Electrode plate-based charged particle beam dispersion elimination method in interference magnetic field environment

Abstract

The invention provides a charged particle beam dispersion elimination method in an interference magnetic field environment based on an electrode plate. The method comprises the following steps: step 1, acquiring magnetic induction intensity and a target spot position; step 2, obtaining emission directions of charged particles with different energies at an outlet of the electrode plate according to a result in the step 1; 3, obtaining the optical axial direction and the electric field intensity of the beam according to the result in the step 2; step 4, according to a result in the step 3, calculating energy of charged particles with different energies at an outlet of the electrode plate and a target position # imgabs0 # and updating, and obtaining a convergence solution after multiple times of iteration updating; and 5, adjusting the attitude of the accelerator according to the result in the step 4, and arranging an electrode plate to eliminate the dispersion of the charged particle beam. The method is high in practicability, can be applied to the last stage of various accelerator devices of various charged particles, and can effectively eliminate dispersion, improve the target-reaching precision of charged particle beams and the beam flux density and improve the beam irradiation effect.

Description

Technical Field

[0001] The invention belongs to the technical field of accelerator system design, relates to a method for eliminating dispersion, and specifically relates to a method for eliminating dispersion of a charged particle beam in an interfering magnetic field environment based on an electrode plate. Background Art

[0002] Particle accelerators can be used for industrial irradiation processing, irradiation sterilization, cancer treatment, etc. In these applications, particle beams at the target point mostly require a smaller beam spot size and a higher flux density. In non-magnetic shielding scenarios, charged particles may be disturbed by external magnetic field environments such as the geomagnetic field during the transmission path, resulting in beam displacement and dispersion at the target point.

[0003] The particle beam generated by an actual particle accelerator has a certain energy distribution, so different path trajectories will be produced under the action of a magnetic field. The dispersion effect refers to the fact that particles with different momentum / energy starting from the same object point are distributed at different positions on the image plane, resulting in a larger beam spot size and a smaller flux density on the target surface, which is difficult to meet the needs of actual applications. Summary of the invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for eliminating dispersion of a charged particle beam in an interfering magnetic field environment based on an electrode plate, so as to solve the technical problem that the charged particle beam is prone to dispersion in the prior art.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions to achieve the above problems:

[0006] A method for eliminating dispersion of a charged particle beam in an interfering magnetic field environment based on an electrode plate, the method comprising the following steps:

[0007] Step 1: Obtain magnetic induction intensity and target location

[0008] Step 2: According to the magnetic induction intensity obtained in step 1 and target location Calculate the emission direction of charged particles with different energies at the outlet of the electrode plate.

[0009] Step three, according to the emission direction of charged particles with different energies at the outlet of the electrode plate in step two, calculate the optical axis direction and electric field strength of the beam.

[0010] Step 4: Calculate the energy of charged particles with different energies at the electrode plate exit based on the electric field strength obtained in step 3, and calculate the target position based on the beam optical axis and electric field strength obtained in step 3. and update; after multiple iterations, a converged solution is obtained, that is, the final electric field intensity, the voltage operating range corresponding to the electric field intensity, and the optical axis of the beam before deflection are obtained.

[0011] Step 5: Adjust the accelerator posture according to the optical axis of the beam before deflection obtained in step 4, and set the electrode plate according to the final electric field strength obtained in step 4 and the voltage working range corresponding to the electric field strength to eliminate the dispersion of the charged particle beam.

[0012] The present invention also has the following technical features:

[0013] Specifically, in step 1, the magnetic induction intensity The corresponding magnetic field is a uniform magnetic field or a segmented uniform magnetic field.

[0014] Specifically, in step 1, the magnetic induction intensity When acquiring, it is necessary to measure the magnetic induction intensity on the charged particle beam path. Take measurements.

[0015] Specifically, in step 4, the calculation process of the converged solution specifically includes the following steps:

[0016] Step 401, based on the electric field strength obtained in step 3, calculate the energy of charged particles with different energies at the electrode plate outlet, and calculate the target point position based on the beam optical axis and electric field strength obtained in step 3 and update.

