steps:

[0017] S111. Construct a three-dimensional model of a microchannel plate position-sensitive anode photon counting imaging detector and set the initial environment for the space charge behavior of the microchannel plate position-sensitive anode photon counting imaging detector; and

[0018] S112. Construct a secondary electron multiplication model within the microchannel plate and obtain the results of the emitted charge trajectory of the secondary electron multiplication model within the microchannel plate.

[0019] In one embodiment of the present invention, in step S111, a three-dimensional model of a microchannel plate position-sensitive anode photon counting imaging detector is constructed using the parametric modeling module of COMSOL Multiphysics software. The electrostatic field analysis module in COMSOL Multiphysics software is selected to set boundary conditions for the incident surface of the microchannel plate, the exit surface of the microchannel plate, the vacuum chamber wall, and the position-sensitive anode, thereby restoring the potential value of the space charge at each point when the three-dimensional model of the microchannel plate position-sensitive anode photon counting imaging detector is in its initial state.

[0020] In one embodiment of the present invention, in step S112, the charged particle tracking module in COMSOL Multiphysics software is selected. Based on the principle of secondary electron emission, the Monte Carlo method is used to simulate the motion process of space charge in the microchannel plate, or the secondary electron emission coefficient curve of the microchannel plate is consulted. The secondary electron emission coefficient is embedded into COMSOL Multiphysics software, and the boundary conditions when the space charge collides with the channel wall of the microchannel plate are set. Within the set simulation time step Δt, the velocities v(x,y,z) and displacements s(x,y,z) of all space charges in the model are calculated. Based on the kinematic equations (1) and (2) of the space charge, the COMSOL Multiphysics software calculates the motion state of any point (x,y,z) in space, completes the tracking process of secondary electron multiplication in the microchannel plate, and obtains the result of the trajectory of the emitted charge in the secondary electron multiplication model in the microchannel plate:

[0021]

[0022]

[0023] In formulas (1) and (2), m is the particle mass, q is the charge, and E(x,y,z) is the electric field intensity at any point in space.

[0024] In one embodiment of the present invention, the space charge behavior model between the microchannel plate emission end and the sensing layer film includes a space charge motion model under the action of a combined electromagnetic field and a space charge motion model under the action of matter. Step S12 includes the following steps:

[0025] S121. Inheriting the results of the secondary electron multiplication model of the microchannel plate, the range of space charge movement is extended to the entire vacuum chamber. The magnetic field analysis module and the custom equation module are selected. Based on the Liner-Wiescher potential formula and the electromagnetic field formula (3) and (4) of the electromagnetic field of the electromagnetic field generated by the electromagnetic field of any moving charged particle, the electromagnetic disturbance generated by the microchannel plate at different times is coupled with the original electrostatic field to establish a space charge movement model under the action of the comprehensive electromagnetic field:

[0026]

[0027] B0 = e r ×E0 / c (4)

[0028] In formulas (3) and (4), E0 is the perturbation electric field; B0 is the perturbation magnetic field; ε0 is the vacuum permittivity; e is the charge; c is the speed of light; v = v(t') is the velocity of the particle at the moment of radiation t', t' = t + r / c, and the position vector x of the particle at this moment is... e (t'); r = xxe (t') is the position vector of the particle pointing to the field point x at time t', and r is the distance from the particle to the field point at time t'; e r It is the unit vector in the r direction;

[0029] S122. Based on the theory of interaction between high-energy particles and matter, the data processing module of COMSOL Multiphysics software is used to statistically classify all motion states of space charges when emitted charges from the edge of the microchannel plate collide with the vacuum chamber wall, and a motion model of space charges under the action of matter is established.

[0030] In one embodiment of the present invention, in step S13, by using a custom equation module, according to Fick's diffusion law, space charge diffuses upon landing on the sensing layer. Formulas (5) to (7) are used to solve for the time-varying electron number density n, thus obtaining the distribution of space charge in the sensing layer film at each moment. The result of the space charge distribution model under the combined electromagnetic field is used as input. The diffusion coefficient of the sensing film is checked or tested to establish a diffusion model of space charge in the sensing layer film at each moment t. The post-processing function of COMSOL Multiphysics software is used to statistically analyze the image charge diffusion distribution.

[0031]

[0032]

[0033]

[0034] In formulas (5), (6), and (7), D is the diffusion coefficient and the thermodynamic factor. As a constant, a n Effective electrons in the material, D p It is the electron diffusion constant, k B Where μ is Boltzmann constant, T is temperature, and μ is the constant. p Hall mobility.

