Accelerator parameter optimization allocation method based on digital twinning

Abstract

The invention discloses an accelerator parameter optimization allocation method based on digital twinning, which relates to the technical field of accelerators, and comprises the following steps: installing at least one beam position detector with a strip-shaped structure along a linear accelerator, and measuring the orbit change of a particle beam along the accelerator; describing the motion state of the particles in a two-dimensional phase space by adopting a two-dimensional vector; analyzing an element off-axis of the linear accelerator and a beam off-axis caused by a stray magnetic field; calculating the amplitude and phase change caused by the cavity coupler on the transverse plane; judging whether the position of the output particle flow exceeds a preset threshold range or not; using a one-to-one correction method to optimize the syndrome to reduce the beam off-axis at the beam position detector with the maximum beam off-axis change; sequentially optimizing all correctors at the upstream by using an overall orbit correction method; the particle beams coming out of the accelerating tube are transmitted along a direction close to the central axis. The orbit of the beam in the accelerator is strictly controlled by optimizing the parameters of the corrector in the accelerator.

Description

Technical Field

[0001] The present invention relates to the field of accelerator technology, and in particular to an accelerator parameter optimization and adjustment method based on digital twins. Background Art

[0002] An accelerator is a device that uses artificial means to accelerate charged particles to higher energies. The X-ray tube was the earliest electron accelerator. Since then, various particle accelerators have been widely developed, and the energy obtained by particles has gradually increased. While higher-energy particles are used in nuclear physics experiments, more accelerators are widely used in industry, agriculture, medicine and health.

[0003] Electron linear accelerators are divided into low-energy and high-energy types. Due to the lower energy and shorter accelerator, the beam trajectory is easier to control. For high-energy accelerators, due to the longer distance of beam transmission, the deviation of the beam trajectory during the beam transmission process has a greater impact on the quality of the accelerator exit beam. Therefore, the trajectory correction system must be used to correct the beam trajectory to reduce the loss of the beam due to the deflection during the acceleration process and the increase of the beam normalized emittance. Summary of the invention

[0004] In order to solve the above technical problems, a method for optimizing and adjusting accelerator parameters based on digital twins is provided. This technical solution solves the problems raised in the above background technology.

[0005] In order to achieve the above purpose, the technical solution adopted by the present invention is:

[0006] A method for optimizing and adjusting accelerator parameters based on digital twins, comprising:

[0007] S101: installing at least one beam position detector of a strip structure along the linear accelerator to measure the change of the particle beam along the trajectory of the accelerator;

[0008] S102: Use two-dimensional vectors to describe the motion state of particles in two-dimensional phase space, and simulate the initial beam state emitted from the electron gun based on digital twins;

[0009] S103: analyzing the component deflection of the linear accelerator and the beam deflection caused by the stray magnetic field, wherein the component deflection includes the deflection of the quadrupole lens, the deflection of the accelerating tube and the deflection caused by the installation of the beam position detector, and the stray magnetic field includes the earth's magnetic field, the leakage field of the isolator or the magnetron and the magnetic field generated by the AC power supply;

[0010] S104: Calculate the amplitude and phase changes caused by the cavity coupler on the transverse plane and build a digital twin model of the linear accelerator;

[0011] S105: Based on the digital twin model of the linear accelerator, determine whether the output particle flow position exceeds the preset threshold range. If so, the output beam is too off-axis and parameter optimization is required. If not, the output beam meets the standard and the optimization ends.

[0012] S106: Optimizing the horizontal and vertical correction factors by using a one-to-one correction method to reduce the beam deflection at the beam position detector where the beam deflection variation is the largest;

[0013] S107: using the overall orbit correction method to sequentially optimize each upstream correction factor, taking into account the beam off-axis at each downstream beam position detector, to obtain the optimal beam orbit;

[0014] S108: Using the zero position adjustment correction method at the end of the accelerating tube, the particle beam coming out of the accelerating tube is transmitted along a direction close to the central axis, and then returning to step S103.