[0017] Step 402: compare the energy of charged particles with different energies at the electrode plate outlet with the updated target position. Re-substitute into step 2 to update the emission direction at the electrode plate exit.

[0018] Step 403, resubstituting the emission direction at the electrode plate outlet updated in step 2 into step 3 to update the electric field strength.

[0019] Step 404, substitute the updated electric field strength into step 4 to calculate the target point position And update the descendants and enter step 2.

[0020] Step 401, step 402, step 403 and step 404 are repeated for multiple iterations, and then a converged solution is obtained, that is, the final electric field intensity, the voltage operating range corresponding to the electric field intensity, and the optical axis of the beam before deflection are obtained.

[0021] Specifically, in step four, based on the maximum deflection angle required for charged particles of different energies, the charge of the charged particles, the static mass of the charged particles, the radius of the charged particle beam, and the energy range of the charged particle beam, the minimum electrode plate spacing required for the electrode plates and the upper limit of the required electric field strength are calculated, and then the voltage operating range corresponding to the electric field strength is obtained.

[0022] Specifically, the maximum deflection angle required for charged particles of different energies is based on the magnetic induction intensity The size range and target location The range of magnitude and magnetic induction intensity Direction and target location The range of the angle between the directions is obtained.

[0023] Preferably, in step five, there are two ways to generate the magnitude and direction of the electric field strength. One is two groups of electrode plates that are perpendicular to each other and respectively have voltage sources, which respectively generate electric field strengths with adjustable magnitudes in two directions. The required magnitude and direction of the electric field strength can be obtained by superimposing the approximate vectors of the adjustable electric field strengths in the two directions generated; the other is a group of electrode plates with a voltage source and a rotating mechanism, the rotating mechanism adjusts the direction of the electric field strength, and the voltage source adjusts the magnitude of the electric field strength.

[0024] Specifically, in step five, the method for adjusting the accelerator posture is to adjust the beam direction of the accelerator to adjust the beam direction of the accelerator to the target direction.

[0025] Preferably, the adjustment method is to move the accelerator and the beam optical device as a whole through a two-degree-of-freedom robotic arm, and make the electric field generated by the electrode plate always remain perpendicular to the beam.

[0026] Compared with the prior art, the present invention has the following technical effects:

[0027] (I) The method of the present invention is highly practical and can be applied to the last stage of various accelerator devices for various charged particles. The method can effectively eliminate dispersion, improve the accuracy of charged particle beam to target and the beam flux density, and enhance the beam irradiation effect.

[0028] (II) The method of the present invention has strong applicability and can be used to eliminate dispersion at any spatial magnetic field and any target position within a certain range.

[0029] (III) The method of the present invention has strong real-time performance and can perform real-time dispersion elimination and device adjustment according to the changes in the magnetic field in the scene.

[0030] (IV) The present invention can achieve the de-dispersion of charged particle beams in a magnetic field environment by only using two groups of electrode plates or one group of electrode plates plus a rotating mechanism. The device is small in scale, occupies little space, and has good economic efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The figure is a flow chart of a method for eliminating dispersion of a charged particle beam in an interfering magnetic field environment based on electrode plates.

[0032] Figure 2 is the emission direction and target position of a single charged particle at the electrode plate exit Schematic diagram of the angle.

[0033] Figure 3 A diagram illustrating the deflection angle of a single charged particle passing through an electrode plate.

[0034] Figure 4 This is a transmission diagram of a charged particle beam without dedispersion under a spatial interference magnetic field in an embodiment.

[0035] Figure 5 This is a diagram of the transmission of a charged particle beam in a spatial interference magnetic field after de-dispersion using an electrode plate in an embodiment.