[0035] In one embodiment of the present invention, in step S14, the inter-electrode crosstalk effect is analyzed using discrete components of a charge-segmented anode inter-electrode crosstalk model, wherein the inter-electrode capacitance C of the position-sensitive anode is... ij Using the collected induced charge Q ij Perform the calculation:

[0036]

[0037] The interaction between multiple electrodes is expressed by equation (9):

[0038]

[0039] In formulas (8) and (9), i = 1, 2, 3, ..., j = 2, 3, 4, ..., V i V j Let C be the potential of different electrodes. ij =C ji .

[0040] In one embodiment of the present invention, in step S3, the image resolution and the precision of image nonlinearity are set, wherein,

[0041] Image resolution similarity is denoted as A1, S 输 S is the input image resolution. 仿 The output image resolution is calculated using formula (10):

[0042]

[0043] The image nonlinearity is B1, calculated by formula (11). Select m points from the input image, calculate the distance d between two selected points in the input image and the corresponding distance d' between two points in the simulation image, then the distortion value B1 of the system is:

[0044]

[0045] In one embodiment of the present invention, in step S4, the microchannel plate-based position-sensitive anode photon counting imaging detector is optimized by iteratively adjusting the parameters of the microchannel plate electron multiplication model, the motion model parameters between the microchannel plate and the sensing field film, the diffusion model parameters of the sensing layer film, and the crosstalk effect model parameters between the position-sensitive anodes.

[0046] The beneficial effects of the optimization method of the present invention based on a microchannel plate position-sensitive anode photon counting imaging detector are as follows:

[0047] The optimization method for a microchannel plate position-sensitive anode photon counting imaging detector of the present invention proposes an integrated simulation model consisting of a microchannel plate space charge behavior model, a space charge behavior model between the microchannel plate emitting end and the sensing layer film, a space charge diffusion behavior model within the sensing layer film, and a charge-segmented anode crosstalk model. This model can model and simulate the space charge behavior within the microchannel plate, reconstruct the behavior trajectory of incident photons after photoelectric conversion and electron multiplication effect, and make up for the shortcomings of existing imaging models that use empirical formulas to simplify the simulation of the microchannel plate emitting charge distribution, providing accurate input for subsequent charge behavior modeling.

[0048] The optimization method of the microchannel plate position-sensitive anode photon counting imaging detector of the present invention considers the interaction between particles and fields (electromagnetic field disturbance caused by moving charges) and the interaction between particles and matter (charge accumulation caused by charge bombardment of the chamber wall, etc.), specifically quantifies the effect of these factors on image quality degradation, makes up for the lack of simulation modeling of space charge behavior in the detector, provides theoretical support for the optimization of the vacuum chamber wall structure of the detector, can comprehensively and realistically reflect the space charge behavior in the detector, and is conducive to the overall optimization and improvement of detector performance.

[0049] The optimization method of the microchannel plate position-sensitive anode photon counting imaging detector of the present invention establishes a thin film diffusion model of the sensing layer and a charge-segmented anode inter-electrode crosstalk mathematical model, so as to remove the inter-electrode crosstalk effect in the subsequent centroid decoding algorithm and provide theoretical support for the optimization of position-sensitive anode structural parameters.

[0050] To address the demand for high-performance photon counting imaging detectors in modern solar-terrestrial space astronomical observations, this invention utilizes electromagnetic field finite element analysis and charged particle tracing techniques to establish a series of process models, including space charge photoelectric conversion, multiplication, interaction with the vacuum chamber wall, diffusion of the sensing layer thin film, and crosstalk between anodes, and connects these models in series. Within a unified input framework, the influence of parameters at each stage on the detector's image quality is analyzed, establishing a correlation between the design parameters or output characteristics of each stage and the system's output image. This lays a solid theoretical foundation and provides technical assurance for improving existing microchannel plate charge-segmented anode photon counting imaging detectors and developing novel high-resolution detectors.

[0051] The further objects and advantages of the invention will become fully apparent from the following description and accompanying drawings. Attached Figure Description

[0052] Figure 1A This is a schematic diagram of the structure of the microchannel plate position-sensitive anode photon counting imaging detector of the present invention;

[0053] Figure 1B for Figure 1A The diagram shown is a schematic of the internal structure of a microchannel plate position-sensitive anode photon counting imaging detector.