[0015] Preferably, the two-dimensional vector is used to describe the motion state of particles in the two-dimensional phase space, and the initial beam state emitted from the electron gun based on the digital twin simulation specifically includes:

[0016] Two-dimensional vectors are used in the horizontal space and the vertical space to describe the motion state of particles in the two-dimensional phase space;

[0017] Simulate the initial beam state emitted from the electron gun based on digital twin;

[0018] Simulate and output the beam transmission matrix when the particle beam passes through the linear section, quadrupole lens, accelerating element and correction element;

[0019] Calculate the beam off-axis at each beam position detector based on the beam transmission matrix;

[0020] The two-dimensional vector is:

[0021]

[0022] Where X and Y are two-dimensional vectors used to describe particle motion in the transverse and longitudinal spaces, respectively; x and x' are the transverse position and deflection angle of the beam, respectively; y and y' are the longitudinal position and deflection angle of the beam, respectively; (x x') T represents the transposed matrix of (x x');

[0023] The beam transmission matrix is:

[0024]

[0025] Where M i is the beam transmission matrix of the i-th element in the accelerator, and m is the beam transmission matrix parameter based on digital twin simulation;

[0026] The beam off-axis at each beam position detector is:

[0027]

[0028] In the formula, x j is the beam offset at the jth beam position detector, x0 is the initial offset when it is emitted from the electron gun, N j is the total number of elements upstream of the j-th beam position detector.

[0029] Preferably, the analyzing the component deflection of the linear accelerator and the beam deflection caused by the stray magnetic field specifically includes:

[0030] The position tolerance of each component is calculated using the root mean square error formula;

[0031] Calculating component off-axis of the linear accelerator based on position tolerances at each component;

[0032] Obtaining the magnetic field intensity component of the stray magnetic field in a direction perpendicular to the accelerator axis;

[0033] Based on the magnetic field intensity components, calculating the beam deflection caused by the stray magnetic field at the end of the accelerating tube;

[0034] The root mean square error formula is:

[0035]

[0036] In the formula, Δx i is the position tolerance of the ith component, x i ' is the beam offset at the upstream beam position detector closest to the i-th element, n i is the total number of beam position detectors upstream of the ith element;

[0037] The element eccentricity is:

[0038]

[0039] In the formula, x j ' is the beam deflection of the jth beam position detector due to the deflection of the i-th element, I is the unit matrix, specifically

[0040] The beam deflection caused by the stray magnetic field is:

[0041]

[0042] Where s is the beam deflection caused by the stray magnetic field at the end of the accelerating tube, e is the charge carried by the particle, and B yis the magnetic field strength component of the stray magnetic field in the direction perpendicular to the accelerator axis, v is the velocity of the particle at the end of the accelerating tube, L is the length of the accelerating tube, g is the acceleration gradient of the accelerator, u0, u L are the energies of the particles at the beginning and end of the accelerating tube, respectively.

[0043] Preferably, the calculating the amplitude and phase changes caused by the cavity coupler on the transverse plane and constructing the digital twin model of the linear accelerator specifically includes:

[0044] Obtaining the magnetic field intensity component of the magnetic field in the cavity coupler in a direction perpendicular to the accelerator axis;

[0045] Calculate the axial component of the high-frequency field in the transverse plane of the coupler cavity;

[0046] Using the electron relative field formula, calculate the changes in the amplitude and phase of the electron relative field;

[0047] A digital twin model of the linear accelerator is constructed based on the beam deflection at each beam position detector, the component deflection of the linear accelerator, the beam deflection caused by the stray magnetic field at the end of the accelerating tube, and the changes in the amplitude and phase of the electron relative field.

[0048] The high-frequency field axial component of the coupler cavity transverse plane is:

[0049]

[0050] In the formula, E z is the axial component of the high-frequency field in the transverse plane of the coupler cavity, x is the transverse position of the beam, B y ' is the magnetic field intensity component of the magnetic field in the cavity coupler in the direction perpendicular to the accelerator axis, t is the time parameter, For E z Partial derivative with respect to x;

[0051] The electron relative field formula is:

[0052]

[0053] In the formula, j is an imaginary unit, E(x) and θ(x) are the changing functions of the amplitude and phase of the electron relative field, respectively. is the phase of the electron relative to the field.