[0036] The specific contents of the present invention are further explained in detail below in conjunction with embodiments. DETAILED DESCRIPTION

[0037] It should be noted that, unless otherwise specified, all raw materials and instruments used in the present invention are raw materials and instruments known in the prior art. For example, the accelerator uses a known accelerator. All units of physical quantities used in the present invention are units commonly known in the art.

[0038] The uniform magnetic field in the present invention can also be understood as a near-uniform magnetic field. A near-uniform magnetic field means that the partial derivative of the magnetic field with respect to the spatial coordinate is small, which also means that the magnetic field is approximately a uniform dipole magnetic field. The near-uniform magnetic field has a small partial derivative with respect to the spatial coordinate to ensure that the magnetic fields at different positions of the same beam cross section are close.

[0039] In the present invention, the magnetic induction intensity refers to the magnetic induction intensity of the spatial interference magnetic field.

[0040] In the present invention, the target point position refers to the position of the target point relative to the charged particles at the outlet of the electrode plate.

[0041] In the present invention, the exit velocity refers to the velocity at the exit of the electrode plate.

[0042] In the present invention, the electric field strength refers to the electric field strength of the electrode plate.

[0043] In the present invention, the incident direction refers to the emission speed direction of the charged particles at the initial moment, that is, the speed direction of the charged particles before entering the electrode plate.

[0044] In the present invention, the electrode plate length refers to the corrected length after taking the fringe field into account.

[0045] The method of the present invention can only eliminate the influence of dispersion on the beam spot divergence when reaching the target, and cannot solve the influence of the initial beam divergence angle θ on the beam spot size. Therefore, even if the Coulomb repulsion is ignored, the minimum beam spot divergence radius to the target in theory is greater than

[0046] In accordance with the above technical scheme, specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent changes made on the basis of the technical scheme of this application fall within the protection scope of the present invention.

[0047] Embodiment 1:

[0048] This embodiment provides a method for eliminating dispersion of a charged particle beam in an interfering magnetic field environment based on an electrode plate, such as Figure 1 As shown, the method comprises the following steps:

[0049] Step 1: Obtain magnetic induction intensity and target location

[0050] In step 1, the magnetic induction intensity The corresponding magnetic field is a uniform magnetic field or a segmented uniform magnetic field.

[0051] In step 1, the magnetic induction intensity When acquiring, it is necessary to measure the magnetic induction intensity on the charged particle beam path. Take measurements.

[0052] In step 1, preferably, the magnetic induction intensity When the corresponding magnetic field change is small and the distance is short, only the magnetic induction intensity at a single location is measured. Otherwise, it is necessary to measure at multiple points on the charged particle beam path, and the multi-point measurement results are weighted and regarded as a nearly uniform magnetic field or a segmented nearly uniform magnetic field during calculation. The small change of magnetic field over time ensures the effectiveness of each solution result in de-dispersion of the charged particle beam over a period of time.

[0053] In this embodiment, the magnetic induction intensity The size is 1mT, the target location The size is 1m.

[0054] In this embodiment, the charged particles are electrons and the energy distribution of the charged particle beam is 0.4-0.6 MeV.

[0055] If the emission direction of the charged particle beam at the electrode plate outlet is directly calculated based on the central energy of the charged particle beam, the transmission and distribution of the charged particle beam to the target are as follows: Figure 4 As shown in the figure (to show the influence of dispersion, the charged particle beam has no divergence angle and no radial distribution, and is initially on the optical axis of the beam), the size of the charged particle beam to the target is about 5 cm, and the flux to the target will drop significantly. Therefore, the charged particle beam needs to be de-dispersed.

[0056] Step 2: According to the magnetic induction intensity obtained in step 1 and target location Calculate the emission direction of charged particles with different energies at the electrode plate exit. The calculation method for a single charged particle is:

[0057] 1) When the magnetic induction intensity obtained in step 1 When the corresponding magnetic field is a uniform magnetic field:

[0058] i) If the magnetic induction intensity Direction and target location The directions of are parallel to each other, then the emission direction of a single charged particle at the outlet of the electrode plate is the target position direction.