[0054] Figure 2 This is a flowchart illustrating the optimization method of the microchannel plate position-sensitive anode photon counting imaging detector of the present invention.

[0055] Figure 3A for Figure 1A The diagram shows a three-dimensional structure of a microchannel plate based on a microchannel plate position-sensitive anode photon counting imaging detector with the microchannel plate portion cut open.

[0056] Figure 3B for Figure 1AThe diagram shown illustrates the secondary electron emission principle of a microchannel plate position-sensitive anode photon counting imaging detector.

[0057] Figure 4 for Figure 1A The diagram shows the diffusion process of the thin film of the position-sensitive anode sensing layer in a microchannel plate position-sensitive anode photon counting imaging detector.

[0058] Figure 5 for Figure 1A The diagram shows a position-sensitive anode structure for a microchannel plate position-sensitive anode photon counting imaging detector.

[0059] Figure 6 for Figure 1A The diagram shown is an equivalent circuit diagram of a wedge-shaped readout anode based on a microchannel plate position-sensitive anode photon counting imaging detector.

[0060] The reference numerals are as follows: 1. Microchannel plate; 2. Sensing layer film; 3. Position-sensitive anode structure; 4. Imaging charge; 5. Encapsulation shell. Detailed Implementation

[0061] The following description is intended to disclose the present invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art. The basic principles of the invention defined in the following description can be applied to other embodiments, modifications, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of the invention.

[0062] Those skilled in the art should understand that, in the disclosure of this invention, the terms "vertical," "horizontal," "up," "down," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting this invention.

[0063] It is understood that the term "a" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element can be multiple, and the term "a" should not be understood as a limitation on the number.

[0064] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows for communication; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0065] Because microchannel plate (MCP) position-sensitive anode photon counting imaging detectors operate under high-pressure vacuum, real-time observation of internal charges is difficult. To effectively assess the impact of space charge behavior within the detector on imaging performance and achieve overall detector optimization, simulation methods are indispensable, especially integrated simulation models of the entire process of space charge behavior within MCP position-sensitive anode photon counting imaging detectors. Therefore, this invention proposes a method using charged particle tracing technology and electromagnetic field finite element analysis to comprehensively reproduce the dynamic processes of photon incident MCP, electron multiplication, transit, diffusion, and crosstalk. This enables a three-dimensional visualization model and optimization method for MCP position-sensitive anode photon counting imaging detectors, making the temporal and spatial distribution of charges within the detector measurable and visualized. It also establishes the correlation between design parameters or output characteristics of each stage and the system output image, providing a theoretical basis for overall detector optimization design.

[0066] Specifically, existing MCP-based position-sensitive anode photon counting imaging detector models lack comprehensiveness and cannot fully and realistically reflect the behavior of space charge within the detector. Therefore, to overcome the shortcomings of existing MCP-based position-sensitive anode photon counting imaging detector models, this invention provides an optimization method for a microchannel plate position-sensitive anode photon counting imaging detector. This method provides a full-link simulation method for detector imaging charge motion, including: modeling the behavior of space charge within the MCP, modeling the behavior of space charge between the MCP output end and the sensing layer film, modeling the diffusion behavior of space charge within the sensing layer film, and modeling charge-segmented anode crosstalk. The results of the previous step are used as inputs for the next step, realizing the correlation between the design parameters or output characteristics of each step and the system output image, thus completing the overall optimized design of the MCP-based position-sensitive anode photon counting imaging detector.

[0067] The following will combine Figures 1A to 6 The present invention will specifically describe the optimization method of the microchannel plate position-sensitive anode photon counting imaging detector, including the specific steps and the corresponding technical effects that can be achieved.

[0068] like Figure 1A and Figure 1B As shown, the overall packaging structure and the structure of the cut-out shell of the MCP-based position-sensitive anode photon counting imaging detector of the present invention are illustrated. The MCP-based position-sensitive anode photon counting imaging detector includes a packaging shell 5, a position-sensitive anode structure 3 disposed in the packaging shell 5, a sensing layer film 2 covering the back of the position-sensitive anode structure 3, and a microchannel plate 1 disposed at intervals on the sensing layer film 2. The position-sensitive anode structure 3 collects induced charges, and crosstalk effect is generated between each anode. The imaging charge 4 diffuses on the sensing layer film 2, and the imaging charge 4 undergoes a secondary electron multiplication effect in the microchannel plate 1.

