A parameter optimization simulation design method for beam nanosecond pulse shaping system

Abstract

The present invention discloses a parameter optimization simulation design method for a beam nanosecond pulse shaping system, which belongs to the technical field of parameter optimization design of pulse shaping systems, and includes the following steps: S1: establishing a beam line design scheme for a pulsed neutron generator and its beam pulse shaping system; S2: establishing a PIC simulation model according to the beam line design scheme established in step S1; S3: setting simulation parameters of the beam pulse shaping system according to the PIC simulation model, and calculating the results; S4: verifying the calculation results of the simulation model; S5: repeating steps S3 and S4 to optimize the PIC simulation model of the beam pulse shaping system. The present invention establishes a beam line design scheme for a pulsed neutron emitter and a beam pulse shaping system, and establishes a PIC simulation model using the beam line design scheme, and continuously optimizes the setting parameters of the PIC simulation model, thereby ensuring the accuracy of the established PIC simulation model, and providing strong data support for the design of the beam nanosecond pulse shaping system.

Description

Technical Field

[0001] The invention belongs to the technical field of pulse shaping system parameter optimization design, and in particular relates to a beam nanosecond pulse shaping system parameter optimization simulation design method. Background Art

[0002] Pulsed neutron generators are a type of high-tech equipment with important scientific research purposes and industrial application value. They are key devices for conducting neutron nuclear data measurement, nuclear fusion and nuclear fission related research, material element analysis research, etc. The United States built nanosecond pulsed neutron generators in the 1960s and Japan in the 1980s, and carried out a large amount of neutron nuclear data and secondary neutron energy spectrum measurement work, and did a lot of work for the establishment and continuous improvement of the US nuclear database ENDF / B-6 and the Japanese nuclear database JENDL-3.2. At the beginning of this century, my country successfully developed the nanosecond pulsed neutron generator CIAE600kV, which played an important role in the establishment of my country's nuclear database CENDL-3.2.

[0003] In recent years, on the one hand, the nanosecond pulsed neutron generators built in the last century have reached the retirement age, and the aging equipment is difficult to operate in the best state; on the other hand, the development and research of nanosecond pulsed neutron application technology urgently needs nanosecond pulsed neutron generators that can carry out related research work. Therefore, many countries have started the development of a new generation of nanosecond pulsed neutron generators, such as the high-current nanosecond pulsed neutron generator FRANZ that has been built in Germany, and China is conducting research on a new type of nanosecond pulsed neutron source using the principle of linear induction acceleration. In the pulsed neutron generator, the beam nanosecond pulse shaping system is the core key technology, so the optimization and simulation of the parameters of the existing beam pulse shaping system is the main research direction at present, which is of great significance to the research and development of pulsed neutron generators. Summary of the invention

[0004] The purpose of the present invention is to provide a parameter optimization simulation design method for a beam nanosecond pulse shaping system in response to the defects existing in the prior art. A beam line design scheme for a pulsed neutron emitter and a beam pulse shaping system is established, and a PIC simulation model is established using the beam line design scheme. The setting parameters of the PIC simulation model are continuously optimized, the reliability of the calculation results of the simulation model is verified, the accuracy of the established PIC simulation model is guaranteed, and strong data support is provided for the design of the beam nanosecond pulse shaping system.

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

[0006] A beam nanosecond pulse shaping system parameter optimization simulation design method specifically comprises the following steps:

[0007] S1: Establish the beamline design of the pulsed neutron generator and its beam pulse shaping system;

[0008] S2: Establishing a PIC simulation model according to the beam design scheme established in step S1;

[0009] S3: Set the simulation parameters of the beam pulse shaping system according to the PIC simulation model and calculate the results;

[0010] S4: Verify the calculation results of the simulation model. If the verification fails, adjust the model. If the verification passes, complete the construction of the PIC simulation model prototype.

[0011] S5: Repeat steps S3 and S4 to optimize the beam pulse shaping system PIC simulation model until the PIC simulation model has sufficient accuracy to design the beam nanosecond pulse shaping system.