[0054] Preferably, the digital twin model based on the linear accelerator determines whether the output particle flow position exceeds a preset threshold range specifically includes:

[0055] Based on the digital twin model of the linear accelerator, the movement of the particle flow from being ejected from the electron gun to being ejected from the accelerator is simulated;

[0056] A maximum error value is preset, and a circle is drawn with the accelerator center axis point as the origin and the preset maximum error value as the radius, and the area within the circle is defined as the preset threshold range;

[0057] Determine whether the output particle flow position exceeds the preset threshold range. If so, the output beam is too off-axis and parameter optimization is required. If not, the output beam meets the standard and the optimization ends.

[0058] Preferably, the step of optimizing the horizontal and vertical correction factors by a one-to-one correction method to reduce the beam deflection at the beam position detector where the beam deflection variation is the largest specifically includes:

[0059] Calculating the difference of beam off-axis at each adjacent beam position detector;

[0060] Two horizontal and vertical correction magnets are arranged in a nested manner upstream of the beam position detector where the difference is the largest;

[0061] Calculate the magnetic field strength of the required horizontal and vertical correction magnets using the correction sub strength formula;

[0062] The syndrome intensity formula is:

[0063]

[0064] In the formula, x j is the beam off-axis at the beam position detector with the largest difference, B is the magnetic field strength of the required horizontal and vertical correction magnets, and E z1 , E z2 are the high-frequency field axial components in the transverse plane at the correction and beam position detectors, respectively, and v z1 , v z2 are the particle velocities at the correction and beam position detectors, respectively.

[0065] Preferably, the method of using the overall trajectory correction method to sequentially optimize each upstream correction factor while taking into account the beam off-axis at each downstream beam position detector to obtain the optimal beam trajectory specifically includes:

[0066] At least one correction factor is arranged between each beam position detector;

[0067] Define the correction function of each syndrome;

[0068] Calculate the value of the magnetic field strength of each correction element when the partial derivative of the correction function with respect to the magnetic field strength of each correction element is zero;

[0069] Optimizing each upstream syndrome based on the magnetic field strength of the syndrome;

[0070] The correction function is:

[0071]

[0072] Where f is the correction function, x j is the beam off-axis at the jth beam position detector, B i is the magnetic field strength of the ith correction factor, M ij is the beam transmission matrix between the i-th syndrome and the j-th beam position detector.

[0073] Preferably, the step of using a zero adjustment correction method at the end of the accelerating tube to transmit the particle beam coming out of the accelerating tube along a direction close to the central axis specifically includes:

[0074] A correction factor is arranged upstream of a beam position detector at the end of the accelerating tube;

[0075] The required magnetic field strength of the correction element is calculated using the zero adjustment correction formula;

[0076] Based on the magnetic field strength optimization correction, the particle beam from the accelerating tube is transmitted along a direction close to the central axis;

[0077] The zero adjustment correction formula is:

[0078]

[0079] In the formula, B L is the magnetic field strength of the last correction sub-son, M L is the beam transfer matrix of the last beam position detector, x L is the beam off-axis at the last beam position detector.

[0080] Compared with the prior art, the present invention has the following beneficial effects:

[0081] By optimizing the correction sub parameters in the accelerator, strictly controlling the trajectory of the beam in the accelerator, reducing the growth of the normalized beam emittance caused by the initial beam offset, the quadrupole lens offset and the installation error of the accelerating tube, the beam is made to move along the axis as much as possible, optimizing the beam optical path, reducing the loss during beam transmission, and improving the efficiency and stability of beam transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0082] Figure 1 This is a flow chart of the accelerator parameter optimization and adjustment method based on digital twins of the present invention;

[0083] Figure 2 A flow chart of a method for using a two-dimensional vector to describe the motion state of particles in a two-dimensional phase space according to the present invention;

[0084] Figure 3 A flow chart of a method for analyzing component deflection of a linear accelerator and beam deflection caused by a stray magnetic field according to the present invention;

[0085] Figure 4 A flow chart of a method for calculating amplitude and phase changes caused by a cavity coupler on a transverse plane according to the present invention;

[0086] Figure 5 A flow chart of a method for determining whether the position of an output particle flow exceeds a preset threshold range according to the present invention;

[0087] Figure 6 A flow chart of a method for optimizing horizontal and vertical correction sub-groups using a one-to-one correction method according to the present invention;

[0088] Figure 7 This is a flow chart of a method for sequentially optimizing each upstream correction sub-method using the overall orbit correction method of the present invention;

[0089] Figure 8 The present invention is a flow chart of the method for using the zero position adjustment correction method at the end of the accelerating tube. DETAILED DESCRIPTION

[0090] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are only examples, and those skilled in the art may think of other obvious variations.