[0059] ii) If the magnetic induction intensity Direction and target location The directions are perpendicular to each other, then a single charged particle moves in a circular motion in the space interference magnetic field, and the motion radius R is:

[0060]

[0061] Where:

[0062] R is the motion radius of a single charged particle;

[0063] m 0 is the static mass of a single charged particle;

[0064] γ is the relativistic factor;

[0065] v is the emission velocity of a single charged particle;

[0066] B is the magnetic induction intensity size;

[0067] q is the charge of a single charged particle.

[0068] like Figure 2 As shown, perpendicular to the magnetic induction intensity The plane in which the direction of the single charged particle is located can be used to calculate the emission direction and target position of the single charged particle at the electrode plate exit. The angle between the directions The solution process is:

[0069]

[0070] Where:

[0071] is the emission direction and target position of a single charged particle at the electrode plate exit The angle between the directions of

[0072] r is the target position size;

[0073] R is the motion radius of a single charged particle;

[0074] B is the magnetic induction intensity size;

[0075] q is the charge of a single charged particle;

[0076] m 0 is the static mass of a single charged particle;

[0077] γ is the relativistic factor;

[0078] v is the emission velocity of a single charged particle.

[0079] Figure 2 In the figure, S represents the source and T represents the target.

[0080] Target location is the origin, the target position The direction is the x-axis, and the magnetic induction intensity The direction of the z-axis is the z-axis, and the direction perpendicular to the x-axis and z-axis is the y-axis. The coordinate system is established, and the emission direction of a single charged particle at the outlet of the electrode plate is for:

[0081]

[0082] iii) If the magnetic induction intensity Direction and target location The direction is neither parallel nor perpendicular. Let the angle between the two be α. Then the motion of a single charged particle is decomposed into two parts parallel to the magnetic induction intensity. The direction is perpendicular to the magnetic induction intensity direction.

[0083] Target location is the origin, the magnetic induction intensity The direction is the z-axis, The direction is the y-axis, and the direction perpendicular to the y-axis and z-axis is the x-axis. Establish a coordinate system. is the emission direction and magnetic induction intensity of a single charged particle at the outlet of the electrode plate The angle between the directions of It is the angle between the projection of the emission direction of a single charged particle at the outlet of the electrode plate on the xoy plane and the x-axis.

[0084] The velocity of a single charged particle along the z-axis is:

[0085] v / / =v cosθ

[0086] Where:

[0087] v / / is the magnitude of the exit velocity of a single charged particle along the z-axis;

[0088] v is the emission velocity of a single charged particle;

[0089] is the emission direction and magnetic induction intensity of a single charged particle at the outlet of the electrode plate The angle between the directions.

[0090] The exit velocity of a single charged particle in the xoy plane is:

[0091] v ⊥ =v sinθ

[0092] Where:

[0093] v ⊥ is the emission velocity of a single charged particle in the xoy plane;

[0094] v is the emission velocity of a single charged particle;

[0095] is the emission direction and magnetic induction intensity of a single charged particle at the outlet of the electrode plate The angle between the directions.

[0096] The radius of the circle of a single charged particle moving in the xoy plane is:

[0097]

[0098] Where:

[0099] R is the radius of the circle of motion of a single charged particle in the xoy plane;

[0100] m 0is the static mass of a single charged particle;

[0101] γ is the relativistic factor;

[0102] v ⊥ is the emission velocity of a single charged particle in the xoy plane;

[0103] B is the magnetic induction intensity size;

[0104] q is the charge of a single charged particle;

[0105] v is the emission velocity of a single charged particle;

[0106] is the emission direction and magnetic induction intensity of a single charged particle at the outlet of the electrode plate The angle between the directions.

[0107] A single charged particle moves along the z-axis to the target location The time required for projection on the z-axis is:

[0108]

[0109] Where:

[0110] t is the movement of a single charged particle from the z axis to the target position The time required for projection on the z-axis;

[0111] r is the target position size;

[0112] α is the magnetic induction intensity Direction and target location The angle between the directions of

[0113] v is the emission velocity of a single charged particle;

[0114] is the emission direction and magnetic induction intensity of a single charged particle at the outlet of the electrode plate The angle between the directions.