[0012] The pulse neutron generator in step S1 includes a high-voltage platform, an ion source, an accelerating tube, a ground electrode, a three-unit quadrupole magnetic lens, a switch magnet, a solenoid lens, a beam cutter, a buncher, a power supply system and a rotating target. The beam cutter is composed of a pair of parallel scanning plates and a beam selection flange, and the buncher adopts a double-gap bunching structure; the beam pulse shaping system includes a beam cutter, a buncher and a power supply system.

[0013] The specific working process of the pulsed neutron generator is as follows: the deuterium beam generated by the ion source is accelerated to an energy of 400 keV by an accelerating tube, and after being transversely focused by a three-unit quadrupole magnetic lens and deflected by a switch magnet, the beam enters a pulse beam line, and then after being transversely focused by a three-unit quadrupole magnetic lens, it enters a beam cutter, and under the action of a high-frequency electric field of a scanning plate inside the beam cutter, the beam scans forward, and a beam selection flange prevents the beam from being scanned outside the beam selection aperture, and part of the beam passing through the beam selection aperture forms a long pulse bunch, and after the long pulse bunch is longitudinally focused by a buncher, a longitudinal focus is formed at a rotating target position, and a solenoid lens transversely focuses the bunch.

[0014] The initial parameters of the PIC simulation model in step S3 are: the mass of the deuterium ion is 2, the charge is 1, the energy is 400 keV, the beam intensity is 0.25 mA, and the beam diameter is 4 mm.

[0015] The parallel scanning plate and the beam selection flange are both made of stainless steel, and the parallel scanning plate includes an upper scanning plate and a lower scanning plate. The upper scanning plate applies a high-frequency electric field, and the lower scanning plate is grounded, so that a high-frequency electric field is formed between the upper and lower scanning plates. The beam selection flange is grounded, and the upper scanning plate applies a sinusoidal high-frequency voltage V(t), which is expressed as

[0016] V(t)=V(0)sin(ωt)

[0017] Where: V(0) is the high-frequency voltage amplitude, ω is the angular frequency, and t is the time.

[0018] The cylindrical electrode in the middle of the buncher is connected to a high-frequency power supply, and the cylindrical electrodes on both sides are grounded respectively. The electrodes are made of stainless steel. b (t) is expressed as

[0019] V b (t) = V b0 sin(ω b t+φ)

[0020] Where: V b0 is the high frequency voltage amplitude, ω b is the angular frequency, t is the time, and φ is the initial phase.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention establishes a beam line design scheme for a pulsed neutron emitter and a beam pulse shaping system, and uses the beam line design scheme to establish a PIC simulation model. By continuously optimizing the setting parameters of the PIC simulation model, the reliability of the simulation model calculation results is verified, the accuracy of the established PIC simulation model is guaranteed, and strong data support is provided for the design of the beam nanosecond pulse shaping system. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the structure of a nanosecond pulse DD / DT neutron generator in an embodiment of the present invention.

[0024] Figure 2 Schematic diagram of the structure of the nanosecond pulse beam forming system in an embodiment of the present invention.

[0025] Figure 3 It is the spatiotemporal evolution process of the pulse beam in the beam cutter in the embodiment of the present invention.

[0026] Figure 4 Schematic diagram of experimental results of the relationship between the amplitude and pulse width of the sinusoidal high-frequency voltage in an embodiment of the present invention.

[0027] Figure 5 It is the instantaneous electric field intensity Ey of the beam cutter along the X-axis in the Y direction in the embodiment of the present invention.

[0028] Figure 6 It is the instantaneous electric field intensity Ex of the buncher along the X-axis in the X direction in the embodiment of the present invention.

[0029] Figure 7 It is the spatiotemporal evolution process of the deuterium beam from entering the beam cutter to reaching the collector in the embodiment of the present invention.