[0091] Reference Figure 1 As shown, a method for optimizing and adjusting accelerator parameters based on digital twins includes:

[0092] S101: installing at least one beam position detector of a strip structure along the linear accelerator to measure the change of the particle beam along the trajectory of the accelerator;

[0093] S102: Use two-dimensional vectors to describe the motion state of particles in two-dimensional phase space, and simulate the initial beam state emitted from the electron gun based on digital twins;

[0094] S103: analyzing the component deflection of the linear accelerator and the beam deflection caused by the stray magnetic field, wherein the component deflection includes the deflection of the quadrupole lens, the deflection of the accelerating tube and the deflection caused by the installation of the beam position detector, and the stray magnetic field includes the earth's magnetic field, the leakage field of the isolator or the magnetron and the magnetic field generated by the AC power supply;

[0095] S104: Calculate the amplitude and phase changes caused by the cavity coupler on the transverse plane and build a digital twin model of the linear accelerator;

[0096] S105: Based on the digital twin model of the linear accelerator, determine whether the output particle flow position exceeds the preset threshold range. If so, the output beam is too off-axis and parameter optimization is required. If not, the output beam meets the standard and the optimization ends.

[0097] S106: Optimizing the horizontal and vertical correction factors by using a one-to-one correction method to reduce the beam deflection at the beam position detector where the beam deflection variation is the largest;

[0098] S107: using the overall orbit correction method to sequentially optimize each upstream correction factor, taking into account the beam off-axis at each downstream beam position detector, to obtain the optimal beam orbit;

[0099] S108: Using the zero position adjustment correction method at the end of the accelerating tube, the particle beam coming out of the accelerating tube is transmitted along a direction close to the central axis, and then returning to step S103.

[0100] Reference Figure 2 As shown in the figure, a two-dimensional vector is used to describe the motion state of particles in the two-dimensional phase space. The initial beam state emitted from the electron gun based on the digital twin simulation specifically includes:

[0101] Two-dimensional vectors are used in the horizontal space and the vertical space to describe the motion state of particles in the two-dimensional phase space;

[0102] Simulate the initial beam state emitted from the electron gun based on digital twin;

[0103] Simulate and output the beam transmission matrix when the particle beam passes through the linear section, quadrupole lens, accelerating element and correction element;

[0104] Calculate the beam off-axis at each beam position detector based on the beam transmission matrix;

[0105] The two-dimensional vector is:

[0106]

[0107] Where X and Y are two-dimensional vectors used to describe particle motion in the transverse and longitudinal spaces, respectively; x and x' are the transverse position and deflection angle of the beam, respectively; y and y' are the longitudinal position and deflection angle of the beam, respectively; (x x') T represents the transposed matrix of (x x');

[0108] The beam transmission matrix is:

[0109]

[0110] Where M i is the beam transmission matrix of the i-th element in the accelerator, and m is the beam transmission matrix parameter based on digital twin simulation;

[0111] The beam off-axis at each beam position detector is:

[0112]

[0113] In the formula, xj is the beam offset at the jth beam position detector, x0 is the initial offset when it is emitted from the electron gun, N j is the total number of elements upstream of the j-th beam position detector.

[0114] Since the initial beam state coming out of the electron gun is non-ideal, the beam has a certain initial offset. After passing through a series of accelerating elements, this causes the downstream beam orbit to shift. A very small initial beam offset may cause a large beam offset after passing through a series of accelerating tube elements. This is especially true for accelerators with longer distances, where the impact is more significant.