[0115] If you need to reach the target location The chord length of the trajectory of a single charged particle in the xoy plane at this moment must be exactly equal to the target position. The projection distance on the z-axis is rsinα, that is:

[0116]

[0117] Where:

[0118] m 0is the static mass of a single charged particle;

[0119] γ is the relativistic factor;

[0120] v is the emission velocity of a single charged particle;

[0121] is the emission direction and magnetic induction intensity of a single charged particle at the outlet of the electrode plate The angle between the directions of

[0122] B is the magnetic induction intensity size;

[0123] q is the charge of a single charged particle;

[0124] r is the target position size;

[0125] α is the magnetic induction intensity Direction and target location The angle between the directions.

[0126] In the above formula, only θ is an unknown quantity, and the minimum solution (the solution whose motion in the xoy plane does not exceed half a period) can be obtained by bisection.

[0127] The angle between the projection of the emission direction of a single charged particle at the outlet of the electrode plate on the xoy plane and the x-axis is:

[0128]

[0129] Where:

[0130] is the angle between the projection of the emission direction of a single charged particle at the outlet of the electrode plate on the xoy plane and the x-axis;

[0131] r is the target position size;

[0132] α is the magnetic induction intensity Direction and target location The angle between the directions of

[0133] R is the radius of the circle of motion of a single charged particle in the xoy plane;

[0134] B is the magnetic induction intensity size;

[0135] q is the charge of a single charged particle;

[0136] m 0 is the static mass of a single charged particle;

[0137] r is the target position size;

[0138] v is the emission velocity of a single charged particle;

[0139] is the emission direction and magnetic induction intensity of a single charged particle at the outlet of the electrode plate The angle between the directions.

[0140] Finally, the emission direction of a single charged particle at the outlet of the electrode plate is obtained for

[0141]

[0142] After calculating the emission directions of single charged particles at the electrode plate outlet respectively, the angle δ between the emission directions of charged particles with different energies at the electrode plate outlet is calculated according to the emission directions of two charged particles with different energies at the electrode plate outlet.

[0143] 2) When the magnetic induction intensity obtained in step 1 When the corresponding magnetic field is a segmented uniform magnetic field:

[0144] The first solution is performed according to the above uniform magnetic field solution method, and then the emission direction at the electrode plate outlet obtained by the solution is substituted into the segmented uniform magnetic field, and the target position is gradually adjusted to obtain the emission direction of the particles at the electrode plate outlet in this case.

[0145] In this embodiment, the magnetic induction intensity Direction and target location The directions are perpendicular to each other, and the effective length of the electrode plate used is 0.1m; the target position is the origin, the target position The direction is the x-axis, and the magnetic induction intensity The direction is the z-axis, and the direction perpendicular to the x-axis and z-axis is the y-axis. A coordinate system is established.

[0146] Then, the emission direction of the electrons at the electrode plate exit when the electron energy is 0.4 MeV is calculated. When the electron energy is 0.6MeV, the direction of the electron emission at the electrode plate exit is The angle between the two emission directions at the outlet of the electrode plate is δ=0.048 rad.

[0147] Step 3: According to the emission direction of charged particles with different energies at the electrode plate exit in step 2, the optical axis of the beam and the electric field strength are calculated to make the emission direction of charged particles with different energies at the electrode plate exit close to the incident direction. Figure 3 shown.

[0148] The specific solution method is:

[0149] The motion equation of charged particles in the electrode plate is:

[0150]

[0151] Where:

[0152] p x is the projection of the momentum of a single charged particle on the x-axis;

[0153] p y is the projection of the momentum of a single charged particle on the y-axis;

[0154] p z is the projection of the momentum of a single charged particle on the z-axis;

[0155] q is the charge of a single charged particle;

[0156] E is the magnitude of the electric field strength;

[0157] t is the time that the charged particles are in the electrode plates.