[0030] Figure 8 It is a schematic diagram of collecting the temporal structure information and beam intensity of the upper pulse bunch in an embodiment of the present invention. DETAILED DESCRIPTION

[0031] The present invention will be described in detail below in conjunction with specific embodiments and drawings. The exemplary embodiments and descriptions of the present invention are used to explain the present invention but are not intended to limit the present invention.

[0032] Example 1

[0033] A beam nanosecond pulse shaping system parameter optimization simulation design method specifically includes the following contents:

[0034] 1. Simulation Model

[0035] 1.1 Beam pulse shaping system solution

[0036] Establish as Figure 1 The beam line design of the nanosecond pulse DD / DT neutron generator shown in the figure mainly consists of a high-voltage platform, an ion source, an accelerator tube, a ground electrode, a three-unit quadrupole magnetic lens, a switch magnet, a solenoid lens, a beam cutter, a buncher, a rotating target, etc. The beam pulse shaping system mainly consists of a beam cutter, a buncher, a power supply system, etc. Figure 2 shown.

[0037] The specific working process of the pulsed neutron generator is as follows: the deuterium beam generated by the ion source is accelerated to an energy of 400keV by an accelerating tube, and after being transversely focused by a three-unit quadrupole magnetic lens and deflected by a switch magnet, the beam enters a pulse beam line, and then after being transversely focused by a three-unit quadrupole magnetic lens, it enters a beam cutter, and under the action of a high-frequency electric field of a scanning plate inside the beam cutter, the beam scans forward, and a beam selection flange prevents the beam from being scanned outside the beam selection aperture, and part of the beam passing through the beam selection aperture forms a long pulse bunch, and after the long pulse bunch is longitudinally focused by a buncher, a longitudinal focus is formed at a rotating target position, and a solenoid lens transversely focuses the bunch.

[0038] 1.2 Simulation parameter settings

[0039] Will be based on Figure 1-2 The beam pulse shaping system shown in the figure establishes a PIC simulation model. In the PIC simulation, the initial parameters of the deuterium beam are set as follows: the mass of the deuterium ion is 2, the charge is 1, the energy is 400keV, the beam intensity is 0.25mA, and the beam diameter is 4mm. The simulation parameters of the beam cutter and buncher are as follows.

[0040] 1.2.1 Beam Cutter Parameters

[0041] The beam cutter consists of a pair of parallel scanning plates and a beam selection flange, such as Figure 1As shown, the parallel scanning plate and the beam selection flange are both made of stainless steel, and the parallel scanning plate includes an upper scanning plate and a lower scanning plate. The upper scanning plate of the beam cutter applies a high-frequency electric field, and the lower scanning plate is grounded, thereby forming a high-frequency electric field between the upper and lower scanning plates. The beam selection flange is grounded, and the upper scanning plate applies a sinusoidal high-frequency voltage V(t), which is expressed as

[0042] V(t)=V(0)sin(ωt)

[0043] Where: V(0) is the high-frequency voltage amplitude, ω is the angular frequency, and t is the time.

[0044] The structure and high-frequency voltage parameters of the beam cutter are shown in Table 1.

[0045] Table 1 Structure and high frequency voltage parameters of beam cutter

[0046] Scanning board length / cm 20 Gap between upper and lower scanning plates / cm 2 Select flange aperture / cm 3 Distance between scanning plate and beam selection flange / cm 240 <![CDATA[High-frequency voltage amplitude V (0) / kV]]> 1 High frequency voltage angular frequencyω / MHz 10

[0047] 1.2.2 Buncher parameters

[0048] The buncher adopts a double-gap bunching structure, such as Figure 1 As shown, the cylindrical electrode in the middle of the buncher is connected to a high-frequency power supply, and the cylindrical electrodes on both sides are grounded respectively. The electrodes are made of stainless steel. b (t) is expressed as

[0049] V b (t) = V b0 sin(ω b t+φ)

[0050] Where: V b0 is the high frequency voltage amplitude, ω b is the angular frequency, t is the time, and φ is the initial phase.

[0051] The structure and high-frequency voltage parameters of the buncher are shown in Table 2.