[0069] Specifically, such as Figure 3A As shown, the microchannel plate 1 is a thin circular sheet composed of multiple hollow cylinders arranged in parallel, with multiple hollow cylindrical channels. The inner wall of each channel is coated with a conductive secondary electron emission film, thus the microchannel plate has continuous electron multiplication capability.

[0070] like Figure 3B As shown, four channels are used to describe the principle of secondary electron emission on a microchannel plate: voltages -V and +V are applied to the incident and exit ends of the MCP, respectively. Photoelectrons are incident on the MCP channel (structural parameters: aperture diameter D, bevel angle θ, thickness L), and bombard the inner wall under the action of the accelerating electric field, which will excite multiple secondary electrons. This process is repeated to achieve the electron multiplication effect.

[0071] Furthermore, such as Figure 4 As shown, the back of the position-sensitive anode structure 3 is covered with a sensing layer film 2. Figure 4 The process of the imaging charge 4 diffusing on the sensing layer film 2 is illustrated.

[0072] like Figure 5 As shown, in this embodiment of the present invention, taking the WSZ anode basic structure as an example, the position-sensitive anode structure 3 collects induced charges, and crosstalk effects occur between the anodes. Figure 5 In the diagram, W represents a wedge-shaped anode, S represents a strip-shaped anode, and Z represents a Z-shaped anode.

[0073] like Figure 1A and Figure 1BAs shown, this invention is based on the principle and structure of a MCP-based position-sensitive anode photon counting imaging detector. It utilizes the parametric modeling module, electric field module, magnetic field module, charged particle tracking module, and custom equation module in COMSOL Multiphysics software to conduct an integrated simulation model study of the detector. It is understood that space charge behavior is a process under the coupling of multiple fields such as electric field, magnetic field, and charged particle tracking. By decomposing the space charge behavior process within the detector into the charge distribution within the MCP, the charge distribution between the MCP and the sensing layer film, the charge distribution on the sensing layer film, and the charge distribution of the position-sensitive anode, the amount of charge collected by the position-sensitive anode is substituted into the centroid decoding algorithm to obtain a simulated image. Spatial resolution and image nonlinearity are important indicators for evaluating detector performance. By comparing the spatial resolution and image nonlinearity of the input image and the simulated image, the detector imaging model parameters are iteratively optimized, thereby improving the imaging performance of this type of detector.

[0074] like Figures 2 to 6 As shown, the specific implementation scheme of the optimization method of the present invention based on a microchannel plate position-sensitive anode photon counting imaging detector is as follows:

[0075] 1. Three-dimensional modeling and initial environment setting for space charge behavior of an MCP-based position-sensitive anode photon counting imaging detector. The parametric modeling module of COMSOL Multiphysics software was used to model and set the properties of the MCP-based position-sensitive anode photon counting imaging detector, such as... Figure 1A and Figure 1B As shown. In the initial state, the detector is in a high-voltage electrostatic field. By selecting the electrostatic field analysis module in the software, the boundary conditions of the MCP incident surface, MCP exit surface, vacuum chamber wall, and position-sensitive anode can be set, thereby restoring the potential value of each point in the detector model in the initial state.

[0076] 2. Implementation of the secondary electron multiplication model within the MCP. For example... Figure 3A As shown, the MCP is composed of multiple glass microchannels stacked in parallel, with the inner walls coated with a high-resistivity secondary electron emission material and the two end faces coated with a nickel-chromium metal film, such as... Figure 3BAs shown, its internal charge behavior is mainly electron multiplication. The charged particle tracking module in COMSOL Multiphysics software is selected. Based on the principle of secondary electron emission, the Monte Carlo method is used to simulate the motion of space charges in the MCP, or the secondary electron emission coefficient curve of the MCP is consulted. The secondary electron emission coefficient is embedded into the COMSOL Multiphysics software, and the boundary conditions when space charges collide with the MCP channel wall are set. Within the set simulation time step Δt, the velocities v(x,y,z) and displacements s(x,y,z) of all space charges in the model are calculated. Based on the kinematic equations (1) and (2) of space charges, the COMSOL Multiphysics software calculates the motion state of any point (x,y,z) in space, completing the tracking process of secondary electron multiplication within the microchannel plate, and obtaining the trajectory of the emitted charges from the secondary electron multiplication model within the microchannel plate:

[0077]

[0078]

[0079] In formulas (1) and (2), m is the particle mass, q is the charge, and E(x,y,z) is the electric field intensity at any point in space.