[0115] Reference Figure 3 As shown in the figure, the analysis of the linear accelerator's component deflection and the beam deflection caused by the stray magnetic field specifically includes:

[0116] The position tolerance of each component is calculated using the root mean square error formula;

[0117] Calculating component off-axis of the linear accelerator based on position tolerances at each component;

[0118] Obtaining the magnetic field intensity component of the stray magnetic field in a direction perpendicular to the accelerator axis;

[0119] Based on the magnetic field intensity components, calculating the beam deflection caused by the stray magnetic field at the end of the accelerating tube;

[0120] The root mean square error formula is:

[0121]

[0122] In the formula, Δx i is the position tolerance of the ith component, x i ' is the beam offset at the upstream beam position detector closest to the i-th element, n i is the total number of beam position detectors upstream of the ith element;

[0123] The element eccentricity is:

[0124]

[0125] In the formula, x j ' is the beam deflection of the jth beam position detector due to the deflection of the i-th element, I is the unit matrix, specifically

[0126] The beam deflection caused by the stray magnetic field is:

[0127]

[0128] Where s is the beam deflection caused by the stray magnetic field at the end of the accelerating tube, e is the charge carried by the particle, and B y is the magnetic field strength component of the stray magnetic field in the direction perpendicular to the accelerator axis, v is the velocity of the particle at the end of the accelerating tube, L is the length of the accelerating tube, g is the acceleration gradient of the accelerator, u0, u L are the energies of the particles at the beginning and end of the accelerating tube, respectively.

[0129] For low-energy accelerators, due to the short distance, simple structure and easy operation, the method of shielding the magnetic field is usually adopted; for high-energy accelerating tubes, due to the long distance and complex structure, a combination of compensation and shielding is usually adopted. For example, in order to compensate for the geomagnetic field, in addition to using vertical and horizontal coils, a thick slope film alloy shielding layer can also be used at the same time.

[0130] Reference Figure 4 As shown in the figure, the amplitude and phase changes caused by the cavity coupler on the transverse plane are calculated, and the digital twin model of the linear accelerator is constructed, which specifically includes:

[0131] Obtaining the magnetic field intensity component of the magnetic field in the cavity coupler in a direction perpendicular to the accelerator axis;

[0132] Calculate the axial component of the high-frequency field in the transverse plane of the coupler cavity;

[0133] Using the electron relative field formula, calculate the changes in the amplitude and phase of the electron relative field;

[0134] A digital twin model of the linear accelerator is constructed based on the beam deflection at each beam position detector, the component deflection of the linear accelerator, the beam deflection caused by the stray magnetic field at the end of the accelerating tube, and the changes in the amplitude and phase of the electron relative field.

[0135] The high-frequency field axial component of the coupler cavity transverse plane is:

[0136]

[0137] In the formula, E z is the axial component of the high-frequency field in the transverse plane of the coupler cavity, x is the transverse position of the beam, B y ' is the magnetic field intensity component of the magnetic field in the cavity coupler in the direction perpendicular to the accelerator axis, t is the time parameter, For E z Partial derivative with respect to x;

[0138] The electron relative field formula is:

[0139]

[0140] In the formula, j is an imaginary unit, E(x), θ9x) are the changing functions of the amplitude and phase of the electron relative field, respectively. is the phase of the electron relative to the field.

[0141] Due to the need for cavity couplers for accelerator input and output energy, in the case of cavity couplers, the existence of the coupling window destroys the symmetry of the field in the coupler cavity, that is, the field on the transverse plane in the disk-loaded waveguide is radially symmetrically distributed. Near the waveguide axis in the light speed section, for a certain longitudinal position, the amplitude and phase of the field are the same. Due to the existence of the coupling window, the amplitude and phase of the electron relative field in the coupler cavity change on the transverse plane.

[0142] Reference Figure 5 As shown, based on the digital twin model of the linear accelerator, judging whether the output particle flow position exceeds the preset threshold range specifically includes:

[0143] Based on the digital twin model of the linear accelerator, the movement of the particle flow from being ejected from the electron gun to being ejected from the accelerator is simulated;

[0144] A maximum error value is preset, and a circle is drawn with the accelerator center axis point as the origin and the preset maximum error value as the radius, and the area within the circle is defined as the preset threshold range;

[0145] Determine whether the output particle flow position exceeds the preset threshold range. If so, the output beam is too off-axis and parameter optimization is required. If not, the output beam meets the standard and the optimization ends.

[0146] By presetting the maximum error value, it is determined whether the particle flow output by the current accelerator meets the requirements of actual applications, so that the parameters of the corrector of the non-compliant accelerator can be optimized in a timely manner.