[0052] Table 2 Structure and high frequency voltage parameters of the buncher

[0053] High frequency high voltage electrode length / cm 46.5 High frequency high voltage electrode inner radius / cm 2 Left grounded cylindrical electrode length / cm 7.9 Length of right grounded cylindrical electrode / cm 7.9 Gap between high frequency electrode and left and right ground electrodes / cm 2.1 <![CDATA[High-frequency voltage amplitude V b0 / kV]]> 30 <![CDATA[Angular frequency ω of high-frequency voltage b / MHz]]> 40 High frequency voltage initial phase φ / rad 7π16

[0054] 1.3 Simulation model verification

[0055] In order to verify the reliability of the calculation results of the simulation model, the PIC simulation model of the beam cutter is established according to the experimental data of the beam cutter. Figure 3 shown. Figure 3The transmission of the beam in the beam cutter is given. It can be seen that after the beam cutter, a pulse bunch is formed behind the beam selection flange. According to the experimental data of the beam cutter, the pulse width of the pulse bunch is simulated and calculated when the amplitude of the parallel scanning plate sinusoidal high-frequency voltage is 1, 2, 3, and 4 kV respectively. The results are shown in Figure 4 As shown. Figure 4 It can be seen that the simulation results are basically consistent with the theoretical results and have the same variation trend as the experimental data. The simulation results show that the PIC simulation model has sufficient accuracy to design the beam nanosecond pulse shaping system.

[0056] 2 Simulation Results

[0057] 2.1 Electric field

[0058] The beam cutter is loaded with a high-frequency sinusoidal voltage to observe the instantaneous electric field distribution and electric field strength at a certain moment. Through the program, the instantaneous value of the component Ey of the electric field strength along the axis X in the Y direction is observed. The simulation results are as follows Figure 5 As shown. Figure 5 It can be seen that at 158.426ns, along the axis X, from 300 to 500mm, the component Ey value of the high-frequency electric field in the Y direction is about -5×10 4 V / m, the negative sign indicates that the electric field direction is along the negative direction of the Y axis. There is a diffuse electric field at the edge of the beam cutter, and the edge diffuse electric field drops rapidly on both sides of the beam cutter. The electric field strength Ey values ​​are about 30mm from the left and right edges of the beam cutter scanning plate, respectively, from -5×10 4 V / m drops to -1×10 4 V / m, decreased by about 80%.

[0059] The buncher is loaded with a high-frequency sinusoidal voltage to observe the instantaneous electric field distribution and electric field strength at a certain moment. The program gives the distribution and magnitude of the X-direction component Ex of the electric field strength along the X-axis. The simulation results are shown in Figure 6 As shown. Figure 6 It can be seen that at 3.301ns, the maximum value of Ex between the left ground electrode and the middle high-frequency voltage electrode is about -1.1×10 6 V / m, the negative sign indicates that the electric field is pointing to the negative X-axis direction. There is a diffuse electric field on both sides of the gap, which decreases exponentially. The maximum value of Ex between the right ground electrode and the middle high-frequency voltage electrode is about 1.1×10 6 V / m, the direction of the electric field points to the positive X-axis direction. Similarly, there is a diffuse electric field distributed on both sides of the gap, which decreases exponentially; inside the left and right grounding electrodes and the high-frequency high-voltage electrode, the electric field strength values ​​are all 0.

[0060] 2.2 Beam transmission

[0061] Through PIC simulation, the spatiotemporal evolution of the DC deuterium beam from entering the beam cutter to reaching the collector was observed. At 1.994us, the spatiotemporal evolution simulation results of the deuterium beam are as follows: Figure 7 As shown. Figure 7 It can be seen that a DC D beam is transmitted to the beam cutter, and after being acted on by the high-frequency electric field of the beam cutter, it evolves into a beam with a sine wave shape in the drift interval. After passing through the beam selection flange, part of the beam passing through the beam selection flange forms a long pulse bunch, and the rest of the beam is blocked by the beam selection flange and lost. Then, after passing through a drift interval, the long pulse bunch enters the buncher, and after the longitudinal focusing of the long pulse bunch by the double-gap buncher, it passes through a drift interval and finally forms a short pulse bunch, which is received by the collector.