[0080] It is understood that the MCP-based position-sensitive anode photon counting imaging detector model proposed in this invention models and simulates the behavior of space charge within the MCP, reconstructs the behavior trajectory of incident photons after photoelectric conversion and electron multiplication effect, and makes up for the shortcomings of existing imaging models that use empirical formulas to simplify the simulation of the outgoing charge distribution of the MCP, providing accurate input for the charge behavior modeling of subsequent stages.

[0081] 3. The realization of the space charge motion model between the MCP emitter and the sensing layer film mainly includes two parts: the interaction between particles and the field, and the interaction between particles and matter. In other words, the space charge behavior model between the microchannel plate emitter and the sensing layer film includes a space charge motion model under the combined electromagnetic field and a space charge motion model under the influence of matter.

[0082] 3.1 Inheriting the results of the MCP secondary electron multiplication model regarding the trajectory of emitted charges, the range of space charge motion is extended to the entire vacuum chamber. The accelerated motion of space charges within the vacuum chamber will disturb the original electrostatic field, causing it to become non-uniformly distributed. By selecting the magnetic field analysis module and the custom equation module, and based on the Liner-Wiescher potential formula, the disturbed electromagnetic field generated by the electromagnetic field of any moving charged particle is given by equations (3) and (4). By coupling the electromagnetic disturbance generated by the emitted charges of MCP at different times with the original electrostatic field, a space charge motion model under the combined electromagnetic field can be established:

[0083]

[0084] B0 = e r ×E0 / c (4)

[0085] In formulas (3) and (4), E0 is the perturbation electric field; B0 is the perturbation magnetic field; ε0 is the vacuum permittivity; e is the charge; c is the speed of light; v = v(t') is the velocity of the particle at the moment of radiation t', t' = t + r / c, and the position vector x of the particle at this moment is... e (t'); r = xx e (t') is the position vector of the particle pointing to the field point x at time t', and r is the distance from the particle to the field point at time t'; e r It is the unit vector in the r direction.

[0086] 3.2 When charges are emitted from the edge of the MCP, there is a possibility of collision with the vacuum chamber wall. Electrons accelerated under high voltage possess high energy. Based on the theory of high-energy particle-matter interaction, the software backend data processing module statistically classifies all possible motion states of space charges during collision with the vacuum chamber wall, establishing a space charge motion model under the influence of matter.

[0087] It is understood that the optimization method of the microchannel plate position-sensitive anode photon counting imaging detector of the present invention considers the interaction between particles and fields (electromagnetic field disturbance caused by moving charges) and the interaction between particles and matter (charge accumulation caused by charge bombardment of the chamber wall, etc.), specifically quantifies the effect of these factors on image quality degradation, makes up for the lack of simulation modeling of space charge behavior in the detector, and provides theoretical support for the optimization of the vacuum chamber wall structure of the detector.

[0088] 4. Implementation of the space charge diffusion model for the sensing layer thin film (e.g.) Figure 4 (As shown). Through a custom equation module, based on Fick's diffusion law, the diffusion distribution of charge n on the sensing layer film over time is related to the macroscopic diffusion current J. P Diffusion coefficient D, electric field E, Hall mobility u p The space charge is related to the amount of charge e, as shown in equations (5) to (7). The space charge diffuses as it falls onto the sensing layer. By solving for the electron number density n that varies with time using equations (5) to (7), the distribution of space charge in the sensing layer film at each time step can be obtained. The result of the space charge distribution in 3.1 is used as the input of this model, that is, the result of the space charge distribution of the space charge motion model under the action of the comprehensive electromagnetic field is used as the input. By consulting or testing the material parameters such as the diffusion coefficient of the sensing film, the diffusion model of space charge in the sensing layer film at each time step t can be established. The post-processing function of COMSOL software can be used to statistically analyze the diffusion distribution of the imaging charge.

[0089]

[0090]

[0091]

[0092] In formulas (5), (6), and (7), D is the diffusion coefficient and the thermodynamic factor. As a constant, a n Effective electrons in the material, D p It is the electron diffusion constant, k B U is Boltzmann's constant, T is temperature, and u is... p Here is the Hall mobility.

[0093] 5. Implementation of the position-sensitive anode inter-electrode crosstalk model. Discrete components are used to analyze the inter-electrode crosstalk effect (taking the basic structure of the WSZ anode as an example, such as...). Figure 5 As shown), the circuit simulation equivalent diagram for reading the position-sensitive anode is as follows. Figure 6 As shown, the inter-electrode capacitance C of the position-sensitive anode is... ij Using the collected induced charge Q ij Perform the calculation:

[0094]

[0095] The interaction between multiple electrodes is expressed by equation (9):

[0096]

[0097] In formulas (8) and (9), i = 1, 2, 3, ..., j = 2, 3, 4, ..., V i V j Let C be the potential of different electrodes. ij =C ji .