[0147] Reference Figure 6 As shown, the one-to-one correction method is used to optimize the horizontal and vertical correction factors to reduce the beam deflection at the beam position detector where the beam deflection change is the largest, specifically including:

[0148] Calculating the difference of beam off-axis at each adjacent beam position detector;

[0149] Two horizontal and vertical correction magnets are arranged in a nested manner upstream of the beam position detector where the difference is the largest;

[0150] Calculate the magnetic field strength of the required horizontal and vertical correction magnets using the correction sub strength formula;

[0151] The syndrome intensity formula is:

[0152]

[0153] In the formula, x j is the beam off-axis at the beam position detector with the largest difference, B is the magnetic field strength of the required horizontal and vertical correction magnets, and Ez1 , E z2 are the high-frequency field axial components in the transverse plane at the correction and beam position detectors, respectively, and v z1 , v z2 are the particle velocities at the correction and beam position detectors, respectively.

[0154] The one-to-one correction method is that there are two nested correction elements (one in the horizontal and vertical directions) upstream of each beam detector. By adjusting the horizontal and vertical correction elements, multiple iterations are used to minimize the beam off-axis of the beam position detector downstream of each correction element.

[0155] Reference Figure 7 As shown in the figure, the overall orbit correction method is used to optimize the upstream correction factors in turn, taking into account the beam off-axis at the downstream beam position detectors, and the optimal beam orbit is obtained, which specifically includes:

[0156] At least one correction factor is arranged between each beam position detector;

[0157] Define the correction function of each syndrome;

[0158] Calculate the value of the magnetic field strength of each correction element when the partial derivative of the correction function with respect to the magnetic field strength of each correction element is zero;

[0159] Optimizing each upstream syndrome based on the magnetic field strength of the syndrome;

[0160] The correction function is:

[0161]

[0162] Where f is the correction function, x j is the beam off-axis at the jth beam position detector, B i is the magnetic field strength of the ith correction factor, M ij is the beam transmission matrix between the i-th syndrome and the j-th beam position detector.

[0163] There is no restriction on the number of beam position detectors and correctors. If the number of correctors and beam position detectors in the accelerator is large enough, the overall trajectory of the beam in the linear accelerator can be corrected by this method.

[0164] Reference Figure 8 As shown, at the end of the accelerating tube, a zero adjustment correction method is used to transmit the particle beam coming out of the accelerating tube along a direction close to the central axis, specifically including:

[0165] A correction factor is arranged upstream of a beam position detector at the end of the accelerating tube;

[0166] The required magnetic field strength of the correction element is calculated using the zero adjustment correction formula;

[0167] Based on the magnetic field strength optimization correction, the particle beam from the accelerating tube is transmitted along a direction close to the central axis;

[0168] The zero adjustment correction formula is:

[0169]

[0170] In the formula, B L is the magnetic field strength of the last correction sub-son, M L is the beam transfer matrix of the last beam position detector, x L is the beam off-axis at the last beam position detector.

[0171] Due to the existence of correction errors, it is difficult for the beam at the end of the accelerator to be transmitted along the central axis of the accelerating tube. However, what is actually needed at the accelerator exit is a beam that is transmitted as much as possible along the axis of the accelerating tube. The zero adjustment correction method is used at the end of the accelerating tube to make the beam coming out of the accelerating tube transmitted as much as possible along the central axis.

[0172] Furthermore, the present solution also proposes a computer-readable storage medium, on which a computer-readable program is stored. When the computer-readable program is called, the above-mentioned digital twin-based accelerator parameter optimization and adjustment method is executed.

[0173] It is understandable that the storage medium may be a magnetic medium, such as a floppy disk, a hard disk, or a magnetic tape; an optical medium, such as a DVD; or a semiconductor medium, such as a solid state drive (SSD).

[0174] In summary, the advantages of the present invention are: by optimizing the correction sub parameters in the accelerator, strictly controlling the trajectory of the beam in the accelerator, reducing the growth of the normalized emittance of the beam caused by the initial beam eccentricity, the eccentricity of the quadrupole lens and the installation error of the accelerating tube, making the beam move along the axis as much as possible, optimizing the beam optical path, reducing the loss in the beam transmission process, and improving the beam transmission efficiency and stability.