[0062] 2.3 Pulse bunch characteristics

[0063] Through simulation, the temporal structure information and beam intensity of the pulse bunch on the collection pole after the deuterium DC beam passes through the pulse shaping system are given. The simulation results are as follows Figure 8 As shown. Figure 8 It can be seen that the pulse width of the pulse bunch is about 5ns, the repetition frequency is about 3.2MHz, and the peak current of the bunch is about 1.3mA, which meets the preliminary design indicators of the designed beam pulse shaping system.

[0064] The technical solutions provided by the embodiments of the present invention are introduced in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the embodiments of the present invention. The description of the above embodiments is only applicable to help understand the principles of the embodiments of the present invention.

Claims

1. A beam nanosecond pulse shaping system parameter optimization simulation design method, characterized in that: The specific steps include: S1: Establish the beamline design of the pulsed neutron generator and its beam pulse shaping system; S2: Establishing a PIC simulation model according to the beam design scheme established in step S1; S3: Set the simulation parameters of the beam pulse shaping system according to the PIC simulation model and calculate the results; S4: Verify the calculation results of the simulation model. If the verification fails, adjust the model. If the verification passes, complete the construction of the PIC simulation model prototype. S5: repeating steps S3 and S4 to optimize the PIC simulation model of the beam pulse shaping system until the PIC simulation model has sufficient accuracy to design the beam nanosecond pulse shaping system; The pulse neutron generator in step S1 includes a high-voltage platform, an ion source, an accelerating tube, a ground electrode, a three-unit quadrupole magnetic lens, a switch magnet, a solenoid lens, a beam cutter, a buncher, a power supply system and a rotating target, wherein the beam cutter is composed of a pair of parallel scanning plates and a beam selection flange, and the buncher adopts a double-gap bunching structure; the beam pulse shaping system includes a beam cutter, a buncher and a power supply system; The specific working process of the pulsed neutron generator is as follows: the deuterium beam generated by the ion source is accelerated to an energy of 400 keV by an accelerating tube, and after being transversely focused by a three-unit quadrupole magnetic lens and deflected by a switch magnet, the beam enters a pulse beam line, and then transversely focused by a three-unit quadrupole magnetic lens, enters a beam cutter, and under the action of a high-frequency electric field of a scanning plate inside the beam cutter, the beam scans forward, a beam selection flange prevents the beam from scanning outside the beam selection aperture, and part of the beam passing through the beam selection aperture forms a long pulse bunch, and after being longitudinally focused by a buncher, the long pulse bunch forms a longitudinal focus at a rotating target position, and a solenoid lens transversely focuses the bunch; The initial parameters of the PIC simulation model in step S3 are: the mass of the deuterium ion is 2, the charge is 1, the energy is 400 keV, the beam intensity is 0.25 mA, and the beam diameter is 4 mm; The parallel scanning plate and the beam selection flange are both made of stainless steel, and the parallel scanning plate includes an upper scanning plate and a lower scanning plate. The upper scanning plate applies a high-frequency electric field, and the lower scanning plate is grounded, so that a high-frequency electric field is formed between the upper and lower scanning plates. The beam selection flange is grounded, and the upper scanning plate applies a sinusoidal high-frequency voltage V(t), which is expressed as V(t)=V(0)sin(ωt) Where: V(0) is the high-frequency voltage amplitude, ω is the angular frequency, and t is the time; The cylindrical electrode in the middle of the buncher is connected to a high-frequency power supply, and the cylindrical electrodes on both sides are grounded respectively. The electrodes are made of stainless steel. The high-frequency voltage V b (t) is expressed as V b (t)=V b0 sin(ω b t+φ) Where: V b0 is the high frequency voltage amplitude, ω b is the angular frequency, t is the time, and φ is the initial phase.

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