[0098] The amount of charge on each output anode panel is counted and input into the subsequent centroid decoding algorithm, which can output a detector simulation image.

[0099] It is understood that the optimization method of the microchannel plate position-sensitive anode photon counting imaging detector of the present invention establishes a thin film diffusion model of the sensing layer and a charge-segmented anode inter-electrode crosstalk mathematical model, so as to remove the inter-electrode crosstalk effect in the subsequent centroid decoding algorithm and provide theoretical support for the optimization of position-sensitive anode structural parameters.

[0100] It is worth mentioning that the optimization method of the microchannel plate position-sensitive anode photon counting imaging detector of the present invention is applicable to wedge-shaped, Vernier, MAMA, cross-line, delay line, or future self-designed position-sensitive anodes. It is also applicable to various cascading methods of multiple MCPs, such as two MCPs in a "V" cascade or three MCPs in a "Z" cascade. In other words, this model is applicable to all MCP position-sensitive anode photon counting imaging detectors. Any changes to the anode structure or the MCP cascading method fall within the protection scope of this solution.

[0101] 6. Image Evaluation. The image resolution and non-linearity precision are set, and calculations are performed based on image resolution similarity and the non-linearity formula. If the input image meets the set precision, the system does not need optimization. If the system does not meet the set image precision, it enters the iterative optimization process.

[0102] Image resolution similarity is denoted as A1, S 输 S is the input image resolution. 仿 The output image resolution is calculated using formula (10):

[0103]

[0104] The image nonlinearity is B1, calculated by formula (11). Select m points from the input image, calculate the distance d between two selected points in the input image and the corresponding distance d' between two points in the simulation image, then the distortion value B1 of the system is:

[0105]

[0106] 7. Iterative Optimization. The detector system is optimized by iteratively adjusting the parameters of the MCP electron multiplication model, the motion model parameters between the MCP and the sensing field thin film, the diffusion model parameters of the sensing layer thin film, and the crosstalk effect model parameters between the position-sensitive anodes.

[0107] Understandably, this invention utilizes electromagnetic field finite element analysis and charged particle tracing technology to establish a series of process models, including space charge photoelectric conversion, multiplication, interaction with the vacuum chamber wall, diffusion of the sensing layer thin film, and crosstalk between anodes, and connects them in series. Within a unified input framework, it analyzes the impact of parameters at each stage on the detector's image quality, achieving a correlation between the design parameters or output characteristics of each stage and the system's output image. This lays a solid theoretical foundation and provides technical assurance for improving existing MCP-based charge-segmentation anode photon counting imaging detectors and developing novel high-resolution detectors.

[0108] In other words, the integrated simulation model constructed by the optimization method of the microchannel plate position-sensitive anode photon counting imaging detector of the present invention is composed of a series of models: the space charge behavior model within the microchannel plate, the space charge behavior model between the microchannel plate emitting end and the sensing layer film, the space charge diffusion behavior model within the sensing layer film, and the charge segmentation type anode crosstalk model. These models are not independent but rather use the results of the previous step as inputs to the next step to correlate the design parameters or output characteristics of each step with the system output image, thus completing the overall optimization design of the MCP position-sensitive anode photon counting imaging detector.

[0109] It is also understood that the optimization method of the microchannel plate position-sensitive anode photon counting imaging detector of the present invention uses COMSOL Multiphysics software to model an integrated simulation model. COMSOL Multiphysics software provides the ability to calculate, simulate, and model the coupling process of multiple physical fields. The simulation study of charged particle tracking and coupling of physical fields such as electromagnetic fields in this software has been applied to the field of magnetic proton inversion spectrometer, making the present invention easy to implement and practically operable.

[0110] It is worth mentioning that, in some embodiments of the present invention, the optimization method of the microchannel plate position-sensitive anode photon counting imaging detector of the present invention can also be constructed using software such as CST software that has particle tracking module, electromagnetic field module and custom equation module for integrated simulation model construction, and the present invention does not limit this.