[0175] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions only describe the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention. These changes and improvements fall within the scope of the present invention. The scope of protection claimed by the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for optimizing and adjusting accelerator parameters based on digital twins, characterized in that: include: S101: installing at least one beam position detector of a strip structure along the linear accelerator to measure the change of the particle beam along the trajectory of the accelerator; S102: Use two-dimensional vectors to describe the motion state of particles in two-dimensional phase space, and simulate the initial beam state emitted from the electron gun based on digital twins; S103: analyzing the component deflection of the linear accelerator and the beam deflection caused by the stray magnetic field, wherein the component deflection includes the deflection of the quadrupole lens, the deflection of the accelerating tube and the deflection caused by the installation of the beam position detector, and the stray magnetic field includes the earth's magnetic field, the leakage field of the isolator or the magnetron and the magnetic field generated by the AC power supply; S104: Calculate the amplitude and phase changes caused by the cavity coupler on the transverse plane and build a digital twin model of the linear accelerator; S105: Based on the digital twin model of the linear accelerator, determine whether the output particle flow position exceeds the preset threshold range. If so, the output beam is too off-axis and parameter optimization is required. If not, the output beam meets the standard and the optimization ends. S106: Optimizing the horizontal and vertical correction factors by using a one-to-one correction method to reduce the beam deflection at the beam position detector where the beam deflection variation is the largest; S107: using the overall orbit correction method to sequentially optimize each upstream correction factor, taking into account the beam off-axis at each downstream beam position detector, to obtain the optimal beam orbit; S108: Using the zero position adjustment correction method at the end of the accelerating tube, the particle beam coming out of the accelerating tube is transmitted along a direction close to the central axis, and then returning to step S103.

2. According to the method for optimizing accelerator parameters based on digital twins according to claim 1, it is characterized in that: The two-dimensional vector is used to describe the motion state of particles in the two-dimensional phase space, and the initial beam state emitted from the electron gun based on the digital twin simulation specifically includes: Two-dimensional vectors are used in the horizontal space and the vertical space to describe the motion state of particles in the two-dimensional phase space; Simulate the initial beam state emitted from the electron gun based on digital twin; Simulate and output the beam transmission matrix when the particle beam passes through the linear section, quadrupole lens, acceleration element and correction element; Calculate the beam off-axis at each beam position detector based on the beam transmission matrix; The two-dimensional vector is: Where X and Y are two-dimensional vectors used to describe particle motion in the transverse and longitudinal spaces, respectively; x and x' are the transverse position and deflection angle of the beam, respectively; y and y' are the longitudinal position and deflection angle of the beam, respectively; (x x') T represents the transposed matrix of (x x'); The beam transmission matrix is: Where M i is the beam transmission matrix of the i-th element in the accelerator, and m is the beam transmission matrix parameter based on digital twin simulation; The beam off-axis at each beam position detector is: In the formula, x j is the beam offset at the jth beam position detector, x0 is the initial offset when it is emitted from the electron gun, N j is the total number of elements upstream of the j-th beam position detector.

3. The accelerator parameter optimization and deployment method based on digital twin according to claim 2 is characterized in that: The analysis of the linear accelerator component deflection and the beam deflection caused by the stray magnetic field specifically includes: The position tolerance of each component is calculated using the root mean square error formula; Calculating component off-axis of the linear accelerator based on position tolerances at each component; Obtaining the magnetic field intensity component of the stray magnetic field in a direction perpendicular to the accelerator axis; Based on the magnetic field intensity components, calculating the beam deflection caused by the stray magnetic field at the end of the accelerating tube; The root mean square error formula is: In the formula, Δx i is the position tolerance of the ith component, x i ' is the beam offset at the upstream beam position detector closest to the i-th element, n i is the total number of beam position detectors upstream of the ith element; The element eccentricity is: In the formula, x j ' is the beam deflection of the jth beam position detector due to the deflection of the i-th element, I is the unit matrix, specifically The beam deflection caused by the stray magnetic field is: Where s is the beam deflection caused by the stray magnetic field at the end of the accelerating tube, e is the charge carried by the particle, and B y is the magnetic field intensity component of the stray magnetic field in the direction perpendicular to the accelerator axis, v is the velocity of the particle at the end of the accelerating tube, L is the length of the accelerating tube, g is the acceleration gradient of the accelerator, u0, u L are the energies of the particles at the beginning and end of the accelerating tube, respectively.