[0158] After calculation, the deflection angle of the charged particle after passing through the electrode plate is:

[0159]

[0160] Where:

[0161] is the emission direction and magnetic induction intensity of a single charged particle at the outlet of the electrode plate The angle between the directions of

[0162] c is the speed of light;

[0163] v 0 is the velocity of a single charged particle before it enters the electrode plate;

[0164] h is the distance between the electrode plates;

[0165] q is the charge of a single charged particle;

[0166] E is the magnitude of the electric field strength;

[0167] p 0 is the momentum of a single charged particle before it enters the electrode plate;

[0168] D is the length of the electrode plate.

[0169] Substituting single charged particles of different energies into the above formula, the corresponding deflection angle under a specific electric field strength can be obtained as:

[0170]

[0171] Where:

[0172] is the emission direction and magnetic induction intensity of a single charged particle at the outlet of the electrode plate The angle between the directions of

[0173] c is the speed of light;

[0174] v 01 It is the speed of a single charged particle with lower energy before it enters the electrode plate;

[0175] h is the distance between the electrode plates;

[0176] q is the charge of a single charged particle;

[0177] E is the magnitude of the electric field strength;

[0178] p 01 It is the momentum of a single charged particle with lower energy before it enters the electrode plate;

[0179] D is the length of the electrode plate;

[0180] v 02 It is the velocity of a single charged particle with higher energy before it enters the electrode plate;

[0181] p 02 It is the momentum of a single charged particle with higher energy before it enters the electrode plate.

[0182] By using the dichotomy method, we can obtain the electric field strength required to produce an angle δ in the emission direction of charged particles with different energies at the electrode plate exit. According to the deflection angle of the charged particles under this electric field strength, we can obtain the direction of the charged particles before deflection, which is the optical axis of the beam. Since the energy dispersion range of charged particles is relatively small, it can be considered that the emission direction of charged particles at the electrode plate exit is approximately linearly related to the energy.

[0183] In this embodiment, after performing the dichotomy, the required electric field strength E=1.408MV / m is obtained. Under this electric field, the deflection angle of 0.4MeV electrons is θ 1 =0.167rad, then the optical axis of the beam before deflection is

[0184]

[0185] Step 4: Calculate the energy of charged particles with different energies at the electrode plate exit based on the electric field strength obtained in step 3, and calculate the target position based on the beam optical axis and electric field strength obtained in step 3. and update; after multiple iterations, a converged solution is obtained, that is, the final electric field intensity, the voltage operating range corresponding to the electric field intensity, and the optical axis of the beam before deflection are obtained.

[0186] In step 4, the calculation process of the converged solution specifically includes the following steps:

[0187] Step 401, based on the electric field strength obtained in step 3, calculate the energy of charged particles with different energies at the electrode plate outlet, and calculate the target point position based on the beam optical axis and electric field strength obtained in step 3 and update.

[0188] Step 402: compare the energy of charged particles with different energies at the electrode plate outlet with the updated target position. Re-substitute into step 2 to update the emission direction at the electrode plate exit.

[0189] Step 403, resubstituting the emission direction at the electrode plate outlet updated in step 2 into step 3 to update the electric field strength.

[0190] Step 404, substitute the updated electric field strength into step 4 to calculate the target point position And update the descendants and enter step 2.

[0191] Step 401, step 402, step 403 and step 404 are repeated for multiple iterations, and then a converged solution is obtained, that is, the final electric field intensity, the voltage operating range corresponding to the electric field intensity, and the optical axis of the beam before deflection are obtained.

[0192] In step 4, based on the maximum deflection angle required for charged particles of different energies, the charge of the charged particles, the static mass of the charged particles, the radius of the charged particle beam, and the energy range of the charged particle beam, the minimum electrode plate spacing required and the upper limit of the required electric field strength are calculated, thereby obtaining the voltage operating range corresponding to the electric field strength.