[0111] Furthermore, in this field, simulation modeling studies of inter-electrode capacitance values ​​for multi-plane structures have been applied to capacitance tomography sensors. Using inter-electrode capacitance values ​​to perform equivalent analysis of the inter-electrode crosstalk effect in charge-segmented anode detectors is practically feasible. The integrated simulation model established in this invention is based on existing physical theories for each link, making it easy to implement and possessing a certain degree of universality.

[0112] In summary, the integrated model constructed by the optimization method of the microchannel plate position-sensitive anode photon counting imaging detector of this invention possesses a certain degree of completeness, can compensate for the shortcomings of existing research, comprehensively and systematically analyzes the impact of space charge behavior within the detector on image quality, and realizes the correlation between the design parameters or output characteristics of each link and the system output image, providing a corresponding theoretical basis for the overall detector design optimization. Furthermore, this optimization design method has the advantages of high efficiency and low cost. The optimization method of the microchannel plate position-sensitive anode photon counting imaging detector of this invention also has a certain degree of universality, applicable to any MCP position-sensitive anode photon counting imaging detector; it provides important theoretical basis and new ideas for my country's future research and development of novel high-resolution anode detectors, enhancing my country's ionospheric detection capabilities.

[0113] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0114] The above embodiments merely illustrate preferred implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention should be determined by the appended claims.

Claims

1. An optimized method for a microchannel plate position-sensitive anode photon counting imaging detector, characterized in that, Including the following steps: S1. The space charge behavior within the microchannel plate position-sensitive anode photon counting imaging detector is decomposed into the charge distribution within the microchannel plate, the charge distribution between the microchannel plate and the sensing layer film, the charge distribution on the sensing layer film, and the charge distribution of the position-sensitive anode. Based on the charge distribution within the microchannel plate, the charge distribution between the microchannel plate and the sensing layer film, the charge distribution on the sensing layer film, and the charge distribution of the position-sensitive anode, an integrated simulation model of the microchannel plate position-sensitive anode photon counting imaging detector is constructed, consisting of a microchannel plate space charge behavior model, a microchannel plate emission end and sensing layer film space charge behavior model, a sensing layer film space charge diffusion behavior model, and a charge segmentation type anode crosstalk model. S2. Calculate the amount of charge on the position-sensitive anode panel, and substitute the amount of charge collected by the position-sensitive anode into the centroid decoding algorithm to obtain a simulated image; S3. Compare the image resolution and nonlinearity of the input image and the simulation image to determine whether the input image meets the set accuracy. as well as S4. When the input image does not meet the set accuracy, iteratively optimize the parameters of the integrated simulation model based on the microchannel plate position-sensitive anode photon counting imaging detector.

2. The method according to claim 1, characterized in that, Step S1 includes the following steps: S11. Construct a model of space charge behavior within a microchannel plate; S12. Using the results of the space charge distribution of the space charge behavior model in the microchannel plate as input, construct a space charge behavior model between the microchannel plate emission end and the sensing layer film. S13. Using the results of the space charge distribution model between the microchannel plate emission end and the sensing layer film as input, construct a space charge diffusion behavior model within the sensing layer film. as well as S14. Using the results of the space charge distribution model of the space charge diffusion behavior model in the sensing layer film as input, construct a charge segmentation type anode crosstalk model.

3. The method according to claim 2, characterized in that, Step S11 includes the following steps: S111. Construct a three-dimensional model of a microchannel plate position-sensitive anode photon counting imaging detector and set the initial environment for the space charge behavior of the microchannel plate position-sensitive anode photon counting imaging detector; and S112. Construct a secondary electron multiplication model within the microchannel plate and obtain the results of the emitted charge trajectory of the secondary electron multiplication model within the microchannel plate.

4. The method according to claim 3, characterized in that, In step S111, the parametric modeling module of COMSOL Multiphysics software is used to construct a three-dimensional model of a microchannel plate position-sensitive anode photon counting imaging detector. The electrostatic field analysis module in COMSOL Multiphysics software is selected to set boundary conditions for the incident surface of the microchannel plate, the exit surface of the microchannel plate, the vacuum chamber wall and the position-sensitive anode, and to restore the potential value of the space charge at each point when the three-dimensional model of the microchannel plate position-sensitive anode photon counting imaging detector is in the initial state.