4. The accelerator parameter optimization and deployment method based on digital twin according to claim 3 is characterized in that: The calculation of the amplitude and phase changes caused by the cavity coupler on the transverse plane and the construction of the digital twin model of the linear accelerator specifically include: Obtaining the magnetic field intensity component of the magnetic field in the cavity coupler in a direction perpendicular to the accelerator axis; Calculate the axial component of the high-frequency field in the transverse plane of the coupler cavity; Using the electron relative field formula, calculate the changes in the amplitude and phase of the electron relative field; A digital twin model of the linear accelerator is constructed based on the beam deflection at each beam position detector, the component deflection of the linear accelerator, the beam deflection caused by the stray magnetic field at the end of the accelerating tube, and the changes in the amplitude and phase of the electron relative field. The high-frequency field axial component of the coupler cavity transverse plane is: In the formula, E z is the axial component of the high-frequency field in the transverse plane of the coupler cavity, x is the transverse position of the beam, B y ' is the magnetic field intensity component of the magnetic field in the cavity coupler in the direction perpendicular to the accelerator axis, t is the time parameter, For E z Partial derivative with respect to x; The electron relative field formula is: In the formula, j is an imaginary unit, E(x) and θ(x) are the changing functions of the amplitude and phase of the electron relative field, respectively. is the phase of the electron relative to the field.

5. The accelerator parameter optimization and deployment method based on digital twin according to claim 4 is characterized in that: The digital twin model based on the linear accelerator determines whether the output particle flow position exceeds the preset threshold range specifically includes: Based on the digital twin model of the linear accelerator, the movement of the particle flow from being ejected from the electron gun to being ejected from the accelerator is simulated; A maximum error value is preset, and a circle is drawn with the accelerator center axis point as the origin and the preset maximum error value as the radius, and the area within the circle is defined as the preset threshold range; Determine whether the output particle flow position exceeds the preset threshold range. If so, the output beam is too off-axis and parameter optimization is required. If not, the output beam meets the standard and the optimization ends.

6. The accelerator parameter optimization and deployment method based on digital twin according to claim 5 is characterized in that: The method of optimizing the horizontal and vertical correction factors by a one-to-one correction method to reduce the beam deflection at the beam position detector where the beam deflection variation is the largest specifically includes: Calculating the difference of beam off-axis at each adjacent beam position detector; Two horizontal and vertical correction magnets are arranged in a nested manner upstream of the beam position detector where the difference is the largest; Calculate the magnetic field strength of the required horizontal and vertical correction magnets using the correction sub strength formula; The syndrome intensity formula is: In the formula, x j is the beam off-axis at the beam position detector with the largest difference, B is the magnetic field strength of the required horizontal and vertical correction magnets, and E z1 , E z2 are the high-frequency field axial components in the transverse plane at the correction and beam position detectors, respectively, and v z1 , v z2 are the particle velocities at the correction and beam position detectors, respectively.

7. The accelerator parameter optimization and adjustment method based on digital twin according to claim 6 is characterized in that: The method of using the overall orbit correction method to sequentially optimize each upstream correction factor and taking into account the beam off-axis at each downstream beam position detector to obtain the optimal beam orbit specifically includes: At least one correction factor is arranged between each beam position detector; Define the correction function of each syndrome; Calculate the value of the magnetic field strength of each correction element when the partial derivative of the correction function with respect to the magnetic field strength of each correction element is zero; Optimizing each upstream syndrome based on the magnetic field strength of the syndrome; The correction function is: Where f is the correction function, x j is the beam off-axis at the jth beam position detector, B i is the magnetic field strength of the ith correction factor, M ij is the beam transmission matrix between the i-th syndrome and the j-th beam position detector.

8. The accelerator parameter optimization and deployment method based on digital twin according to claim 7 is characterized in that: The method of using the zero position adjustment correction method at the end of the accelerating tube to transmit the particle beam coming out of the accelerating tube along a direction close to the central axis specifically includes: A correction factor is arranged upstream of a beam position detector at the end of the accelerating tube; The required magnetic field strength of the correction element is calculated using the zero adjustment correction formula; Based on the magnetic field strength optimization correction, the particle beam from the accelerating tube is transmitted along a direction close to the central axis; The zero adjustment correction formula is: In the formula, B L is the magnetic field strength of the last correction sub-son, M L is the beam transfer matrix of the last beam position detector, x L is the beam off-axis at the last beam position detector.

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