[0193] The maximum deflection angle required for charged particles of different energies is based on the magnetic induction intensity The size range and target location The range of magnitude and magnetic induction intensity Direction and target location The range of the angle between the directions is obtained.

[0194] Due to the deflection of the electrode plate electric field and the change of the beam optical axis, the position of the charged particles at the electrode plate exit moves, so the target position will also change accordingly. In addition, the electric field will change the energy of the charged particles. Therefore, it is necessary to calculate the corresponding target position when the beam optical axis is in step 3. The energy of the charged particles after leaving the electrode plate is recalculated and obtained after multiple iterations.

[0195] In this embodiment, since the electric field will increase the electron energy, under the electric field strength obtained in step 3, it is calculated that the energy of 0.4MeV electrons at the electrode plate outlet becomes 0.409MeV and the energy of 0.6MeV electrons at the electrode plate outlet becomes 0.606MeV.

[0196] At the same time, the electrode plate changes the electron exit position. It is calculated that for 0.4MeV electrons and 0.6MeV electrons, under the electric field strength and beam optical axis obtained in step 3, the positions of the electrode plate exit become (-0.0003, 0.0084, 0) and (-0.0002, 0.0060, 0) respectively. Then the target position Updated to as well as The changed charged particle energy and the target position Re-substitute to calculate the emission direction at the electrode plate exit, and then update the required electric field strength, electron energy at the electrode plate exit and target position After multiple iterations of this method, a converged solution can be obtained, that is, the electric field strength E = 0.956 MV / m and the optical axis of the beam before deflection

[0197]

[0198] Step 5: Adjust the accelerator posture according to the optical axis of the beam before deflection obtained in step 4, and set the electrode plate according to the final electric field strength obtained in step 4 and the voltage working range corresponding to the electric field strength to eliminate the dispersion of the charged particle beam.

[0199] In step 5, there are two ways to generate the magnitude and direction of the electric field strength. One is to use two sets of mutually perpendicular electrode plates with voltage sources to generate adjustable electric field strengths in two directions. The required magnitude and direction of the electric field strength can be obtained by superimposing the approximate vectors of the adjustable electric field strengths in two directions. The other is to use a set of electrode plates with voltage sources and a rotating mechanism to adjust the direction of the electric field strength and the voltage source to adjust the magnitude of the electric field strength. This can eliminate the influence of dispersion and achieve accurate target, smaller target beam spot radius and larger target flux density.

[0200] In step five, the beam direction itself needs to be adjusted to point in the direction of the target.

[0201] In step five, the direction of adjustment is achieved by moving the accelerator and beam optical device as a whole through a mechanical device with two degrees of freedom, and the electric field generated by the electrode plate is always perpendicular to the beam.

[0202] When the target is confined to a small range in the beam pointing direction, no beam pointing adjustment is performed.

[0203] In this embodiment, after setting the electric field intensity and beam optical axis obtained in step 4, the beam transmission and distribution to the target can be obtained as follows: Figure 5 As shown in the figure, the target position The size is less than 1mm, compared to Figure 4 In the case of an undispersed charged particle beam, the target position The size of the probe is significantly reduced and the flux to the target is significantly enhanced.

Claims

1. A method for eliminating dispersion of a charged particle beam in an interfering magnetic field environment based on an electrode plate, characterized in that: The method comprises the following steps: Step 1: Obtain magnetic induction intensity and target location Step 2: According to the magnetic induction intensity obtained in step 1 and target location Calculate the emission direction of charged particles with different energies at the electrode plate exit; Step 3, according to the emission direction of charged particles with different energies at the outlet of the electrode plate in step 2, the optical axis of the beam and the electric field intensity are calculated; Step 4: Calculate the energy of charged particles with different energies at the electrode plate exit based on the electric field strength obtained in step 3, and calculate the target position based on the beam optical axis and electric field strength obtained in step 3. and update; after multiple iterations, a converged solution is obtained, that is, the final electric field intensity, the voltage operating range corresponding to the electric field intensity, and the optical axis of the beam before deflection are obtained; Step 5: Adjust the accelerator posture according to the optical axis of the beam before deflection obtained in step 4, and set the electrode plate according to the final electric field strength obtained in step 4 and the voltage working range corresponding to the electric field strength to eliminate the dispersion of the charged particle beam.