5. The method according to claim 4, characterized in that, In step S112, the charged particle tracking module in COMSOL Multiphysics software is selected. Based on the principle of secondary electron emission, the Monte Carlo method is used to simulate the motion of space charges in the microchannel plate, or the secondary electron emission coefficient curve of the microchannel plate is consulted. The secondary electron emission coefficient is embedded into COMSOL Multiphysics software. The boundary conditions when the space charge collides with the channel wall of the microchannel plate are set. Within the set simulation time step Δt, the velocities v(x,y,z) and displacements s(x,y,z) of all space charges in the model are calculated. COMSOL Multiphysics software calculates the motion state of any point (x,y,z) in space according to the kinematic equations (1) and (2) of the space charge, and completes the tracking process of secondary electron multiplication in the microchannel plate, obtaining the results of the trajectory of the emitted charge in the secondary electron multiplication model in the microchannel plate: In formulas (1) and (2), m is the particle mass, q is the charge, and E(x,y,z) is the electric field intensity at any point in space.

6. The method according to claim 5, characterized in that, The space charge behavior model between the microchannel plate emission end and the sensing layer film includes a space charge motion model under the combined electromagnetic field and a space charge motion model under the influence of matter. Step S12 includes the following steps: S121. Inheriting the results of the secondary electron multiplication model of the microchannel plate, the range of space charge movement is extended to the entire vacuum chamber. The magnetic field analysis module and the custom equation module are selected. Based on the Liner-Wiescher potential formula and the electromagnetic field formula (3) and (4) of the electromagnetic field of the electromagnetic field generated by the electromagnetic field of any moving charged particle, the electromagnetic disturbance generated by the microchannel plate at different times is coupled with the original electrostatic field to establish a space charge movement model under the action of the comprehensive electromagnetic field: B0=e r ×E0 / c (4) In formulas (3) and (4), E0 is the perturbation electric field; B0 is the perturbation magnetic field; ε0 is the vacuum permittivity; e is the charge; c is the speed of light; v = v(t') is the velocity of the particle at the moment of radiation t', t' = t + r / c, and the position vector x of the particle at this moment is... e (t'); r = xx e (t') is the position vector of the particle pointing to the field point x at time t', and r is the distance from the particle to the field point at time t'; e r It is the unit vector in the r direction; S122. Based on the theory of interaction between high-energy particles and matter, the data processing module of COMSOL Multiphysics software is used to statistically classify all motion states of space charges when emitted from the edge of the microchannel plate collides with the vacuum chamber wall, and a motion model of space charges under the action of matter is established.

7. The method according to claim 6, characterized in that, In step S13, using a custom equation module, based on Fick's diffusion law, space charge diffuses upon landing on the sensing layer. Formulas (5) to (7) are used to solve for the time-varying electron number density n, thus obtaining the distribution of space charge in the sensing layer film at each moment. The results of the space charge distribution model under the combined electromagnetic field are used as input. The diffusion coefficient of the sensing film is then checked or tested to establish a diffusion model of space charge in the sensing layer film at each moment t. The post-processing function of COMSOL Multiphysics software is then used to statistically analyze the image charge diffusion distribution. In formulas (5), (6), and (7), D is the diffusion coefficient and the thermodynamic factor. As a constant, a n Effective electrons in the material, D p It is the electron diffusion constant, k B Where μ is Boltzmann constant, T is temperature, and μ is the constant. p Hall mobility.

8. The method according to claim 7, characterized in that, In step S14, the inter-electrode crosstalk effect is analyzed using discrete components of a charge-segmented anode crosstalk model, wherein the inter-electrode capacitance C of the position-sensitive anode is... ij Using the collected induced charge Q ij Perform the calculation: The interaction between multiple electrodes is expressed by equation (9): In formulas (8) and (9), i = 1, 2, 3, ..., j = 2, 3, 4, ..., V i V j Let C be the potential of different electrodes. ij =C ji .

9. The method according to any one of claims 1 to 8, characterized in that, In step S3, the image resolution and the precision of image nonlinearity are set, wherein, Image resolution similarity is denoted as A1, S 输 S is the input image resolution. 仿 The output image resolution is calculated using formula (10): The image nonlinearity is B1, calculated by formula (11). Select m points from the input image, calculate the distance d between two selected points in the input image and the corresponding distance d' between two points in the simulation image, then the distortion value B1 of the system is:

10. The method according to any one of claims 1 to 8, characterized in that, In step S4, the microchannel plate-based position-sensitive anode photon counting imaging detector is optimized by iteratively adjusting the parameters of the microchannel plate electron multiplication model, the motion model between the microchannel plate and the sensing field film, the diffusion model of the sensing layer film, and the crosstalk effect model between the position-sensitive anodes.

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