2. The method for eliminating dispersion of charged particle beam in an interfering magnetic field environment based on electrode plates according to claim 1, characterized in that: In step 1, the magnetic induction intensity The corresponding magnetic field is a uniform magnetic field or a segmented uniform magnetic field.

3. The method for eliminating dispersion of charged particle beam in an interfering magnetic field environment based on electrode plates as claimed in claim 1, characterized in that: In step 1, the magnetic induction intensity When acquiring, it is necessary to measure the magnetic induction intensity on the charged particle beam path. Take measurements.

4. The method for eliminating dispersion of charged particle beam in an interfering magnetic field environment based on electrode plates as claimed in claim 1, characterized in that: In step 4, the calculation process of the converged solution specifically includes the following steps: Step 401, based on the electric field strength obtained in step 3, calculate the energy of charged particles with different energies at the electrode plate exit, and calculate the target point position based on the beam optical axis and electric field strength obtained in step 3 and update; Step 402: compare the energy of charged particles with different energies at the electrode plate outlet with the updated target position. Resubstitute into step 2 to update the emission direction at the electrode plate exit; Step 403, resubstituting the emission direction at the electrode plate exit updated in step 2 into step 3 to update the electric field strength; Step 404, substitute the updated electric field strength into step 4 to calculate the target point position And update the next step into step 2; Step 401, step 402, step 403 and step 404 are repeated for multiple iterations, and then a converged solution is obtained, that is, the final electric field intensity, the voltage operating range corresponding to the electric field intensity, and the optical axis of the beam before deflection are obtained.

5. The method for eliminating dispersion of charged particle beam in an interfering magnetic field environment based on electrode plates as claimed in claim 1, characterized in that: In step 4, based on the maximum deflection angle required for charged particles of different energies, the charge of the charged particles, the static mass of the charged particles, the radius of the charged particle beam, and the energy range of the charged particle beam, the minimum electrode plate spacing required and the upper limit of the required electric field strength are calculated, thereby obtaining the voltage operating range corresponding to the electric field strength.

6. The method for eliminating dispersion of charged particle beam in an interfering magnetic field environment based on electrode plates as claimed in claim 5, characterized in that: The maximum deflection angle required for charged particles of different energies is based on the magnetic induction intensity The size range and target location The range of magnitude and magnetic induction intensity Direction and target location The range of the angle between the directions is obtained.

7. The method for eliminating dispersion of charged particle beam in an interfering magnetic field environment based on electrode plates as claimed in claim 1, characterized in that: In step five, there are two ways to generate the magnitude and direction of the electric field strength. One is two sets of electrode plates that are perpendicular to each other and each has a voltage source, which generate electric field strengths with adjustable magnitudes in two directions respectively. The required magnitude and direction of the electric field strength can be obtained by superimposing the approximate vectors of the adjustable electric field strengths in two directions generated; the other is a set of electrode plates with a voltage source and a rotating mechanism, the rotating mechanism adjusts the direction of the electric field strength, and the voltage source adjusts the magnitude of the electric field strength.

8. The method for eliminating dispersion of charged particle beam in an interfering magnetic field environment based on electrode plates as claimed in claim 1, characterized in that: In step five, the method for adjusting the accelerator posture is to adjust the beam direction of the accelerator to adjust the beam direction of the accelerator to the target direction.

9. The method for eliminating dispersion of charged particle beam in an interfering magnetic field environment based on electrode plates as claimed in claim 8, characterized in that: The adjustment method is to move the accelerator and the beam optical device as a whole through a two-degree-of-freedom mechanical arm, and make the electric field generated by the electrode plate always remain perpendicular to the beam.

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